Finding a novel QTL responsible for kernel cracking resistance from CSSLs of ‘Itadaki’ ( O. sativa L.) × donor O. rufipogon

To find new QTLs responsible for kernel cracking resistance, we screened 50 CSSLs derived from the moderately resistant cultivar 'Itadaki' (O. sativa L.) and the donor O. rufipogon. Two lines, IRSL 30 and IRSL 37, were selected as resistant. QTL analyses of the percentage of cracked kernels (PCK) in F4 individuals derived from "Itadaki/IRSL 30" and "Itadaki/IRSL 37" identified a major QTL, qCR (Cracking Resistance) 8-2, at the same position on chromosome 8 in both populations. 'IRSL 30' and 'IRSL 37' had a reduced PCK. These results show that qCR8-2 is likely to be an important QTL for kernel cracking resistance. Both lines had long awns, linked to qCR8-2, but the awnless line 'Chukei 19301' was also derived from "Itadaki/IRSL 37", so qCR8-2 is distinct from the gene for awn development. We consider that qCR8-2 will help in the breeding of new rice cultivars with high cracking resistance and in elucidating the physiological mechanism of kernel cracking.