Single independent genes confer resistance to faba bean rust (Uromyces viciae-fabae) in the current Australian cultivar Doza and a central European line Ac1655

Abstract

Faba bean (Vicia faba L.) is one of the oldest grain legumes and is grown in many countries for both human consumption and animal feed. Faba bean rust, caused by Uromyces viciae-fabae, is a serious disease of faba beans in the subtropical agricultural region of Australia. Experiments were conducted to assess the genetic variation for rust resistance in Australian faba bean germplasm and to determine the genetic basis of rust resistance in selected germplasm. Resistant lines were identified, subsequently crossed to agronomically suitable parents and the ensuing progeny were evaluated for resistance. Many derived lines showed a higher level of resistance than the current cultivars, although none were rated immune. This level of resistance was considered adequate for reliable crop production when combined with limited fungicide application. Genetic studies from the seedling test of F2 and F3 progenies derived from two crosses based on two different sources of resistance showed three distinct responses; highly resistant, moderately resistant and susceptible. However, no homozygous family with a moderate response was found in the F3 progeny test, hence, this infection type could not be attributed to independent gene(s). The segregation ratio in both F2 and F3 in the population derived from Doza#12035, a selection from the commercial cultivar Doza, indicated a single dominant gene was responsible for conferring resistance. In the other population developed from the resistant parent Ac1655, it is likely that also a single dominant gene confers resistance even though the F3 segregation ratio deviated significantly from a one gene hypothesis. An allelism test revealed that each of the resistant parents (Doza#12035 and Ac1655) carried a single and independent gene for resistance, thus providing at least two genes for breeders to choose or pyramid for improving the rust resistance in faba bean.