Novel Loci for Kernel Hardness Appeared as a Response to Heat and Combined Heat-Drought Conditions in Wheat Harboring Aegilops tauschii Diversity

Gamila Mohamed Idris Elhadi,Yuji Yamasaki,Nasrein Mohamed Kamal,Hiroyuki Tanaka,Yasir Serag Alnor Gorafi,Hisashi Tsujimoto,Keita Kato,Yusuke Ban,Izzat Sidahmed Ali Tahir,Takayoshi Ishii

doi:10.3390/agronomy11061061

Abstract

Kernel hardness influences the milling and baking quality of wheat. Stress environments such as heat and combined heat-drought can produce harder kernels, thereby affecting the overall wheat quality. Beside puroindoline genes that are known to determine hardness, other QTLs contribute to the hardness. These QTLs, especially under stress conditions, need extensive research. Moreover, understanding the modification or stabilization of hardness under stress condition and the relationship with stress tolerance will facilitate the selection of superior lines that maintain both high yield and quality even under the stress environment. Therefore, in the current work, we aimed to identify the genetic loci and marker trait associations (MTAs) that contributes for hardness under optimum conditions in Japan, and heat and combined heat-drought (HD) conditions in Sudan. We used a panel of multiple synthetic derivatives (MSD) having diverse Aegilops tauschii genome segments and investigated the association between hardness stabilization and stress tolerance. Under stress conditions, we observed that less reduction of kernel weight is associated with either low change or stable kernel hardness. We identified 47 markers associated with hardness under all conditions; the D genome was the main contributor. For the first time, we found a significant association with hardness under stress conditions on chromosome 4D. We dissected several candidate genes associated with the change of hardness under stress conditions. Our results will improve the understanding of the genetic factors that affect wheat hardness stability.

Highlights

We selected 140 multiple synthetic derivatives (MSD) lines out of the original 400 lines based on their suitability to grow under Sudanese conditions to understand the effect of the heat and HD environments on the hardness and to detect the different factors that influence the hardness under stress conditions
We investigated the relationship between hardness and kernel weight for heat and heat-drought susceptibility index (HSI and HDSI) for the MSD lines (Figure 2)
We aimed to identify marker trait associations (MTAs), and possible candidate genes that contributed to the stability or modification of kernel hardness under heat and combined heat-drought conditions, and to investigate whether the stabilization of kernel hardness under stress was associated with stress-tolerance genes

Summary

Introduction

Kernel hardness is an important quality trait that greatly influences the milling and baking quality of wheat. The world wheat trade is largely carried out based on hardness grades. Wheat hardness is a quantitative trait with classes ranging from soft to hard [1]. Two genes mainly determine hardness, puroindoline a and b (Pina and Pinb), which are located on the short arm of chromosome 5D (5DS) and form the molecular basis of wheat hardness [2]. The presence of the wild-type form of these genes is associated with the soft kernel phenotype in hexaploid wheat. The absence or mutation in either gene results in a hard kernel phenotype [3]

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