Estimation of combining ability and gene effect in rapeseed lines (Brassica napus L.) using line × tester analysis under salinity stress

In order to estimate the general and specific combining ability and type of gene effect, 15 hybrids from the intersection of 5 lines and 3 testers with their parents were examined in two conditions of normal irrigation and salinity stress in the randomized complete block design with 3 replications in Kerman Agricultural Research Station in 2018-2020. The studied traits included plant height, number of days taken to 50% of flowering, number of days to maturity, pod length, number of pod per plant, number of seed per pod, 1000-seed weight and seed yield. The mean squares of general and specific combining ability were significant for most traits showed that the differences between cultivars in terms of general combining ability, and crosses in terms of specific combining ability, respectively. Estimation degree of dominance for plant height, number of days taken to 50% flowering, number of pod per plant and 1000-seed weight under normal irrigation conditions and seed yield under salinity stress were less than one and for other traits in both experimental conditions greater than one, which indicates the existence of incomplete and over-dominant action, respectively. Under normal and stress conditions for pod length, 1000-seed weight and grain yield per plant, SPN193 and Dalgon parents had the highest general combining ability among the experimental materials. Under normal irrigation conditions, hybrid SPN192 × Dalgon and under salinity stress conditions SPN179 × RGS003 with the highest values of specific combining ability were the best hybrids in terms of seed yield and are recommended.