Morpho-physiological characterization and gene expression profiling of foxtail millet genotypes for waterlogging tolerance at seedling stage
Loading...
Date
2023
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
RPCAU, Pusa
Abstract
The present study entitled “Morpho-physiological characterization and gene expression profiling of foxtail millet genotypes for waterlogging tolerance at seedling stage” was carried out to identify the best screening methodologies for early seedling stage waterlogging tolerance, identification of tolerant genotypes and identification of candidate genes responsible for ameliorating waterlogging tolerance. Altogether, 26 foxtail millet genotypes were used for morpho-physiological characterization and screening at three stages of growth under six different conditions (two in each stage) of waterlogging, to identify the best screening method and tolerant genotypes. The selected highly tolerant and highly susceptible genotypes were used for the gene expression study of the identified candidate genes, to determine their differential expression pattern in leaves under the identified short- and long-term stress conditions.
The screening at germination stage revealed that foxtail millet is vulnerable to waterlogging stress. A significant reduction in the performance of the 26 genotypes evaluated in the present study was observed for both 3 days and 8 days stress conditions. A significant change in the performance of 26 genotypes under 12 h and 24 h waterlogging stress was observed at the seedling establishment stage. The waterlogging tolerance indices, waterlogging tolerance coefficient (WTC), root length stress index(RLSI), shoot length stress index (SLSI) and seed vigour wrt seedling length (SVI), significantly contributed to the variations observed among the genotypes, as revealed by Principal Component Analysis (PCA) and were found to be significantly correlated. A significant reduction in these parameters during 12 h stress suggests that even 12h of flooding at seedling establishment stage causes waterlogging stress in foxtail millet.The grouping of the genotypes based on WTC values, identified 4 genotypes (IIMR FxM-7, SiA-4245, GPUF-17) to be highly tolerant, 6 susceptible (CRS FxM-4, SiA-4243, ST.4, ST.5, ST.7 and RK.1) and 16 tolerant. The cluster analysis based on Euclidean distances using UPGMA method grouped the genotypes into five clusters at 40 phenon level. The genotypes RK.1 and ST.4 were present in mono-genotypic clusters. The screening of the selected 14 genotypes at seedling stage showed significant variations in all the six observed morphological characters for 3 days and 6 days stress conditions. A significant variation in physio-biochemical parameters were observed under both stress conditions. An overall reduction in chlorophyll A and total chlorophyll was observed, while value of chlorophyll B showed increase during 3-day stress and decrease 6-day stress. The proline content showed significant reduction while peroxidase activity showed an average increase during 5 day stress. It was notable that the changes in susceptible genotypes were more drastic than tolerant genotype. The performance of the genotype IIMR FxM-7 was found to be the best for both the stress conditions while genotype ST.5 showed poor performance was selected as highly susceptible genotype. The cluster analysis grouped all the susceptible genotypes in a single cluster while the highly tolerant genotype IIMR FxM-7 was present in single mono-genotypic cluster, indicating the effectiveness of this method of characterization in identification of waterlogging tolerant genotypes. The results of all the screening methods concluded that the 12 h waterlogging is short term stress for foxtail millet while 3 days is threshold for early seedling stage.
The in-silico candidate gene search identified 14 candidate genes having probable role in waterlogging tolerance in foxtail millet. Most of the genes belong to ERF, WRKY and RBOHB gene family. The gene expression analysis of the selected five genes (SiRAP 2.2, SiRBOHB, SiRAP2.3, SiRAP2.12 and SiEREB180) in the leaves for tolerant and susceptible genotype under 12 h and 3 days stress revealed differential expression pattern suggesting a role of these genes in waterlogging tolerance mechanism in foxtail millet. The findings provide a fundamental clue for further cloning, characterization and functional analysis of other genes to help understand the molecular mechanism of waterlogging tolerance in foxtail millet.