Genetic basis and mapping of the resistance to rice yellow mottle virus. I. QTLs identification and relationship between resistance and plant morphology

Rice yellow mottle virus (RYMV) resistance QTLs were mapped in a doubled-ha ploid population of rice, 'IR64/Azucena'. Disease impact on plant morpholog y and development, expression of symptoms and virus content were evaluated in field conditions. Virus content was also assessed in a growth chamber. R YMV resistance was found to be under a polygenic determinism, and 15 QTLs w ere detected on seven chromosomal fragments. For all of the resistance QTLs detected, the favourable allele was provided by the resistant parent 'Azuc ena'. Three regions were determined using different resistance parameters a nd in two environments. On chromosome 12, a QTL of resistance that had alre ady been detected in this population and another indica/japonica population was confirmed both in the field and under controlled conditions. Significa nt correlations were observed between resistance and tillering ability, as measured on control non-inoculated plants. In addition, the three genomic f ragments involved in resistance were also involved in plant architecture an d development. In particular, the semi-dwarfing gene sd-l, on chromosome 1, provided by the susceptible parent,'IR64`, mapped in a region where resist ance QTLs were detected with most of the resistance parameters. In contrast , the QTL of resistance mapped on chromosome 12 was found to be independent of plant morphology.