Search Results (55)

Chilli (Capsicum annuum) is a popular spice and vegetable crop of significant economic importance that is cultivated worldwide in warm and humid climatic zones. Although chilli is a thermophilic crop, its quality and yield potential are significantly affected due to various abiotic factors, including extremely fluctuating temperatures beyond the optimum temperatures (18–30 °C). Global warming and anthropogenic activities lead to adverse climatic changes, imposing severe stress on growth, development, and productivity. High temperatures above 43–45 °C adversely affect chilli crops, especially during the reproductive stages, by causing immature fruit dropping, poor seed vigour, reduced number of flowers, flower abscission, aborted reproductive organs, reduced fruit set, and significant yield loss by 50%. Therefore, to reduce quantitative and qualitative losses, heat management is necessary from April to June in Pakistan, when the temperature rises beyond 40 °C. For heat management, the hybridisation of heat-resilient and high-yielding genotypes to develop heat-tolerant high-yielding hybrids appears to be a rational approach. These genetically improved hybrids inherit such characteristics that assist in maintaining vigorous growth, fruit quality, and stable yield without significant yield losses even under heat-stressed conditions. Hence, the thermotolerant chilli hybrids developed through hybridisation help to satisfy the escalating demand for chilli and guarantee the financial stability of farmers. Full article

In the Mediterranean region, the persimmon cultivar ‘Rojo Brillante’ may experience up to four waves of fruit drop. The first is a physiological event during fruit set that is common in woody species, while the subsequent waves are induced by rising temperatures and prolonged summer water stress. These summer drops represent the main limiting factor, leading to yield losses of up to 90%. Organ abscission is a complex process regulated by genetic, hormonal, nutritional, and environmental factors. We hypothesise that calcium (Ca) plays a protective role in the abscission zone (AZ) by inhibiting cell wall-degrading enzymes such as polygalacturonase (PG) and pectin methylesterases (PMEs). Calcium applications every 15 days from anthesis onwards significantly reduced fruit drop. Treatments preserved polar auxin transport—through DkPIN1 expression—and inhibited stage C of the abscission process, decreasing the relative expression of the DkIDL6 gene in the AZ. Moreover, PME and PG activities were significantly lower in Ca-treated fruits, confirming the stabilising effect of calcium on AZ integrity. In summary, pre-anthesis calcium sprays reduced premature fruit drop by about 30% under heat–drought stress by down-regulating key abscission genes (DkIDL6, DkPG20, DkPME41) and preserving cell wall integrity and fruit firmness, supporting the use of Ca treatments as a climate-smart approach to stabilise persimmon yield. Full article

Background: Seed shattering enhances ecological adaptation in perennial grasses but severely limits harvestable seed yield in forage crops. Psathyrostachys juncea is an important perennial forage species in arid and cold regions, yet the genetic basis of its seed shattering remains largely unknown. Here we asked which genomic regions and biological pathways underlie natural variation in seed shattering in P. juncea, and whether cellulose synthase (CESA)-mediated cell-wall formation contributes to abscission-zone strength. Results: We evaluated seed shattering in a diverse association panel of P. juncea across four environment–-year combinations and performed a genome-wide association study (GWAS) using genotyping-by-sequencing single-nucleotide polymorphism (SNP) markers. The analysis identified 36 significant SNP loci distributed on multiple chromosomes, consistent with a highly polygenic and environment-responsive architecture. Candidate-gene annotation highlighted pathways related to cell-wall biosynthesis, hormone signaling and sugar transport. Notably, in the BT23SHT environment a cluster of association signals on chromosome 3D co-localized with several genes annotated as cellulose synthase (CESA). Abscission-zone transcriptome profiling and qRT-PCR at 7, 14, 21 and 28 days after heading revealed that CESA genes, including TraesCS3D02G010100.1 located near the lead SNP Chr3D_3539055, showed higher early expression in low-shattering lines and a decline toward baseline in high-shattering lines. Comparative analyses placed P. juncea CESA proteins within a broadly conserved but lineage-divergent framework among grasses. Conclusion: Together, these results define the genetic landscape of seed shattering in P. juncea and nominate cellulose-biosynthetic genes on chromosome 3D as promising targets for marker-assisted selection of low-shattering, high-seed-yield forage cultivars. Full article

Boll abscission in cotton (Gossypium spp.) is a key factor that limits yield; however, the molecular mechanisms underlying this process remain poorly understood. In this study, boll abscission characteristics were uncovered in four cotton varieties that exhibited extreme differences in boll abscission rates via tissue sectioning. Transcriptome analysis was performed on the four cotton varieties. Using weighted gene co-expression network analysis (WGCNA) of the transcriptome data, we identified a stearoyl-(acyl-carrier-protein) desaturase (SACPD) as a potential key regulator of boll abscission. We also performed evolutionary analyses on the SACPD gene family across five cotton species and identified 63 members that were classified into four evolutionary clades, with duplication-polyploidization events being a major driver of gene expansion. Tissue-specific expression profiling revealed that Gossypium hirsutum GhSACPD19 is highly expressed in the abscission zone. Our findings suggest a role of GhSACPD19 in regulating boll abscission, likely through metabolism of jasmonate, a well-known positive regulator of abscission. Our work offers new insights into the regulation of organ abscission at cellular and molecular levels and presents a valuable resource for cotton yield improvement. Full article

To calyx persistence in Korla fragrant pear (Pyrus sinkiangensis) significantly impacts fruit marketability, with persistent calyx causing up to 40% reduction in premium-grade fruit yield. Investigating the hormonal mechanisms underlying calyx abscission and persistent in Korla Fragrant Pear, we performed comprehensive phytohormone profiling using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS; EXIONLC system coupled with SCIEX 6500 QTRAP+). Flowers from first-position (persistent-calyx) and fourth-position (deciduous-calyx) inflorescences were collected at six developmental stages (0–10 days after flowering). Fourteen endogenous hormones—ACC, ME-IAA, IPA, TZR, SA, IAA, ICA, IP, tZ, DHJA, ABA, JA-ile, cZ, and JA—were identified in the calyx during the flowering stage. The calyx abscission rate was significantly higher in the fourth position (79%) compared to the first position (32%). ACC and ABA are closely linked to abscission, with increased ACC at 0 DAF signaling early abscission and ABA accumulation accelerating late abscission at 8 DAF. Auxin exhibited spatiotemporal specificity, peaking in first-order flowers at 4–6 DAF, potentially inhibiting abscission by maintaining cell activity. Cytokinins generally decreased, while jasmonates significantly increased during the fourth-position anthesis stage 8–10 DAF, suggesting a role in stress-related senescence. By systematic analysis of the flowers at the first order (persistent calyx) and the fourth order (deciduous calyx) from 0 to 10 days after anthesis, we found three key stages of hormone regulation: early prediction stage (0–2 DAF), ACC accumulation at the fourth order was significantly higher than that at the first order at 0 days after anthesis, ACC accumulation at the early stage predicted abscission; During the middle maintenance stage (4–6 DAF), the accumulation of cytokinin decreased significantly, while the accumulation of IAA increased significantly in the first position (persistent calyx); Execution Phase (8–10 DAF), ABA reached its peak at 8 DAF, coinciding with the final separation time. JA played an important role in the late stage. Gibberellin was undetected, implying a weak association with calyx abscission. Venn diagram identified N6-(delta 2-Isopentenyl)-adenine (IP) in first-position flowers, which may influence calyx persistence or abscission. These findings elucidate hormone interactions in calyx abscission, offering a theoretical basis for optimizing exogenous hormone application to enhance fruit quality. Full article

Actinidia arguta (A. arguta) is valued for its nutritional richness, but physiological fruit abscission severely limits production efficiency in elite cultivars. To unravel the molecular basis of this process, we compared two cultivars: abscission-prone ‘KL’ and abscission-resistant ‘JL’. During fruit development, ‘KL’ exhibited an earlier decline in auxin (AUX) levels within the fruit abscission zone (FAZ), coupled with persistently higher ethylene (ETH) concentrations and polygalacturonase (PG) activity compared to ‘JL’. Comparative transcriptomics identified abscission-related genes enriched in plant hormone signaling (AUX, ETH, ABA, JA, BR), starch/sucrose metabolism, and photosynthesis pathways. AUX signaling diverged predominantly during early development, while ETH, BR, and JA pathways varied across multiple stages. Exogenous applications of plant growth regulators (ethephon, 2,4-D, methyl jasmonate, and 2,4-epibrassinolide) and transient overexpression of key genes (AaETR1, AaERF035, AaPME68, AaPP2C27, AaMYC1, and AaPMEI10) validated their roles in modulating hormone crosstalk and cell wall remodeling. Overexpression of AaERF035 and AaPME68 likely accelerated abscission by enhancing ETH biosynthesis and pectin degradation, while AaPMEI10 and AaMYC1 potentially delayed abscission via suppression of cell wall-modifying enzymes. This study elucidates the hormonal and transcriptional networks governing fruit abscission in A. arguta, providing insights for targeted breeding and cultivation strategies to mitigate yield loss. Full article

Severe physiological fruit abscission significantly limits yield potential in macadamia. Polygalacturonase (PG), a key hydrolytic enzyme in pectin degradation, plays a critical role in fruit abscission. However, in the macadamia genome, the PG gene family and the members involved in fruit abscission remain poorly understood. In this study, 56 PG gene family members, which were unevenly distributed across 13 of the 14 chromosomes, were identified in the macadamia genome. Phylogenetic analysis clustered these genes into seven clades, with most members found in clades D and E. The MiPGs contained 3–11 exons and 2–10 introns, and except for those in clades E and G, most contained conserved domains I–IV and were predicted to be localized exclusively to the cell membrane. MiPG promoter analysis revealed numerous light-, phytohormone-, and stress-responsive cis-elements. Expression profiling during fruit development showed that twelve MiPGs were either undetectable or expressed at low levels in the fruit abscission zone, whereas eight were highly expressed. MiPG9, MiPG37, and MiPG53 were significantly upregulated during abscission induced by a combination of girdling with defoliation and ethephon treatments. Moreover, transient MiPG37 overexpression in lily petals promoted premature abscission, suggesting that this gene plays a pivotal role in macadamia fruit abscission. These findings advance the functional characterization of macadamia PG genes and highlight a subset of candidate genes for further genetic manipulation to improve fruit retention. Full article

Background: Polygalacturonase (PG) genes regulate plant organ abscission by degrading pectin in the cell wall. However, their association with pedicel abscission susceptibility in pepper remains poorly understood. Methods: 47 CaPG genes were identified were identified in the ‘Zunla1’ genome and characterized by structural, evolutionary, and comparative genomic analyses. Their expression profiles across various tissues and fruit development stages were examined using transcriptome data. Ethephon treatment and qRT-PCR were employed to assess gene responses during ethylene-induced pedicel abscission. Results: The 47 CaPG genes were distributed across 12 chromosomes, with CaPG1 to CaPG5 unanchored. Most proteins were hydrophilic, nuclear-localized, and had promoters enriched in light-responsive elements. Collinearity analysis revealed limited segmental duplication, and Ka/Ks values indicated strong purifying selection. Phylogenetic and collinearity analyses showed that CaPG genes are more closely related to those in tomato than in Arabidopsis or maize. Expression profiling revealed tissue- and stage-specific patterns, with 21 CaPG genes associated with pedicel abscission susceptibility. Ethephon treatment enhanced abscission and upregulated several CaPG genes. Conclusions: This study offers insights into the CaPG gene family’s structure, evolution, and function. Specific CaPG genes likely contribute to ethylene-mediated pedicel abscission, providing potential targets for improving fruit-retention traits in pepper. Full article

Apples are widely cultivated primarily for fresh consumption. During mechanized harvesting, the extraction of fruit stalks can significantly impact the storage duration of fresh apples. The tensile force applied to the abscission layers is a critical factor in retaining the stalks; yet, few researchers have focused on preventing stalk pull-out during picking. In this research, we studied the phenomenon of missing stalks during mechanical picking by analyzing the tensile force exerted on the abscission layer during picking and optimizing the attitude of the end effector to achieve the highest stalk retention rate. Firstly, the tangential and normal energy release rates of the abscission layer were used as key parameters to model the cohesive zone of the abscission layer, a finite element model of the fruit–stalk–branch system was developed, based on which the actual fruit picking process using direct-pulling and twisting was simulated. Subsequently, the data obtained from the simulation were analyzed using response surface analysis, and the maximum tensile force at the time of fracture of the delamination and the time of its fracture were used as optimization parameters to find the optimal solution of the angle, direct-pulling speed, and twisting speed d to achieve the highest stalk retention rate. Finally, through field experiments, it was demonstrated that the optimal picking conditions could effectively improve the picking success rate and stalk retention rate. The results show that, when the end effector picks close to the fruit at about 58°, the stalk retention rate can reach 94.0%. Full article

Seed shattering (SS) functions are a survival mechanism in plants, enabling them to withstand adverse environmental conditions and ensure reproduction. However, this trait limits seed yield. Psathyrostachys juncea, a perennial forage grass with many favorable traits, is constrained by SS, limiting its broader application. To investigate the mechanisms underlying SS, second-generation Illumina sequencing and third-generation PacBio sequencing were conducted on abscission zone tissues of P. juncea at 7, 14, 21, and 28 days after heading. GO enrichment analysis identified several significant biological processes, including the “cell wall macromolecule catabolic process”, “cell wall polysaccharide catabolic process”, “hemicellulose catabolic process”, and “xylan catabolic process”, all involved in cell wall degradation. KEGG enrichment analysis showed that differentially expressed genes were predominantly enriched in pathways related to “starch and sucrose metabolism”, “fructose and mannose metabolism”, “phenylpropanoid biosynthesis”, “pentose and glucuronate interconversions”, and “galactose metabolism”, each linked to both the synthesis and degradation of the cell wall. Further analysis of the “starch and sucrose metabolism” pathway revealed genes encoding fructokinase, hexokinase, β-glucosidase, sucrose phosphate synthase, sucrose synthase, and endoglucanase, all of which affected cellulose content. Reduced cellulose content can alter cell wall structure, leading to SS. These findings provide new insights into the regulation of SS in P. juncea and offer valuable references for other species within the Poaceae family. Full article

To solve the problem of the lack of physical properties of pedicels and the changing pattern for designing the end-effector of tomato harvesting robot and different harvesting modes, research was conducted on the physical properties of tomato pedicels and their change patterns. Using a Universal TA texture analyzer, tensile, three-point bending, and shearing tests were performed on tomato pedicels in the early firm-ripening stage. The tomato variety used was Syngenta Spectrum, cultivated seasonally with two crops per year. Spring crop tomatoes were used in this study. The experimental results provide a theoretical basis for designing tomato harvesting robots across three harvesting modes. Tensile tests measured the pull-off force and tensile strength of the abscission zone with varying diameters. These results are crucial for designing robots using a tensile harvesting mode. The location of the tomato pedicel significantly affects the shearing force. A one-way test was conducted on the shearing part. The results showed that the shearing force and energy required for the proximal pedicel are significantly greater than for the distal pedicel. To reduce the shearing force and energy needed by the end-effector’s shearing mechanism on distal pedicels, a response surface test was conducted. Three factors were examined: shearing speed, angle, and distal pedicel diameter. Design–Expert software optimized these factors to minimize shearing energy and force, leading to the best shearing parameters for different distal pedicel diameters. From the three-point bending tests, the average maximum bending breaking force, bending modulus, and bending strength of the tomato abscission zone were determined. These findings offer a theoretical basis for designing tomato harvesting robots with a bending-type harvesting mode. Full article

The abscission of fruits has a significant impact on yield, which in turn has a corresponding effect on economic benefits. In order to better understand the molecular mechanism of early coconut fruit abscission, the morphological and structural characteristics, cell wall hydrolysis and oxidase activities, phytohormones, and transcriptomes were analyzed in the abscission zone (AZ) from early-abscised coconut fruits (AFs) and non-abscised coconut fruits (CFs). These results indicated that the weight and water content of AFs are significantly lower than those of CFs, and the color of AFs is a grayish dark red, with an abnormal AZ structure. Cellulase (CEL), polygalacturonase (PG), pectinesterase (PE), and peroxidase (POD) activities were significantly lower than those of CFs. The levels of auxin (IAA), gibberellin (GA), cytokinins (CKs), and brassinosteroid (BR) in AFs were significantly lower than those in CFs. However, the content of abscisic acid (ABA), ethylene (ETH), jasmonic acid (JA), and salicylic acid (SA) in AFs was significantly higher than in CFs. The transcriptome analysis results showed that 3601 DEGs were functionally annotated, with 1813 DEGs upregulated and 1788 DEGs downregulated. Among these DEGs, many genes were enriched in pathways such as plant hormone signal transduction, carbon metabolism, peroxisome, pentose and gluconate interconversion, MAPK signaling pathway—plant, and starch and sucrose metabolism. Regarding cell wall remodeling-related genes (PG, CEL, PE, POD, xyloglucan endoglucosidase/hydrogenase (XTH), expansin (EXP), endoglucanase, chitinase, and beta-galactosidase) and phytohormone-related genes (IAA, GA, CKs, BR, ABA, JA, SA, and ETH) were significantly differentially expressed in the AZ of AFs. Additionally, BHLH, ERF/AP2, WRKY, bZIP, and NAC transcription factors (TFs) were significantly differently expressed, reflecting their crucial role in regulating the abscission process. This study’s results revealed the molecular mechanism of early fruit abscission in coconuts. This provided a new reference point for further research on coconut organ development and abscission. Full article

Programmed cell death (PCD) is common in plant growth and development, such as xylem development, organ senescence, and abscission. Calyx abscission in Korla fragrant pear contributes to fruit quality, while it was not clear whether PCD occurred during calyx abscission and which signals regulated the process. Therefore, it is imperative to clarify the process of PCD in the process of calyx abscission in Korla fragrant pear under natural conditions to enrich the mechanism of calyx abscission. The results showed that the total time of calyx abscission of Korla fragrant pear began from 6 days after pollination (DAP) to 13 DAP, and the peak of calyx abscission occurred 10 DAP. During the whole process of calyx abscission, PCD started 6 DAP. At 9 DAP, the degree of PCD deepened. At 12 DAP, the cells in the abscission zone showed asymmetry on both sides, the organelles in the distal cells of the abscission zone degraded into apoptotic fragments, and the protective layer of the normal development of cells located at the proximal end of the abscission zone region ended the PCD process. ETH concentrations in the abscission zone of the decalyx fruit were significantly higher than those of the persistent calyx fruits in each period during calyx abscission, and high levels of ethylene and hydrogen peroxide and low contents of the GA₃, ZT, and hydroxyl radicals promoted calyx abscission before the formation of the abscission zone. At 3 DAP, the ethylene concentration (43.97 ppm) and H₂O₂ content (8.49 μmol/g) of decalyx fruit in the abscission zone were significantly higher than those of persistent calyx fruit by 67.69% and 27.86%, respectively; however, the GA₃, ZT, and hydroxyl radicals showed the opposite. Overall, PCD in the abscission zone of decalyx fruits did occur during the calyx abscission of Korla fragrant pear, and ethylene and H₂O₂ might play major roles in initiating the PCD process during Korla fragrant pear calyx abscission. Full article

MADS-box transcription factors act as the crucial regulators in plant organ differentiation. Crop yields are highly influenced by the flower number and fruit growth. However, flower identification is a very complex biological process, which involves many cascade regulations. The molecular mechanisms underlying the genetic regulation of flower identification in cultivated plants, such as tomato, are intricate and require further exploration. In this study, we investigated the vital function of a SEPALLATA (SEP) MADS-box gene, SlMBP21, in tomato sympodial inflorescence meristem (SIM) development for the conversion from SIMs to floral meristems (FMs). SlMBP21 transcripts were primarily accumulated in young inflorescence meristem, flowers, sepals, and abscission zones. The Ailsa Craig (AC⁺⁺) tomato plants with suppressed SlMBP21 mRNA levels using RNAi exhibited a large increase in flower number and fruit yields in addition to enlarged sepals and inhibited abscission zone development. Scanning electron microscopy (SEM) revealed that the maturation of inflorescence meristems (IMs) was repressed in SlMBP21-RNAi lines. RNA-seq and qRT-PCR analyses showed that numerous genes related to the flower development, plant hormone signal transduction, cell cycle, and cell proliferation et al. were dramatically changed in SlMBP21-RNAi lines. Yeast two-hybrid assay exhibited that SlMBP21 can respectively interact with SlCMB1, SFT, JOINTLESS, and MC, which play key roles in inflorescence meristems or FM development. In summary, our data demonstrate that SlMBP21 functions as a key regulator in SIM development and the conversion from SIMs to FMs, through interacting with other regulatory proteins to control the expression of related genes. Full article

Cassava whitefly, Bemisia tabaci, directly damages cassava leaves by feeding on phloem, causing chlorosis and abscission, leading to a yield loss of up to 50%. The pest also causes indirect damage through sooty mold formation. Most Ugandan cassava varieties resist cassava mosaic disease (CMD) and tolerate cassava brown streak disease (CBSD), but little is known about their response to whitefly infestation. The main objective of this study was to identify cassava genotypes with putative resistance to whitefly in Uganda. This was conducted on 24 improved cassava varieties in three agro-ecological zones during the second rains of 2016. Monthly data were taken for adult and nymph counts, whitefly and sooty mold damage, and CMD and CBSD severities from 2 to 9 months after planting (MAPs). The results show that the whitefly population is highly significantly (p < 0.000) amongst varieties across the three agro-ecological zones. Mkumba consistently supported the low adult numbers and nymphs. The findings demonstrate the potential of the improved cassava varieties as sources of whitefly resistance for sustainable management. Full article