Graphic analysis of trait relations and stability of faba bean genotypes using the biplot method

Faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed. It can be used in diet as a vegetable, green or dried, fresh or canned. It is a very valuable legume crop that contributes to the sustainability of cropping systems by its ability of biological N2 fixation. The aim of the study were to determine the magnitude of G × E interaction and to identify high yielding and stable or specifically adapted genotypes for target environment(s). Furthermore to evaluating cultivars based on multiple traits and studying relationship among traits, The GT biplot was used.

In this research to finding interrelationships between different traits and adoptability faba bean promising lines, 9 faba bean lines as well as check cultivar, Barekat were evaluated using randomized complete block design with three replications in three agricultural research field stations of Gorgan, Zanjan (Tarom) and , Zabol for two cropping seasons (2016-17 and 2017-18). The plant height (PH) and lowest pod height was calculated before harvesting, in each plot were harvested by hand at harvest maturity stage and seed number/pod (SP), pod number/plant (PN) and hundred seed weight (100SW) measured on ten plants selected randomly from all plots. Data were analyzed using SAS software and the means were compared using LSD test at a probability level of 5%. A GGE-Biplot was used to analyse G x E interaction and stability of the genotypes based on the trait grain yield (kg ha-1). In order to determining the interrelationships among traits and identifying suitable traits for indirect selection, the genotype by trait (GT) was done.

.Combined analysis of variance showed significant effects of genotype, environment, genotype × environment intraction, on grain yield. Stability in performance of the 10 genotypes was tested using GGE-Biplot approach across five environments. GGE-Biplot analysis using a genotype × environment interaction (GEI) model explained 95.1% of total interaction effect variance. View of polygon graph revealed two superior mega-environments and the compatible genotypes were determined for each mega-environment; Gorgan and Tarom (Line G9), Zabol (Line G1). Lines G9, G4, G7 and G1 with average seed yield of 3.22, 3.06, 2.88 and 2.87 t/ha, respectively, had higher seed yield and yield stability. Based on GEI and GGE-Biplot analysis, Tarom experimental environments had good differentiation ability. The GT biplot for genotype data explained 61% of total variation of the standardized data. GT biplot analysis showed positive relationship between yield and other traits number of pods per plant, Green pod yield, harvest index and Height of lowest pod, they are identified as important traits for yield improvement. Hence, these traits could be considered as key components during the selection process aiming towards the breeding of faba bean genotypes for high yield.

Finally, genotypes G9, G4 and G7 had the highest yield and the most stable genotypes with wider adaptation to all the test environments and can be recommended as the superior genotypes for being release as new commercial faba bean cultivars.