Search

Drought stress is one of the most important factors of physiological stress and the major constraint on crop productivity which limits plant growth and metabolism. The goal of this work was to study the differential response of groundnut genotypes to drought stress at the physiological, biochemical, and molecular levels during summer in the field. Thirty days old seedlings of six genotypes of groundnut viz. Kadiri 9, Narayani, Dharani, JL24, TPT-3, and Kadiri 6 were subjected to drought stress by withdrawing irrigation for 15 days. The results suggested a significant influence of drought stress on the physiological and biochemical levels in all the groundnut genotypes. A substantial decrease for physiological parameters viz. membrane stability index, chlorophyll stability index, and relative water content was observed under moderate and severe stress conditions compared to control across all genotypes. The high proline accumulating genotypes also exhibited lower lipid peroxidation under all stress periods. In Kadiri 9, Narayani, and Dharani genotypes, the antioxidant enzyme activity of superoxide dismutase, catalase, peroxidase, and glutathione reductase was significantly higher than JL24, TPT-3, and Kadiri 6 genotypes under all stress regimes. Among the genotypes tested, Kadiri 9, Narayani, and Dharani retained higher growth, yield, and seed quality characteristics showing tolerance for drought stress. qPCR analysis revealed stress-responsive existence of the selected genes, heat shock protein 70 (HSP70), dehydration-responsive element binding-2A (DREB2A), and no apical meristem, ATAF1/2, cup-shaped cotyledon 2 (NAC4) with 30 fold increase in the level of expression in Kadiri 9 compared to Kadiri 6.

With progressive climate change and the associated increase in mean temperature, heat stress tolerance has emerged as one of the key traits in the product profile of the maize breeding pipeline for lowland tropics. The present study aims to identify the genomic regions associated with heat stress tolerance in tropical maize. An association mapping panel, called the heat tolerant association mapping (HTAM) panel, was constituted by involving a total of 543 tropical maize inbred lines from diverse genetic backgrounds, test-crossed and phenotyped across nine locations in South Asia under natural heat stress. The panel was genotyped using a genotyping-by-sequencing (GBS) platform. Considering the large variations in vapor pressure deficit (VPD) at high temperature (Tmax) across different phenotyping locations, genome-wide association study (GWAS) was conducted separately for each location. The individual location GWAS identified a total of 269 novel significant single nucleotide polymorphisms (SNPs) for grain yield under heat stress at a p value of –5. A total of 175 SNPs were found in 140 unique gene models implicated in various biological pathway responses to different abiotic stresses. Haplotype trend regression (HTR) analysis of the significant SNPs identified 26 haplotype blocks and 96 single SNP variants significant across one to five locations. The genomic regions identified based on GWAS and HTR analysis considering genomic region x environment interactions are useful for breeding efforts aimed at developing heat stress resilient maize cultivars for current and future climatic conditions through marker-assisted introgression into elite genetic backgrounds and/or genome-wide selection.

Zinc (Zn) deficiency is a major risk factor for human health, affecting about 30% of the world’s population. To study the potential of genomic selection (GS) for maize with increased Zn concentration, an association panel and two doubled haploid (DH) populations were evaluated in three environments. Three genomic prediction models, M (M1: Environment + Line, M2: Environment + Line + Genomic, and M3: Environment + Line + Genomic + Genomic x Environment) incorporating main effects (lines and genomic) and the interaction between genomic and environment (G x E) were assessed to estimate the prediction ability (rMP) for each model. Two distinct cross-validation (CV) schemes simulating two genomic prediction breeding scenarios were used. CV1 predicts the performance of newly developed lines, whereas CV2 predicts the performance of lines tested in sparse multi-location trials. Predictions for Zn in CV1 ranged from −0.01 to 0.56 for DH1, 0.04 to 0.50 for DH2 and −0.001 to 0.47 for the association panel. For CV2, rMP values ranged from 0.67 to 0.71 for DH1, 0.40 to 0.56 for DH2 and 0.64 to 0.72 for the association panel. The genomic prediction model which included G x E had the highest average rMP for both CV1 (0.39 and 0.44) and CV2 (0.71 and 0.51) for the association panel and DH2 population, respectively. These results suggest that GS has potential to accelerate breeding for enhanced kernel Zn concentration by facilitating selection of superior genotypes.

The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals.

Globally, downy mildews are among the important foliar diseases of maize that cause significant yield losses. We conducted a genome-wide association study for sorghum downy mildew (SDM; Peronosclerospora sorghi) resistance in a panel of 368 inbred lines adapted to the Asian tropics. High density SNPs from Genotyping-by-sequencing were used in GWAS after controlling for population structure and kinship in the panel using a single locus mixed model. The study identified a set of 26 SNPs that were significantly associated with SDM resistance, with Bonferroni corrected P values ≤ 0.05. Among all the identified SNPs, the minor alleles were found to be favorable to SDM resistance in the mapping panel. Trend regression analysis with 16 independent genetic variants including 12 SNPs and four haplotype blocks identified SNP S2_6154311 on chromosome 2 with P value 2.61E-24 and contributing 26.7% of the phenotypic variation. Six of the SNPs/haplotypes were within the same chromosomal bins as the QTLs for SDM resistance mapped in previous studies. Apart from this, eight novel genomic regions for SDM resistance were identified in this study; they need further validation before being applied in the breeding pipeline. Ten SNPs identified in this study were co-located in reported mildew resistance genes.

Rice is the most widely grown and consumed cereal across the world, where Asian countries are the topmost with 80%, since it meets half of the worldwide dietary. Rice is an extensive freshwater user through conventional puddled cultivation. However, as a result of changing climate, water scarcity is increasing, threatening rice cultivation. Therefore, it is imperative for genetic improvement of rice cultivars suitable to grow under water deficit conditions. While the significance of root traits in water uptake is unambiguously putative which is significantly correlated with higher water use efficiency. Besides water, plants need balanced mineral nutrients in each stage of its development to attain maximum yield. Among the essential nutrients, nitrogen (N) is one of the most important; with its deficiency, plants have limited growth, yield, and quality. Plants obtain N from the soil solution in two forms: NO3− and NH4+. Since plants mainly uptake N as NO3− form root-specific transporters, but 1/3 of the applied N is leaching as NO3−. However, earlier findings found that N use efficiency (NUE) may be enhanced through genetic improvement. There are two-gene (NRT1 and NRT2) families of nitrate transporters encoding NO3− uptake proteins. Among them, NRT2 gene encodes the high-affinity transporters under low nitrate concentration, while NRT1 gene facilitates the root low-affinity transporters. In the chapter, we discussed various techniques/strategies in improving NUE and WUE in rice through phenotypic architecture particularly root and shoot, genetic engineering and molecular strategies in a range of plant species aimed at enhancing uptake, translocation, and remobilization of N as a sustainable way to increase rice productivity and quality and also and to incorporate into rice improvement programs through modern breeding and molecular approaches.

In the last two decades, people are suffering from malnutrition due to the deficiency of certain vitamins and micronutrients in the daily diet worldwide. Micronutrient malnutrition, known as hidden hunger, has been well recognized in the developing world which relayed on cereal-based staple food, particularly in Asian countries, where more than half of the world’s population used rice as a staple food. It is well-confirmed that around 60%, 30%, and 15% of the world population are assumed to be deficient in iron (Fe), zinc (Zn), and selenium (Se). As a result, the importance of micronutrient nutrition has to increase at a great pace. In the chapter, we highlight the importance of biofortification in rice and also discuss the agronomic, traditional breeding, biotechnology, molecular, transgenics, and gene editing as potential approaches to combat widespread micronutrient deficiencies in humans.

More than 50% of the population in the world consumed rice as basic food, particularly in Asian countries. However, as a tropical cereal and also due to the changing climate, major abiotic stresses and also deficit nutrients in the soils have limited the rice production globally. These threats are not solely liable for a drastic reduction in the yield of rice but also interrupt the human beings who consume rice as a basic cereal. Usually, plants can survive against the modest level of environmental stresses. But once stresses exceed the threshold level, survival mechanisms including physio-biochemical and molecular mechanisms break down causing death of the plants and drastically reducing the final yield. It is recognized that plants follow several mechanisms to survive against stress, including stress escaping, avoidance, physio-biochemical mechanisms, and genes that confer tolerance against stress. In the case of physio-biochemical mechanisms, plants have numerous internal and external adaptation strategies including phytohormones (PH), osmoprotectants, signaling molecules, and trace elements to survive against abiotic stresses. Among these natural adaptation strategies, target PH such as gibberellins (PHGAs), cytokinins (PHCKs), auxin or indole-3-acetic acid (PHIAA), salicylic acid (PHSA), abscisic acid (PHAA), ethylene (PHET), brassinosteroids (PHBS), strigolactone (PHSL), and jasmonates (PHJAs) have a great role against environmental stresses. Since PH of plants have already proved their importance against abiotic stresses, therefore PH engineering could be a perfect platform to improve environmental stress-tolerant crops under the changing climate. This book chapter outlines the importance of PH, particularly against abiotic stresses, in plants including rice and also highlights the metabolic engineering of PH for enhancing the adaptability of rice against the harsh environment.