Ideotype breeding in kabuli chickpea: extra large-seeded, double-podded and resistant to ascochyta blight [Ascochyta rabiei Pass. (Labr.)] via marker assisted selection

The concept of 'crop ideotype' is coined as a desirable plant model expected to better perform for grain yield, oils and other useful characteristics when developed a cultivar and it consists of two major approaches such as (i) 'defect elimination' that is integration of disease resistance to a susceptible genotype from resistant genotype and (ii) 'selection for yield' improving yield after crosses between desirable parents. Here we determined an ideotype in chickpea (Cicer arietinum L.) having high-yielding, extra large-seeded, multi-podded and resistant to ascochyta blight [Ascochyta rabiei Pass. (Labr.)], caused considerable yield losses. For these purposes, Sierra having single-podded per node, unifoliolate leaf, the large-seeded (47 g per 100-seed weight) and resistant to ascochyta blight was crossed with CA 2969 having twin-podded per node, imparipinnate leaf, small-seeded (27 g per 100-seed weight) and resistant to ascochyta blight, and then advanced to F3 generation with single plant progeny. In F3 popuation, multi-flowered or podded progeny were noticed as a result of epistasis of double-podded gene in suitable conditions. A total of 626 F3 generation plants was evaluated for agro-morphological traits dividing into six classes namely; (i) imparipinnate leaf and single-podded progeny, (ii) imparipinnate and double-podded progeny, (iii) imparipinnate and multi-podded progeny, (iv) unifoliolate leaf and single-podded progeny, (v) unifoliolate leaf and double-podded progeny, (vi) unifoliolate leaf and multi-podded progeny. A total of 152 F4 generation lines having 100-seed weight ≥45 g and double- or multi-podded traits were studied for resistance to ascochyta blight using molecular markers including SCY17590 and CaETR-1. Inheritance pattern of extra large-seeded trait was found to be polygenic controlled partial dominant alleles according to distribution of F3 population. Transgressive segregations, progeny having higher or lower values in segregations than their own parents, were determined for all studied traits indicating that seed size in chickpea could be improved crossing suitable parents since large seed size in chickpea are preferred by farmers due to having high price. Selection for large seed size could be based on biological and seed yields per plant since the seed yield had the highest direct effect on 100-seed weight in path analysis. To select high yielding progeny, one of the following traits such as biological yield, number of pods and seeds per plant and canopy width could be assessed because these traits along with seed yield were found in the same factor. Imparipinnate leaf and single podded progeny had the largest seed size and followed by imparipinnate leaf and double-podded progeny. Imparipinnate leaf and multi-podded progeny had not only highest yield but also number of pods and seeds per plant. SCY17590 and CaETR-1 markes located on LG4 related to QTLAR2 and QTLAR1 were found in 9 lines among 152 F4 lines. Six lines carrying both of two resistance markers attained extra-large seeds as high as 50-60 g per 100-seed weight. Some progeny in F3 with 100-seed weight of ≥ 50 g, double- or multi-podded and resistant to ascochyta blight had extra larger seed size than that of the best parent (47 g). These superior lines attained high yield were subjected to heat stress during flowering (more than 31 oC) and pod setting (more than 39 oC) stages. As a suggestion, high yielding, extra large-seeded, double- and multi-podded traits and resistance to ascochyta blight were integrated in ideotype chickpea via intraspecific crossing of suitable 'kabuli' chickpeas and marker assisted selection.