Abstract
Moderate leaf rolling is considered optimal for the ideal plant type in rice (Oryza sativa L.), as it improves photosynthetic efficiency and, consequently, grain yield. Determining the genetic basis of leaf rolling via the identification of quantitative trait loci (QTLs) could facilitate the development of high-yielding varieties. In this study, we identified three stable rice QTLs, qARO1, qARO5, and qARO9, which control adaxial leaf rolling in a recombinant inbred line (RIL) population derived from a cross between Tong 88-7 (T887) and Milyang 23 (M23), using high-density SNP markers. These QTLs controlled the rolling phenotype of both the flag leaf (FL) and secondary leaf (SL), and different allelic combinations of these QTLs led to a wide variation in the degree of leaf rolling. Additive gene actions of qARO1 and qARO9 on leaf rolling were observed in a backcross population. In addition, qARO1 (markers: 01id4854718 and 01asp4916781) and qARO9 (markers: 09id19650402 and 09id19740436) were successfully fine-mapped to approximately 60- and 90-kb intervals on chromosomes 1 and 9, respectively. Histological analysis of near-isogenic lines (NILs) revealed that qARO1 influences leaf thickness across the small vein, and qARO9 affects leaf thickness in the entire leaf and bulliform cell area, thus leading to adaxial leaf rolling. The results of this study advance our understanding of the genetic and molecular bases of adaxial leaf rolling, and this information can be used for the development of rice varieties with the ideal plant type.
Highlights
Leaf is the major organ responsible for photosynthesis and transpiration
Among the recombinant inbred line (RIL) derived from a cross between Tong 88-7 (T887) and Milyang 23 (M23), the value of flag leaf rolling index (FLRI) varied from 0%
In the RIL population derived from a cross between T887 and M23, the FLRI and secondary leaf rolling index (SLRI) values showed transgressive segregation in the positive direction, implying that the genetic factors responsible for adaxial leaf rolling could have originated from either parent (Figure 1B)
Summary
Leaf is the major organ responsible for photosynthesis and transpiration. In rice (Oryza sativa L.), leaf shape is one of the main factors affecting the rice plant type. It is considered an important agronomic trait determining photosynthetic potential and grain yield in rice (Smith and Dilday, 2002; Yang and Hwa, 2008). The V-shape or moderate rolling of leaves increases canopy photosynthesis by enhancing CO2 penetration (Chakraborty, 2001) and improves light capture by reducing mutual shading (Defeng et al, 2001). Moderately rolled leaves are thought to support higher grain yield than flat leaves (Setter et al, 1995).
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