Screening of Bread Wheat Genotypes for Drought Tolerance Using Phenotypic and Proline Analyses

Abstract

Drought stress is one of the leading constraints to wheat (Triticum aestivum L.) production globally. Breeding for drought tolerance using novel genetic resources is an important mitigation strategy. This study aimed to determine the level of drought tolerance among diverse bread wheat genotypes using agronomic traits and proline analyses and to establish correlation of proline content and agronomic traits under drought-stress conditions in order to select promising wheat lines for breeding. Ninety-six diverse genotypes including 88 lines from the International Maize and Wheat Improvement Center (CIMMYT)'s heat and drought nurseries, and eight local checks were evaluated under greenhouse and field conditions during 2014/15 and 2015/16 making four testing environments. The following phenotypic traits were collected after stress imposed during the heading to anthesis period: the number of days to heading (DTH), days to maturity (DTM), productive tiller number (TN), plant height (PH), spike length (SL), spikelet per spike (SPS), kernels per spike (KPS), thousand kernel weight (TKW) and grain yield (GY) and proline content (PC). Analysis of variance, Pearson's correlation coefficient, principal component and stress tolerance index were calculated. Genotypes with high yield performance under stressed and optimum conditions maintained high values for yield components. Proline content significantly increased under stress, but weakly correlated with agronomic traits under both optimal and water limited conditions. The positive correlation observed between grain yield and proline content under-drought stress conditions provides evidence that proline accumulation might ultimately be considered as a tool for effective selection of drought tolerant genotypes. The study selected 12 genotypes with high grain yields under drought stressed conditions and favorable adaptive traits useful for breeding.

Variance components and heritability of yield and yield components of wheat under drought-stressed and non-stressed conditions

“…Previous studies identified some of the major QTL encoding for functional genes that control most agronomic traits in wheat under drought-stressed conditions (Spielmeyer et al, 2007;Mathews et al, 2008;Li et al, 2015;Mwadzingeni et al, 2016a). Some of the genetic components affecting plant height could also influence spike length since the two traits are highly correlated, and both have high heritability estimates (Mwadzingeni et al, 2016b). Owing to the high heritability estimates observed in this study, association mapping based on the studied set of germplasm and traits could probably identify genetic determinants influencing these traits under contrasting environments.…”

“…This study partitioned variance components and estimated their influence on heritability values of yield and yield related traits in a set of candidate wheat germplasm. The lines were selected from CIMMYT pre-breeding nurseries for drought and heat tolerance and found to be useful for drought tolerance breeding (Mwadzingeni et al, 2016b). The significant genotypic differences (P < 0.001) observed for the studied traits reflects that the germplasm pool from which the sampled lines were selected contains a broad genetic base (Table 1).…”

“…Generally marked genotypic variation existed among the studied traits, except for the number of days to maturity, number of productive tillers and grain yield that were considerably influenced by the environment. The mean values of traits, the least significant differences (LSD) and the coefficient of variation (CV) were presented by Mwadzingeni et al (2016b). Spike length, number of spikelets per spike, plant height, number of kennels per spike, number of days-to-heading and thousand seed weight had moderate to high genotypic variances (σ 2 g ) of 73%, 44%, 51%, 32.98%, 44.24% and 22.98%, respectively, largely due to genotypic differences, hence, had high heritability estimates above 50% (Table 2).…”

“…These genetic resources were found to be tolerant to drought and heat stresses. The lines were screened for drought tolerances based on phenotypic and proline analyses (Mwadzingeni et al, 2016b). The germplasm needs to be further evaluated for genetic worthiness and selection response towards improved grain yield and it component traits.…”

Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants

“…Thus, a simultaneous increase (or decrease) in T 2 and LWW for a specific water compartment is strong evidence for a change in water content in the cell compartment without taking other mechanisms such as solute concentration or membrane permeability, into account. All of these mechanisms can be affected by water stress, a reduction in the water in the leaf and hence in the vacuoles is a known effect of water stress [25] as is an increase in the concentration of soluble compounds [53]. Moreover, the permeability of the tonoplast increases [54,55] or decreases [56,57] depending on the stress and the species.…”