Among the diseases of the common bean, the angular leaf spot (ALS) can cause reduction in yield and quality of grain produced, and forward the great variability of these pathogens, the enduring strength of many cultivars was not reached. A large number of molecular markers was associated with QTLs for resistance to this disease, so it is possible to perform marker-assisted selection. According to studies of our research group, ALS quantitative standard genetic resistance shows and several QTLs introgressed should be to produce a lasting resistance to different races of the pathogen. The technique of AB-QTL (Advanced backcross QTL Analysis) is intended to select, and introgress simultaneously map the QTL, through backcrossing, so that the effects (epistatic and pleiotropic) the combination of different QTLs can be measured, and only the QTLs favorable to be transferred, without losing the quality of elite cultivar to be used as the recurrent parent. While other methods of assisted selection are based on first performing the mapping of QTLs for then transferring those favorable, this technique of AB-QTL suggests that families and/or strains are phenotypically evaluated simultaneously with the introgression of QTL, reducing it is the problem of linkage drag and negative interactions. Phenotypic selection eliminates the progenies with lower performance, even those who have the favorable QTL introgressed, but can have their values changed by genetic epistatic interactions, pleiotropic effects or by genotype x environment. The objective of this project is to use the technique of AB-QTL to promote a gain of genetic resistance to ALS in common bean breeding program of the IAC. For this, the 'IAC Milênio' (susceptible, parental applicant) will be crossed with the cultivar 'AND 277' (resistant, parental donor). Phenotypic to select plants that have desirable patterns for common bean crop selection will be made in RC1 and RC2, and evaluation of molecular markers in large scale occur in F5BC22. In this generation, the QTLs are mapped and near isogenic lines (QTL-NILs) will be evaluated. The phenotyping for the disease will be taken in the greenhouse during mapping, but then the selection will be conducted in experimental field conditions with natural infection. It is expected that new cultivars can be recommended in a common bean breeding program of the IAC and that they show effective resistance in planting conditions.
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