Abstract
Severe lodging has occurred in many improved rice varieties after the recent strong typhoons in East and Southeast Asian countries. The indica variety Takanari possesses strong culm characteristics due to its large section modulus, which indicates culm thickness, whereas the japonica variety Koshihikari is subject to substantial bending stress due to its thick cortical fibre tissue. To detect quantitative trait loci (QTLs) for lodging resistance and to eliminate the effects of genetic background, we used reciprocal chromosome segment substitution lines (CSSLs) derived from a cross between Koshihikari and Takanari. The oppositional effects of QTLs for section modulus were confirmed in both genetic backgrounds on chromosomes 1, 5 and 6, suggesting that these QTLs are not affected by the genetic background and are controlled independently by a single factor. The candidate region of a QTL for section modulus included SD1. The section modulus of NIL-sd1 was lower than that of Koshihikari, whereas the section modulus of NIL-SD1 was higher than that of Takanari. This result indicated that those regions regulate the culm thickness. The reciprocal effects of the QTLs for cortical fibre tissue thickness were confirmed in both genetic backgrounds on chromosome 9 using CSSLs.
Highlights
Occurs in many of these improved rice varieties when strong typhoons hit East and Southeast Asian countries
Several QTL and their responsive genes associated with a strong culm have been identified because this complex trait is controlled by multiple genes
An improved high-yielding indica variety with strong, thick culms, we detected QTLs associated with a thick culm: SCM1 on chromosome 1 and STRONG CULM2 (SCM2) on chromosome 6
Summary
Occurs in many of these improved rice varieties when strong typhoons hit East and Southeast Asian countries. Several genes associated with grain yield and biomass production have been identified, including GN1A4,5, GS36, DEP17, APO18, WFP9 and NAL110. To sustain this breeding objective, it is necessary to develop new strategies to improve lodging resistance in rice. BS is associated with properties such as the morphology of cortical fibre tissue[12] and cell wall components such as lignin, cellulose and hemicellulose[13]. No QTLs associated with cortical fibre tissue thickness have been reported in rice or other gramineous crops, it is necessary to identify the QTLs for these traits
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