Transfer of disease resistance alleles in plants can be expedited by the use of DNA molecular markers. If the markers are tightly linked to the resistance alleles they can be used for marker assisted selection (M.A.S.). One effective use of M.A.S. is found in the process of pyramiding resistance alleles. By using M.A.S., in three backcross generations, the Bean Breeding Program of BIOAGRO, Federal University of Viçosa (Minas Gerais, Brazil), has obtained bean (Phaseolus vulgaris) lines phenotypically similar to cultivar Rudá (recurrent) and resistant to anthracnose, rust and angular leaf spot. Seeds of BC3F4 lines currently are being multiplied to undergo inoculation with specific pathogens and agronomic performance tests. The Soybean Quality Breeding program of BIOAGRO used molecular markers to identify quantitative trait loci (QTLs) associated with resistance to soybean cyst nematode (SCN). Two microsattelite markers (Satt038 and Satt163) flanking the allele rhg1 were identified. Markers linked to a QTL that confers resistance to SCN race 14 were also identified. This QTL explains more than 40% of the resistance present in soybean (Glycine max) cultivar Hartwig, one of the most import resistance sources for SCN. The use of M.A.S. is a reality in several breeding programs around the that are trying to develop disease resistant cultivars. The effective use of this tool depends on a greater understanding between the breeder and the plant molecular biologist.
plant breeding; gene pyramiding; annual crops; Glycine max; Phaseolus vulgaris
