Genome-Wide Association Mapping Identifies Novel Panicle Morphology Loci and Candidate Genes in Sorghum.

Lihua Wang,Hari D. Upadhyaya,Rajendra Kumar,Jieqin Li,C. L. L. Gowda,Yi-Hong Wang,Yongqun Zhu,Jian Zheng,Yanlong Liu,Shailesh Kumar Singh

doi:10.3389/fpls.2021.743838

Abstract

Panicle morphology is an important trait in racial classification and can determine grain yield and other agronomic traits in sorghum. In this study, we performed association mapping of panicle length, panicle width, panicle compactness, and peduncle recurving in the sorghum mini core panel measured in multiple environments with 6,094,317 single nucleotide polymorphism (SNP) markers. We mapped one locus each on chromosomes 7 and 9 to recurving peduncles and eight loci for panicle length, panicle width, and panicle compactness. Because panicle length was positively correlated with panicle width, all loci for panicle length and width were colocalized. Among the eight loci, two each were on chromosomes 1, 2, and 6, and one each on chromosomes 8 and 10. The two loci on chromosome 2, i.e., Pm 2-1 and Pm 2-2, were detected in 7 and 5 out of 11 testing environments, respectively. Pm 2-2 colocalized with panicle compactness. Candidate genes were identified from both loci. The rice Erect Panicle2 (EP2) ortholog was among the candidate genes in Pm 2-2. EP2 regulates panicle erectness and panicle length in rice and encodes a novel plant-specific protein with unknown functions. The results of this study may facilitate the molecular identification of panicle morphology-related genes and the enhancement of yield and adaptation in sorghum.

Highlights

The sorghum inflorescence consists of a single panicle with many racemes and is an important determinant of grain yield (Hmon et al, 2013)
In the 11 ICRISAT testing environments (Supplementary Table 1), panicle width was more variable across the environments than panicle length as measured by the coefficient of variation (CV)
When panicle compactness was scored only as compact, semi-compact, and loose, panicle length and width were negatively correlated with panicle compactness with r = −0.40 and −0.27, respectively, in Environment 1 at ICRISAT, and both were significant at P < 0.001

Summary

Introduction

The sorghum inflorescence consists of a single panicle with many racemes and is an important determinant of grain yield (Hmon et al, 2013). The compact panicle is typical of domesticated sorghum, especially elite high-yielding modern commercial varieties (Kimber, 2000; Brown et al, 2006; Dillon et al, 2007; OGTR, 2017), whereas undomesticated species are more likely to have open panicles (Harlan and de Wet, 1972). Plants with open or loose panicles are more likely to be smallseeded, reducing grain yield (Desmae et al, 2016). Race guinea with loose panicles is more common in wet environments to prevent grain molding, and race durra with compact panicles is more common in dry environments (Harlan and de Wet, 1972; Doggett, 1988; Ayana and Bekele, 1998)

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