Quantitative Trait Loci for Sink Size and Ripening Traits in Rice (Oryza sativa L.).

Abstract

Quantitative trait loci (QTLs) that affect sink size and ripening, which are often negatively correlated, were analyzed in two inbred lines of rice (Oryza sativa L.) derived from crosses between the semi-dwarf indica and japonica cultivars. Recombinant inbred lines (RILs) from Milyang23 (indica)/Akihikari (japonica), and back-crossed inbred lines (BCILs) from Sasanishiki (japonica)/Habataki(indica)//Sasanishiki///Sasanishiki were studied over a period of two years. A major QTL that was related to the number of spikelets per panicle was found in the same region of chromosome 1 in both populations. The indica allele increased the number of spikelets and reduced the ripening percentage. The indica allele of the QTL, which was found in both populations but at different locations on chromosome 6, also increased the number of spikelets per panicle, although to a lesser extent than in the case of the QTL on chromosome 1. In this instance, the number of spikelets per panicle did not have a negative effect on the ripening percentage. The increased number of spikelets produced by the QTL on chromosome 6 was due mainly to an increase in the number of primary rachis branches. In contrast, the effect of the QTL on chromosome 1 relied on an increase in the number of secondary rachis branches. In addition, dry matter production tended to increase when the QTL region of chromosome 6 belonged to the indica genotype. Therefore, both panicle structure and source productivity might contribute to the increase of the sink size without reducing the ripening percentage. We also found two loci on chromosomes 11 and 12 of the RILs that were associated with the percentage of incompletely filled spikelets, but which did not affect the sink size. It is considered that these QTLs could contribute significantly to the breeding of cultivars with increased sink size and increased ripening.

A Quantitative Trait Locus for Chlorophyll Content and its Association with Leaf Photosynthesis in Rice

“…of lines Fig. 1 Frequency distribution of SPAD value of flag leaves at heading and days-to-heading in 85 BILs derived from a cross of Sasanishiki × Habataki (Nagata et al 2002). Vertical lines denote mean parental values; horizontal lines denote SD.…”

“…Then we identified a candidate QTL controlling SPAD value of flag leaves at heading stage by using backcross inbred lines (BILs) derived from a cross between japonica cultivar Sasanishiki and indica cultivar Habataki (Nagata et al 2002). To confirm the putative QTL and to assess its association with leaf photosynthesis, we used chromosome segment substitution lines (CSSLs).…”

Quantitative Trait Loci Controlling the Number of Spikelets and Component Traits in Rice: Their Main Effects and Interaction with Years

“…Therefore, qSN-1 seems to correspond to the QTL assumed to exist in region 3. Yagi et al (2001) and Nagata et al (2002) also detected QTLs with strong effects (LOD scores of more than 8.0) on the number of spikelets per panicle and the number of SBs at almost the same position as region 3 in another mapping population derived from the cross of a japonica-cultivar Akihikari and an indica-cultivar Milyang 23. Sasahara et al (1999) mapped several QTLs controlling the number of PBs in the same mapping population as that used in the present study by interval mapping.…”

“…In most of these studies, the QTL-by-environment interactions detected were evaluated by comparing the LOD-scores of the regions of interest between all the environmental conditions examined (Zhuang et al 1997, Austin and Lee 1998, Nagata et al 2002. On the other hand, several models and procedures have been developed to detect and map the genotype-by-environment interaction onto the genome (Hayes et al 1993, Jansen et al 1995, Romagosa et al 1996, Wang et al 1999.…”

QTLs for Shoot Length and Chlorophyll Content of Rice Seedlings Grown under Low-Temperature Conditions, using a Cross between Indica and Japonica Cultivars

“…Of them, indica originated in the tropical area, and is considered to be more sensitive to low temperatures than japonica, which is adapted to the temperate area (Mackill and Lei, 1997;Zhao and Takahashi 1999;Ohsumi et al, 2012). Indica cultivars generally have bigger heads and are used as mother plants to improve yielding capacity (Nagata et al, 2002;Ando et al, 2008;Terao et al, 2010). However, the sensitivity to low temperatures at the seedling stages limits the utilization of indica-based cultivars in cold temperate areas.…”