Inﬂuence of Parental Dura and Pisifera Genetic Origins on Oil Palm Fruit Set Ratio and Yield Components in Their D × P Progenies

: This research was conducted to study the performance of biparental dura × pisifera (D × P) progenies and their parental genetic origins on fruit set and yield components. Twenty-four D × P progenies developed from 10 genetic origins were used for this study. Analysis of variance showed that there was genetic variability based on the evaluation of individual progenies. Deli Ulu Remis × Nigeria of progeny ECPHP500 recorded the highest bunch number (22.91), and fresh fruit bunch (184.62 kg palm − 1 year − 1 ) and Deli Banting dura × AVROS pisifera (ECPHP550) had the highest average bunch weight (10.36 kg bunch − 1 ). Progenies PK4674 (61.12%) and PK4465 (60.93%) had the highest fruit set, and the highest oil yield of 52.66 kg palm − 1 year − 1 was noticed by progeny PK4674. Estimation of variance components, coe ﬃ cients of variation, heritability, and genetic gain were calculated to establish the genetic variability. To validate the genetic disparity among the progenies, an unweighted pair-group procedure with arithmetic mean (UPGMA) and principal component was employed based on their quantitative traits. Through the UPGMA and principal component, the 24 progenies were clustered into 7 clusters, whereas cluster V had the highest fruit set (60.62%) and cluster IV had the highest oil yield (43.71 kg palm − 1 year − 1 ). For oil palm tissue culture and breeding programs, progeny PK4674 will be more useful for developing planting materials of high oil yielding with stable performance. However, we recommend that future studies incorporate molecular studies with conventional breeding. ﬀ P and their genetic on oil deep peat were hybridized with either the same female dura or male pisifera parents.


Introduction
Oil palm (Elaeis guineensis Jacq.) is the highest oil-producing crop and the most important source of vegetable oil among 17 major oil-and fat-producing crops in international trade. The demand for vegetable oil is on a continuous increase due to an increase in the world population. Oil palm is the highest oil-producing crop among cultivated oilseed crops efficiently producing a sufficient amount to meet the rising demand. Barcelos et al. [1] projected that by the year 2050, oil palm production may have to reach 240 million tons. The Elaeis guineensis Jacq. commonly known as the African palm and Elaeis oleifera from Latin America are the two outstanding species [2], the former being the largest cultivated oil-producing species originated from West Africa compared to other known oil crops [3]. Intraspecific dura (D) × pisifera (P) hybrids are the majority of commercial seeds today [1,4]. The shell thickness has a significant influence on the oil content and with teneras in bunches having 30% more mesocarp and 30% higher oil content than duras [4]. Due to their higher oil yields, tenera palms are selected [1], which are derivatives from the crosses of dura × pisifera.
Indonesia and Malaysia are the largest agricultural exports of palm oil, producing 10 and 5% of their exports, respectively [5]. Four million smallholder farmers and workers in Indonesia and 721,000 in Malaysia are working in the sector; another 11 million in the two countries are indirectly reliant on it. The majority of oil palm jobs are located in remote rural areas, where alternative employment is scarce, thereby helping to foster rural growth and alleviate poverty [5]. Therefore, low oil yield will cause a decline in the economic contribution of the industry. High oil-yielding palm varieties have potential economic benefits in growing nations, especially for the small-scale farmers. Millions of people from Malaysia and Indonesia have been lifted out of poverty through the palm oil industry, which jointly accounts for about 85% of global production [6]. Through high oil yield, 4.5 million people are employed by the Indonesian palm oil industry and account for 1.6% of gross domestic product (GDP) [6]. Oil palm is the biggest single contributor in the economy of Indonesia with a yearly foreign exchange of more than $18 billion, since a huge quantity of the harvest is exported [6].
Oil palm fruit set and oil yield could be influenced by different genetic materials that have been used as parents to develop, for example, dura × pisifera progenies. Unsuitable D × P progeny planting materials may result in a low fruit set coupled with a loss in oil yield. The need for fresh planting materials with ample genetic variability for future development has been realized by many breeders [1]. Higher oil yield can only be attained when there is an increase in fruit set. The yield per unit area could be improved by using D × P progeny planting materials that have high fruit set/fertile fruit to bunch (FS/FFTB) value. Fruit set is essential for the evaluation of progenies for high fresh fruits to bunch (FFB) and oil yield (POY). The performance of individual progeny differs from one another, and, therefore, the evaluation of individual progeny is extremely important. Arolu et al. [7] demonstrated that progenies varied significantly in their performance for FFB yield, recording a trial mean of 192.93 kg palm −1 year −1 from a range of values at 166.49 to 220.06 kg palm −1 yr −1 . Oil yield ranged between 44.06 to 67.18 kg palm −1 yr −1 with a trial mean of 53.91 kg palm −1 year −1 [8]. The PS10 was developed from 8 duras and 2 teneras (10 palms) through biparental hybridization programs via progeny testing, which is presently being utilized in oil palm breeding programs. Mean FFB and oil yield ranged from 171.9 to 221.3 kg palm −1 yr −1 and 28.2 to 52.9 kg palm −1 yr −1 , respectively [8]. The study proposed that it is essential and profitable to cultivate biparental D × P progenies that have the potential to produce higher fruit set and oil yield. Oil palm is raised by smallholder farmers and large companies, and the cultivation and expansion effect of oil palm on other scopes of human welfare and economic growth have been examined by numerous studies [9]. By further intensifying the oil palm growing area and or increasing its yield, the rising worldwide demand could be met [9]. Higher priority should be given to rising oil palm yields, because the loss of tropical rain forests may occur due to an area expansion [9].
Several attempts have been made by the Malaysian Palm Oil Board (MPOB) and other earlier researchers to address the problem of low fruit set by developing varieties of D × P progenies as planting materials. The single gene inheritance in oil palm has been completely exploited to produce the best higher oil-yielding planting materials [10]. Presently, most cultivated commercial oil palm is tenera hybrids that were derived from different dura and pisifera planting materials, and are presently being cultivated in commercial plantations, manifesting a high dissimilarity in yield among the high-yielding progenies. Fundamentally, the F 1 hybrids contain desirable characters from both parents, which have given rise to the improvement in fresh fruit bunch and oil yield. The oil palm breeding cycle is wide, approximately 12-19 years, and has a limitation in hybrid requirements [11]. Therefore, genotype × environment (G × E) would not be appropriate in this current study since the 11-year-old progeny palms were only planted in one location on deep peat soil.
Efforts and urgent attention are still needed to improve the yield of oil palm fruit set and oil yield, due to the growing demand for palm oil. Murphy [12] reported that by the year 2050, the world population is likely to increase by up to 10 billion. Looking at the demand for vegetable oil, it is essential to increase oil palm yield from 3.5 tons to 9-12 tons as the potential yield to feed the projected population. The primary objective of oil palm growers and breeding programs is to increase oil yield. To achieve maximum output per unit area, emphasis on genetic planting materials is the first stage in high yield achievement. For the past years, there has been a continuous decline in oil palm fruit set and oil yield. Differences in genetic origins may have contributed to the decline in fruit set and a reduction in oil yield. Amiruddin et al. [13] reported that the dominant gene, additive gene, or a combination of both were responsible for controlling yield due to the type of raising planting material and its growing environment. It is significant to constantly increase Malaysia's oil yield ha −1 to uphold the economic advantage in the global market [14].
The utmost efficient and appropriate means of increasing oil palm yield is through the use of genetic materials that are known to be high yielding and resilient to endure the hazards of major pests and diseases so that optimum growth and outstanding economic returns throughout the production life span of the palm are realized. The prerequisite in any breeding program is the relative involvement of dissimilar characters to yield, the familiarity of association of nature among different characters, and the existence of adequate genetic variability [15]. Thus, breeding for yield improvement in crops formulated breeding procedures in which genetic gain entails are of utmost importance. Through the selection and breeding of novel materials of the 10 dura and pisifera genetic origins carried out by MPOB, the best performing progenies developed through D × P hybridization were used. Considering the importance of oil palm in the economy of Malaysia and other oil palm-growing countries like Sierra Leone, this study needed to investigate parental dura and pisifera genetic origins on fruit set and yield components in their D × P progenies.

Planting Materials (Genetic Origins and Their D × P Progenies)
The best performing progenies from six duras and four pisiferas from genetic origins of Angola × AVROS, Tanzania × Nigeria, Deli Serdang × Cameroon, Deli Ulu Remis × Nigeria, Tanzania × AVROS, Angola × Nigeria, Deli Johor Labis × AVROS, Deli Banting × AVROS, Deli Ulu Remis × Yangambi, and Deli Ulu Remis × AVROS, developed through D × P hybridization, were used. A total of 24 progenies of genetic materials derived from the pedigree crosses are presented in Table 1. The materials used were F 1 hybrid-single generation, developed from closely pollinated duras and pisiferas materials at the MPOB Research Station, Kluang. Figure 1 illustrates the photographic details of single generation D × P progenies plant materials.

Study Location and Experimental Design
The progeny testing of biparental (Bips) breeding design with derivative progenies from pedigree crosses was planted by MPOB in September 2008 in Trial 0.502, Field 6B1, at Teluk Intan research station, in Bagan Datuk, Perak (3.49 • N, 101.06 • E), Malaysia. The total area of the experiment was 12.06 ha with 1930 palms. The total number of research palms was 1520 with an area of 9.5 ha (160 palms/ha). A total of 410 palms were used as guided palms with an area of 2.56 ha. An equilateral triangular planting design with a planting distance of 8.5 × 8.5 × 8.5 m was utilized. Independent completely randomized design (ICRD) as delineated by Rafii et al. [16] with 4 replications of 16 palms per progeny, per replicate was adopted for use in the present study. The ICRD was used as a design in the study due to the large experimental area with unequal replications. This is a result of the limited availability of progeny planting materials during the planting period and the homogeneity of the planting medium (peat soil).
The site of the experimental plot was flat with fairly homogenous soil conditions, with consistent and moderate rainfall distribution. The soil in this area had 3.4 pH and was categorized as a very profound peat soil with 33.6% carbon. The mean yearbook temperature was approximately 27 • C, with 32 • C maximum, 21 • C minimum, and relative humidity of about 85%. The total mean yearly precipitation was approximately 2100 mm [17]. An ideal growth and high yield of oil palm on peat soil can be achieved sustainably at the maximum ground-water level. In Malaysia, rainfall levels are among the highest, with high humidity of about 90%, and the peak rainy season is from November to January, and in January, precipitation reaches 368 mm (14.5 inches) [18]. Special irrigation was not required in the 11-year-old oil palm plantation; however, an efficient and appropriate drainage system served as a major factor for oil palm cultivation on peat soil and was constantly managed. The agronomic activities such as drainage maintenance, fertilizer application. and other necessary farm practices were carried out following optimum protocols.

Data Collection
The performances of the biparental progenies such as yield records and yield characters were evaluated based on individual progeny data, which entailed bunch number (BNO), average bunch weight (BWT), and fresh fruit bunch (FFB). The procedure used by Shabanimofrad et al. [19] was followed in carrying out data collection for yield and yield characters of diverse progenies for 5 years, which was undertaken by MPOB. Subsequent processes such as bunch analysis and fruit composition were carried out at regular intervals of 4 months, making a total of 3 rounds of data collection yearly (15 rounds for 5 years). Bunch yield was carried out in 14-day intervals or 2 rounds per month (120 rounds for 5 years), following procedures of Rafii et al. [20,21]. Throughout the harvesting rounds, data were collected on individual palms, including bunch number, bunch weight based on their progenies, other different relevant components regarding fresh fruit bunch quality characters, yield, and nonsexual and functional traits. The standard technique for bunch analysis and fruit composition was conducted following procedures of the Nigerian Institution for Oil Palm Research (NIFOR). Bunch analysis and fruit components were conducted at four-month intervals for five years (15 rounds) as described by Black et al. [22] and Rao et al. [23]. A simplified non-destructive method designed by Corley et al. [24] and verified by Breure and Powell [25] was used to determine single-round vegetative and physiological traits measurement.

Statistical Analysis
All collected data were calculated based on progeny. Mean values of progenies were used in the analysis, in which bunch number per palm (BNO/palm) was the overall number of bunches recorded. Fresh fruit bunch per palm (FFB/palm) was the total bunch weight per palm and the quotient of FFB/palm and BNO/palm was the average bunch weight per palm. Version 9.4 of the statistical analysis system (SAS) was used in the analysis of data. Analysis of variance (ANOVA) was calculated using the general linear model (PROC GLM) of SAS due to unequal distribution of progenies. Duncan's new multiple range tests (DNMRT) for multiple mean comparisons of progenies at the 5% level of probability, and simple descriptive statistics such as mean and standard error (Stderr) were used. The SAS 9.4 method for PROC VARCOMP restricted maximum likelihood (REML) was used for variance components estimations. The different genetic structural parameters which included phenotypic and genotypic variances, heritability (h 2 B ), phenotypic coefficients of variation (PCV), genotypic coefficients of variation (GCV), and genetic advance (GA) as a percentage of the mean were estimated.
The estimation procedure described by Singh and Chudhary [26] for GCV and PCV were followed and their estimated values were categorized according Oladosu et al. [27] as high (>20%), intermediate (10-20%), and low (<10%). The estimate for broad-sense heritability (%) was performed based on the formula given by Johnson et al. [28] and Falconer [29]. As proposed by Johnson et al. [28], h 2 B was categorized as high (h 2 B >60%), moderate (h 2 B = 30-60%), and low (h 2 B <30%). The calculation for the expected genetic advance (GA) and as the percentage of mean was performed using the technique developed by Assefa et al. [30], and the estimated GA values based on Johnson et al. [28], categorized as high (GA > 20%), intermediate (GA = 10-20%), and low (GA <10%), were used. Cluster analysis using analysis of multivariate (numerical taxonomy and multivariate analysis system (NTSYS-PC)) software and principal component analysis (PCA) were used to assess the genetic differences amid the progenies.

Yield and Yield Characters (BNO, FFB, and ABW) of Biparental Full-Sib Progenies
The ANOVA of the 24 D × P progenies exhibited highly significant effects (p ≤ 0.01) for yield and bunch yield traits as shown in Table 2. Junaidah et al. [31] reported highly significant differences among the total 25 progenies analyzed. Highly significant (p ≤ 0.01) dissimilarity effects among progenies' yield component traits were also reported by Marhalil et al. [32] in the evaluation of elite novel progenies of the dura (MPOB-Nigeria) × pisifera (AVROS). Similarly, Arolu et al. [7], in their studies on D × P progenies for yield and bunch yield components (BNO, FFB, and ABW), observed highly significant effects.
Based on the results presented in Table 2, sufficient genetic variations existed among the progenies in the study, which could suggest a satisfactory likelihood for selection. Genetic dissimilarities are known to be substantial in oil palm breeding programs since genetic variations aid as a basis for new genes to broaden the oil palm narrow genetic base when introgressed. In support, Rajanaidu and Ainul [8] revealed that owing to the narrow hereditary base in the oil palm population, the intended purpose for germplasm prospection is aroused, resulting in the introgression of novel genes. In addition, Arolu et al. [33] cited that the most sustainable and efficient way of increasing the yield production of oil palm is through the use of cultivated materials that are of better yielding with a proven outstanding genetic base.
High variance components were detected in genetic variance (σ 2 g ) which varied from 67.76 to 78.62% (Table 2). Based on the results obtained, this could be ascribed to gene effect. The estimation of genetic variance (σ 2 g ) for yield components in ascending order showed that FFB was lower than BNO and high variances in the study for yield traits were recorded by ABW. Similarly, error variances (σ 2 e ) were the lower variance components which varied from 21.38 to 32.24%, with high error variance percentages for FFB followed by BNO. The absolute results exhibited both environmental and genetic variation effects on biparental progenies' performance on yield component traits with the genetic variance being the highest contributor. However, Sarkar et al. [34] revealed that the negative impacts of climate change on agricultural production are more vast than its positive impacts. An adverse significant relationship exists between oil palm production and annual average temperature, and the yield of oil palm can decline from 10 to 41% as a result of a rise in temperature by 1 to 4 • C [34]. Note: S/V = source of variation, Code = progeny code, D/F = degree of freedom, BNO = bunch number (bunches palm −1 yr −1 ), FFB = fresh fruit bunch (kg palm −1 yr −1 ), ABW = average bunch weight (kg bunch −1 ), σ 2 g = genotypic variance, σ 2 e = error variance, σ 2 ph = phenotypic variance, ** = highly significant at p ≤ 0.01, p ≤ 0.05, ns = non-significant p >0.05, The phenotypic variance in percentage are the values in brackets, Stderr = standard error. Means with the same letters within the same column are not significantly dissimilar at p ≤ 0.05, based on Duncan's new multiple range tests (DNMRT).
The performances of the individual progenies based on means for BNO, FFB, and ABW are summarized in Table 2. The overall trial mean for BNO, FFB, and ABW were 17.48 bunch palm −1 yr −1 , 145.20 kg palm −1 yr −1 and 8.39 kg bunch −1 , respectively. BNO and ABW of the individual biparental progenies ranged from 11.65 to 22.91 bunch palm −1 yr −1 and 6.22 to 10.36 kg bunch −1 , respectively. About 50% of the progenies were above the respective trial mean for BNO and ABW. Among the progenies, FFB yield ranged from 88.90 to 184.61 kg palm −1 yr −1 , where 54.17% FFB had yield above the trial mean. The FFB from the present study exhibited a decline in yield when compared to the findings by Rajanaidu and Ainul [8] and Arolu et al. [7]. The highest ABW was observed in ECPHP550 and ECPHP500, which recorded the highest BNO and FFB with moderate ABW. Ultimately, the results obtained revealed that ECPHP500 attained the highest FFB yield because its BNO was above the trial mean with a moderate ABW. Studies by Gurmit and Musa [35] were in agreement with Sapey et al. [36] who reported that to achieve higher FFB yield, selection for high ABW combined with moderate BNO should be considered. Comparatively, the results were in agreement with Arolu et al. [33] and Myint et al. [37]. The results indicated that FFB yield was influenced by BNO among the progenies. Raffi et al. [14] reported that it is appropriate to identify genotypes with satisfactory high FFB yield and oil yield in plant selection and breeding programs over the environment with stable performance.

Individual Parental Performance of D × P Progenies on Fresh Fruit Bunch
The 24-biparental progenies were categorized according to their parental genetic origins. Five out of ten genetic origins were above the parental mean value of 142.40 kg palm −1 yr −1 for FFB yield and it ranged from 114.71 to 169.24 kg palm −1 yr −1 . The highest FFB yield was observed in Deli Ulu Remis × Yangambi, and Tanzania × AVROS had the lowest FFB yield when compared with the rest of the parental genetic origins ( Figure 2). As illustrated in Figure 2, the parental performance showed Deli Ulu Remis × Yangambi followed by Angola × Nigeria as the most outstanding parents for FFB yield; therefore, they should be recommended as parents for hybridization programs using modern breeding methods. Breeding research may lead to an increase in the productivity of oil palm [38]. Modern breeding technologies may be advantageous to breed highly productive oil palm varieties that are more tolerant to climate stress and altitude [38,39].
The findings of the present study were in agreement with Junaidah et al. [31], in their studies reporting that D × P (Yangambi) attained the highest FFB and oil to bunch (OTB) ratio. Soh et al. [40], reported that the Yangambi pisiferas lineage was characterized in several breeding populations worldwide as male parents due to their outstanding growth performance and larger fruits with an attribute of high oil yield. The main emphasis of plant breeding and selection is the production of dura × pisifera high-yielding palms as commercial planting materials, especially by research institutions and seed producers [41]. However, the generally low performance among the parental genetic origins could be due to the pisifera effect. Arolu et al. [33] reported that during the analysis of the North Carolina Model 1 (NCM1) in Nigerian palms, the pisifera effect was also found to cause low FFB yield. Currently, the pedigree of some breeding parents in oil palm for hybrid tenera production for yield improvement programs indicates the close relatedness of the parents used [42]. Even though promising results through the use of markers in oil palm were obtained, due to low polymorphism, baffling effects in the developmental stages of the plant, and its susceptibility to environmental factors, morphological markers are not adequately reliable to be used in oil palm [42]. Therefore, field quantitative data of hybridized biparental progenies were used to identify a better progeny and their origins for oil palm FSR and POY.

Replications
The findings were parallel with those of Marhalil et al. [32], except for PTB, and therefore exhibited the presence of large genetic dissimilarity among the progenies. In bunch weight determination, bunch quality components played a fundamental part as they constituted the most vital economic portion of the oil palm bunch. Due to the improvement of the existing biparental planting materials for the expansion of the narrow genetic base, the occurrence of high genetic variation was very crucial, whereas the replication effect remained insignificant. Table 3 also shows bunch quality trait of variance components which varied from 16.76 to 55.53% for the estimation of genetic variance component (σ 2 g ), with the highest observed in MTF. The error variance (σ 2 e ) percentage ranged from 44.47 to 83.24% and the highest σ 2 e was recorded in PTB. In esteems of variance components, MTF, KTF, STF, and OTB, had the highest σ 2 g , which suggested the presence of genetic effects. Alternatively, a high manifestation of σ 2 e was observed among the remaining traits. The result was similar to Noh et al. [43] and Gomes et al. [44], but contrary to Myint et al. [37]. The σ 2 e was considerably higher when compared with σ 2 g for the majority of the traits. Hence, the high σ 2 e may have occurred as a result of the environmental effects, since water, temperature, and sunlight were considered to be the center bolt of environmental consequences. Several authors have reported differences in oil palm physiological responses to drought [45,46], or morphological and physiological variations between drought-tolerant and drought-susceptible content [39,47]. Vogelgesang et al. [48] reported that for oil palm to flourish, adequate water supply and warm temperatures coupled with lots of sunlight were desirable. Slight variations in environmental factors can disturb the survival of substantial fruit set development, especially at the time of anthesis.
The individual performance of 24 biparental progenies, together with the trial average values of each of the 19 traits analyzed based on bunch quality characters, are summarized in Table 4. All progenies were balanced in their performances for MFW, PTB, MTF, OTDM, OTWM, FFTB, OTB, KTB, FFB1, and PKY. Significant effects were noticed in the majority of these components, which indicated the reliability in their performance among the D × P progenies. Rafii et al. [21] reported that in Malaysia, as the dura × pisifera palms were planted under different organizations and planting density, genetic inconsistency was found in their yields and components of fruit bunch quality.   However, 14 out of 24 progenies had FTB above the trial mean value of 57.03% and the highest FTB was recorded in progenies PK4674 and PK4465. About 50% of the progenies had FFTB above the trial mean (53.54%) and the highest FFTB was found in progenies KP4674 and PK4465. Progeny PK4674 had the highest POY as a result of high FFTB yield. Among the 24 progenies, only PK4674, PK4465, and PK4482 were above the critical range of 60% fruit set.
Mesocarp to fruit, oil-to-wet mesocarp to fruit, as well as fruit to bunch were considered as the key contributing characters in determining oil to bunch. According to Corley [49], one of the most significant traits of bunch quality was mesocarp to fruit (MTF) because 95% of palm oil yield (POY) was always found within MTF of the palm fruit. There were substantial effects among the genetic origin materials of their progenies for MTF (Table 4), resulting in noticeable variations in oil to bunch (OTB). Previous studies by Krualee et al. [50] showed that MTF ranged from 47.90 to 73.81% in Thailand. Shi et al. [51] also reported that in Hainan Island, MTF was recorded at 74.26%.
In the present study in Malaysia, MTF was in the range of 69.54 to 84.98%, with 76.77% as the trial mean. Amiruddin et al. [13] reported that hybrids generally manifest low MTF and low total OTB but high STF. Progeny ECPHP618 had the highest MTF. The highest KTF was observed in PK4570 (13.09%) with a trial mean of 9.48%. However, ECPHP618 recorded conflicting results in MTF. KTF yielded a moderate mean of 7.46%.
Results of the present study showed that MTF had a highly significant relationship but negatively associated with the kernel to fruit (r = −0.71, p <0.001). The trial mean for OTWM was 50.81%, with values in the range of 46.11 to 55.14%, with the highest OTWM for progenies of PK4648 and PK4535. The OTB ranged between 16.71 to 28.58% with a trial mean of 22.24%, and the lowest OTB was measured in progeny PK4570 which was significantly influenced through the lowest values observed in MTF and OTWM. Low FFTB coupled with FTB was also observed. Meanwhile, the highest OTB percentage was detected in PK4674 gained through high matching FTB, FFTB, MTF OTDM, and OTWM. According to Mohd [52], oil to bunch can be considered high when OTB is above twenty-five percent. Noh et al. [43] also reported that in oil palm breeding and selection, OTB stands as a significant character. Therefore, in the present study, the highest achieving progeny in terms of OTB was PK4674 (28.58%) and hence, for oil improvement, it could be selected based on OTB.
In terms of KTB, 50% of the progenies were above the trial mean (5.06%) with a performance ranging from 3.11 to 7.63%. Progeny PK4482 scored the highest KTB, followed by PK4465 of the same genetic origin parental lines. Meanwhile, since there was a non-significant difference between PK4648 and ECPHP500 in KTB, these were recorded as the least KTB. Their low performance in KTB may have occurred as a result of the similar genetic makeup of the same parental family. The net gain was directly influenced in the present study as a result of an increase in KTB. Rajanaidu [53] reported that with the introduction of the pollinator insect (Elaeidobius kamerunicus) to Malaysia in 1983, the KTB tremendously increased from 5 to 7%. In terms of KTB yield, 50% of the progenies had above 5% KTB yield. According to Myint et al. [37], it is essentially gainful to develop palm materials of high KTB as planting materials. For POY, 14 progenies yielded above trial average value (39.03 kg palm −1 yr −1 ), which ranged between 25.59 to 52.66 kg palm −1 yr −1 , and PK4674 produced the highest POY. Results showed declining POY when compared to the findings of Rajanaidu and Ainul [8] and Arolu et al. [7], but the POY yield performance of progenies proved better when compared with the findings of Rafii et al. [14] from the same location. According to Rafii et al., in comparison to 38 DP oil palm progenies with the other three sites (Kluang in Johor, Kepong in Selangor, and Carey Island in Selangor), Teluk Intan was the best environment for oil yield and the means of progenies over locations shows that DP23 has the highest oil yield at 41.59 kg palm −1 year −1 . However, progeny PK4674 improvement in oil content occurred due to its high FFTB and, therefore, could have influenced high POY.
The trial was laid down on a deep peat soil of low soil fertility and lacked the advantage of holding the palms upright. This could have caused the environment and genetic origins to influence fruit set and oil yield among the progenies. Therefore, based on the results obtained, Deli Ulu Remis × AVROS was the most outstanding progeny. Its performance was above the trial mean in all bunch fruit quality components except in MNW, STF, KTB, and PKY. Deli Ulu Remis was found to be a good combiner with AVROS pisifera due to its overall performance in bunch quality components.
This result was in agreement with Malike et al. [10], who stated that AVROS pisifera and Deli dura were good general combiners. Kushairi et al. [54] also reported that since late 1959, Malaysia and other oil palm-growing countries worldwide, commonly used Deli dura crossed with AVROS pisifera as their commercial planting materials. AVROS pisiferas were eminent for their precocious bearing and high oil yield [40].

Performance of Dura and Pisifera Parental Genetic Origins on Four Key Components
The performance of genetic origins for OTB, MTF, OTWM, and FTB are presented in Figure 3. Five of the parental genetic origins were above the parental means of 21.55% for OTB and 53.27% for FTB, while four of the parents had above parental mean values of 76.43% for MTF and 50.47% for OTWM. The results indicated that substantial genetic dissimilarity occurred among the parental origins of these traits. The influence on genetic origins could be attributed to the environment. Noh et al. [55] reported that the precondition for high oil to bunch is high fruit to bunch, since oil to bunch is considered as a derived component which comprised fruit to bunch, mesocarp to fruit, and oil-to-dry mesocarp.  Figure 3 displays a positive relationship among the traits in all the genetic origins in this study. An increase in MTF enables an increase in other traits, suggesting that for future breeding and selection programs, Deli Ulu Remis × AVROS would be an outstanding parent. According to Laichhane et al. [56], crop farmers in Europe lacked access to adequate numbers and varieties of crop species. They further cited that more efforts are required in plant breeding to develop novel crops to substitute diversity in the present cropping system with local adaptation characteristics. Table 5 presents the analysis of variance for vegetative characters of 24 D × P progenies. The influence of genetic origins exhibited highly significant effects (p ≤ 0.01) amid the trait performance of their D × P progenies, which signified the occurrence of substantial variations. For future breeding as well as selection improvement in oil palm, such materials with better performance can be exploited. On the contrary, a non-significant difference was observed in replications, which manifested that homogeneity existed in the planting medium (peat soil). In selecting desirable palms for oil palm breeding, vegetative traits should be taken into consideration [57,58].  The genetic variance component (σ 2 g ) for vegetative traits ranged from 35.24 to 82.56% and 14 out of 16 traits, or 87.50%, proved to be high in σ 2 g . Palm height (HT) was recorded as the highest σ 2 g , while LW was regarded as the lowest. With all indications regarding the variance components, it was evidenced that σ 2 g had a high influence on the vegetative traits as it was also examined for yield and yield traits, except for LW and FI which showed to be influenced by the environment.

Vegetative Traits of Diverse Progenies of Oil Palm
The performance of the D × P progeny means, as well as trial means for vegetative characters, are presented in Table 6. The DNMRT exhibited frond production (FP) ranging from 24.25 to 27.80 fronds palm −1 yr −1 with a trial mean of 26.49 fronds palm −1 yr −1 . Comparatively, this result was in agreement with Rafii et al. [21] who reported that palms at age 12 to 14 years after planting produced 20 to 25 leaves per year. It showed that progeny PK4118 from parental origins of Deli Ulu Remis × AVROS recorded the highest, followed by Deli Ulu Remis × Nigeria of progeny ECPHP500. The higher the frond production in oil palm, the higher the likelihood for a higher bunch yield, because each frond produced subtends of one individual inflorescence which could be possibly female or male or hermaphrodite, and of which a greater percentage could be female flowers, except in sterile palms. The increase in frond production of ECPHP500 enhanced high BNO production. In the determination of oil palm BNO, frond production assumed a significant role [21]. According to Woittiez [59], the potential quantity of inflorescence in oil palm was directly determined by the leaf initiation rate and the single inflorescence originates in each leaf axis.   In oil palm breeding and selection programs, palm trunk height (HT), slighter trunk diameter (DIAM), smaller petiole cross section (PCS), and shorter rachis length (RL) are generally ideal vegetative traits. The HT and DIAM are well preferred in palm compactness; hence, in FFTB and FFB production, more nutrients could be grasped as an alternative of nonsexual growth and care, and possibly lengthen the economic life span of the palm. The RL may well be used in place as a reference guide in planting density determination. Palms might be planted with shorter RL within a unit area with high yield performance.
Murugesan and Shareef [60] reported that for spacing in commercial palm domains, and for high-density planting, RL and HI remained to be significant traits. DNMRT indicated that HT, DIAM, PCS, and RL were significantly different in their performance among the progenies. The HT, DIAM, PCS, and RL average values varied from 3.82 to 5.28 m, 0.47 to 0.59 m, 18.38 to 30.18 cm 2 , and 4.38 to 5.60 m with trial means of 4.51 m, 0.52 m, 26.00 cm 2 , and 5.11 m, respectively. For HT, progenies PK4548 (Deli Ulu Remis × Yangambi) and PK4651 (Tanzania × Nigeria) were observed as the tallest since there was no significant effect between these two progenies even though they were hybridized from different genetic materials.
Palms with larger diameters influence an increase in frond production with an increase in BNO. DNMRT showed that progeny ECPHP500 recorded the largest DIAM and the highest BNO by progeny ECPHP500, which occurred due to its large DIAM and high frond production. Additionally, palms with bigger DIAM could be used in the construction of local bridges and as a source for timber harvesting. Based on the petiole cross section (PCS), progenies ECPHP415 and PK4118 recorded the highest PCS. Regarding the rachis length (RL), which is considered as one of the most important vegetative characters, 54.17% of the progenies were above the RL trial means, and Deli Ulu Remis × Yangambi (PK4548) had the longest RL (Table 6).
Conversely, results of the present study were in disagreement with those obtained by Junaidah et al. [31] in which D × P (Yangambi) of progeny DA39 recorded the longest RL at 6.79 m, and progeny DA84 was the shortest at 5.60 m. This may have occurred as a result of different dura materials being crossed with Yangambi pisifera. Characters such as leaflet width (LW), leaflet length (LL), and leaflet number (LN) ranged from 4.80 to 5.48 cm, 81.74 to 98.18 cm, and 150.08 to 179.34 (no.), with trial average values of 5.12 cm, 87.19 cm, and 165.99 (no.), respectively. DNMRT proved that progeny PK4621 possessed a high value of LL and LW, and ECPHP500 had high LN. Based on DNMRT, there was a non-significant variation among progenies PK4651 and PK4548 for LL, PK4118, and PK4674 for LW. The same dura parent was used in the hybridization of some of these progenies, which may have resulted in a non-significant difference in their LL, LW, and LN.
The leaf area (LA) magnitude ranged from 6.74 to 9.96 m 2 with a trial mean (8.54 m 2 ), and progeny PK4648 had a larger LA value. The leaf area index (LAI) ranged from 3.99 to 9.90 between the smallest and largest with a trial mean of 5.05. DNMRT confirmed that significant differences occurred among the progenies with maximum LAI being realized in progeny PK46. 48. The results of this present investigation were in contrast with previous results obtained by Breure,[61], who stated that LAI ranged between 5.5 to 6.0 in Southeast Asia. It was also divergent to the findings of Arolu et al. [7], in their previous studies, where it was reported that LAI had 5.78 as a trial mean and ranged from progeny DP18 (4.58) to progeny DP29 (7.72).
Variations in the findings may have occurred due to different genetic structures and the environment in which they were cultivated. DNMRT showed a significant difference among the biparental progenies in the leaf area ratio (LAR), with values ranging from 15.39 to 19.68. Progenies PK4535, PK4648, and PK4570 were not significantly different and they obtained the highest proportion of LAR (Table 6) with a trial mean of 17.42.
Additionally, mean leaf dry weight (LDW), total dry weight (TDW), and frond dry weight (FDW) ranged from 2.09 to 3.29, 10.57 to 19.76, and 56.81 to 91.03 kg, respectively. Their trial averages were LDW (2.87), TDW (14.93), and FDW (76.11 kg), respectively. Among the progenies in this study, the highest LDW was perceived in progenies ECPHP415 and PK4118. For TDW and FDW, the highest was shown in progenies ECPHP500 and PK4118. However, these results were contrary to earlier findings reported by Myint et al. [37], which found that amid the MPOB-Senegal germplasm, the LDW ranged from 1.38 to 2.33 kg, while TDW varied from 14.14 to 25.89 kg. It was also observed that the mean range in FDW was 41.86 to 71.31. In general, variations in findings may have occurred due to differences in the genetic make-up of planting materials, soil types, and locations.

Genetic and Heritability Parameters for Yield and Fruit Bunch Quality Components of D × P Biparental Progenies
The estimates of broad-sense heritability (h 2 B ), phenotypic coefficient variation (PCV), genotypic coefficient variation (GCV), and genetic advance (GA) for yield and fruit bunch quality traits are presented in Table 7. According to Johnson et al. [28], h 2 B was categorized as high (>60%), intermediate (30-60%), and low (<30%). In the present study, PKY, OTWM, OTDM, OTF, and PTB were low in h 2 B . Only ABW, BNO, and FFB scored high h 2 B (>60%), while the majority of the fruit bunch quality components were observed with moderate h 2 B (30-60%). Based on BNO yield, many rank orders of h 2 B estimates have been reported. BNO was considered as the highest normal estimate, followed by ABW in oil palm [21,62]. The h 2 B estimates in the present study revealed that the average bunch weight (78.56%) was higher than the palm bunch number (74.29%), while the lowest was fresh fruit to bunch (67.76%). Noh et al. [43] in their study reported that shell to fruit and mesocarp to fruit showed moderate heritability values. Conversely, this current investigation exhibited that h 2 B for STF was moderate while MTF was low.  The phenotypic and genotypic phases can display dissimilarity amidst the natural population of cross-pollinated plants. In the proof of distinctiveness of the components with better responses to selection, phenotypic and genotypic coefficients of variations remained to be a supportive indication [63]. The categorized estimation values indicated (high (>20%), intermediate (10-20%), low (<10%)) as reported by Oladosu et al. [27] for both PCV and GCV were adopted. The lowest value of the PCV was observed in OTDM (3.18%) and the highest value was recorded in PTB (55.09%). Low PCV was observed in OTWM, MTF, and OTDM.
Whereas moderate PCV was found in FFB, BNO, OTB, ABW, FFB1, OTF, and FFTB, the remaining traits were observed to be high in PCV (Table 7). The majority of the fruit bunch quality components varied largely. The result suggested the influence among the biparental progenies; hence, there is a greater possibility for selection. On the contrary, all of the yield traits and FFTB were noted to be moderate. This could have occurred as a result of both genetic and environmental effects. The GCV for yield and fruit bunch characters ranged from 1.41 to 22.59%, and the last and highest were obtained in OTDM and PTB, respectively. Among all the traits analyzed, only PTB, MNW, and KTF had high GCV. Eleven out of twenty-two of the traits were moderate, whereas FFB1, FFTB, FTB, MC, OTF, MTF, OTWM, and OTDM were regarded as low (Table 7).
In terms of genetic variation, characters with low GCV values implied an inadequate level for selection. The yield and fruit bunch traits for PCV and GCV exhibited that the PCV was three times higher than the GCV, and, therefore, the environment had greater effects on the characters. These findings are in agreement with prior findings by Rajanaidu and Rao [64], in which yield and yield traits and genetic variation were very low. On that note, FFTB at 11.58% PCV and 6.97% GCV implied that environmental factors had been the highest contributor for low FFTB. Likewise, genetic advance (GA) was categorized according to the procedure developed by Johnson et al. [28] and Falconer and Mackay [65]. The GA percentage ranged from OTDM (1.28%) to MNW (30.70%). High GA was noted in a descending order as MNW, KTF, BNO, STF, FFB, ABW, and MFW, whereas FTB, FFTB, MTF, OTF, OTWM, and OTDM were found to be low in GA (Table 7). Hence, the genetic variation of fresh fruit bunch, fertile fruit to bunch, and oil yield contributed at 82.31, 60.19, and 63.07%, respectively, to phenotypic variation.

Genetic and Heritability Parameters for Vegetative and Physiological Traits
The physiological traits for h 2 B , PCV, GCV, and GA are presented in Table 8. The trait selection was governed by the potential measure of variability presented by Shi et al. [51]. The prerequisite in all breeding programs was the disparity in treatments, the objective of which was to improve the characters for better productivity [63]. To distinguish among progenies (treatments), characters with better variability had the potential of interest [51,66]   PCV was high in OEI, TEI, TOEI, ABDM, and BDM, while 62.07% (or 18 out of 29) had medium PCV. Low PCV (<10%) was noted in a decreasing order for LAR, RL, LL, DIAM, LW, LN, FVM (f), and FP. The GCV for the vegetative and the physiological characters were high in an increasing order at OEI, TOEI, TEI, and ABDM. Only 13.79% of the characters were observed to have high GCV. This was followed by moderate GCV (44.83%) of salient traits which occurred between plant heights to bunch dry matter. The remaining vegetative and physiological traits were observed to have low GCV. The results obtained indicated that traits with high PCV and GCV evidenced the occurrence of high variability which could be an opportunity for selection when equated to other characters.
Based on the categorization estimates, high (>20%), intermediate (10-20%), and low (<10%), of genetic advance (GA) by earlier researchers, such as Johnson et al. [28] and Falconer and Mackay [65], high GA for vegetative and physiological components was not found. However, moderate GA was observed for FDW, ABDM, ATDM, BDM, TDM, and TDW. Twenty-one traits were considered to be low in GA. Plant traits with economic importance are the sole interest of plant breeders. Estimates of h 2 B , PCV, GCV, and GA parameters are ideal limitations in the selection of characters with high variability. According to Bhagasara et al. [63], characters with less variability enhance the difficulty in crop improvement through direct selection.

Cluster Examination and Principal Integral Distance Parallel Matrix Analysis Based on Quantitative Characters
Multivariate analysis (MVA) is founded on multivariate statistical principles that necessitate observation and analysis of more than one response variable at a stretch. The statistical dependence of such variables is often considered in such an analysis. Fundamentally, MVA is an efficient instrument that deals with the analysis of large data on plant components. One of the most widely used statistical procedures is principal component analysis (PCA). In hybridization and selection, the plant breeder is normally aided by PCA information in identifying inadequate characters for utilization [67]. Therefore, in the assessment of the genetic variation of D × P biparental progenies, PCA discriminates and clustering analysis (CA) remains to be efficacious multivariate instruments, and in several crops, such tools have been utilized for analysis [68]. From the cluster and principal component analysis in this present study, 24 progenies were notable based on 21 characters.
The Euclidean distances among progenies and unweighted pair-group procedure with arithmetic mean (UPGMA) dendrogram in Figure 4 was constructed based on the calculated data from the traits of assorted progenies. The progenies appeared to form 7 core groups (clusters) at the 0.33 coefficient level. Cluster I had the highest, with 9 progenies, followed by cluster V with 8 progenies ( Table 9). The analysis revealed that Cluster I comprised 7 D × P genetic origins (DB × AVROS, DUR × AVROS, DS × C, A × AVROS, T × N, A × N and DUR × Y) and Cluster V contained 5 parental origins (DUR × N, DUR × AVROS, DUR × Yangambi A × N and A × N). Cluster III had 2 progenies of 2 genetic origins (DUR × AVROS, and DUR × N). Cluster IV had 2 progenies of 2 origins (DJL × AVROS and A × AVROS). However, Clusters II (A × AVROS), IV (T × AVROS), and VII (A × AVROS) were regarded as the least clusters with 1 elite progeny each. Oladosu et al. [69] attested that accessions within the same cluster were evidenced to be genetically analogous, while arbitrarily distributed accessions in their respective clusters remained diversified. Further, most of these progenies originated from the same dura or pisifera parental lines.   The analyzed data for yield and bunch yield showed that Cluster II recorded the highest FFB (173.93 kg palm −1 yr −1 ) and BNO (20.13 bunches palm −1 yr −1 ), whereas the least FFB and BNO were found in Cluster VII, with a mean value of 88.90 kg palm −1 yr −1 and 14.22 bunches palm −1 yr −1 , respectively. Cluster VI recorded the highest ABW (9.16 kg bunch −1 ), followed by Custer II at 8.65 kg bunch −1 , while Cluster VII continued to record the least ABW (6.25 kg bunch −1 ). The highest performance in FFB yield in Cluster II occurred as a result of high BNO coupled with moderate ABW.
Based on fruit bunch quality characters, the highest FTB (64.00%) and FFTB (60.62%) were observed in Cluster VII and the lowest values of both traits were noticed in Cluster IV. However, Cluster VI (44.20 kg palm −1 yr −1 ), followed by Cluster I (40.58 kg palm −1 yr −1 ), yielded the best POY, and Cluster IV (25.49 kg palm −1 yr −1 ) achieved the lowest POY. It was noted that some of the progenies shared parental lines in common which may have influenced the similarities based on their performances ( Table 9).
The advantage with Cluster VI in POY performance occurred due to the elite progenies from outstanding parental lines. Cluster VI recorded highest in MTF, FFTB1, TEP, and TOT. The highest yield performance of Cluster VI in FFB, MTF, and OTDM enhanced its outstanding oil yield. Conversely, Cluster IV was ranked as the lowest in terms of POY with a mean value of 25.59 kg palm −1 yr −1 . Cluster IV's low output rose as a result of its genetic parental line and most of the palms from progeny PK4570 of Cluster IV were abnormal among other experimental palms. Cluster IV recorded the least values for MTF, MFW, FFTB1, and the highest parthenocarpic fruit to bunch at 5.81% was noticed in Cluster II. Cluster III had the highest OTWM (53.25%) and the lowest was seen in Cluster VII. However, cluster analysis might not have comprehensively given adequate representation about traits' contributions towards genetic effect and, hence, further approaches like principal component analysis could be used as a complementary method [67]. Based on the vector dimensional PCA, 7 groups were constructed from 21 traits, and this was analogous to the obtainable cluster results. In Figure 5, it can be observed that group 1 comprised 8 progenies of 6 parental origins, while group 2 had only 1 progeny of 1 genetic origin. Groups 3 and 4 obtained 2 progenies and 2 origins each, while group 5 recorded 7 progenies from 5 origins. Similarly, group 6 had 3 progenies from 3 genetic origins and group 7 had only 1 progeny from 1 parental origin. The PCA analysis revealed that Deli Ulu Remis × Nigeria and Ulu Remis × AVROS of progenies PK4648 and PK4118, respectively, as well as Tanzania × Nigeria of progeny PK4474, indicated dissimilarity between the dendrogram and vector PCA. In the dendrogram illustrations, progenies PK4648 and PK4118 were found in group 5, and PK4474 in group 1, whereas, in the PCA, these progenies were found in groups 1, 6, and 4. Regarding the influence of genetic origins on their biparental progenies in this study, vector PCA showed that progenies that were within the same group were similar in their genetic make-up, whereas those that were far apart from the center of origin were divergent in their genetic structures and could be used in breeding and selection. Progenies PK4482 in group 7, ECPHP500 in group 5, PK4621 and PK4535 in group 3 were far apart from the center of origin ( Figure 5). The similarities in their divergence occurred as a result of similar parents being hybridized with one another either as female or male. In general, PCA exhibited that variation existed among the progenies and most of the traits were identified based on the key role in determining the variation that occurred among progenies and genetic parental lines. Traits that contributed to high fertile fruit to bunch and high oil yield could be used as selection criteria for the intensification and improvement of the best hybridized progenies. It was observed from the PCA analysis that PCA-1 and PCA-2 accounted for 62.42 and 21.21%, respectively, making a total of approximately 83.63% variation, hence indicating that there is room for selection.

Conclusions
It was discovered from this research that progenies exhibited the most significant economic characteristics that are essential for the oil palm fruit set and oil yield improvement program, with a high genetic dissimilarity ranging from 67.76 to 78.62% of genetic variance among the D × P biparental progenies yield and yield traits. Fresh fruit bunch (FFB), bunch number (BNO), and average bunch weight (ABW) recorded high heritability. Therefore, to boost the oil palm breeding program, these characteristics should be exploited. The yield range of the FFB of the progenies was 88.90 to 184. 62 kg palm −1 yr −1 . Progeny ECPHP500 had the highest FFB, and parental genetic origins of Deli Ulu Remis × Yangambi recorded the highest FFB followed by Angola × Nigeria. As a consequence of the pisifera effect, the poor output of these progenies for yield and yield traits may have been correlated with a genetic effect. A moderate heritability of the majority of the bunch quality component characteristics was detected; hence, high environmental impact was observed with the largest error variance in bunch quality characteristics, which varied from 44.47 to 83.24%. However, in progenies PK4674 and PK4465, the highest fertile fruit to bunch/fruit set was observed at 61.12 and 60.93%, respectively, and only 12.5% of the total progenies had a normal oil palm fruit set above the 60% fruit set critical level. Progeny oil yields ranged from 25.29 to 52.66 kg palm −1 yr −1 , and the highest oil yield was provided by progeny PK4674 which could be an essential source for oil yield improvement. The phenotypic coefficient of variation (PCV) was three times higher than the genotypic coefficient of variation (GCV), suggesting that the climate had a greater impact on the characteristics of the oil palm progeny studied. Progeny PK4674 of Deli Ulu Remis × AVROS had better output in most of the economic characteristics based on the results and was marked as a prospective progeny for high fruit set and oil yield. To boost the traits of the fruit set and oil yield, this potential progeny (PK4674) of Deli Ulu Remis × AVROS oil palm origin could be hybridized with other palms of economic traits. The highest average values for OTB and FTB were observed in Deli Ulu Remis × AVROS, while the highest MTF was recorded in Deli Johor Labis × AVROS to produce high oil yield. High genetic variations were found in most distant progenies from different clusters and could be used for tissue culture and hybridization programs. The methods employed in this study were useful to investigate D × P progenies and their genetic origins on oil palm fruit set and oil yield on Malaysia deep peat soil, but the result could have presented more details if molecular research was used alongside conventional study since most of the progenies were hybridized with either the same female dura or male pisifera parents.