3.1.1. Assessments of Disease Tolerances
The observation of diseases was carried out in the middle of the cycle for all crops, specifically on the 92nd, 111th, 118th, and 156th days after sowing at the Meknes, Berrechid, Lahri, and El Kebab sites in 2017–2018, respectively. The three most important diseases attacking oats in Morocco are crown rust (Puccinia coronata f. sp. avenae), BYDV, and powdery mildew (Blumeria graminis
f. sp. avenae
). Crown rust developed by the middle of the cycle at the Berrechid site but was not observed at the other locations until very late in the growth cycle. We therefore assessed crown rust severity only at Berrechid via visual scoring using the modified Cobb scale [17
]. Following this we performed a two-factor ANOVA, with the summary table showing only significant differences presented in Table 3
. Powdery mildew was only observed at Berrechid and was therefore not scored. As for BYDV, it was observed at all sites, though infestations within a given site did not appear to be uniform.
In the 2018–2019 experiments, observations of diseases were made on the 152nd day after sowing at the Meknes and El Kebab sites and on the 154th and 161st days for the Bouchane and Tiflet sites, respectively. The assessment focused on two diseases: crown rust and BYDV.
For the assessment of crown rust tolerance, the lines and blocks terms showed no significant differences among the 41 lines (Table 3
) in 2017–2018. On the other hand, the lines*blocks interaction showed a highly significant difference, indicating that there was likely a non-uniform infestation across the plots—something that should not be surprising given that oat is a rare crop in these growing areas of central Morocco. During a 209th day post-sowing visit at Lahri, controls T1 and T2, as well as lines A01, and A02 displayed crown rust symptoms. At Meknes and El Kebab, we noticed some symptoms of crown rust on several lines at harvest time.
As expected, the appearance of crown rust depended heavily on the climatic conditions of the test site. Whereas crown rust only partly appeared in 2017–2018 at Berrechid, the disease only appeared at Bouchane and Tiflet in 2018–2019. According to the ANOVA results from the Bouchane site (Table 3
), significant differences were found among lines, while the non-significant differences for crown rust infestation detected by the line*block ANOVA interaction indicated there was uniform infestation throughout the plots. At Tiflet, the infestation was assessed on only the first block; however, from the ANOVA it is clear that there were significant differences among the lines and there was likely an exogenous source of the inoculum. Because of its relative proximity to the Atlantic Ocean, the Tiflet site experiences chronic crown rust infestations [18
]. The narrow gradient of the distribution can be explained by the dissemination of the pathogenic agent into the experimental plot, which was cleared of riparian vegetation and cultivated for the first time for this particular study.
Since humid conditions favor the development of the Puccinia coronata fungus, drought conditions during winter 2018–2019 at Meknes and El Kebab likely explained the absence of crown rust infestations at these study sites. This can also possibly be explained by local applications of fungicides on nearby cereal fields, especially at Meknes where the plots were located on a large commercial farm within the Domaine Royaume. This hypothesis is supported by the results from the prior year’s study when little crown rust appeared, in spite of more abundant precipitation.
The means comparison for degree of BYDV infestation at El Kebab in 2018–2019 enabled us to distinguish three homogeneous groups, with lines A01 and A03 being the most susceptible (data not shown). The average infestation at El Kebab was the lowest in both growing seasons.
For BYDV, the disease was present at all sites, with by far the highest incidence being at Tiflet. This observation is not surprising, given the relative abundance and diversity of aphid vectors of this disease [18
], combined with A. magna
’s well-known susceptibility to BYDV [1
]. However, the lowest incidence of BYDV in both growing seasons was at El Kebab, suggesting that the relatively lower temperatures, higher elevation, and distance from oceanic humidity at this site were unfavorable for the aphid vectors of this disease. Future A. magna
germplasm enhancement will have to put more effort into BYDV tolerance, but it will likely rely on variation induction because of the lack of resistance genes in the wild species [1
3.1.2. Analyses of Agro-Morphological Traits
Significant agro-morphological effects at the eight environments are highlighted via descriptive statistics provided in Table 4
and two-way ANOVA Table 5
. Variables studied included the measured parameters, the calculated parameters, the thousand-seed weight (TSW) and the harvest index (HI).
Agro-morphological evaluation of the A. magna lines was performed for the following characters: plant height (PH), root length (RL), number of fertile tillers per plant (NFT), root weight (RW), dry matter weight per plant (DYP), grain yield per plant (GYP), number of grains per plant (NGP), thousand-seed weight (TSW), grain yield per hectare (GYH), dry matter yield per hectare (DYH), and harvest index (HI).
Descriptive statistics of the agro-morphological traits are presented in Table 4
. Based on the internal analyses at each site, PH and TSW were the most stable variables as they present low coefficients of variation. The highest CVs were observed for DYP, NGP, and GYP. In the first growing season of 2017–2018, plant development was much greater than the second season. The PH values measured between 110.24 and 176.86 cm in the first year and 45.15 and 79.14 cm the second year, and the average grain yield between 36.79 and 14.78 q/ha in the two years, respectively.
In the 2018–2019 season, Bouchane had the shortest plant size (45.15 cm) in comparison to the other sites, and the average RL of the lines was more proportionate to the PL than at the other sites. This demonstrated the capacity of A. magna
ssp. domestica roots to penetrate deeply into sandy-loamy soils under harsh growing conditions (Figure 2
The accessions in Tiflet presented the lowest values for the agro-morphological parameters (Table 4
). We suspect this was mainly due to the poorer growing conditions of the trial of the new managed loamy-sandy soil of an organic farm. The plants were also exposed to severe competition from weeds, pests, and diseases, which strongly impacted the growth and development of the lines (Figure 2
The two-factor ANOVA revealed significant differences among accessions. At Berrechid, the genotype effect was highly significant for the variables PH and GYH and moderately significant for RW and HI (Table 5
). The line*block interaction was moderate for the PH parameter and minor for RW, NGP, GYP, and GYH.
The Bouchane site ANOVA analysis showed highly significant genotypic effects for six of ten variables (NFT, RW, GYP, GYH, DYH, and HI), a moderate effect of PH, and a minor effect of RL (Table 5
). The block factor had significant effects on all the variables except RL. The line*block interaction effect was highly significant for PH, moderate for RW and GYP, and significant at the 5% level for the rest of the parameters.
At the Lahri site, the ANOVA (Table 5
) showed no significant effects linked to the line factor for only RW. The block factor showed highly to moderately significant effects for all the traits. The line*block interaction showed highly significant effects for all parameters and slightly significant (at the 5% level) for RW and DYH.
At El Kebab the effect of the lines factor was highly significant for all the parameters in the 2018–2019 growing season but not significant for DYP, NGP, and GYP for the 2017–2018 season (Table 5
). There was no significant block effect for PH, RL, NGP, and GYP for the first year trials. Finally, the line*block interaction was highly significant for PH in the first season and for NGP, DYH, and HI in the second season.
At Meknes, the 2018–2019 trial revealed significant differences among lines for GYP and GYH, and highly significant differences for the rest of the traits (Table 5
). The block and line*block interaction factor effects were highly significant for PH, DYP, NGP, GYP, GYH, DYH, and HI, but the block factor was not significant for the NFT and the line*block interaction for RL.
At the Tiflet site, the test detected highly significant differences among the lines for all the variables except NFT (Table 5
). The block factor had only a slightly significant effect on DYP, DYH, and HI and no effect on all other variables. The line*block interaction was highly significant for PH, RL, NFT, DYP, DYH, and HI but not for RW, NGP, GYP, and GYH.
3.1.3. Analyses of Productivity Traits
To assess the productivity of the A. magna
oat lines, we analyzed the GYH, DYH, and HI of the eight experimental trials. Descriptive statistics for these productivity traits appear in Table 6
and the rankings of the 41 lines in Table 7
In comparing the two seasons, genotype variability as measured by intra-site CV’s was much higher in the second year (2018–2019), 83.66% against 48.19% for GYH 70.21% against 40.47% for DYH, and 45.17% against 27.62% for HI (Table 6
). For GYH, the greatest variability was found at Meknes (96.55%), which explains the high variability of HI in the same trial (0.66%). DYH was most variable at Bouchane (CV = 88.71%). Berrechid had the least variability for both productivity traits; GYH (40.69%), and DYH (33.98%). The highest HI variability (66.32%) was that of Meknes in the second trial season, 2018–2019.
In general, the productivity parameters for the 2017–2018 trials were higher than the 2018–2019 trials, with respective means of 43.48 and 14.68 q/ha for GYH and 161.92 and 39.85 q/ha for DYH (Table 6
). The HI values were lower in the first season with an average of 22.52% compared to the second season (28.76%). The overall mean grain yield was 29.08 q/ha, with the highest value at Berrechid (63.56 q/ha) followed by Meknes’s first season (56.56 q/ha), and the lowest at Tifelt (5.10 q/ha). For DYH, the average overall yield was 100.89 q/ha with a maximum at Berrechid (255.08 q/ha) and a minimum at Tifelt (18.08 q/ha). The best HI was that of Bouchane (39.24%) and the lowest at Lahri (17.30%).
In 2017–2018, the Meknes site had the second-highest HI, with an average of 22.57%. The two lowest sites for HI in 2017–2018 were Berrechid and Lahri, 20.12 and 17.30%, respectively. In the second-year trial, Bouchane, followed by El Kebab, presented the highest HI (39.24 and 33.40%, respectively), compared to Meknes and Tifelt at 18.72 and 23.70%, respectively (Table 6
The two-way ANOVA detected highly significant differences for GYH among the 41 lines at all sites except Meknes in 2017–2018 (Table 5
). For DYH and HI, the differences were highly significant at six and eight sites, respectively, and were slightly significant (at the 5% level) at the Berrechid and Meknes first-year trials for DYH.
The overall ranking of lines for GYH, DYH, and HI are presented in Table 7
. GYH ranged from a low of 16.96 q/ha for A22 to a high of 30.28 q/ha for A23; the A40 control line yield across the eight sites was 20.82 q/ha. DYH ranged from 64.44 to 102.83 q/ha with the respective accessions A22 and A02. For HI, A15 had the best value of 32.19% and A25 the lowest of 23.21%; the HI of the control, A40 was 24.36%.
In the first year of trials, A35, A27, and A14 ranked first in Berrechid for GYH, reaching yields of 108.73, 88.85, and 85.45 q/ha, respectively (Table 8
). The control (A40) yielded 73.18 q/ha while line A22 produced the lowest GYH (38.83 q/ha) at the site. Meknes the second-best site; A37 and A16 ranked first with GYH at 83.90 and 75.02 q/ha, respectively; line A40 produced 61.82 q/ha; and the last lines, A36 and A13, yielded 39.22 and 34.87 q/ha, respectively.
In the first-year trials at El Kebab, lines A04, A15, and A25 had the lowest GYH 15.09, 15.23, and 15.41 q/ha, respectively, the control yield was 20.08 q/ha, and A36 and A38 recorded the highest GYH, 44.80 and 38.34 q/ha, respectively. The most productive line in Lahri, A16, produced 48.57 q/ha and the lowest yielding accession, A42 produced only 9 q/ha.
In the second-year trial in Bouchane, lines A10, A12, A22, and A42 ranked last for GYH, 9.08, 8.44, 7.96, and 7.94 q/ha respectively (Table 8
). A40, the control, produced 9.14 q/ha, and line A20 presented the highest GYH, 28.86 q/ha. At El Kebab, lines A12, A15, and A22 had the lowest GYH, 6.39, 5.29, and 2.34q/ha, respectively, and A02 and A41 recorded the highest yields, respectively 44.80 and 38.34 q/ha as compared to the control yield of 14.33 q/ha at the same site.
In the second-year trial, the early inauspicious conditions for optimum plant growth (December–February) were suitable for genotype discrimination at Bouchane and Tiflet. At Bouchane, lines A20 and A33 were the highest yielding genotypes, 28.86 and 26.29 q/ha, respectively (Table 8
). The exceptionally dry conditions at the Bouchane site are best conveyed photographically; Figure 2
shows conditions on 3 May, approximately one month before harvest, where the A. magna
plots provided seed when the wheat and barley crops elsewhere on the farm were a complete loss, being plowed under or opened up for livestock grazing. In terms of dry matter yield, line A02 was highest at 43.93 q/ha.
At Tiflet, line A20 recorded the highest GYH, at 20.34 q/ha (Table 8
). The highest DYQ was in lines A33 and A41 with a biomass production of 32.93 and 31.14 q/ha, respectively. As with the agro-morphological traits, the lines at the Tiflet site were likely well below their productivity potential due to the poorly managed organic production conditions.
At El Kebab, GYH and HI were higher compared to the other sites. Line A02 produced an average yield of 44.8 q/ha, followed by A41 with a yield of 38.34 q/ha (Table 8
). Lines A43, A02, and A44 had the highest harvest indices at 40.52%, 39.23%, and 39.22%, respectively. The grain yield results at the El Kebab site were significantly higher in the second experimental campaign (2018–2019) compared to the first (2017–2018) because of the improved soil tillage during cultivation, fertilization, and irrigation along with the warmer temperatures and the absence of prolonged cold period.
The Meknes trial was characterized by relatively high biomass production. The DYH reached 179.3 q/ha for line A02 and 133.46 q/ha for A17. The results at Meknes in 2018–2019 were lower, though consistent with, those of the previous year in the same region.
The ranking of the genotypes changed from one environment to another. The genotypes yield fluctuation across the locations and years is an indication of the significant effects of the G
E interaction and a differential performance of the genotypes across the environments as well as yield instability between the experimental locations [12