Mapping of angular leaf spot resistance QTL in common bean (Phaseolus vulgaris L.) under different environments.
BACKGROUND
Common bean (Phaseolus vulgaris L.) is the most important grain legume for human diet worldwide and the angular leaf spot (ALS) is one of the most devastating diseases of this crop, leading to yield losses as high as 80%. In an attempt to breed resistant cultivars, it is important to first understand the inheritance mode of resistance and to develop tools that could be used in assisted breeding. Therefore, the aim of this study was to identify quantitative trait loci (QTL) controlling resistance to ALS under natural infection conditions in the field and under inoculated conditions in the greenhouse.


RESULTS
QTL analyses were made using phenotypic data from 346 recombinant inbreed lines from the IAC-UNAxCAL 143 cross, gathered in three experiments, two of which were conducted in the field in different seasons and one in the greenhouse. Joint composite interval mapping analysis of QTLxenvironment interaction was performed. In all, seven QTLs were mapped on five linkage groups. Most of them, with the exception of two, were significant in all experiments. Among these, ALS10.1DG,UC presented major effects (R2 between 16%-22%). This QTL was found linked to the GATS11b marker of linkage group B10, which was consistently amplified across a set of common bean lines and was associated with the resistance. Four new QTLs were identified. Between them the ALS5.2 showed an important effect (9.4%) under inoculated conditions in the greenhouse. ALS4.2 was another major QTL, under natural infection in the field, explaining 10.8% of the variability for resistance reaction. The other QTLs showed minor effects on resistance.


CONCLUSIONS
The results indicated a quantitative inheritance pattern of ALS resistance in the common bean line CAL 143. QTL x environment interactions were observed. Moreover, the major QTL identified on linkage group B10 could be important for bean breeding, as it was stable in all the environments. Thereby, the GATS11b marker is a potential tool for marker assisted selection for ALS resistance.
Departamento de Genética e Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil.
Paula Rodrigues
PR
Oblessuc
Renata Moro
RM
Baroni
Antonio Augusto Franco
AA
Garcia
Alisson Fernando
AF
Chioratto
Sérgio Augusto Morais
SA
Carbonell
Luis Eduardo Aranha
LE
Camargo
Luciana Lasry
LL
Benchimol
D002874:Chromosome Mapping / Q000379:methods*; D003433:Crosses, Genetic; D060467:Disease Resistance / Q000235:genetics*; D059647:Gene-Environment Interaction; D008040:Genetic Linkage; D027805:Phaseolus / Q000235:genetics*; D010935:Plant Diseases / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics; D040641:Quantitative Trait Loci