Genotype-environment interaction and stability of quantitative traits in garden pea (Pisum sativum L.)

Peas are among the most common and widely cultivated annual legumes. Productivity potential of most modern pea varieties is high but limited by their low homeostasis and sensitivity to abiotic stress, i.e., the varieties tend to reduce adaptability. Therefore, one of the main challenge in pea breeding is to create an optimal genotype capable of realizing the biological potential and adequately responding to changes in growing conditions. Therefore, environmental testing remains relevant. This paper is the first assessment of the breeding samples of the pea working collection (Maritsa Vegetable Crop Research Institute, Plovdiv, Bulgaria) with respect to their ability to form economically significant quantitative traits. Three sources of variability (genotype, environment, and genotype-environment interaction) were found to be statistically significant for the total number of pods, the number of productive nodes with two pods per plant, pod weight, and grain weight. In 2018-2020, the phenotypic stability of ten pea ( Pisum sativum L.) genotypes was assessed, including four perspective lines (22/16-af, 22/16-n, B4/34-n, and 1/17-n) and six varieties (Kazino-af, Plovdiv-n, Marsy-n, Echo-af, Shugar dwarf-n, and Vecherniza-n). The main examined quantitative traits were the number of pods per plant, the number of fertile nodes with one pod per plant, the number of fertile nodes with two pods per plant, pod length, pod width, pod weight per plant, and grain weight per plant. The effect of all factors of variation on the number of pods per plant, number of fertile nodes with two pods per plant, weight of pods per plant, and grain weight per plant is statistically significant. The strongest was the effect of the environmental factor on the manifestation of the number of pods per plant (52.20 %) and the number of fertile nodes with two pods per plant (59.00 %). The genotype factor has the largest contribution to the total variability of the weight of pods per plant (64.10 %) and grain weight per plant (67.40 %). Therefore, an effective breeding should be focusing on these traits regardless of the environmental conditions. The number of pods per plant and pod length requires more trials to give a more accurate estimate due to the superiority of the genotype½environment interaction variance over the genotype variance. Our findings indicate that the varieties Marsy-n and Echo-af are the most valuable genotypes for the number of pods per plant. The varieties Kazino-af, Plovdiv-n and the line 1/17-ob are highly variable and form fewer pods. For pod weight, all genotypes showed good responsiveness, especially Plovdiv-n (bi = 2.68), 1/17-ob (bi = 2.63), and Marsy-n (bi = 2.18), all three having a higher pod weight, and the Echo-af variety shows better stability (bi = 1.39; Si2 = 1.91). For the grain weight per plant, the Marsy-n (bi = 3.08), 1/17-ob (bi = 2.62), and Plovdiv-n (bi = 4.02) are highly productive but also the most variable.