PROGRESS TOWARDS MAPPING ALLIUM ROYLEI DERIVED BOTRYTIS LEAF BLIGHT RESISTANCE IN ONION

P. Goldschmied, J. Lorbeer, D. Loparco, E. Cobb, M. Mutschler

Most onions are susceptible to Botrytis leaf blight (BLB). The wild onion relative A. roylei possesses strong BLB resistance that could be transferred to commercially useful onion lines. This transfer is a focus of the onion breeding program, but in the process, information regarding the number and location of BLB resistance genes is sought to facilitate the transfer.

Interspecific sexual barriers profoundly reduce male fertility and seed set, impeding gene transfer. It is relatively easy to make the interspecific F1, however sexual barriers severely limit seed production in subsequent generations. However segregation for fecundity yielded two BLB resistant BC1F2 plants capable of generating higher levels BC2F1 seed. The resulting BC2F1 plants had horticultural characteristics much closer to onion, and segregated for both BLB resistance and fecundity. In 2004, BC2F2 and BC3F1 populations derived from BC2F1 selections were screened for BLB resistance and used for seed production. Selection for both traits was successful.

DNA was saved from BLB resistant selections, as well as susceptible sib plants, in each generation, to identify molecular markers associated with BLB resistance. EcoRI - Mse and Pst - Mse digestion of sample DNAs was used prior to the first cycle of amplification in AFLP analysis. Primary amplification was performed using primers with 1 selective base. Primers with 3 selective bases were used in the second cycle of amplification to reduce band number, improving clarity. AFLP generates numerous A. roylei or A. cepa specific bands. Progress in detecting such markers will be discussed.

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