Genetic Characterization of Self-incompatible Lines and Strategies for Heterosis Breeding in Cauliflower

Abstract

ABSTRACTCauliflower (Brassica oleracea var. botrytis L.) is a thermosensitive crop grown almost all year-round in North Indian plains due to development of genotypes for production under different temperature regimes. Comparatively, varieties of early and mid-maturity group cauliflowers exhibit low yield compared to that of late maturing snowball types. Despite the presence of a higher level of heterosis in Indian cauliflower, development of hybrids in India is lacking due to nonavailability of strong self-incompatibility-based hybrids suitable for different seasons. To identify diverse parental lines for breeding in early and mid-maturity Indian cauliflower, genetic characterization of self-incompatible inbred lines was carried out based on quantitative and molecular analyses. To study heterotic performance of these lines in relation to divergence, 80 and 54 F1 hybrids of early and mid-maturity groups, respectively, were developed into a Line × Tester mating design and evaluated for yield and related traits. The mid-maturity group had higher diversity compared to that of early maturity group. Of 32 random amplified polymorphic DNA (RAPD) and 38 simple sequence repeat (SSR) primers, 25 RAPD and 3 SSRs exhibited polymorphism and generated a total of 164 reproducible amplicons, of which 37 were polymorphic. The average number of amplicons per primer was 6.71 and the maximum number of polymorphic amplicons (three) was obtained from RAPD primer SK-14. In SSR markers, the average number of polymorphic amplicons was 1.48 per primer. The SSR marker BoREM-1b indicated heterozygosity in the self-incompatible lines ccm-8 and cc-35L and further inbreeding may produce homozygosity in these lines. Lines cc-32E (early) and cc-22 (mid-maturity) had the most heterotic crosses for marketable curd weight and moderate diversity at the molecular level could be utilized for heterosis breeding. The molecular makers with quantitative analysis may be utilized for assessment of genetic diversity, testing of hybrid purity, and protection of superior lines and hybrids.