Abstract
Aliphatic glucosinolates are the predominant sulfur-rich plant secondary metabolites in economically important Brassica crops. Glucosinolates and their hydrolysis products are involved in plant–microbe, plant–insect, plant–animal, and plant–human interactions. It is, therefore, important to manipulate glucosinolate profiles and contents in Brassica species. In this study, aliphatic glucosinolates were genetically manipulated through homoeologous recombination in backcross lines followed by marker assisted selection in B. rapa. A resynthesized B. napus line, from a cross between B. rapa and B. oleracea, was backcrossed with Chinese cabbage doubled haploid line, RI16. Marker assisted selection for non-functional gene was performed in each backcross generations. Advanced backcross progenies (BC3F2) were developed to identify homoeologous gene replacement and/or introgression. Reduction in 5C aliphatic glucosinolates (gluconapoleiferin, glucoalyssin, and glucobrassicanapin) was observed in BC3F2 progenies of the recurrent parent that carried the GSL-ELONG- gene. The GSL-ELONG- positive backcross progenies were also screened by the A-genome and BraGSL-ELONG gene specific marker, which linked with 5C aliphatic glucosinolates. The A-genome specific marker was absent in the plants of advanced backcross progenies which showed reduction in 5C aliphatic glucosinolates. The results suggest that the functional allele had been replaced by the non-functional GSL-ELONG- allele from B. oleracea. Some advanced backcross progenies (BC3F2) positive for the GSL-ELONG- allele and the A-genome specific SCAR marker BraMAM1-1 did not show reduction in 5C aliphatic glucosinolates, suggesting that GSL-ELONG- allele is recessive. Replacement of the functional locus in the A-genome by non-functional counterpart in the C-genome reduced the content of 5C aliphatic glucosinolates in B. rapa seeds with 20 μmol/g.
Highlights
In the genus Brassica, three diploid species, B. rapa L., B. oleracea L., and B. nigra L
PLANT MATERIALS AND BACKCROSS BREEDING SCHEME A high glucosinolate content B. rapa double haploid (DH) line, RI16 was crossed with a B. oleracea white cauliflower accession Snowball 76, and an embryo rescue technique was employed to produce resynthesized B. napus lines
CROSSABILITY OF DIGENOMIC TRIPLOID HYBRID WITH RECURRENT B. rapa A resynthesized B. napus line was developed by a cross between B. rapa genotype and B. oleracea white cauliflower genotype
Summary
In the genus Brassica, three diploid species, B. rapa L., B. oleracea L., and B. nigra L. Alien chromosome addition monosomic and disomic lines have been successfully developed and proven to be useful resources for gene identification and chromosome homoeology studies between Brassica genomes of B. rapa × B. oleracea, B. napus × B. nigra, and B. rapa × B. oxyrrhina (McGrath and Quiros, 1990; Hu and Quiros, 1991; Chen et al, 1992; Cheng et al, 1994; Srinivasan et al, 1998). Disease resistance, morphological, and quality traits such as erucic acid content, flowering time, seed coat color, and stem rot resistance have been successfully introgressed into cultivated Brassica crops through regular two parental crosses and subsequent backcrossing (Banga, 1988; Cheng et al, 1994; Navabi et al, 2010)
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