Producing inter-specific hybrids between Brassica juncea (L.) Czern & Coss and B. oleracea (L.) to synthesize trigenomic (abc) Brassica

Abstract

Polyploidy is recognized as a major mechanism in plant evolution. Polyploid crops often have wider adaptation, better quality and higher yielding capacity than their diploid counterparts. Although many successful natural and man-made hexaploid crops are existing, hexaploid Brassica are still not available. So far, relatively a limited work has been conducted to synthesize hexaploid Brassica with A, B and C genomes, which will provide a very good potential to create new crops for domestication. An investigation was conducted to evaluate the possibility of synthesizing trigenomic (AABBCC) hexaploid Brassica by crossing Brassica juncea (L.) Czern & Coss and B. oleracea (L.). Five genotypes of B. juncea (AC 0747, 0790, 1099, 2180 and 7700) and five genotypes of B. oleracea (Chinese Broccoli, Broccoli-var. Shogun, Cauliflower-var. Snowball and var., Phenomenon Early and Cabbage-var. Sweet Eureka) were selected for the study. Hand pollination was done by emasculating buds of one species and pollination using another species in both directions. Success of pod formation of the crosses of B. juncea (♀) x B. oleracea (♂) was 25%. Totally 893 putative hybrid seeds were harvested. Although 9% pod formation was observed in reciprocal crosses, no seeds were developed. Evaluation of 80 putative hybrids by molecular markers and agro-morphological characterization confirmed four true hybrids resulting crosses between AC 0747 x Chinese Broccoli, AC 0790 x Chinese Broccoli and AC 2180 x Broccoli-var. Shogun. The present investigation confirms that hybridization of tetraploid B. juncea (4x, AABB) with diploid B. oleracea (2x, CC) is a potential approach to produce hexaploid Brassica (6x, AABBCC) genotypes.