Isolation of a Novel Lodging Resistance QTL Gene Involved in Strigolactone Signaling and Its Pyramiding with a QTL Gene Involved in Another Mechanism

Abstract

Lodging has been a major roadblock to attaining increased crop productivity. In an attempt to understand the mechanism for culm strength in rice, we isolated an effective quantitative trait locus (QTL), STRONG CULM3 (SCM3), the causal gene of which is identical to rice TEOSINTE BRANCHED1 (OsTB1), a gene previously reported to positively control strigolactone (SL) signaling. A near-isogenic line (NIL) carrying SCM3 showed enhanced culm strength and increased spikelet number despite the expected decrease in tiller number, indicating that SL also has a positive role in enhancing culm strength and spikelet number. We produced a pyramiding line carrying SCM3 and SCM2, another QTL encoding APO1 involved in panicle development. The NIL-SCM2+SCM3 showed a much stronger culm than NIL-SCM2 and NIL-SCM3 and an increased spikelet number caused by the additive effect of these QTLs. We discuss the importance of utilizing suitable alleles of these STRONG CULM QTLs without inducing detrimental traits for breeding.

Engineering the lodging resistance mechanism of post-Green Revolution rice to meet future demands

“…To further enhance the lodging resistance of NIL- SCM2 , Yano et al 37) attempted to pyramid another lodging resistance QTL into it. QTL pyramiding is an approach to introgress highly advantageous combinations of QTLs into one variety, and theoretically, superior alleles from a number of parental varieties can be introgressed into an elite variety, and this is exemplified by introducing favorable traits such as grain yield and resistance against pathogens as attempted by some researchers.…”

The genetic architecture of biomechanical traits in sorghum

“…For example, semidwarfism reduces grain and biomass yield in rice (Yano et al., 2015), oats (Milach et al., 2002), and sorghum (George‐Jaeggli, Jordan, Van Oosterom, & Hammer, 2011, 2013). In rice, the mutation of the semidwarf ( sd1 ) gene, which encodes the GA biosynthesis enzymes, affects biomass, grain weight, culm morphology and reduces stem strength by decreasing stem diameter and wall thickness (Nomura, Arakawa, Yamamoto, Ueda, & Adachi, 2019; Okuno et al., 2014; Yano et al., 2015). Similarly, the reduce‐height ( Rht ) genes in wheat are reported to have negative effects on anatomical traits affecting breaking strength by altering the cell wall chemistry of fibers (Paolillo & Niklas, 1996).…”

“…Additional QTL, STRONG CULM3 (SCM3) and STRONG CULM4 (SCM4), were identified using backcross inbred lines from a cross between tropical japonica variety Chugoku and the japonica variety Koshihikari (Ookawa et al., 2014; Ookawa et al., 2016; Nomura et al., 2019). The SCM3 causal gene was identical to the TEOSINTE BRANCHED1 ( OsTB1 ), which is an ortholog of FINE CULM1 ( FC1 ) (Minakuchi et al., 2010; Nomura et al., 2019; Takeda et al., 2003; Yano et al., 2015). The same group also confirmed QTL in rice on chromosomes 1, 5, and 6 that affect the section modulus of stems using CSSLs of reciprocal crosses between cultivars Koshihikari and Takanari (Ookawa et al., 2016).…”

New path towards a better rice architecture

“…Indeed, most genes inducing large panicle, such as IPA1/OsSPL14 [4] and SCM3/OsTB1 [11], can increase the grain number per panicle, but at the same time, decrease the tiller number per plant. In the same manner, the OsOTUB1 discussed by Wang et al also appears to follow the same trade-off trend, but with good results in terms of high grain yield and lodging resistance.…”