Physio-morphological Traits Research Articles

Physio-Morphological Traits Contributing to Genotypic Differences in Nitrogen Use Efficiency of Leafy Vegetable Species under Low N Stress

Soil fertility is declining in low-input agriculture due to insufficient fertilizer application by small-scale farmers. On the other hand, concerns are rising regarding the environmental pollution of both air and water in high-input agriculture due to the excessive use of N fertilizers in short growing seasons for vegetable crops, which is directly linked to the health of human beings and environmental safety. This study aimed to determine genotypic differences in the Nitrogen Use Efficiency (NUE) levels of different leafy vegetable species (Arugula, Spinach, Cress, Parsley, and Dill) grown hydroponically under two different N rates, low N (0.3 mM) and high N (3.0 mM), and to identify the plant traits that are contributing to NUE. A nutrient solution experiment was conducted between March and April 2024 by using an aerated Deep-Water Culture (DWC) technique in a fully automated climate room with a completely randomized block design (CRBD) with three replications for five weeks. The results indicated that shoot growth, as well as root morphological and leaf physiological responses, was significantly (p < 0.001) affected by genotype, the N rate, and genotype–N rate interactions. Shoot growth in some vegetable species (Arugula, Spinach, and Cress) was significantly higher under a low N than a high N rate, illustrating that they have a great capability for NUE under low N stress conditions. Similar results were also recorded for the root growth of the N-efficient species under low N rates. The NUE levels of these species were closely associated with leaf physiological (leaf area, leaf chlorophyll index (SPAD), photosynthesis, and total leaf chlorophyll (a + b) and carotenoids) and root morphological (root length, root volume, and average root diameter) characteristics. These plant traits could be useful indicators for the selection and breeding of ‘N-efficient’ leafy vegetable species for sustainable low-input agriculture systems in the future. However, further investigation should be carried out at the field level to confirm their commercial production viability.

Effects of titanium oxide nanoparticles and 24-epibrassinosteroid to mitigate the toxicity of cadmium (Cd) and improve physio-morphological traits of soybean (Glycine max L.) cultivated under Cd-contaminated soil

Cadmium (Cd) toxicity is a serious environmental threat to living organisms. Nanoparticles (NPs) and plant growth regulators are able to mitigate Cd toxicity and restore crop growth in heavy metals-contaminated soils. However, the synergistic potential of combining 24-epibrassinosteroid (24-epiBRs) and titanium oxide nanoparticles (TiO2-NPs) to alleviate Cd toxicity and restore soybean (Glycine max L.) production remains unexplored. Thus, a pot-based experimental trial was conducted to assess the effects of applying TiO2-NPs (15 mg L−1) and 24-epiBRs (10−7 M), individually and in combination, on soybean growth in soil cultivated with 30 ppm of Cd. The study revealed that Cd toxicity significantly inhibited soybean root length (11.0 %), root dry biomass (63.5 %), root fresh biomass (84.9 %), shoot length (11.7 %), shoot dry biomass (49.0 %), and shoot fresh biomass (27.3 %), compared to the control. Additionally, the toxicity of Cd enhanced the oxidative stress and lowered the photosynthetic efficiency, gas exchange characteristics, and antioxidant defense system of soybeans. Interestingly, the combined application of TiO2-NPs and 24-epiBRs ameliorated the Cd toxic effects and improved the agronomic traits, photosynthesis efficiency, and antioxidant activity in soybeans by lowering oxidative stress. Specifically, the dual application of 24-epiBRs and TiO2-NPs effectively lowered the Cd levels in roots, shoots, and leaves of soybean plants by 62.5, 162.7, and 87.1 %, respectively, relative to the control soybean plants grown under Cd stress. Overall, the combined treatment of TiO2-NPs and 24-epiBRs synergistically reduced Cd uptake and restored soybean physiology in Cd-contaminated soils. Moving forward, further research should include field trials to assess the effectiveness and economic viability of this novel method.

Integrating multilocus genome-wide association studies in chickpea landraces to discern the genetics of drought tolerance

In chickpea breeding, drought is a major concern and a complex trait controlled by several genes. To develop drought-tolerant varieties, it is essential to use the available germplasm and genomic resources. Over the years, the landraces have proven to be a good source for the dissection of genes for different yield and yield-related traits. The present investigation for marker–trait associations (MTAs) and candidate gene identification was conducted by studying 125 chickpea landraces collected from the West Asia and North Africa (WANA) region, along with 4 varieties suitable for irrigated and rainfed environments. This study analyzed 13 physio-morphological traits in 2 consecutive years at two isolated locations (IARI, New Delhi, and Dharwad). A strong correlation coefficient was observed between the trait seed yield (SY) and biological yield (BY) under both conditions. The Drought Susceptibility Index (DSI) ranged from 0.02 to 1.84 and 0.10 to 2.04 at the IARI, New Delhi and Dharwad locations, respectively. The genotypic data of 6,367 single nucleotide polymorphisms (SNPs) distributed across the genome were used for genetic diversity study, population structure, and genome-wide association study (GWAS). The average polymorphic information content (PIC) value observed was 0.25, and the average linkage disequilibrium (LD) decay distance was 152,269 bp across the genome. A total of four subgroups were observed within the population for genotypic data. Fixed and random model Circulating Probability Unification (FarmCPU) was used for the GWAS analysis, which considered both fixed- and random-effect models. A total of 52 significant SNPs were reported in both irrigated and rainfed conditions at low locations; 7 SNPs were associated with more than one trait, which may have pleiotropic effects. Significant SNPs were annotated in the pulse database. The identified genomic region found in or near MTA under rainfed conditions encodes for guard cell hydrogen peroxide-resistant1 (GHR1), late embryogenesis-abundant, E3 ubiquitin-protein ligase, walls are thin1 (WAT1), and beta-galactosidase that are known to be associated with drought tolerance.

Assessment of physio-morphological traits, genetic variability, and growth performance among amaranth (Amaranthus species) genotypes from Ethiopia

Amaranths are a type of plant that belongs to the NAD-malic enzyme-type C4 metabolism category. They have a unique C4 anatomy, which is present in their bracts, cotyledons, and leaves. This allows them to produce food through the C4 photosynthetic pathway and rapidly adapt to unfavorable environmental conditions. In this study, 120 amaranth genotypes were evaluated for physio-morphological traits, genetic variability, and growth performance assessment from Ethiopia. The results of the analysis of variance showed that all examined physio-morphological parameters, except the rate of photosynthesis and stomata conductance, had mean squares that varied considerably (P < 0.001) owing to genotypes. The estimates of genetic variability, heritability, and expected genetic advance indicated an incredible extent of genetic diversity among amaranth genotypes, with a significant selection pressure for these traits in the population to produce better genotypes for improved amaranth. Selection based on desirable features such as leaf-to-air vapor pressure deficit, transpiration rate, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, leaf area, plant height, leaf number, and root weight can be useful in achieving the intended genetic gains for improvement since these traits appear to be more controlled by additive gene activity. Thus, selection in amaranth genotypes may consider these desired yield-related features. Moreover, the study showed that certain genotypes (ALE-073) exhibited better intercellular CO2 concentration (Ci), leaf-to-air vapor pressure deficit (VPD), transpiration rate (E), and leaf number (LN), resulting in better grain yield. Understanding the relationship between LA and E can help in selecting crops for high E and may provide an avenue to improve leaf yield. Furthermore, some of the selected genotypes in this study could be used as potential parents for improving the genetic gain in amaranth breeding programs. The study concluded that there was additive gene action present since the Ch a, Ch b, TCh, and Tca markers exhibited 100 % heritability. This showed that the use of these characteristics for selection, which indicated a potentially exploitable variation, would be more effective and successful in the long run in breeding programs than the use of other traits for splitting generations.

Drought responses of traditional and modern wheats in different phenological stages

Drought is one of the most pressing issues in many regions worldwide. Selecting wheat genotypes adapted to changing climatic conditions is crucial for sustainable agricultural production, economic development, and food security. In this study, 156 bread wheat genotypes, including landraces from Turkey, Iran, and Afghanistan, which have adapted to changing climatic conditions for thousands of years, and high-yielding modern wheat varieties, including advanced breeding lines and cultivars were evaluated. The genotypes were subjected to seasonal drought treatments under rain shelters, including pre-heading drought (T1), post-heading drought (T2), irrigation based on long-term precipitation (T3), and seasonal precipitation and supplemental irrigation (T4). Grain yield and physio-morphological and quality traits of the genotypes under seasonal drought and irrigated conditions were evaluated. Drought treatments reduced yield and some physio-morphological traits and increased quality traits. Pre-heading drought treatments had the greatest effect on yield and physio-morphological traits while post-heading drought treatments had the greatest effect on quality traits. Modern wheat cultivars had higher grain yields compared to landraces, but some landraces had a lower yield loss compared to modern wheats under drought stress. The higher tillering rate of the landraces resulted in greater biomass production, taller plant height, and peduncle length. Landraces had higher protein content in all treatments, whereas modern wheats had higher protein content in T2 treatments due to the selection pressure that has been ongoing for years. In summary, given that different drought scenarios will be encountered in the future, landraces should be effectively used in the breeding programs to develop seasonal drought-tolerant modern or climate-resilient wheat varieties.

Exploring Drought Tolerance in Wheat: Insights from Biochemical, Morphological, and Physiological Responses

This review paper delves into the intricate biochemical foundations underlying drought tolerance mechanisms in wheat plants. This exploration encompasses multifaceted aspects, ranging from physiological adaptations to gene expression modulation. Plants like wheat employ repertoire of biochemical strategies to bolster their resilience against drought stress. It involves coordinating antioxidant enzymes, osmotic regulators, polyamines, and hormones to combat drought stress. The antioxidant system is crucial, countering reactive oxygen species produced during drought. Enzymes like SOD, CAT, and POD are activated to protect cells. Osmolytes like sugars and polyamines maintain cell integrity and water retention, while hormones like ABA control stomatal closure and water conservation. Gene expression highlights the plant's drought adaptability. AP2/ERF factors boost drought tolerance when overexpressed. Gene repression uses motifs like EAR to reduce expression for environmental adaptation. Gene expression shows the plant's drought adaptability. Overexpressed AP2/ERF factors enhance tolerance. Repression, like the EAR motif, aids variation. The morphological basis study examines how water scarcity affects different growth stages of wheat, such as germination, tillering, flowering, and grain filling. It identifies physio-morphological traits that could serve as the indicators of drought resilience, providing a new way to breed stress resistance. Furthermore, this article also explains plant characteristics important for adapting to drought, including photosynthesis, water relations, nutrient uptake, oxidative state, osmotic balance, and hormonal consequences. Each facet contributes to the intricate web of physiological adaptations that allow wheat plants to withstand and thrive under drought conditions. Comprehending these mechanisms aids breeding for drought-tolerant wheat, ensuring food security amid climate change.

Response of varied rice genotypes on cell membrane stability, defense system, physio-morphological traits and yield under transplanting and aerobic cultivation

Aerobic rice cultivation progresses water productivity, and it can save almost 50% of irrigation water compared to lowland rice with the appropriate development of genotypes and management practices. Two field trials were conducted during 2020, and 2021 seasons to determine the validation of different rice varieties under aerobic cultivation based on their plant defense system, physio-morphological traits, stress indices, grain yield, and water productivity. The experiments were designed in a split-plot design with four replications. Two planting methods, transplanting and aerobic cultivation, were denoted as the main plots, and ten rice genotypes were distributed in the subplots. The results revealed that the planting method varied significantly in all measured parameters. The transplanting method with well watering had the highest value of all measured parameters except leaf rolling, membrane stability index, antioxidant, proline, and the number of unfilled grains. EHR1, Giza179 and GZ9399 as well as A22 genotypes a chief more antioxidant defense system that operated under aerobic conditions. Giza179, EHR1, GZ9399, and Giza178 showed high cell membrane stability and subsequently high validation under such conditions, and also showed efficiency in decreasing water consumption and improving water use efficiency. In conclusion, this study proves that Giza179, EHR1, GZ9399, Giza178, and A22 are valid genotypes for aerobic conditions.

Evaluation of maize germplasm for physio-morphological traits against fall armyworm

The fall armyworm (FAW), scientific name Spodoptera frugiperda (J.E. Smith), poses a significant challenge to farmers and agricultural systems due to its ability to adapt, reproduce rapidly, and develop resistance to pesticides. Hence, it is essential to adopt effective and feasible approaches to managing FAW. The present research aimed at identifying the physio-morphological traits in 22 diverse maize genotypes that influence resistance to FAW. Among the tested ones, moderately resistant genotypes had the highest trichome density (CML 71, CML 67, and CML 335), minimum leaf area, and leaf width (DMRE 63, CML 71, and CML 67). Moderately resistant genotypes, viz., CML 67 (0.14 mm), CML 71 (0.14 mm), CML 561 (0.14 mm), and DMRE 63 (0.14 mm), exhibited significantly higher leaf toughness. Furthermore, the lowest relative water content was recorded in moderately resistant genotypes (DMRE 63, CML 71, and CML 67). The maximum cob length was observed in the moderately resistant genotype, CML 71 (18.56 cm), followed by CML 67 (18.26 cm), which was on par. Among moderately resistant genotypes, CML 71 had the greatest cob width of 4.97 cm, followed by CML 67 (4.88 cm), CML 561 (4.66 cm), CML 335 (4.66 cm), and DMRE 63 (4.62 cm), and these were statistically comparable. Of the genotypes evaluated, the moderately resistant genotypes CML 71, CML 67, and DMRE 63 registered significantly higher yields of 135.04 g/plant, 120.65 g/plant, and 117.92 g/plant, respectively. This information on physio-morphological traits is helpful in breeding programs focusing on maize resistance to FAW.

The Role of Biochar Nanoparticles Performing as Nanocarriers for Fertilizers on the Growth Promotion of Chinese Cabbage (Brassica rapa (Pekinensis Group))

Chinese cabbage (Brassica rapa) belongs to the Pekinensis Group and is grown annually as a salad crop. It is one of the most important food crops in Eastern Asia and the most widely grown vegetable in China, accounting for more one-quarter of the total annual vegetable consumption in northern parts of the country. It is reported that nitrogen (N), phosphorus (P), and potassium (K) fertilizations play important roles in the physio-morphological traits and yields of Chinese cabbage. However, N, P, and K use in agriculture continues to increase. Excessive application of fertilizers has a harmful impact on the environment. Yet how to improve the irrigation effects on Chinese cabbage growth is still limited. In this study, we firstly selected biochar nanoparticles (BNPs) prepared from corn straw, which had been air-dried and heated in a muffle furnace at 350 °C for 120 min, with K (potassium sulfate), N (calcium nitrate tetrahydrate), and P (sodium dihydrogen phosphate dihydrate) fertilizers. Then, a screening experiment (Experiment I) was performed via the response model to find the best solution for Chinese cabbage growth. Treatment with 2 g/kg of N and 2 g/kg of K for 4 weeks was the optimum application to promote Chinese cabbage growth. Then, a comparison experiment (Experiment II) was carried out to test the best formula for Chinese cabbage growth with or without BNPs. After co-irrigation with N and K for 4 weeks, treatment with a combination of 2 g/kg of BNPs, 2 g/kg of N, and 2 g/kg of K was the optimum formula for Chinese cabbage growth. Plant biomass increased by more than 1796.86% and 32.80%, respectively, in two combined treatments of BNPs and fertilizers as compared to the control treatment. After the addition of BNPs, Chinese cabbage height (aboveground) and the dry weight of belowground biomass in the N + K treatment increased to 10.97% and 20.48%, respectively. These results suggest that BNPs have great potential as a nanocarrier for fertilization as they are highly efficient (over 50% increase), reducing fertilizer use while promoting plant growth. The use of BNPs as a nanocarrier for fertilizers represents a step toward more environmentally friendly agriculture.

Genetic and morpho-physiological analyses of the tolerance and recovery mechanisms in seedling stage spring wheat under drought stress.

Drought is one of the complex abiotic stresses that affect the growth and production of wheat in arid and semiarid countries. In this study, a set of 172 diverse spring wheat genotypes from 20 different countries were assessed under drought stress at the seedling stage. Besides seedling length, two types of traits were recorded, namely: tolerance traits (days to wilting, leaf wilting, and the sum of leaf wilting), and recovery traits (days to regrowth, regrowth biomass, and drought survival rate). In addition, tolerance index, recovery index, and drought tolerance index (DTI) were estimated to select the most drought tolerant genotypes. Moreover, leaf protein content (P), amino acid (AM), proline content (PRO), glucose (G), fructose (F), and total soluble carbohydrates (TSC) were measured under control and drought conditions to study the changes in each physiological trait due to drought stress. All genotypes showed a high significant genetic variation in all the physio-morphological traits scored under drought stress. High phenotypic and genotypic correlations were found among all seedling morphological traits. Among the studied indices, the drought tolerance index (DTI) had the highest phenotypic and genotypic correlations with all tolerance and recovery traits. The broad-sense heritability (H2) estimates were high for morphological traits (83.85–92.27), while the physiological traits ranged from 96.41 to 98.68 under the control conditions and from 97.13 to 99.99 under drought stress. The averages of the physiological traits (proteins, amino acids, proline, glucose, fructose, and total soluble carbohydrates) denoted under drought stress were higher than those recorded under well-watered conditions except for proteins. In this regard, amino acids, glucose, and total soluble carbohydrates had a significant correlation with all morphological traits. The selection for drought tolerance revealed 10 tolerant genotypes from different countries (8 genotypes from Egypt, one from Morocco, and one from the United States). These selected genotypes were screened for the presence of nine specific TaDREB1 alleles. Six primers were polymorphic among the selected genotypes. Genetic diversity among the selected genotypes was investigated using 21,450 SNP markers. The results of the study shed light on the different mechanisms for drought tolerance that wheat plants use to tolerate and survive under drought stress. The genetic analysis performed in this study suggested the most suitable genotypes for selective breeding at the seedling stage under water deficit.

Identification of arsenic-tolerant varieties and candidate genes of tolerance in spring wheat (Triticum aestivum L.)

Despite the growing concerns about arsenic toxicity, information on tolerance and responsible genetic factors in wheat remains elusive. To address that, the present study aimed to screen the wheat varieties against arsenic based on growth parameters, yield, grain accumulation, and associated genes. A total of 110 wheat varieties were grown in arsenic-contaminated regions to record physio-morphological traits. The wheat 90K Infinium iSelect SNP array was used for the genome-wide association model to identify genomic regions. Wheat varieties such as Punjab-81, AARI-11, and Daman showed arsenic concentrations >45 μg/kg in similar conditions as well as the impact on grain yield, chlorophyll, Thousand Kernel Weight, and plant height. Contrastingly, varieties like Kohistan-97, As-2002, Barani-70, and Pari-73 showed grain concentrations <5 μg/kg grown under highly contaminated conditions. Three significant loci associated with arsenic accumulation in grain were identified on chromosomes 6A (qASG1-6A) and 6B (qASG3-6B and qASG4-6B). Annotation at these loci identified 39 wheat genes among which several were important for growth and tolerance against stress. The candidate gene (TraesCS6B02G429400) responsible for Glutathione-S-transferase was identified in the present study and must be investigated further using a transcriptomic approach. The present study provided background information for breeding prospects to improve wheat yield and tolerance against arsenic.

Integrated nutrient supply and varietal difference influence grain yield and yield related physio-morphological traits of durum wheat (Triticum turgidum L.) varieties under drought condition

The ever-growing world population entails an improvement in durum wheat grain yield to ensure an adequate food supply, which often gets impaired by several biotic and abiotic factors. Integrated nutrient management, such as nitrogen rate × foliar zinc × sulphur fertilization combined with durum wheat varieties were investigated in order to examine the dynamics of yield and yield related physio-morphological traits under drought conditions. The four durum wheat varieties, three-level of nutrient supply (i.e. control, sulphur, and zinc), and two nitrogen regimes (i.e. zero and 60 kg ha−1) were arranged in split-split plot design with three replications. Zinc and sulphur were applied as foliar fertilisation during the flag leaf stage, both at a rate of 3 and 4 liters ha-1, respectively. Results showed existence of genetic variability for grain yield, plant height, NDVI, SPAD and spike density. Foliar based application of zinc and sulphur at the latter stage improved the plant height. Nitrogen fertilized varieties with lower spike numbers showed to better yield formation. Co-fertilization of nitrogen and zinc improved grain yield of responsive varieties like Duragold by about 21.3%. Spikes per m2 were statistically insignificant for grain yield improvement. It could be inferred that the observed positive effect of sulphur, nitrogen and zinc application on physio-morphology and yield formation substantiates the need to include these essential nutrients in the cultivation system of durum wheat.

Synergistic Modulation of Seed Metabolites and Enzymatic Antioxidants Tweaks Moisture Stress Tolerance in Non-Cultivated Traditional Rice Genotypes during Germination.

Traditional rice landraces are treasures for novel genes to develop climate-resilient cultivars. Seed viability and germination determine rice productivity under moisture stress. The present study evaluated 100 rice genotypes, including 85 traditional landraces and 15 improved cultivars from various agro-ecological zones of Tamil Nadu, along with moisture-stress-susceptible (IR 64) and moisture-stress-tolerant (IR 64 Drt1) checks. The landraces were screened over a range of osmotic potentials, namely (−) 1.0 MPa, (−) 1.25 MPa and (−) 1.5 MPa, for a period of 5 days in PEG-induced moisture stress. Physio-morphological traits, such as rate of germination, root and shoot length, vigor index, R/S ratio and relative water content (RWC), were assessed during early moisture stress at the maximum OP of (−) 1.5 MPa. The seed macromolecules, phytohormones (giberellic acid, auxin (IAA), cytokinin and abscisic acid), osmolytes and enzymatic antioxidants (catalase and superoxide dismutase) varied significantly between moisture stress and control treatments. The genotype Kuliyadichan registered more IAA and giberellic acid (44% and 35%, respectively, over moisture-stress-tolerant check (IR 64 Drt1), whereas all the landraces showed an elevated catalase activity, thus indicating that the tolerant landraces effectively eliminate oxidative damages. High-performance liquid chromatography analysis showed a reduction in cytokinin and an increase in ABA level under induced moisture stress. Hence, the inherent moisture-stress tolerance of six traditional landraces, such as Kuliyadichan, Rajalakshmi, Sahbhagi Dhan, Nootripathu, Chandaikar and Mallikar, was associated with metabolic responses, such as activation of hydrolytic enzymes, hormonal crosstalk, ROS signaling and antioxidant enzymes (especially catalase), when compared to the susceptible check, IR 64. Hence, these traditional rice landraces can serve as potential donors for introgression or pyramiding moisture-stress-tolerance traits toward developing climate-resilient rice cultivars.

Physio-morphological traits and osmoregulation strategies of hybrid maize (Zea mays) at the seedling stage in response to water-deficit stress.

Drought has been identified as a major factor restricting maize productivity worldwide, especially in the rainfed areas. The objective of the present study was to investigate the physiological adaptation strategies and sugar-related gene expression levels in three maize (Zea mays L.) genotypes with different drought tolerance abilities (Suwan4452, drought tolerant as a positive check; S7328, drought susceptible as a negative check; Pac339, drought susceptible) at the seedling stage. Ten-day old seedlings of maize genotypes were subjected to (i) well-watered (WW) or control and (ii) water-deficit (WD) conditions. Leaf osmotic potential of cv. S7328 under WD was significantly decreased by 1.35-1.45 folds compared with cv. Pac339 under WW, whereas it was retained in cv. Suwan4452, which utilized total soluble sugars as the major osmolytes for maintaining leaf greenness, Fv/Fm, ΦPSII, and stomatal function (Pn, net photosynthetic rate; gs, stomatal conductance; and E, transpiration rate). Interestingly, sucrose degradation (65% over the control) in cv. Pac339 under WD was evident in relation to the downregulation of the ZmSPS1 level, whereas glucose enrichment (1.65 folds over the control) was observed in relation to the upregulation of ZmSPS1 and ZmSUS1. Moreover, CWSI (crop water stress index), calculated from leaf temperature of stressed plants, was negatively correlated with E, gs, and Pn. Overall, growth characteristics, aboveground and belowground parts, in the drought-susceptible cv. Pac339 and cv. S7328, were significantly decreased (> 25% over the control), whereas these parameters in the drought-tolerant cv. Suwan4452 were unaffected. The study validates the use of leaf temperature, CWSI, Pn, gs, and E as sensitive parameters and overall growth characters as effective indices for drought tolerance screening in maize genotypes at the seedling stage. However, further experiments are required to validate the results observed in this study under field conditions.

Wheat Responses, Defence Mechanisms and Tolerance to Drought Stress: A Review Article

Wheat (Triticum aestivum L.) is one of the major basic stable crops grown worldwide, however, it is sensitive to environmental stresses like drought. With climate change, drought stress is becoming an increasingly severe constraint on wheat production which affects the plant growth and development, physiological functions, grain formation, grain quality and ultimately the yield. Various responses including biochemical, physiological, morphological, and molecular adaptations are shown by plants to survive in the drought stress condition. Drought escape, avoidance and tolerance are important coping mechanisms of wheat plant under drought environment. Several mechanisms such as accumulation of ABA, osmotic adjustment, and induction of dehydrins may confer drought tolerance by maintaining the high tissue water potential. As the root structure and root biomass define the pattern of water extraction from the soil, enhanced root and suppressed shoot growth resulting in higher root: shoot ratio facilitated plants to drought tolerance. The development of drought tolerance varieties becomes an important due to the uneven distribution of rainfall and water shortage. Some growth stage-specific physio-morphological traits are fundamental targets to breed drought-tolerant wheat varieties. Mutation breeding, molecular breeding, genome engineering techniques including gene pyramiding, gene stacking, and transgenics are employed to breed wheat for tolerance to abiotic stresses including drought. Omics decode the entire genome to have better understanding of plant molecular responses that will provide precise strategies for crop improvement. This paper discusses the wheat plant’s responses to drought stress, their defense mechanisms and modern techniques for the development of drought tolerant wheat varieties.

Assessment of Planting Method and Deficit Irrigation Impacts on Physio-Morphology, Grain Yield and Water Use Efficiency of Maize (Zea mays L.) on Vertisols of Semi-Arid Tropics.

Agriculture in a water-limited environment is critically important for today and for the future. This research evaluates the impact of deficit irrigation in different planting methods on the physio-morphological traits, grain yield and WUE of maize (Zea mays L.). The experiment was carried out in 2015 and 2016, consisting of three planting methods (i.e., BBF, SNF, and DWF) and four irrigation levels (i.e., I10D: irrigation once in ten days, I40: irrigation at 40% DASM, I50: irrigation at 50% DASM, and I60: irrigation at 60% DASM). The results reveal that varying degrees of water stress due to planting methods and irrigation levels greatly influenced the maize physio-morphological traits and yield attributes. The combined effect of DWF + I50 benefited the maize in terms of higher leaf area, RWC, SPAD values, CGR, and LAD, followed by the SNF method at 60 DAS. As a result, DWF + I50 and SNF + I50 had higher 100 grain weight (30.5 to 31.8 g), cob weight (181.4 to 189.6 g cob−1) and grain yield (35.3% to 36.4%) compared to other treatments. However, the reduction in the number of irrigations (24.0%) under SNF + I50 resulted in a 34% water saving. Thus, under a water-limited situation in semi-arid tropics, the practice of the SNF method + I50 could be an alternative way to explore the physio-morphological benefits in maize.

Recent Progress in Germplasm Evaluation and Gene Mapping to Enable Breeding of Drought-Tolerant Wheat.

There is a need to increase wheat productivity to meet the food demands of the ever-growing human population. However, accelerated development of high yielding varieties is hindered by drought, which is worsening due to climate change. In this context, germplasm diversity is central to the development of drought-tolerant wheat. Extensive collections of these genetic resources are conserved in national and international genebanks. In addition to phenotypic assessments, the use of advanced molecular techniques (e.g., genotype by sequencing) to identify quantitative trait loci (QTLs) for drought tolerance related traits is useful for genome- and marker-assisted selection based approaches. Therefore, to assist wheat breeders at a critical time, we searched the recent peer-reviewed literature (2011-current), first, to identify wheat germplasm observed to be useful genetic sources for drought tolerance, and second, to report QTLs associated with drought tolerance. Though many breeders limit the parents used in breeding programs to a familiar core collection, the results of this review show that larger germplasm collections have been sources of useful genes for drought tolerance in wheat. The review also demonstrates that QTLs for drought tolerance in wheat are associated with diverse physio-morphological traits, at different growth stages. Here, we also briefly discuss the potential of genome engineering/editing to improve drought tolerance in wheat. The use of CRISPR-Cas9 and other gene-editing technologies can be used to fine-tune the expression of genes controlling drought adaptive traits, while high throughput phenotyping (HTP) techniques can potentially accelerate the selection process. These efforts are empowered by wheat researcher consortia.

A Physio-Morphological Trait-Based Approach for Breeding Drought Tolerant Wheat.

In the past, there have been drought events in different parts of the world, which have negatively influenced the productivity and production of various crops including wheat (Triticum aestivum L.), one of the world’s three important cereal crops. Breeding new high yielding drought-tolerant wheat varieties is a research priority specifically in regions where climate change is predicted to result in more drought conditions. Commonly in breeding for drought tolerance, grain yield is the basis for selection, but it is a complex, late-stage trait, affected by many factors aside from drought. A strategy that evaluates genotypes for physiological responses to drought at earlier growth stages may be more targeted to drought and time efficient. Such an approach may be enabled by recent advances in high-throughput phenotyping platforms (HTPPs). In addition, the success of new genomic and molecular approaches rely on the quality of phenotypic data which is utilized to dissect the genetics of complex traits such as drought tolerance. Therefore, the first objective of this review is to describe the growth-stage based physio-morphological traits that could be targeted by breeders to develop drought-tolerant wheat genotypes. The second objective is to describe recent advances in high throughput phenotyping of drought tolerance related physio-morphological traits primarily under field conditions. We discuss how these strategies can be integrated into a comprehensive breeding program to mitigate the impacts of climate change. The review concludes that there is a need for comprehensive high throughput phenotyping of physio-morphological traits that is growth stage-based to improve the efficiency of breeding drought-tolerant wheat.

Effect of banana bunch covering technology for quality banana production in Bangladesh

This study was carried out at Horticulture farm of Bangladesh Agricultural University, Mymensingh in order to find out the effects of bunch covering materials on physio-morphological characters and shelf life of banana cv. Mehersagar. The experiment was undertaken during the period from July to November 2016 with four types of bunch covering materials namely white polythene bag, black polythene bag, blue polythene bag and old cloth along with control (no bunch covering). The experiment was laid out in randomized complete block design with five replications. The results of the investigation revealed that blue polythene bag required significantly minimum days to harvest (76.80 days) and maximum days to harvest (97.80 days) were recorded for control. Maximum bunch weight (19.90 kg), finger length (19.59 cm) and finger diameter (3.56 cm) were recorded for blue polythene bag whereas control showed minimum bunch weight (15.20 kg), finger length (14.57 cm) and finger diameter (3.07 cm). It was observed that blue polythene bag covered fruits showed minimum disease infection (2.33%), insect infestation (2.33%) and physiological disorder (1%) compared to control which experienced maximum disease infection (12.67%), insect infestation (50%) and physiological disorder (13.40%). Weight loss (11.18%), pulp moisture (66.16%), peel moisture (70.41%), disease infection (40%), disease severity (70.25%), skin colour change (4.95) were also lower in blue polythene bag than non covering control fruits. The bunches covered with blue polythene bag exhibited superior results in respect of pulp thickness (3.45cm), pulp to peel ratio (2.49), pulp dry matter (33.84%), peel dry matter (29.59%), TSS (24.28 % Brix), shelf life (11.40 days) than the rest of bunch covering materials used in this study. It can be concluded that bunch covering showed significant effect on physio-morphological traits and quality of banana.&#x0D; Progressive Agriculture 30 (3): 238-252, 2019

Physio-morphological traits and drought stress responses in three wild Mediterranean taxa of Brassicaceae

Crop wild relatives (CWRs) have extremely relevant roles in biodiversity conservation, in investigating phylogeny and improving abiotic stress tolerance of crop plants. We screened the variability in leaf functional traits of three CWRs of kale crops (Brassica oleracea) from Sicily, Italy, grown in pots under well-watered and drought conditions. Our aim was to highlight traits in the different genotypes of endemic Sicilian threatened taxa. We measured several structural/anatomical traits (stomatal size, density and stomatal pore index—SPI, leaf mass per area—LMA) and leaf functional traits (stomatal conductance—gs, leaf water potential—ΨL, leaf temperature (TL), leaf relative water content—RWC) at pre-dawn and midday of leaves of three wild taxa: B. macrocarpa, B. rupestris subsp. rupestris and B. villosa subsp. bivoniana. Pressure–volume curves were constructed to obtain leaf water potential at turgor loss point (Ψtlp), osmotic potential at full rehydration (Ψπ100), relative water content at turgor loss point (RWCtlp), elastic bulk modulus (emax) and leaf area specific capacitance at full turgor (Cft*). Several significant differences were found among the taxa: under water deficit, B. macrocarpa had the less negative Ψtlp and showed the smallest ΔΨL between pre-dawn and midday. B. villosa subsp. bivoniana showed the highest SPI and had significantly higher gs under water availability, while under drought it had the most negative ΨL. Each of the taxa investigated possessed traits that confer particular stress tolerance, offer competitive advantage in their natural environment and may be exploited for crop improvement.