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. 2022 Mar 24:13:832542.
doi: 10.3389/fgene.2022.832542. eCollection 2022.

Impact of Pre-Anthesis Drought Stress on Physiology, Yield-Related Traits, and Drought-Responsive Genes in Green Super Rice

Hassaan Ahmad  1 , Syed Adeel Zafar  1 , Muhammad Kashif Naeem  1 , Sajid Shokat  2 , Safeena Inam  1 , Malik Attique Ur Rehman  1 , Shahzad Amir Naveed  3 , Jianlong Xu  3 , Zhikang Li  3 , Ghulam Muhammad Ali  1 , Muhammad Ramzan Khan  1
Affiliations

Impact of Pre-Anthesis Drought Stress on Physiology, Yield-Related Traits, and Drought-Responsive Genes in Green Super Rice

Hassaan Ahmad et al. Front Genet. .

Abstract

Optimum soil water availability is vital for maximum yield production in rice which is challenged by increasing spells of drought. The reproductive stage drought is among the main limiting factors leading to the drastic reduction in grain yield. The objective of this study was to investigate the molecular and morphophysiological responses of pre-anthesis stage drought stress in green super rice. The study assessed the performance of 26 rice lines under irrigated and drought conditions. Irrigated treatment was allowed to grow normally, while drought stress was imposed for 30 days at the pre-anthesis stage. Three important physiological traits including pollen fertility percentage (PFP), cell membrane stability (CMS), and normalized difference vegetative index (NDVI) were recorded at anthesis stage during the last week of drought stress. Agronomic traits of economic importance including grain yield were recorded at maturity stage. The analysis of variance demonstrated significant variation among the genotypes for most of the studied traits. Correlation and principal component analyses demonstrated highly significant associations of particular agronomic traits with grain yield, and genetic diversity among genotypes, respectively. Our study demonstrated a higher drought tolerance potential of GSR lines compared with local cultivars, mainly by higher pollen viability, plant biomass, CMS, and harvest index under drought. In addition, the molecular basis of drought tolerance in GSR lines was related to upregulation of certain drought-responsive genes including OsSADRI, OsDSM1, OsDT11, but not the DREB genes. Our study identified novel drought-responsive genes (LOC_Os11g36190, LOC_Os12g04500, LOC_Os12g26290, and LOC_Os02g11960) that could be further characterized using reverse genetics to be utilized in molecular breeding for drought tolerance.

Keywords: anthesis; correlation; drought; drought-responsive genes; grain yield; pollen fertility.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
PCA showing biplot for genotypes and studied traits (A) under normal condition and (B) under drought stress condition.
FIGURE 2
FIGURE 2
Effect of drought stress on (A) plant height/plant, (B) tillers/plant, (C) grain yield/plant, and (D) straw yield/plant. Values are means ± SD.
FIGURE 3
FIGURE 3
Effect of drought stress on (A) harvest index/plant, (B) total biomass/plant, (C) 1,000-grain weight, and (D) grain length. Values are means ± SD.
FIGURE 4
FIGURE 4
Frequency distribution of drought susceptibility index for grain yield showing the degree of susceptibility to drought stress. Genotypes below the line are declared as most drought-tolerant genotypes.
FIGURE 5
FIGURE 5
Examination of pollen fertility of the 22 GSR lines and 4 checks with I2-KI solution staining of the mature pollen grains. The sterile pollen grains failed to be stained or stained weakly, indicating that they did not contain starch or contained irregularly distributed starch, whereas the viable pollen grains were stained deep brown. Scale bars are 100 µm.
FIGURE 6
FIGURE 6
Effect of drought stress on (A) pollen fertility percentage, (B) normalized difference vegetative index (NDVI), and (C) cell membrane stability (CMS). Values (except CMS) are means ± SD.
FIGURE 7
FIGURE 7
The scatter matrix below the histogram and correlation coefficient value with p-value above the histogram calculated from the means of all the studied traits under well-watered (WW) environmental condition. The p-values of all correlations were 0.05* and 0.01**.
FIGURE 8
FIGURE 8
The scatter matrix below the histogram and correlation coefficient value with p-value above the histogram calculated from the means of all the studied traits under drought stress condition. The p-values of all correlations were 0.05* and 0.01**.
FIGURE 9
FIGURE 9
(qRT)-PCR analysis of drought-responsive genes in NGSR-3, NGSR-15, and NIAB-IR-9 revealed the relative expression in terms of fold change (log2FC). Young panicle tissues (∼1.5 cm) of three selected genotypes were employed in this analysis. Rice actin gene (OsACT1) was the internal control gene. Values of three biological replicates (n = 3) were expressed as mean ± SD.
FIGURE 10
FIGURE 10
Phenotypic comparison of plants, grain length, and shape (husked and de-husked), pollen viability, and panicle fertility of NGSR-15, NGSR-3, and NIAB-IR-9 under well-watered (WW) and drought stress. Abbreviations: F, fertile spikelets; S, sterile spikelets. White arrow heads denote fertile spikelets and yellow arrow heads denote sterile spikelets. Spikelets with open tips represent sterile spikelets with no seed set. Scale bars are approximately 15 cm (A,G, M), 5 mm (B,C,H,I,N, O), 5 cm (F,L, R), and 50 µm (D,E,J,K,P, Q).
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