Physio-Morphological and Biochemical Trait-Based Evaluation of Ethiopian and Chinese Wheat Germplasm for Drought Tolerance at the Seedling Stage

Zn Fertilizer and Mycorrhizal Inoculation Effect on Bread Wheat Cultivar Grown under Water Deficit

During drought stress, many enzymes are inactivated in plants due to Zn deficiency. Zn application and arbuscular mycorrhiza fungi (AMF)-wheat symbiosis reportedly improve the tolerance of plants to drought stress. This study was done to investigate the effect of Zn and AMF on plant growth, yield attributes, relative water content (RWC), harvest index (HI), photosynthetic activity, solute accumulation, glycine betaine (GB) accumulation, antioxidant activities [(catalase (CAT) and superoxide dismutase (SOD)], and ionic attributes in a bread wheat cultivar (SST806) under drought-stress in plants grown under greenhouse conditions. Zn application and AMF inoculation, separately and combined, enhanced all plant growth parameters and yield. Root dry weight (RDW) was increased by 25, 30, and 46% for these three treatments, respectively, under drought conditions compared to the control treatment. Overall, Zn application, AMF inoculation, and their combination increased protein content, RWC, and harvest index (HI) under drought stress. However, AMF inoculation improved proline content more than Zn application under the same conditions. Regarding GB accumulation, AMF, Zn, and the combination of Zn and AMF increased GB under drought compared to well-watered conditions by 31.71, 10.36, and 70.70%, respectively. For the antioxidant defense, AMF inoculation and Zn application improved SOD and CAT activity by 58 and 56%, respectively. This study showed that Zn and/or AMF increased antioxidant levels and ionic attributes under abiotic stress.

Photosynthetic activity and metabolic profiling of bread wheat cultivars contrasting in drought tolerance

The rapid increase in population growth under changing climatic conditions causes drought stress, threatening world food security. The identification of physiological and biochemical traits acting as yield-limiting factors in diverse germplasm is pre-requisite for genetic improvement under water-deficit conditions. The major aim of the present study was the identification of drought-tolerant wheat cultivars with a novel source of drought tolerance from local wheat germplasm. The study was conducted to screen 40 local wheat cultivars against drought stress at different growth stages. Barani-83, Blue Silver, Pak-81, and Pasban-90 containing shoot and root fresh weight >60% of control and shoot and root dry weight >80% and 70% of control, respectively, P (% of control >80 in shoot and >88 in root), K⁺ (>85% of control), and quantum yield of PSII > 90% of control under polyethylene glycol (PEG)-induced drought stress at seedling stage can be considered as tolerant, while more reduction in these parameters make FSD-08, Lasani-08, Punjab-96, and Sahar-06 as drought-sensitive cultivars. FSD-08 and Lasani-08 could not maintain growth and yield due to protoplasmic dehydration, decreased turgidity, cell enlargement, and cell division due to drought treatment at adult growth stage. Stability of leaf chlorophyll content (<20% decrease) reflects photosynthetic efficiency of tolerant cultivars, while ~30 µmol/g fwt concentration of proline, 100%-200% increase in free amino acids, and ~50% increase in accumulation of soluble sugars were associated with maintaining leaf water status by osmotic adjustment. Raw OJIP chlorophyll fluorescence curves revealed a decrease in fluorescence at O, J, I, and P steps in sensitive genotypes FSD-08 and Lasani-08, showing greater damage to photosynthetic machinery and greater decrease in JIP test parameters, performance index (PI_ABS), maximum quantum yield (Fv/Fm) associated with increase in Vj, absorption (ABS/RC), and dissipation per reaction center (DIo/RC) while a decrease in electron transport per reaction center (ETo/RC). During the present study, differential modifications in morpho-physiological, biochemical, and photosynthetic attributes that alleviate the damaging effects of drought stress in locally grown wheat cultivars were analyzed. Selected tolerant cultivars could be explored in various breeding programs to produce new wheat genotypes with adaptive traits to withstand water stress.

Screening Bambara Groundnut (Vigna subterranea L. Verdc) Genotypes for Drought Tolerance at the Germination Stage under Simulated Drought Conditions

Bambara groundnut (Vigna subterranea L. Verdc) is grown by smallholders and subsistence farmers in the marginal parts of sub-Saharan Africa. This legume is native to Africa and is cultivated throughout semi-arid sub-Saharan Africa. It is hardy and has been recognized as a nutritious food source in times of scarcity. Drought can negatively affect the germination or establishment of seedlings in the early stages of crop growth. Drought can limit the growing season of certain crops and create conditions that encourage the invasion of insects and diseases. Drought can also lead to a lack of crop yield, leading to rising food prices, shortages, and possibly malnutrition in vulnerable populations. A drought-tolerant genotype can be identified at the germination stage of Bambara groundnut by screening for drought-tolerance traits, and this knowledge can be applied to Bambara crop improvement programs to identify drought-tolerant traits during early growth phases. As an osmolyte, polyethylene glycol (PEG 6000) reduced water potential and simulated drought stress in Bambara groundnut seeds of different genotypes. Osmolytes are low-molecular-weight organic compounds that influence biological fluid properties. In this study, 24 Bambara groundnut genotypes were used. Data were collected on seed germination percentage (G%), germination velocity index (GVI), mean germination time (MGT), root dry mass (RDM), root fresh mass (RFM), and seven drought tolerance indices: mean productivity (MP), tolerance index (TOL), geometric mean productivity (GMP), stress susceptibility index (SSI), yield index (YI), yield stability index (YSI), stress tolerance index (STI) as well as seed coat color measurements. The data were applied to the mean observation of genotypes under simulated drought conditions (Ys) and the mean observation of genotypes under controlled conditions (Yp). Germination%, germination velocity index (GVI), mass germination time (MGT), and root fresh mass (RFM) differed significantly (p < 0.001) between the two stress conditions. Bambara genotypes Acc 82 and Acc 96 were found to be the most drought-tolerant.

Impression of foliar-applied folic acid on coriander (Coriandrum sativum L.) to regulate aerial growth, biochemical activity, and essential oil profiling under drought stress

Drought is one of the major environmental limitations in the crop production sector that has a great impact on food security worldwide. Coriander (Coriandrum sativum L.) is an herbaceous angiosperm of culinary significance and highly susceptible to rootzone dryness. Elucidating the drought-induced physio-chemical changes and the foliar-applied folic acid (FA; vitamin B9)-mediated stress tolerance mechanism of coriander has been found as a research hotspot under the progressing water scarcity challenges for agriculture. The significance of folic acid in ameliorating biochemical activities for the improved vegetative growth and performance of coriander under the mild stress (MS75), severe stress (SS50), and unstressed (US100) conditions was examined in this study during two consecutive seasons. The results revealed that the plants treated with 50 mM FA showed the highest plant fresh biomass, leaf fresh biomass, and shoot fresh biomass from bolting stage to seed filling stage under mild drought stress. In addition, total soluble sugars, total flavonoids content, and chlorophyll content showed significant results by the foliar application of FA, while total phenolic content showed non-significant results under MS75 and SS50. It was found that 50 mM of FA upregulated the activity of catalase, superoxide dismutase, and ascorbate peroxidase enzymes in MS75 and SS50 plants compared with untreated FA plants. Thus, FA treatment improved the overall biological yield and economic yield regardless of water deficit conditions. FA-accompanied plants showed a decline in drought susceptibility index, while it improved the drought tolerance efficiency, indicating this variety to become stress tolerant. The optimum harvest index, essential oil (EO) percentage, and oil yield were found in MS75 followed by SS50 in FA-supplemented plants. The gas chromatography-mass spectrometry analysis revealed a higher abundance of linalool as the major chemical constituent of EO, followed by α-terpeniol, terpinene, and p-Cymene in FA-treated SS50 plants. FA can be chosen as a shotgun tactic to improve drought tolerance in coriander by delimiting the drastic changes due to drought stress.

Screening and identification of drought tolerance of spring soybean at seedling stage under climate change

Drought is one of the major abiotic stress factors limiting soybean growth and yield, and it frequently occur globally. Therefore, exploring resistant varieties from soybean germplasm is important under climate change. To screen drought resistant spring soybean varieties at seedling stage, pot experiment was used to detect the Survival percentage after drought stress of 60 soybean varieties at seedling stage, twice drought rehydration treatments on seedlings, to evaluate the drought tolerance of spring soybean. The results showed that at the seedling stage, seven varieties were considered drought tolerant, 17 varieties were considered drought sensitive, and 36 varieties were considered to be moderately drought tolerant. Based on this experiment, number 44 (heinong37), 48 (heinong44), 49 (heinong45), 52 (heinong48) is considered the best drought resistant, and number 3 (dongnong48), 4 (dongnong52), 27 (suinong25), 60 (heinong65) is the most sensitive. These varieties provide a reference for further study on drought tolerance and stress resistance gene screening of soybean at the molecular level. The selected soybean varieties can be planted in areas with suitable climates and frequent drought to meet the local soybean demand. In other regions, although cannot be directly grown, they can still be used as parents of selected varieties or as materials for gene screening and extraction, to assist crop breeding at the molecular level in response to increasingly severe drought stress problems under the current climate trends.

Bread Wheat (Triticum aestivum) Responses to Arbuscular Mycorrhizae Inoculation under Drought Stress Conditions

Abiotic constraints such as water deficit reduce cereal production. Plants have different strategies against these stresses to improve plant growth, physiological metabolism and crop production. For example, arbuscular mycorrhiza (AM)—bread wheat association has been shown to improve tolerance to drought stress conditions. The objective of this study was to determine the effect of AM inoculation on plant characteristics, lipid peroxidation, solute accumulation, water deficit saturation, photosynthetic activity, total phenol secretion and enzymatic activities including peroxidise (PO) and polyphenol oxidase (PPO) in two bread wheat cultivars (PAN3497 and SST806) under well-watered and drought-stressed conditions in plants grown under greenhouse conditions, to determine whether AM can enhance drought tolerance in wheat. AM inoculation improved morphological and physiological parameters in plants under stress. The leaf number increased by 35% and 5%, tiller number by 25% and 23%, chlorophyll content by 7% and 10%, accumulation of soluble sugars by 33% and 14%, electrolyte leakage by 26% and 32%, PPO by 44% and 47% and PO by 30% and 37% respectively, in PAN3497 and SST806, respectively. However, drought stress decreased proline content by 20% and 24%, oxidative damage to lipids measured as malondialdehyde by 34% and 60%, and total phenol content by 55% and 40% respectively, in AM treated plants of PAN3497 and SST806. PAN3497 was generally more drought-sensitive than SST806. This study showed that AM can contribute to protect plants against drought stress by alleviating water deficit induced oxidative stress.