Heterosis and gene action studies for agro-physiological traits in Indian mustard ( Brassica juncea L.)

Indian mustard ( Brassica juncea L) is an important rabi oilseed crop in India and contributes more than 80% of total rapeseed-mustard production in the country. Present study was carried out with 45 F 1 hybrids along with 10 parents in a randomized block design. Observations were recorded on seven morpho-physiological traits. The ANOVA for combining ability revealed the significance of mean squares due to gca and sca for most of the traits. Out of 10 parents, only one parent EC 511664 exhibited significantly positive gca effects for relative water content, chlorophyll content, membrane stability index and significantly negative effect for excised leaf water loss. Parent DRMR 1165-40 showed significantly positive gca effects for 1000-seed weight. Hence these are good general combiners of these traits. Only one F 1 hybrid (BPR 543-2 × Rohini) showed a significantly positive sca effect and heterobeltiosis (51.84%) for seed yield per plant whereas two hybrids (Urvashi × DRMR 1165-40; Urvashi × Rohini) exhibited significantly positive sca effect and average heterosis for thousand seed weight. F 1 Hybrid, Urvashi × Rohini showed significantly negative sca effect and average heterosis for excised leaf water loss and significantly positive sca effect and heterobeltiosis for thousand seed weight. Three crosses (NRCDR 02 × Rohini, NRCHB 101 × DRMR IJ-31, NRCHB 101 × Rohini) exhibited significant heterosis in desired directions for excised leaf water loss, membrane stability index and relative water content. Clustering based on seven traits grouped 10 parental lines into two clusters. The identified promising cross combinations may be advanced for identifying transgressive segregants or can be exploited through heterosis breeding. Good combiner parents DRMR 1165-40 and EC-511664 which showed high heterosis in F 1 identified as promising genotypes for 1000-seed weight and physiological traits respectively, to breed heat tolerant genotypes.