Identification of SSR markers linked to resistance of rice to Rhizoctonia solani

In order to investigate rice resistance to Rhizoclonia solani, which causes rice sheath rot (PDV), by use of microsatellite SSR markers (Simple Sequence Repeats), two crossbreeding were made between commercial rice cultivars (Palmar x Fonaiap 1 and Jefferson x Fonaiap 2000). The plants were inoculated at the beginning of the emergence of the panicle and then placed in a humid chamber for a week. Afterwards, the area affected by the disease was determined (0 = no lesions, up to 9 = 100% affected area); the plants were grouped according to the evaluation scale. The SSR markers were evaluated once DNA was extracted from leaves following methodology described by Zambrano, but using larger fragments obtained by the polymerase chain reaction (PCR); PCR products were observed by electrophoresis in agarose gels to 3%. To determine QTL, which measures the resistance to PDV, the composite interval mapping method was used; the threshold LOD > 2.4 indicated that QTL was present. The progeny of Palmar x Fonaiap 1 crossbreeding showed 3 QTL located on chromosomes 1, 4 and 12; they were outflanked by the markers RM 572 and RM 449, RM 273 and RM 3471, RM 3472 and RM 309, respectively. No QTL were detected in the progeny from Jefferson x Fonaiap 2000 crossbreeding. The QTL founds in this work are a valuable contribution to study the rice resistance to R. solani.