Mapping QTL for Spikelets Per Panicle in Near-isogenic Lines Derived From an Interspecific Cross in Rice

We constructed a high-resolution physical map for the qSPP7 QTL for spikelets per panicle on rice chromosome 7 across a 28.6-kb region containing 4 predicted genes. Using a series of BC₇F₄ nearly isogenic lines (NILs) derived from a cross between the Korean japonica cultivar ‘Hwaseongbyeo’ and Oryza minuta (IRGC Acc. No. 101144), 3 QTLs for the number of spikelets per panicle (SPP), grains per panicle, and primary branches were identified in the cluster (P ≤ 0.01). All 3 QTLs were additive, and alleles from the O. minuta parent were beneficial in the ‘Hwaseongbyeo’ background. qSPP7 was mapped to a 28.6-kb region between the 2 simple sequence repeat (SSR) markers RM4952 and RM21605. The additive effect of the O. minuta allele at qSPP7 was 23 SPP, and 43.6% of the phenotypic variance was explained by the segregation of the SSR marker RM4952. Colocalization of the 3 QTLs suggested that this locus was associated with panicle structure and had pleiotropic effects. The NIL populations and molecular markers are useful for cloning qspp7.