Introgression of Maize Diversity for Drought Tolerance: Subtropical Maize Landraces as Source of New Positive Variants

Current climate change models predict an increased frequency and intensity of drought for much of the developing world within the next 30 years. These events will negatively affect maize yields, potentially leading to economic and social instability in many smallholder farming communities. Knowledge about the genetic resources available for traits related to drought tolerance has great importance in developing breeding program strategies. The aim of this research was to study a maize landrace introgression panel to identify chromosomal regions associated with a drought tolerance index. For that, we performed Genome-Wide Association Study (GWAS) on 1326 landrace progenies developed by the CIMMYT Genetic Resources Program, originating from 20 landraces populations collected in arid regions. Phenotypic data were obtained from early testcross trials conducted in three sites and two contrasting irrigation environments, full irrigation (well-watered) and reduced irrigation (drought). The populations were genotyped using the DArTSeq® platform, and a final set of 5,695 SNPs markers was used. The genotypic values were estimated using spatial adjustment in a two-stage analysis. First, we performed the individual analysis for each site/irrigation treatment combination. The best linear unbiased estimates (BLUEs) were used to calculate the Harmonic Mean of Relative Performance (HMRP) as a drought tolerance index for each testcross. The second stage was a joint analysis, which was performed using the HMRP to obtain the best linear unbiased predictions (BLUPs) of the index for each genotype. Then, GWAS was performed to determine the marker-index associations and the marker-Grain Yield (GY) associations for the two irrigation treatments. We detected two significant markers associated with the drought-tolerance index, four associated with GY in drought condition, and other four associated with GY in irrigated conditions each. Although each of these markers explained less than 0.1% of the phenotypic variation for the index and GY, we found two genes likely related to the plant response to drought stress. For these markers, alleles from landraces provide a slightly higher yield under drought conditions. Our results indicate that the positive diversity delivered by landraces are still present on the backcrosses and this is a potential breeding strategy for improving maize for drought tolerance and for trait introgression bringing new superior allelic diversity from landraces to breeding populations.

Screening of Blackgram Genotypes for Drought Tolerance using PEG (Polyethylene Glycol) Induced Drought Stress at Seedling Stage

Background: Drought is one of the abiotic factor. It is considered to be a moderate loss of water. Water is main source involving for all activities of plant growth throughout the crop plants. Seed germination is considered as one of the first and foremost fundamental life stages of a plant, where the success in growth and yield is also depending on this stage. Methods: An experiment was conducted in order to study the effect of different concentrations (i.e., 0, 10, 20 and 30%) of polyethylene glycol (PEG) stress on germination and early growth stages of 28 genotypes of black gram. Different germination indices such as germination percent, radical length, plumule length, along with drought parameters like drought tolerance index was measured. Conclusion: Results showed significant differences among the cultivars at each drought stress level and significant decrease was observed in germination, length of radical and plumule and radical and plumule dry matter parameters, among all the genotypes genotypes Nirmal 7, NRIB 002, MDU 1, VBN 8 and NUL 7 VISWAS showed their efficiency in terms of germination and germination attributes to with stand to the drought conditions.

"Evaluation of The Performance of Genotypes of Bread Wheat ( Triticum Aestivum L.) for Drought Tolerance Using Drought Indexes and Analysis of Multiple Variables "

"ltural Research Ministry of Agriculture several drought indexes have been used to determine the best genotypes of (Triticum eastivum L.) for drought tolerance in the central region of Iraq, Determination of the efficacy of drought indexes for knowledge the genotypes of drought-tolerant and susceptibility and interpretation of the relationship between drought index used by primary component analysis, cluster analysis and rank sum. experiment was conducted to investigate water stress effect for the some traits of selected genotypes, using split plot arrangement within RCBD with 3 replications. The main plots included 2 levels of water stress (20% and 80%) depletion of available water while, the 9th selected genotypes and the control variety IPA99 occupied sub plots. The use of the best index of drought tolerance, MP, GMP and STI, led to the diagnosis of tolerant and stress-sensitive genotypes due to their association with grain yield in both stress and irrigation (YS and YP), The results of drought tolerance index showed that genotypes 186, 179 and 45 were the most tolerant of drought, while genotypes IPA 99, 117, 27 and 17 were the most sensitive to water stress and the other genotypes 44, 129, 147, middle tolerance or water stress sensitivity, Therefore, we recommend the cultivation of genotypes 186, 179 and 45 in the central region as they are most resistant to drought"

Loci discovery, network-guided approach, and genomic prediction for drought tolerance index in a multi-parent advanced generation intercross (MAGIC) cowpea population

Cowpea is a nutrient-dense legume that significantly contributes to the population’s diet in sub-Saharan Africa and other regions of the world. Improving cowpea cultivars to be more resilient to abiotic stress such as drought would be of great importance. The use of a multi-parent advanced generation intercross (MAGIC) population has been shown to be efficient in increasing the frequency of rare alleles that could be associated with important agricultural traits. In addition, drought tolerance index has been reported to be a reliable parameter for assessing crop tolerance to water-deficit conditions. Therefore, the objectives of this study were to evaluate the drought tolerance index for plant growth habit, plant maturity, flowering time, 100-seed weight, and grain yield in a MAGIC cowpea population, to conduct genome-wide association study (GWAS) and identify single nucleotide polymorphism (SNP) markers associated with the drought tolerance indices, to investigate the potential relationship existing between the significant loci associated with the drought tolerance indices, and to conduct genomic selection (GS). These analyses were performed using the existing phenotypic and genotypic data published for the MAGIC population which consisted of 305 F8 recombinant inbred lines (RILs) developed at University of California, Riverside. The results indicated that: (1) large variation in drought tolerance indices existed among the cowpea genotypes, (2) a total of 14, 18, 5, 5, and 35 SNPs were associated with plant growth habit change due to drought stress, and drought tolerance indices for maturity, flowering time, 100-seed weight, and grain yield, respectively, (3) the network-guided approach revealed clear interactions between the loci associated with the drought tolerance traits, and (4) the GS accuracy varied from low to moderate. These results could be applied to improve drought tolerance in cowpea through marker-assisted selection (MAS) and genomic selection (GS). To the best of our knowledge, this is the first report on marker loci associated with drought tolerance indices in cowpea.

The response of garden pea cultivars to simulated drought

This study aimed to estimate genetic variability among four pea cultivars and determine seed physiological quality and initial growth of garden pea (Pisum sativum L.) under drought stress. Seeds of the pea cultivars were subjected to water stress induced by polyethylene glycol PEG 6000 at three stress levels (0; -0.15; -0.49, and -1.03 MPa). The experiment was conducted under laboratory conditions, in a completely randomized design with four replications, to estimate germination energy, germination, abnormal seedlings, fresh and dry shoot and root biomass, and drought tolerance index. Drought stress significantly affected germination and the other traits, with the stress effects being proportional to the stress level applied. Findings point to the fact that the osmotic potential of -0.49 MPa might be the germination sensitivity threshold for pea cultivars. The pea cultivar C1 was the most tolerant, having the highest germination, fresh and dry shoot and root biomass, and DTI under severe drought stress. Further research on the assessment of physiological and biochemical responses to drought stress is needed to confirm the findings of the present study.

DROUGHT TOLERANCE OF THE NEW SELF-POLLINATED LINES OF MAIZE AND THE METHODS OF ITS ESTIMATION

More than half of the maize crops in the Russian Federation are located in areas with insufficient and unstable moisture. With this in mind, Z. mays breeding for drought tolerance is extremely important. The purpose of the current study is: investigate the drought tolerance of self-pollinated maize lines by various methods, identify the best samples for further breeding, establish indirect criteria for estimating drought tolerance. The study was conducted at the Agricultural Research Center “Donskoy” located in the southern part of the Rostov region, which is characterized by unstable moisture. The years of the study turned out to be dry (Selyaninov Hydrothermal Coefficient (HTC) = 0.32–0.89). The new self-pollinated lines of maize were used as initial material and studied for resistance to water stress (41 pcs. in 2011–2013, 39 pcs. in 2015–2017, 25 pcs. in 2018–2020). According to the guidelines for maize breeding, the following indicators of productivity were taken into account: number of ears per plant, weight of one ear, 1000-grain weight, number of grains per ear, etc. In 2011–2013, based on the comprehensive estimation, new middle-early drought-tolerant self-pollinated lines of maize ‘DK47111’, ‘SP203’, ‘KS211’, ‘S204’ and ‘S238’ were identified. They were characterized by the low values of residual water deficit both in the flowering (6.9 – 12.8%) and milk-wax (9.0 – 13.4%) stage, high drought tolerance index (68.6 – 85.6%), deep root system (force of uprooting the plants from the ground was 54.0–67.7 kgf), minimum gap in the flowering of male and female inflorescences (1–2 days). In 2015–2017, according to the method of residual water deficit (RWD), the following lines were identified ‘KV334’, ‘RD6’, ‘DS498/217-4’, ‘DS257/85-3’, ‘DS257/85-1’, ‘DS257/85-6’, ‘DS257/85-4’. In 2018–2020, the new self-pollinated lines of maize ‘KS317A’, ‘KV240’, ‘LSh16’, ‘S86’, ‘LSh17’ and ‘LSh2’ showed high resistance to water stress. We recommend the following selection criteria when creating new lines: absence of infertility and kernel percentage of the ears.

Metal-Based Nanoparticles Enhance Drought Tolerance in Soybean

Drought is a major abiotic stress that negatively impacts plant growth and crop production. Among various techniques used to alleviate drought stress in plants, nanoparticle application is considered to be effective and promising. In this study, the responses of plants treated with iron, copper, cobalt, and zinc oxide nanoparticles (NPs) were analyzed in soybean under drought-induced conditions. The obtained results indicated that these metal-based NPs supported the drought tolerance of NP-treated plants. The desired physiological traits, viz., relative water content, drought tolerance index, and biomass reduction rate, were significantly improved, especially in iron NP-treated plants. At the molecular level, quantitative PCR analysis of several drought-responsive genes revealed a gene-, tissue-, and NP-dependent upregulation of gene expression. Iron NP treatment promoted the expression of all tested genes in roots; additionally, the expression of three drought-responsive genes increased in leaves of all NP-treated plants, while the expression of GmERD1 (Early Responsive to Dehydration 1) was induced in both roots and shoots under the four NP treatments tested. Our findings suggest that NP application can improve drought tolerance of soybean plants by triggering drought-associated gene expression.

ABA analogue produced by Bacillus marisflavi modulates the physiological response of host-plant under drought stress

ABSTRACTPresent study aims to understand the molecular mechanism involved in beneficial rhizobacteria mediated alleviation of drought stress in host plant. Bacillus marisflavi CRDT-EB-1 isolated from the rhizosphere soil was found effective in inducing resistance against drought stress in mustard seedlings. Among the different bacterial derivatives tested, the culture filtrate was found to contain bioactive molecules. Solvent extract of bacterial culture filtrate yielded seven distinct bands/ fractions on thin layer chromatography (TLC). The fraction four (F4) with Rf value 0.35-0.40 was significant in reducing adverse effect of drought stress in host plants. Application of F4 resulted in delayed drooping point and higher drought tolerance index (3.34), induced stomatal closure (9.648 μ), seed germination inhibition (12%), and reduced the GA3 induced α-amylase activity in germinating barley seeds. On TLC, F4 turned colorless to orange color upon the spray of 2,4-dinitrophenylhydrazine reagent indicated the presence of aldehyde group. Supporting to this, the peaks between 9.8 to 10.0 ppm in 1H-NMR chromatogram confirmed the presence of aldehyde group. Upon LC-MS/MS analysis of crude extract of culture filtrate and F4 revealed the presence of compounds with the molecular mass 250.33 and 266.33. By analyzing these data, the identity of the bioactive compounds were predicted as xanthoxin and xanthoxic acid, which are well-known precursor of Abscisic acid (ABA) in plants. The present study concludes the capability of ABA analogue (xanthoxin like compounds) production by B. marisflavi CRDT-EB-1 and its involvement in inducing drought stress tolerance in the host plant.

Assessment of Selected Landrace and Improved Groundnut (Arachis hypogaea L.) Genotypes under Stressed and Non-stressed Conditions

Drought is one of the most essential and critical abiotic restraints to groundnut production and yields in the Northern Region of Ghana. A field experiment was conducted to assess selected landrace and improved groundnut genotypes for agronomic performance in the 2017 and 2018 minor seasons. Groundnut genotypes were treated under normal irrigation (W/W) and water-stressed (W/S) conditions. A Randomized Completely Block Design (RCBD) with four replications was adopted. Total experimental area was 23.4m x 2.4 m with a planting distance of 40 cm x 20 cm for both environments. Data collected include; days to 50% emergence and flowering, plant height at maturity (cm), growth appearance, days to maturity, number of pods/plot, number of seeds/plot, pod weight (g), seed weight (g), fresh and dry biomass weights (g), SPAD chlorophyll meter reading at 60 and 80 days after planting, harvest index (HI) and drought tolerance index (DTI). The data were subjected to analysis of variance (ANOVA) using GenStat, version 12.0, Exploratory Analysis, descriptive Statistics (mean comparison of plant characteristics by varieties at 5% level using Tukey’s groups) was conducted; Correlation Analysis and Multivariate Analyses were performed using the Wilk’s Lambda to test for significant difference at 5% and 1% levels respectively. Means were separated using S.E.D. of means at 95% confidence level. Results from the growth features indicated a higher percentage of the groundnut varieties sprouted earlier under well-watered conditions. There was no significant difference among the groundnuts regarding the numbers of days to flowering. The groundnuts took approximately 104 days after planting to mature under both water conditions. Chlorophyll content and distribution in the groundnut leaves was high the well-watered plants. The chlorophyll content among the groundnut crops showed no significant difference between the chlorophyll content at 60-days after planting and 80-days after planting under the water-stressed condition. However, chlorophyll content of leaves at the 60-days after planting was 2.94 lower than that under 80 days after planting. Maturity and flowering (0.768), as well as plant height and seed yield (0.501) were highly significantly and highly positively correlated. The seed characteristics were also highly, significantly and positively correlated with the pod characteristics of the crop. The biomass measure also correlated with the pod and seed traits. Groundnuts genotypes under well-watered environment generally performed better in terms of yield than those under water-stressed environment.

Relationships between Nutrient Uptake and Nitrogen Fixation with Aflatoxin Contamination in Peanut under Terminal Drought

Terminal drought greatly enhanced Aspergillus flavus Link infection (AI) and aflatoxin contamination (AC) in peanut. Identification of new surrogate traits which have an association with AC may be effective to improve peanut varieties with reduced AI and AC. The objective of this work was to examine the relationships of nutrient uptake and N2-fixation (NF) with AC in peanut in a terminal drought condition. Five peanut varieties were tested in well-watered (WW) and terminal drought (TD) conditions (1/3 available water (AW) from R7 (7th reproductive growth stage; beginning of pod maturity stage)). Data were collected for nutrient uptake (nitrogen, phosphorus, potassium, calcium, magnesium), nodule dry weight (NDW), and NF. AI and AC were also examined. Nutrient uptake, NDW, and NF had negative and significant correlations with AI and AC in the TD condition. Negative and significant correlations of the drought tolerance index of nutrient uptake, NDW, and NF with AI and AC were also observed in the TD condition. The results showed that the ability to maintain nutrient uptake and NF in TD might be a mechanism of tolerance to AI and AC. Moreover, due to their negative impacts on AI and AC, nutrient uptake and NF could be used as selection traits for resistance to AI and AC in peanut in TD.