Groli Eder Licieri, Frascaroli Elisabetta, Maccaferri Marco, Ammar Karim, Tuberosa Roberto
Department of Agricultural and Food Sciences, DISTAL, University of Bologna, Bologna, Italy.
International Maize and Wheat Improvement Center, CIMMYT, El Batán, Mexico.
Front Plant Sci. 2024 Jun 28;15:1393349. doi: 10.3389/fpls.2024.1393349. eCollection 2024.
Heat stress negatively affects wheat production in several ways, mainly by reducing growth rate, photosynthetic capacity and reducing spike fertility. Modeling stress response means analyzing simultaneous relationships among traits affecting the whole plant response and determinants of grain yield. The aim of this study was to dissect the diverse impacts of heat stress on key yield traits and to identify the most promising sources of alleles for heat tolerance.
We evaluated a diverse durum wheat panel of 183 cultivars and breeding lines from worldwide, for their response to long-term heat stress under field conditions (HS) with respect to non stress conditions (NS), considering phenological traits, grain yield (GY) and its components as a function of the timing of heat stress and climatic covariates. We investigated the relationships among plant and environmental variables by means of a structural equation model (SEM) and Genetic SEM (GSEM).
Over two years of experiments at CENEB, CIMMYT, the effects of HS were particularly pronounced for the normalized difference vegetation index, NDVI (-51.3%), kernel weight per spike, KWS (-40.5%), grain filling period, GFP (-38.7%), and GY (-56.6%). Average temperatures around anthesis were negatively correlated with GY, thousand kernel weight TKW and test weight TWT, but also with spike density, a trait determined before heading/anthesis. Under HS, the correlation between the three major determinants of GY, i.e., fertile spike density, spike fertility and kernel size, were of noticeable magnitude. NDVI measured at medium milk-soft dough stage under HS was correlated with both spike fertility and grain weight while under NS it was less predictive of grain weight but still highly correlated with spike fertility. GSEM modeling suggested that the causal model of performance under HS directly involves genetic effects on GY, NDVI, KWS and HD.
We identified consistently suitable sources of genetic resistance to heat stress to be used in different durum wheat pre-breeding programs. Among those, Desert Durums and CIMMYT'80 germplasm showed the highest degree of adaptation and capacity to yield under high temperatures and can be considered as a valuable source of alleles for adaptation to breed new HS resilient cultivars.
热应激通过多种方式对小麦产量产生负面影响，主要表现为降低生长速率、光合能力以及穗育性。模拟应激反应意味着分析影响整株植物反应的性状与籽粒产量决定因素之间的同步关系。本研究的目的是剖析热应激对关键产量性状的多种影响，并确定最有前景的耐热等位基因来源。
我们评估了来自世界各地的183个硬粒小麦品种和育种系组成的多样化群体，在田间条件下（热应激，HS）相对于非应激条件（NS）对长期热应激的反应，将物候性状、籽粒产量（GY）及其组成部分视为热应激时间和气候协变量的函数。我们通过结构方程模型（SEM）和遗传结构方程模型（GSEM）研究了植物和环境变量之间的关系。
在国际玉米小麦改良中心（CIMMYT）的CENEB进行的为期两年的实验中，热应激对归一化植被指数（NDVI，下降51.3%）、每穗粒重（KWS，下降40.5%）、灌浆期（GFP，下降38.7%）和籽粒产量（GY，下降56.6%）的影响尤为明显。开花期前后的平均温度与GY、千粒重（TKW）和容重（TWT）呈负相关，但也与穗密度呈负相关，穗密度是在抽穗/开花前确定的一个性状。在热应激条件下，GY的三个主要决定因素，即可育穗密度、穗育性和籽粒大小之间的相关性显著。在热应激条件下中等乳熟-软面团期测得的NDVI与穗育性和粒重均相关，而在非应激条件下，它对粒重的预测性较低，但仍与穗育性高度相关。GSEM建模表明，热应激条件下表现的因果模型直接涉及对GY、NDVI、KWS和抽穗期（HD）的遗传效应。
我们确定了在不同硬粒小麦预育种计划中持续适用的耐热遗传抗性来源。其中，沙漠硬粒小麦和国际玉米小麦改良中心80年代种质在高温下表现出最高程度的适应性和产量能力，可被视为适应高温、培育新的耐热品种的宝贵等位基因来源。
