Comparative Proteome Analysis of the Penultimate Internodes of Barley Genotypes Differing in Stem Reserve Remobilization Under Drought Stress

Barley yield relies more on stem reserves under stress conditions at the grain filling stage. At terminal drought stresses, the remobilization of reserved assimilates from stem to seed contributes a major role in yield. To understand the molecular mechanism of stem reserve utilization during drought stress, a comparative proteome and physiological analyses were performed on the penultimate internodes of three genotypes of barley Yousef (tolerant), Morocco (susceptible), and PBYT17 (semi-tolerant) under drought stress at 21 and 28 days after anthesis (DAA). Under water stress and well-watered conditions Yousef showed significantly higher RWC, grain yield, and stem reserve remobilization capacity than susceptible and semi-tolerant genotypes. The proteome analysis led to the identification of 1580 differentially abundant proteins (DAPs), of which 759 and 821 proteins were differentially expressed at 21 and 28 DAA, respectively. Tolerant genotype in response to drought stress increased the abundance of several plant cell wall polysaccharide degradation proteins and protein kinases associated with posttranslational-associated, which might accelerate remobilization process for seed biomass formation compared to susceptible one under drought stress. However, the susceptible genotype increased the abundance of proteins involved in RNA metabolism and transcriptional changes to save energy sources for the growth and survival during drought stress. These findings suggest that barley might response to water stress by efficiently remobilize assimilates from stem to grain through specific remobilization processes.

Identifying Traits Associated With Terminal Drought Tolerance in Sesame (Sesamum indicum L.) Genotypes

Sesame is predominantly cultivated in rainfed and low fertile lands and is frequently exposed to terminal drought. Sesamum species inhabiting dryland ecosystems adaptively diverge from those inhabiting rainfed habitats, and drought-specific traits have a genetic basis. In sesame, traits associated with drought conditions have not been explored to date, yet studies of these traits are needed given that drought is predicted to become more frequent and severe in many parts of the world because of climate change. Here, 76 accessions from the available Indian core set were used to quantify variation in several traits under irrigated (WW) and terminal drought stress (WS) conditions as well as their association with seed yield over two consecutive years. The range of trait variation among the studied genotypes under WW and WS was significant. Furthermore, the traits associated with seed yield under WW and WS differed. The per se performance of the accessions indicated that the expression of most traits was reduced under WS. The correlation analysis revealed that the number of branches, leaf area (LA), leaves dry weight (LDW), number of capsules plant–1, and harvest index (HI) were positively correlated with seed yield under WW and WS, and total dry matter (TDM), plant stem weight, and canopy temperature (CT) were negatively correlated with seed yield under WW and WS, indicating that smaller and cooler canopy genotypes had higher yields. The genotypes IC-131936, IC-204045, IC-204861, IC-205363, IC-205311, and IC-73576 with the highest seed yields were characterized by low canopy temperature, high relative water content, and high harvest index under WS. Phenotypic and molecular diversity analysis was conducted on genotypes along with checks. Phenotypic diversity was assessed using multivariate analysis, whereas molecular diversity was estimated using simple sequence repeat (SSR) loci to facilitate the use of sesame in breeding and genetic mapping. SSRs showed low allelic variation, as indicated by a low average number of alleles (2.31) per locus, gene diversity (0.25), and polymorphism information content (0.22). Cluster analysis (CA) [neighbor-joining (NJ) tree] revealed three major genotypic groups and structure analysis showed 4 populations. The diverse genotypes identified with promising morpho-physiological traits can be used in breeding programs to develop new varieties.

Screening and Validation of Drought Tolerance and Fusarium Wilt Resistance in Advance Breeding Lines of Chickpea (Cicer arietinum L.)

Background: Approximately 90% of the world’s chickpea is grown under rainfed conditions where terminal drought is one of the major constraints limiting productivity. The need of short-duration, Fusarium wilt tolerant cultivars/elite lines and able to escape drought due to early maturity were required. Methods: The present investigation was carried out using 54 genotypes, generated from six diverse crosses, along with ten checks (resistant/tolerance, susceptible) were screened against drought and Fusarium wilt at Zonal Agricultural Research Station, Kalaburagi, Karnataka (Latitude: 17.36 and Longitude: 76.82) during crop season 2018-19. Result: The results revealed that higher PCV, GCV, heritability, percent genetic advance were exhibited by number of pods per plant and seed yield per plot, whereas lower PCV, GCV recorded for days to 50% flowering and days to maturity in both normal and late sown conditions. The advanced breeding lines viz., KCD-8, KCD-24, KCD-28, KCD-32, KCD-37 and KCD-53 were identified as drought tolerant lines based on drought tolerant indices (viz., MP, YSI, DTE and DSI). The lines KCD-48 and KCD-32 were identified as Fusarium wilt resistance with lowest PDI of 1.47 and 2.46 respectively, as they were screened in wilt sick plot and further these were validated and confirmed the resistant alleles using two unpublished SNP markers (FW2_30366110 and FW2_30365816). The advanced breeding lines KCD-32 and KCD-37 were identified as drought tolerant and Fusarium wilt resistant.

Combined application of zinc and silicon alleviates terminal drought stress in wheat by triggering morpho-physiological and antioxidants defense mechanisms

Wheat is an important global staple food crop; however, its productivity is severely hampered by changing climate. Erratic rain patterns cause terminal drought stress, which affect reproductive development and crop yield. This study investigates the potential and zinc (Zn) and silicon (Si) to ameliorate terminal drought stress in wheat and associated mechanisms. Two different drought stress levels, i.e., control [80% water holding capacity (WHC) was maintained] and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar-applied Zn-Si combinations (i.e., control, water spray, 4 mM Zn, 40 mM Si, 4 mM Zn + 40 mM Si applied 7 days after the initiation of drought stress). Results revealed that application of Zn and Si improved chlorophyll and relative water contents under well-watered conditions and terminal drought stress. Foliar application of Si and Zn had significant effect on antioxidant defense mechanism, proline and soluble protein, which showed that application of Si and Zn ameliorated the effects of terminal drought stress mainly by regulating antioxidant defense mechanism, and production of proline and soluble proteins. Combined application of Zn and Si resulted in the highest improvement in growth and antioxidant defense. The application of Zn and Si improved yield and related traits, both under well-watered conditions and terminal drought stress. The highest yield and related traits were recorded for combined application of Zn and Si. For grain and biological yield differences among sole and combined Zn-Si application were statistically non-significant (p>0.05). In conclusion, combined application of Zn-Si ameliorated the adverse effects of terminal drought stress by improving yield through regulating antioxidant mechanism and production of proline and soluble proteins. Results provide valuable insights for further cross talk between Zn-Si regulatory pathways to enhance grain biofortification.

CAMTA1 Transcription Factor Regulates Salinity And Drought Tolerance In Chickpea (Cicer arietinum L.)

Various abiotic stresses like drought, salinity, high temperature, and chilling adversely affect plant growth and productivity. Terminal drought stress is one of the major concerns which limits the growth and yield of chickpea. CAMTA (Calmodulin binding transcription activator) plays a vital role in stress tolerance in plants. In this study, we have selected a CAMTA1 gene to explore its role against salinity and drought stress in an economically important crop, chickpea (Cicer arietinum L.). CAMTA1 gene was then over-expressed in chickpea and was exposed to drought and salinity. The over-expression of CAMTA1 enhanced the activities of various antioxidant enzymes (ascorbate peroxidase; APX, catalase: CAT, glutathione S-transferase; GST, superoxide dismutase; SOD, monodehydroascorbate reductase; MDHAR). The reduced stress markers TBARS and H2O2 enhanced the survival of plants against both stresses. The physiological parameters (net photosynthesis; PN, transpiration; E, stomatal conductance; gs, photochemical quenching; qP, non-photochemical quenching; qN, and electron transport rate; ETR) were improved in the transgenics under both the stresses, that protected the plants from damage. This investigation verified that the CAMTA1 gene provides tolerance against drought and salinity by maintaining biochemical, physiological, and morphological performances, and could be exploited for genetic engineering strategies to overcome the stresses in other economically important crops.

Adaptation of Grain Legumes to Terminal Drought after Rice Harvest in Timor-Leste

In Timor-Leste, most paddy fields are abandoned after rice harvest due to limited water resources for another rice production cycle, particularly in lowland coastal areas. There is substantial scope for including legumes and other crops in the rice–fallow system in Timor-Leste. This study investigated the adaptation of grain legumes to terminal drought. The experiment was undertaken in 2018 and 2019 at field sites in Vemase and Laleia, respectively, on the northeast coast of Timor-Leste. The experiments used a split-plot design with two factors (water treatment and species) and three blocks (Vemase site) or four blocks (Laleia site). In 2018, the water treatments were well-watered control (W0), water withheld from flower initiation to maturity (W1), and water withheld after seedling establishment to maturity (W2). In 2019, the water treatments were well-watered control (W0) and water withheld from flower initiation to maturity (W1). Grain legumes were mungbean and soybean tested against grass pea (cv. Ceora), a well-known drought-adapted grain legume. The measured parameters included soil water content, crop phenology, plant growth and development, yield and yield components. The experiments revealed that mungbean is the most suitable grain legume crop after rice harvest under moderate drought conditions, while soybean is the preferred option under severe drought. Grass pea could be the best adaptive grain legume under severe drought in Timor-Leste when combined with the worsening conditions of climate change.