Effects of genetic background and environment on QTLs and epistasis for rice (Oryza sativa L.) panicle number

A double-haploid (DH) population and a recombinant inbred (RI) line populat ion, derived from a cross between a tropical japonica variety, Azucena. as male parent and two indica varieties, IR64 and IR1552, as female parents re spectively, were used in both field and pot experiments for detecting QTLs and epistasis for rice particle number in different genetic backgrounds and different environments. Particle number (PN) was measured at maturity. A m olecular map with 192 RFLP markers for the DH population and a molecular ma p with 104 AFLP markers and 103 RFLP markers for the RI population were con structed. in which 70 RFLP markers were the same. Six QTLs were identified in the DH population, including two detected from field experiments and fou r from pot experiments. The two QTLs, mapped on chromosomes I and 12, were identical in both field and pot experiments. In the RI population, nine QTL s were detected. five QTLs from field conditions and four from the pot expe riments. Three of these QTLs were identical in both experimental conditions . Only one QTL. linked to CDO344 on chromosome 12. was detected across the populations and experiments. Different epistasitic interaction loci on PN w ere found under different populations and in different experimental conditi ons. One locus. flanked by RG323 and RZ801 on chromosome 1, had an additive effect in the DH population, but epistatic effects in the RI population. T hese results indicate that the effect of genetic background on QTLs is grea ter than that of environments. and epistasis is more sensitive to genetic b ackground and environments than main-effect QTLs. QTL and epistatic loci co uld be interchangeable depending on the genetic backgrounds and probably on the environments where they are identified.