Evaluation of Iraqi Rice Cultivars for Their Tolerance to Drought Stress

Tiba Nazar Ibrahim Al Azzawi,Bong-Gyu Mun,Muhammad Shahid,Murtaza Khan,Byung-Wook Yun,Sang-Uk Lee,Qari Muhammad Imran,Adil Hussain

doi:10.3390/agronomy10111782

Tiba Nazar Ibrahim Al Azzawi, Bong-Gyu Mun + Show 6 more

Open Access

https://doi.org/10.3390/agronomy10111782

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Abstract

Drought stress is a serious problem around the globe and particularly in the Republic of Iraq. Rice is the third most consumed crop for the Iraqi people; however, its cultivation and production is very low due to several challenges including drought. The current study was performed to evaluate five Iraqi rice cultivars along with relevant (drought-tolerant and drought-susceptible) controls under drought stress, either by treatment with 10% PEG (polyethylene glycol) or through water withholding to induce natural drought stress. The phenotypes of all the cultivars were evaluated and the transcriptional responses of key drought-responsive candidate genes, identified through the EST-SSR marker-based approach, were studied. We also studied transcript accumulation of drought-related transcriptional factors, such as OsGRASS23, OsbZIP12, and OsDREB2A. Moreover, the reference cultivars also included a drought-tolerant inter-specific cultivar Nerica 7 (a cross between Oryza sativa ssp. indica X O.glaberrima). Among the cultivars, the more drought-tolerant phenotypic characteristics and higher transcript accumulation of drought-related marker genes OsE647 and OsE1899 and transcriptional factors OsGRASS23, OsbZIP12, and OsDREB2A were observed in four (out of five) significantly drought-tolerant Iraqi cultivars; Mashkab, followed by Furat, Yasmen, and Amber 33. On another note, Amber Barka was found to be significantly drought susceptible. Mashkab and Amber Barka were found to be the most drought-tolerant and-susceptible cultivars, respectively. The identified tolerant cultivars may potentially serve as a genetic source for the incorporation of drought-tolerant phenotypes in rice.

Highlights

Rice is the staple food of more than three billion people in the world [1], and it plays a key role in food security in Iraq and different countries [2]
Our results revealed that after 24 h, the Iraqi rice cultivars Yasmen and Mashkab, together with control cultivar Nerica 7, showed the highest and fastest seed germination, attaining 100% germination after 48 h, compared with the rest of the cultivars (Supplementary Figure S1)
The results indicated that the Iraqi rice cultivar Ambar Barka was the most sensitive to PEG-induced drought stress, having a 100% leaf drying area

Summary

Introduction

Rice is the staple food of more than three billion people in the world [1], and it plays a key role in food security in Iraq and different countries [2]. Its growth and production have been adversely affected by different biotic and abiotic factors, especially drought. Different effects occur in plants following stress exposure at different levels, such as molecular, physiological, and biochemical changes, depending on implied factors, including genotype, stress severity, and developmental stage [8,9]. Drought mitigation through developing drought-tolerant varieties with higher yields suitable for water-limiting environments is a key factor in improving production once the average yield drops [11]. Plants show different mechanisms and specific physiologic responses to drought stress including reduced plant growth and productivity, decreased CO2 assimilation, membrane injury and damage of the affected tissues, and in some cases even inhibition of enzyme activity [14].

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