Two genes encoding caffeoyl coenzyme A O-methyltransferase 1 (CCoAOMT1) are candidate genes for physical seed dormancy in cowpea (Vigna unguiculata (L.) Walp.).

KEY MESSAGE: The major QTL Sdp1.1+ controlling seed dormancy in cowpea was finely mapped, and two CCoAOMT1 genes were identified as candidate genes for the dormancy. Seed dormancy in wild cowpea may be useful in breeding cultivated cowpea with pre-harvest sprouting resistance. A previous study identified a major quantitative trait locus (QTL) for seed dormancy, Sdp1.1+ , using the population of the cross between cultivated cowpea 'JP81610' and wild cowpea 'JP89083.' However, the molecular basis of seed dormancy in cowpea is not yet known. In this study, we aimed to finely map the locus Sdp1.1+ and identify candidate gene(s) for it. Germination tests demonstrated that the seed coat is the major factor controlling seed dormancy in the wild cowpea JP89083. Microscopic observations revealed that wild cowpea seeds, unlike cultivated cowpea seeds, possessed a palisade cuticle layer. Fine mapping using a large F2 population of the cross JP81610 × JP89083 grown in Thailand revealed a single QTL, Sdp1.1+ , controlling seed dormancy. The Sdp1.1+ was confirmed using a small F2 population of the same cross grown in Japan. The Sdp1.1+ was mapped to a 37.34-Kb region containing three genes. Two closely linked genes, Vigun03g278900 (VuCCoAOMT1a) and Vigun03g290000 (VuCCoAOMT1b), located 4.844 Kb apart were considered as candidate genes for seed dormancy. The two genes encoded caffeoyl coenzyme A O-methyltransferase 1 (CCoAOMT1). DNA sequencing and alignment of VuCCoAOMT1a and VuCCoAOMT1b between JP89083 and JP81610 revealed a single nucleotide polymorphism (SNP) causing an amino acid change in VuCCoAOMT1a and several SNPs leading to six amino acid changes in VuCCoAOMT1b. Altogether, these results indicate that VuCCoAOMT1a and VuCCoAOMT1b are candidate genes controlling physical seed dormancy in the wild cowpea JP89083.

Integrative small RNA and transcriptome analysis provides insight into key role of miR408 towards drought tolerance response in cowpea.

KEY MESSAGE: Drought stress response studies and overexpression of vun-miR408 proved it to be essential for abiotic stress tolerance in cowpea. Small RNA and transcriptome sequencing of an elite high-yielding drought-tolerant Indian cowpea cultivar, Pusa Komal revealed a differential expression of 198 highly conserved, 21 legume-specific, 14 less-conserved, and 10 novel drought-responsive microRNAs (miRNAs) along with 3391 (up-regulated) and 3799 (down-regulated) genes, respectively, in the leaf and root libraries. Among the differentially expressed miRNAs, vun-miR408-3p, showed an up-regulation of 3.53-log2-fold change under drought stress. Furthermore, laccase 12 (LAC 12) was identified as the potential target of vun-miR408-3p using 5' RNA ligase-mediated rapid amplification of cDNA ends. The stable transgenic cowpea lines overexpressing artificial vun-miR408-3p (OX-amiR408) displayed enhanced drought and salinity tolerance as compared to the wild-type plants. An average increase of 30.17% in chlorophyll, 26.57% in proline, and 27.62% in relative water content along with lesser cellular H2O2 level was observed in the transgenic lines in comparison with the wild-type plants under drought stress. Additionally, the scanning electron microscopic study revealed a decrease in the stomatal aperture and an increase in the trichome density in the transgenic lines. The expression levels of laccase 3 and laccase 12, the potential targets of miR408, related to lipid catabolic processes showed a significant reduction in the wild-type plants under drought stress and the transgenic lines, indicating the regulation of lignin content as a plausibly essential trait related to the drought tolerance in cowpea. Taken together, this study primarily focused on identification of drought-responsive miRNAs and genes in cowpea, and functional validation of role of miR408 towards drought stress response in cowpea.

Genome-wide analysis of OSCA gene family members in Vigna radiata and their involvement in the osmotic response.

BACKGROUND: Mung bean (Vigna radiata) is a warm-season legume crop and belongs to the papilionoid subfamily of the Fabaceae family. China is the leading producer of mung bean in the world. Mung bean has significant economic and health benefits and is a promising species with broad adaptation ability and high tolerance to environmental stresses. OSCA (hyperosmolality-gated calcium-permeable channel) gene family members play an important role in the modulation of hypertonic stress, such as drought and salinity. However, genome-wide analysis of the OSCA gene family has not been conducted in mung bean. RESULTS: We identified a total of 13 OSCA genes in the mung bean genome and named them according to their homology with AtOSCAs. All the OSCAs were phylogenetically split into four clades. Phylogenetic relationship and synteny analyses showed that the VrOSCAs in mung bean and soybean shared a relatively conserved evolutionary history. In addition, three duplicated VrOSCA gene pairs were identified, and the duplicated VrOSCAs gene pairs mainly underwent purifying selection pressure during evolution. Protein domain, motif and transmembrane analyses indicated that most of the VrOSCAs shared similar structures with their homologs. The expression pattern showed that except for VrOSCA2.1, the other 12 VrOSCAs were upregulated under treatment with ABA, PEG and NaCl, among which VrOSCA1.4 showed the largest increased expression levels. The duplicated genes VrOSCA2.1/VrOSCA2.2 showed divergent expression, which might have resulted in functionalization during subsequent evolution. The expression profiles under ABA, PEG and NaCl stress revealed a functional divergence of VrOSCA genes, which agreed with the analysis of cis-acting regulatory elements in the promoter regions of VrOSCA genes. CONCLUSIONS: Collectively, the study provided a systematic analysis of the VrOSCA gene family in mung bean. Our results establish an important foundation for functional and evolutionary analysis of VrOSCAs and identify genes for further investigation of their ability to confer abiotic stress tolerance in mung bean.

The witchweed Striga gesnerioides and the cultivated cowpea: A geographical and historical analysis of their West African distribution points to the prevalence of agro-ecological factors and the parasite's multilocal evolution potential.

The increasing severity of Striga gesnerioides attacks on cowpea across West Africa has been related to its prolificity, seed mobility and longevity, and adaptation to aridity, in a context of agricultural intensification. To understand this fast extension, we analyzed (1) the distributions of the crop and the witchweed with ecological niche modeling and multivariate climate analysis, and (2) the chronological information available from collections and the literature. The ecoclimatic envelope of S. gesnerioides attacks on cowpea is the same as on wild hosts. Consistently, the modeled distribution of cowpea infestations is closely similar to the simple superposition of the parasite model (involving all hosts) and the crop model. Striga gesnerioides infestations are restricted to the driest component of the cultivated cowpea ecoclimatic niche, corresponding to the Sahelian and Sudano-Sahelian belts and the Dahomey gap. Thus, the parasite distribution, determined by its own requirements, does not constrain cowpea cultivation under Guinean climates. The spatial and temporal distributions of S. gesnerioides field infestations are consistent with an earlier impact on cowpea production in eastern West Africa, related itself to a similar trend in cowpea cultivation intensification from Niger, Nigeria and Benin to Burkina Faso and Ghana. Mali and Senegal were affected later, and literature reports of Senegalese strains of S. gesnerioides from the wild developing virulence on cowpea offer a model for the diffusion of witchweed parasitism by multilocal evolution, through host-driven selection, instead of epidemic diffusion. A contrario, in Côte d'Ivoire, cowpea is much less widespread, so the parasite has remained confined to the wild compartment. Thus, both historical and ecogeographic analyses refute the vision of S. gesnerioides as an invader. Instead, they point to the increasing importance and intensification of the crop, and the consequent loss of biodiversity, as the main drivers of the extension and diversification of its crop-specific strains.

Effect of photoperiod on vitamin E and carotenoid biosynthesis in mung bean (Vigna radiata) sprouts.

Light affects the accumulation of vitamin E and carotenoids in many crops. This study investigated the impact of photoperiods on the metabolic regulation of vitamin E and carotenoids in mung bean sprouts considering their dietary health benefits. Mung beans were germinated under three different photoperiods: constant light, semilight and constant dark. Results revealed that the semilight photoperiod was optimum for vitamin E and carotenoid accumulation in mung bean sprouts. DXS was activated in the constant dark and was inhibited by constant light. GGPPS and HPT were sensitive to semilight photoperiod in the vitamin E biosynthetic pathway, playing dominant roles in vitamin E accumulation. The PSY, LCYE, LUT5, LUT1 and ZE genes, which are associated with carotenoid biosynthesis, were activated under semilight treatment and significantly regulated the accumulation of carotenoids. This knowledge improves knowledge on light-mediated regulation of vitamin E and carotenoids in mung bean sprouts.

Alleviative effects of nitric oxide on Vigna radiata seedlings under acidic rain stress.

Although nitric oxide (NO) is a key regulatory molecule in plants, its function in plants under conditions of simulated acid rain (SAR) has not been fully established yet. In this study, exogenous sodium nitroprusside (SNP) at three different concentrations were applied to mung bean seedlings. Malondialdehyde (MDA), NO, hydrogen peroxide (H2O2), antioxidant enzyme activities, and nitrate reductases (NR) were measured. Real time PCR was used to measure the NR expression. Compared to the control, the NR activity and NO content under the pH 2 SAR decreased by 79% and 85.6% respectively. Meanwhile, the SAR treatment reduced the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), while increased MDA content. Application of SNP could potentially reverse the adverse impact of SAR, depending on its concentration. For plants under the pH 2 SAR and 0.25 mM SNP condition, the activities of SOD, POD, APX increased by 123%, 291%, and 135.7% respectively, meanwhile, MDA concentration decreased by 43%, NR activities increased by 269%, and NO concentration increased by 123.6% compared with plants undergoing only pH 2 SAR. The relative expression of the NR1 gene was 2.69 times higher than that of pH 2 SAR alone. Overall, the application of 0.25 mM SNP eliminated reactive oxygen species (ROS) by stimulating antioxidant enzyme activities, reducing oxidative stress and mitigating the toxic effects of SAR on mung bean seedlings. This research provides a foundation for further research on the mechanism of NO on plants under SAR conditions.

Impact of particulate matter on primary leaves of Vigna radiata (L.) R. Wilczek.

Particulate matter (PM) pollution is of great concern for human health and vegetation. In this study, we investigated the impact of PM on primary (unifoliate) leaves of Vigna radiata (L.) R.Wilczek by exposing leaves' adaxial surface to PM. Leaves exposed to PM showed accumulation of various metal(loid)s even after removal of epicuticular wax (EW) revealing that the metals/metalloids could penetrate through the cuticular barrier. Scanning electron microscopic studies revealed that even after thorough washing with water, a significant amount (~55%) of particles were retained on the leaf surface. Leaves did not show any particles on their surface post EW removal, revealing that particles adhered to EW. Exposing primary leaves to PM did not alter their size but gave rise to smaller sized trifoliate leaves. A decline in Chl a/b of PM-exposed primary leaves suggested that PM cause a shading effect on leaves. PM-exposed primary leaves also showed a decline in sugar levels. However, the trifoliate leaves did not show any variation in Chl a/b as well as sugar levels. Our findings furnish evidence for the negative effects of PM on plants and a probable dietary exposure of humans to PMs, warranting more in-depth studies on the potential risks of PMs in agricultural sector.

The roles of photorespiration and alternative electron acceptors in the responses of photosynthesis to elevated temperatures in cowpea.

We explored the effects, on photosynthesis in cowpea (Vigna unguiculata) seedlings, of high temperature and light-environmental stresses that often co-occur under field conditions and can have greater impact on photosynthesis than either by itself. We observed contrasting responses in the light and carbon assimilatory reactions, whereby in high temperature, the light reactions were stimulated while CO2 assimilation was substantially reduced. There were two striking observations. Firstly, the primary quinone acceptor (QA ), a measure of the regulatory balance of the light reactions, became more oxidized with increasing temperature, suggesting increased electron sink capacity, despite the reduced CO2 fixation. Secondly, a strong, O2 -dependent inactivation of assimilation capacity, consistent with down-regulation of rubisco under these conditions. The dependence of these effects on CO2 , O2 and light led us to conclude that both photorespiration and an alternative electron acceptor supported increased electron flow, and thus provided photoprotection under these conditions. Further experiments showed that the increased electron flow was maintained by rapid rates of PSII repair, particularly at combined high light and temperature. Overall, the results suggest that photodamage to the light reactions can be avoided under high light and temperatures by increasing electron sink strength, even when assimilation is strongly suppressed.

Transgenic cowpea plants expressing Bacillus thuringiensis Cry2Aa insecticidal protein imparts resistance to Maruca vitrata legume pod borer.

KEY MESSAGE: Fertile independent transgenic cowpea lines expressing the BtCry2Aa toxin with increased resistance to the most devastating lepidopteran insect pest, Maruca pod borer has been developed for the first time. Cowpea is a staple legume important for food and nutritional security in sub-Saharan Africa and Asia, where its production is limited by the key pest, legume pod borer (Maruca vitrata). Cowpea varieties resistant to M. vitrata are not known, hence, development of Maruca pod borer resistance cowpea through genetic engineering is a promising approach to improve its production. In the present study, transgenic cowpea plants expressing Bacillus thuringiensis Cry2Aa insecticidal protein were developed for the first time using Agrobacterium tumefaciens-mediated transformation of cotyledonary explants. T0 plants recovered from Agrobacterium cocultured explants on medium containing 120 mgl-1 of kanamycin were identified on the basis of the presence of transgenes by PCR, their integration into genome by Southern hybridization and expression of their transcripts by semi quantitative PCR (sqRT-PCR) and quantitative Real-time-PCR (qRT-PCR) and protein by Western blot analysis. The transformation efficiency obtained was 3.47% with 11 independent T0 transgenic lines. The bioefficacy of Cry2Aa protein expressed in randomly selected four T0 plant's leaves and pods was evaluated by feeding Maruca pod borer demonstrated a significant lower damage and a high level of Maruca mortality (more than 90%) for all these Bt lines. The inheritance of transgenes from T0 to T1 progeny plants was demonstrated by PCR analysis. The transgenic plants generated in this study can be used in cowpea breeding program for durable and sustainable legume pod borer resistance.

Linking plant and soil indices for water stress management in black gram.

Measurement of plant and soil indices as well as their combinations are generally used for irrigation scheduling and water stress management of crops and horticulture. Rapid and accurate determination of irrigation time is one of the most important issues of sustainable water management in order to prevent plant water stress. The objectives of this study are to develop baselines and provide irrigation scheduling relationships during different stages of black gram growth, determine the critical limits of plant and soil indices, and also determine the relationships between plant physiology and soil indices. This study was conducted in a randomized complete block design at the four irrigation levels 50 (I1), 75 (I2), 100 (I3 or non-stress treatment) and 125 (I4) percent of crop's water requirement with three replications in Urmia region in Iran in order to irrigation scheduling of black gram using indices such as canopy temperature (Tc), crop water stress index (CWSI), relative water content (RWC), leaf water potential (LWP), soil water (SW) and penetration resistance (Q) of soil under one-row drip irrigation. The plant irrigation scheduling was performed by using the experimental crop water stress index (CWSI) method. The upper and lower baseline equations as well as CWSI were calculated for the three treatments of I1, I2 and I3 during the plant growth period. Using the extracted baselines, the mean CWSI values for the three treatments of I1, I2 and I3 were calculated to be 0.37, 0.23 and 0.15, respectively, during the growth season. Finally, using CWSI, the necessary equations were provided to determine the irrigation schedule for the four growing stages of black gram, i.e. floral induction-flowering, pod formation, seed and pod filling and physiological maturity, as (Tc - Ta)c = 1.9498 - 0.1579(AVPD), (Tc - Ta)c = 4.4395 - 0.1585(AVPD), (Tc - Ta)c = 2.4676 - 0.0578(AVPD) and (Tc - Ta)c = 5.7532 - 0.1462(AVPD), respectively. In this study, soil and crop indices, which were measured simultaneously at maximum stress time, were used as a complementary index to remove CWSI constraints. It should be noted that in Urmia, the critical difference between the canopy temperature and air temperature (Tc - Ta), soil penetration resistance (Q), soil water (SW) and relative water content (RWC) for the whole growth period of black gram were - 0.036 °C, 10.43 MPa and 0.14 cm3 cm-3 and 0.76, respectively. Ideal point error (IPE) was also used to estimate RWC, (Tc - Ta) and LWP as well as to select the best regression model. According to the results, black gram would reduce its RWC less through reducing its transpiration and water management. Therefore, it can be used as a low-water-consuming crop. Furthermore, in light of available facilities, the farmer can use the regression equations between the obtained soil and plant indices and the critical boundaries for the irrigation scheduling of the field.

Calcium-hydrogen sulfide crosstalk during K+-deficient NaCl stress operates through regulation of Na+/H+ antiport and antioxidative defense system in mung bean roots.

Present investigation reports the role of calcium (Ca2+) and hydrogen sulfide (H2S) crosstalk associated with Vigna radiata seedlings subjected to K+ deficient conditions under short-term (24 h) and long-term (72 h) NaCl stress. Perusal of the data reveals that under short-term NaCl stress an initial decline in K+ level led to the elevation in Ca2+ and H2S levels along with improvement in antioxidant system and reduction in reactive oxygen species (ROS) production. Under long-term NaCl stress a further decline in K+ content was deleterious that led to a lower K+/Na+ ratio. This was followed by reduction in antioxidant system along with excessive accumulation of ROS and methylglyoxal content, and increased membrane damage. However, supplementation of the seedling roots with Ca2+ enhanced biosynthesis of H2S through enhancing cysteine pool. The present findings suggest that synergistic action of Ca2+ and H2S induced the activity of H+-ATPase that created H+ gradient which in turn induced Na+/H+ antiport system that accelerated K+ influx and Na+ efflux. All of these together contributed to a higher K+/Na+ ratio, activation of antioxidative defense system, and maintenance of redox homeostasis and membrane integrity in Ca2+-supplemented stressed seedlings. Role of Ca2+ and H2S in the regulation of Na+/H+ antiport system was validated by the use of sodium orthovanadate (plasma membrane H+-ATPase inhibitor), tetraethylammonium chloride (K+ channel blocker), and amiloride (Na+/H+ antiporter inhibitor). Application of Ca2+-chelator EGTA (ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid) and H2S scavenger hypotaurine abolished the effect of Ca2+, suggesting the involvement of Ca2+ and H2S in the alleviation of NaCl stress. Moreover, use of EGTA and HT also substantiates the downstream functioning of H2S during Ca2+-mediated regulation of plant adaptive responses to NaCl stress. To sum up, present findings reveal the association of Ca2+ and H2S signaling in the regulation of ion homeostasis and antioxidant defense during K+-deficient NaCl stress.

Role of MgO nanoparticles in the suppression of Meloidogyne incognita, infecting cowpea and improvement in plant growth and physiology.

Root-knot disease, caused by Meloidogyne spp., alters histology as well as physiology of the roots thus influencing metabolism of vegetative and reproductive parts leading to huge losses in crop productivity. The experimental plant, Vigna unguiculata L. (cowpea of Fabaceae family) var. Gomti is an economically important pulse crop plant. An experiment was conducted to evaluate the effects of different concentrations (0, 25, 50 or 100 ppm) and various modes of applications (root dip, soil drench or foliar spray) of MgO nanoparticles on cowpea infected with M. incognita. The MgO nanoparticles were synthesized chemically and characterized by transmission and scanning electron microscopy (TEM, SEM), UV-Vis spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The scanning electron microscopy images of second stage juveniles of M. incognita treated with MgO nanoparticles (50 and 100 ppm) exhibited indentations, roughness and distortions in the cuticular surface, in comparison to the control untreated juveniles. MgO nanoparticles, in varying concentrations (50, 100 and 200 ppm), were dispensed into the plants by root dip, soil drench and foliar spray methods and their efficacy was assessed in terms of morphological characteristics, yield parameters and biochemical attributes of M. incognita infected plants. In planta trials revealed that 100 ppm dose of MgO nanoparticles, as root dip application, demonstrated reduced nematode fecundity, decreased number and smaller size of galls; enhanced plant growth, increased chlorophyll, carotenoid, seed protein, and root and shoot nitrogen contents. From these findings it could be inferred that MgO nanoparticles played twin roles, first as a nematicidal agent and the other as growth promotion inducer.

Screening of mungbean for drought tolerance and transcriptome profiling between drought-tolerant and susceptible genotype in response to drought stress.

Mungbean, is a widely cultivated pulse crop in India, experiences severe drought stress during the cultivation period. The mechanism of drought tolerance in mungbean is not well understood. In this presents study we screened 7 widely cultivated mungbean genotypes towards their drought sensitivity at seedling stage and transcriptome sequencing of drought-tolerant and susceptible genotype to understand the drought tolerance mechanism. Our physiological data such as increase in root length, shoot length, fresh weight, dry weight, relative water content (RWC), proline content, MDA content and molecular data in terms of quantitative expression of drought stress responsive genes under 3-d drought stress in mungbean suggests that, K851 seems to be most drought tolerant and PDM-139 as drought susceptible genotype. The transcriptomic study between K-851 and PDM-139 revealed 22,882 differentially expressed genes (DEGs) which were identified under drought stress, and they were mainly mapped to phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis. Out of these, 10,235 genes were up-regulated and 12,647 genes were down-regulated. Furthermore, we found that, the DEGs related to, phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis and they were more induced in K-851. Our data suggested that, the drought tolerant genotype K-851, scavenges the damage of drought stress by producing more amount of osmolytes, ROS scavengers and sugar biosynthesis.

Diallel Analysis and Heritability of Grain Yield, Yield Components, and Maturity Traits in Cowpea (Vigna unguiculata (L.) Walp.).

Information on combining ability and reciprocal effects (REC) facilitates efficient utilization of genetic materials in a breeding program. This study was conducted (at the CSIR-Savanna Agricultural Research Institute, Ghana) to determine general combining ability (GCA) and specific combining ability (SCA), heritability, genetic advance, GCA, and SCA effects as well as the relationship between parents per se performance and progenies for yield components and maturity traits in cowpea. The test populations were derived using a 5 × 5 complete diallel cross of parents with different yield attributes and maturity durations. The results indicated that GCA was predominant for number of days to 90% pod maturity, plant height at maturity, and hundred-seed weight. This showed that genes with additive effects conditioned these traits. Padi-Tuya, Songotra, and IT86D-610 were identified as good general combiners for grain yield, while Sanzi-Nya was identified as a general combiner for developing extra-early duration cowpea varieties. Crosses Songotra × Sanzi-Nya, SARC-1-57-2 × IT86D-610, Songotra × SARC-1-57-2, and Padi-Tuya × Songotra were identified as good specific combiners for days to 50% flowering, pod length, pods per plant, pod yield, grain yield, and seeds per pod. The findings from this study provide useful information on the inheritance of early maturity and yield traits in cowpea. This can be exploited to develop high yielding and early maturing cowpea varieties as climate smart strategy to mitigate climate change via breeding methods such as pedigree selection and marker assisted backcrossing (MABC). Pedigree selection method is being used to develop varieties from the hybrid with high and significant SCA for grain yield, whereas the development of extra-early duration varieties via MABC with Sanzi-Nya (general combiner for earliness traits) as a donor parent is ongoing.

Inoculation with Indole-3-Acetic Acid-Producing Rhizospheric Rhodobacter sphaeroides KE149 Augments Growth of Adzuki Bean Plants Under Water Stress.

The use of plant growth-promoting rhizobacteria is economically viable and environmentally safe for mitigating various plant stresses. Abiotic stresses such as flood and drought are a serious threat to present day agriculture. In the present study, the indole-3-acetic acid-producing rhizobacterium R. sphaeroides KE149 was selected, and its effect on the growth of adzuki bean plants was investigated under flood stress (FS) and drought stress (DS). IAA quantification of bacterial pure culture revealed that KE149 produced significant amount of IAA. KE149 inoculation significantly decreased stress-responsive endogenous abscisic acid and jasmonic acid and increased salicylic acid in plants under DS and FS. KE149 inoculation also increased proline under DS and methionine under FS. Moreover, KE149 inoculation significantly increased the calcium (Ca), magnesium (Mg), and potassium (K) content and lowered the sodium (Na) content in the plant shoot under stress. KE149-treated plants had significantly higher root length, shoot length, stem diameter, biomass, and chlorophyll content under both normal and stressed conditions. These results suggest that KE149 could be an efficient biofertilizer for mitigating water stress.

Selenate and selenite affect photosynthetic pigments and ROS scavenging through distinct mechanisms in cowpea (Vigna unguiculata (L.) walp) plants.

Selenium (Se) is a beneficial element to higher plants. Application of Se at low concentrations enhances the antioxidant metabolism reducing the reactive oxygen species (ROS) generated by plant membrane cells. This study aimed to evaluate how the application of Se in the forms sodium selenate and sodium selenite regulates ROS scavenging in field-grown cowpea plants. Seven Se application rates (0; 2.5; 5; 10; 20; 40 and 60 g ha-1) of each of the two Se forms were applied to plants via the soil. Photosynthetic pigments concentration, gas exchange parameters, lipid peroxidation by malondialdehyde (MDA) concentration, hydrogen peroxide concentration, activity of catalase (CAT, EC:1.11.1.6), glutathione reductase (GR, EC:1.6.4.2), ascorbate peroxidase (APX, EC:1.11.1.11) and Se concentration in leaves and grains were evaluated. In general, Se application led to a decrease in chlorophyll a concentration whilst leading to an increase in chlorophyll b, indicating conservation of total chlorophyll concentration. Application of 2.5 g ha-1 of Se as selenate provided a notable increase in total chlorophyll and total carotenoids compared to the other application rates. Selenate and selenite application decreased lipid peroxidation. However, each Se source acted in a different pathway to combat ROS. While selenate showed more potential to increase activity of APX and GR, selenite showed a higher potential to increase CAT activity. The negative correlation between CAT and GR is indicative that both pathways might be activated under distinct circumstances. The more prominent activity of CAT under high rates of selenite resulted in a negative correlation of this enzyme with chlorophyll a and carotenoids. Both selenate and selenite application increased sucrose and total sugars concentration in leaves of cowpea plants. Overall, these results indicate that application of Se in cowpea under field conditions stimulates distinct pathways to scavenge ROS. This could prove beneficial to mitigate oxidative stress during plant development.

Genetic variation for root architectural traits in response to phosphorus deficiency in mungbean at the seedling stage.

Roots enable the plant to survive in the natural environment by providing anchorage and acquisition of water and nutrients. In this study, root architectural traits of 153 mungbean genotypes were compared under optimum and low phosphorus (P) conditions. Significant variations and medium to high heritability were observed for the root traits. Total root length was positively and significantly correlated with total root surface area, total root volume, total root tips and root forks under both optimum P (r = 0.95, r = 0.85, r = 0.68 and r = 0.82 respectively) and low P (r = 0.95, r = 0.82, r = 0.71 and r = 0.81 respectively). The magnitudes of the coefficient of variations were relatively higher for root forks, total root tips and total root volume. Total root length, total root surface area and total root volume were major contributors of variation and can be utilized for screening of P efficiency at the seedling stage. Released Indian mungbean varieties were found to be superior for root traits than other genotypic groups. Based on comprehensive P efficiency measurement, IPM-288, TM 96-25, TM 96-2, M 1477, PUSA 1342 were found to be the best highly efficient genotypes, whereas M 1131, PS-16, Pusa Vishal, M 831, IC 325828 were highly inefficient. Highly efficient genotypes identified would be valuable genetic resources for P efficiency for utilizing in the mungbean breeding programme.

Quantitative trait loci influencing days to flowering and plant height in cowpea, Vigna unguiculata (L.) Walp.

Cowpea (Vigna unguiculate (L.) Walp.) is a worldwide important multifunctional legume crop for food grain, vegetable, fodder, and cover crop. Nevertheless, only limited research has been conducted on agronomic traits. Here, we report quantitative trait locus (QTL) analysis of the days to flowering (DTF) and plant height (PH) using a dense SNP linkage map recently developed from a recombinant inbred line (RIL) population derived from a cross between Golden Eye Cream and IT98K-476-8. The population was phenotyped for DTF and PH through field and greenhouse trials under two environments. The QTLs controlling these traits were mapped using multiple-environment combined and individual trial phenotypic data. The combined data analysis identified one major QTL (qDTF9.1) for DTF, and one major QTL (qPH9.1) and a minor QTL (qPH4.1) for PH. qDTF9.1 and qPH9.1 were adjacent to each other on Chromosome 9 and each explained 29.3% and 29.5% of the phenotypic variation (PVE), respectively. The individual trial data analysis identified a minor QTL (qDTF2.1) on Chromosome 2 for DTF and two minor QTLs (qPH4.1 and qPH4.2) on Chromosome 4 for PH, while the major QTLs, qDTF9.1 and qPH9.1, were consistently identified in all trials conducted. Epistasis analysis revealed that qDTF9.1 interacted with one locus on Chromosome 4, contributed 50% of the PVE, and qPH9.1 interacted with one locus on each of Chromosomes 4 and 6, contributing 30% and 23% of the PVE, respectively, suggesting that epistasis plays an important role in the trait performance. These results, therefore, provide a deeper understanding of the genetic architecture of plant DTF and PH, and molecular tools necessary for cloning the genes and for enhanced cowpea breeding.

Drought-tolerant and plant growth-promoting endophytic Staphylococcus sp. having synergistic effect with silicate supplementation.

Endophytic bacteria have been reported to have symbiotic, mutualistic, commensalistic or trophobiotic relationships with various plant parts. As part of its adaptation, many endophytic organisms are known to exhibit properties with multiple beneficial effects to the plant system. Even though many bacterial genera have been identified to have endophytic association, isolation of those which were previously demonstrated well for human association is quite interesting. In the study, endophytic bacteria Ceb1 isolated from the rhizome of Curcuma longa was identified by 16S rDNA sequencing as Staphylococcus sp. Further, Ceb1 was observed to have the ability to tolerate drought stress. While screening for the plant growth-promoting traits, Ceb1 was found to be positive for IAA production both under drought-stressed and normal conditions as confirmed by HPLC. The Ceb1 priming with Vigna unguiculata was observed to enhance the growth parameters of the plant. Analysis of Ceb1-treated plants by ICP-MS further showed modulation of both macro- and micronutrients. Upon drought stress induction in Vigna unguiculata, Ceb1 was found to provide synergistic plant growth-promoting effect to the plant along with the supplemented silicate sources. Under the changing agroclimatic conditions, exploring the plant stress-alleviating effects of endophytes is highly significant.

Phytotoxicity of iron-based materials in mung bean: Seed germination tests.

Environmental applications and potential risks of iron-based materials have attracted increasing attention. However, most previous studies focused on a single material. Comparative research using different iron-based materials under the same experimental conditions is still lacking. Here, six iron-based materials, including micro-sized and nanoscale Fe3O4 (i.e., mFe3O4 and nFe3O4), bulk and bare nanoscale zero-valent iron (i.e., mZVI and B-nZVI), starch-supported nZVI (S-nZVI), and activated carbon-supported nZVI (A-nZVI), were studied to compare their phytotoxicity in mung bean grown in suspensions with doses of 0, 300, 600 and 1000 mg/L. Taking the four toxicology parameters (seed germination rate, germination index, seedling elongation and biomass) together, the iron-based materials except mFe3O4 generally produced no significant phytotoxicity to mung bean even at 1000 mg/L. nFe3O4 and B-nZVI showed no higher phytotoxicity than their micro-sized counterparts (mFe3O4 and mZVI). All the materials resulted in increased Fe concentrations in seedlings particularly in roots, and mZVI and B-nZVI produced more significant effects. However, the Fe in the roots was difficultly translocated to the shoots. Compared to B-nZVI, nFe3O4 had lower bioavailability and bioaccumulation potential. XRD results confirmed that most Fe3O4 and B-nZVI remained unchanged during seedling growth, while support materials accelerated the corrosion and transformation of S-nZVI and A-nZVI. In conclusion, the tested nanoscale iron-based materials generally possess no obvious phytotoxicity within the dose range, but cause excess Fe accumulation in seedlings. Introduction of support materials may reduce such risk, allowing safer applications of these iron-based materials.