Molecular and Physiological Responses of Rice and Weedy Rice to Heat and Drought Stress

Leonard Bonilha Piveta,Nilda Roma-Burgos,José Alberto Noldin,Fabiane Pinto Lamego,Claudia De Oliveira,Luis Antonio De Avila,Vívian Ebeling Viana

doi:10.3390/agriculture11010009

Abstract

Rice is the staple food for about half of the world population. Rice grain yield and quality are affected by climatic changes. Arguably, rice cultivars’ genetic diversity is diminished from decades of breeding using narrow germplasm, requiring introgressions from other Oryza species, weedy or wild. Weedy rice has high genetic diversity, which is an essential resource for rice crop improvement. Here, we analyzed the phenotypic, physiological, and molecular profiles of two rice cultivars (IRGA 424 and SCS119 Rubi) and five weedy rice (WR), from five different Brazilian regions, in response to heat and drought stress. Drought and heat stress affected the phenotype and photosynthetic parameters in different ways in rice and WR genotypes. A WR from Northern Brazil yielded better under heat stress than the non-stressed check. Drought stress upregulated HSF7A while heat stress upregulated HSF2a. HSP74.8, HSP80.2, and HSP24.1 were upregulated in both conditions. Based on all evaluated traits, we hypothesized that in drought conditions increasing HSFA7 expression is related to tiller number and that increase WUE (water use efficiency) and HSFA2a expression are associated with yield. In heat conditions, Gs (stomatal conductance) and E’s increases may be related to plant height; tiller number is inversely associated with HSPs expression, and chlorophyll content and Ci (intercellular CO2 concentration) may be related to yield. Based on morphology, physiology, and gene regulation in heat and drought stress, we can discriminate genotypes that perform well under these stress conditions and utilize such genotypes as a source of genetic diversity for rice breeding.

Highlights

The demand for food increases with the increase in population and buying power of densely populated countries [1,2]
The weedy rice from Northern Brazil (WR_RR) was taller (76.7 cm) compared to all others when grown under normal conditions (Figure 2A)
All genotypes were negatively affected by heat stress, except for Weedy rice from RN (WR_RN), which showed a 5% increase in height

Summary

Introduction

The demand for food increases with the increase in population and buying power of densely populated countries [1,2]. Agriculture has the challenge to meet this demand. The efficient use of natural resources, reducing waste, and increasing crop production, are essential to meet the growing food demand worldwide [3,4]. The challenge is to minimize soil degradation, use less water, and maintain ecological biodiversity in a changing climate where the agroecosystems are exposed to increasing abiotic stresses [4,5,6]. In addition to abiotic stresses, weed competition dampens rice production. Called red rice, is considered one of the main weeds in rice areas in southern Brazil [9,10,11,12,13]. Weedy rice infests rice fields in most paddy rice production regions globally [14,15,16,17,18], causing significant yield losses

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