Glucosinolate profiles of Australian canola (Brassica napus annua L.) and Indian mustard (Brassica juncea L.) cultivars: implications for biofumigation

The glucosinolate (GSL) profiles in root, shoot, and seed tissues of 22 Aus tralian canola (Brassica napus) and 15 Indian mustard (Brassica juncea) ent ries were measured in the field. The Indian mustard lines included 12 low s eed GSL lines from a breeding program aimed at producing canola-quality B. juncea cultivars and 3 high seed GSL condiment cultivars. The aromatic gluc osinolate, 2-phenylethyl GSL, was the major GSL found in the roots of both species although Indian mustard also contained 2-propenyl GSL in the roots. The concentration of glucosinolates in the roots varied from 5 to 35 mu mo l/g in B. napus, from 2.5 to 25 mu mol/g in low seed GSL B. juncea, and fro m 10 to 21 mmol/g in high seed GSL B. juncea, but was not correlated with s eed glucosinolate concentrations in either species. Breeding for low seed G SLs in Indian mustard reduced the concentration of 2-propenyl GSL in both r oot and shoot tissues, but levels of 2-phenylethyl GSL in the roots were un affected. The results indicate that high yielding and agronomically adapted varieties of both species could be developed with higher levels of root GS L for enhanced biofumigation potential without compromising seed quality. T he GSLs which liberate isothiocyanates on hydrolysis were found primarily i n the taproot and larger lateral roots (>2 mm) of both species, whereas you nger fine roots (<2 mm diameter) had higher levels of indolyl GSLs. Correla tions between root GSLs and susceptibility of brassicas to root pests and p athogens will need to take account of these differences in GSL profiles amo ng different root classes.