Impact of zinc-tolerant plant growth-promoting rhizobacteria on lentil grown in zinc-amended soil

Though zinc is a plant nutrient at low levels, Zn ions can be highly phytotoxic at higher concentrations found in contaminated soils. Plant growth-promoting rhizobacteria can be used to decrease this toxicity. Indeed, in addition to their role in plant-growth promotion, rhizobacteria also reduce the toxicity of heavy metals. In turn, they can be effective for crops grown in metal-contaminated soils. Here, we isolated a zinc-tolerant plant growth-promoting rhizobacterium, Rhizobium species RL9, from a zinc-contaminated soil and assayed its plant growth-promoting activities in vitro. We found that the rhizobacterium strain RL9 tolerated zinc up to a concentration of 400 $\mu$g mL$^{-1}$ on yeast extract mannitol agar medium. It produced 33 $\mu$g mL$^{-1 }$of indole acetic acid in Luria Bertani broth at 100 $\mu$g mL$^{-1}$ of tryptophan and was positive for siderophore, hydrogen cyanide and ammonia. Such phytohormones released by this strain could help in promoting the growth of legumes. We further tested the effect of rhizobacterium strain RL9 on lentils grown in zinc-amended soil. We found that when the rhizobacterium strain RL9 was added to soil contaminated with Zn at 4890 mg/kg, lentil dry matter increased by 150%, nodule numbers by 15%, nodule dry mass by 27%, leghaemogloblin by 30%, seed yield by 10% and grain protein by 8%, compared with uninoculated plants. We also found that the concentration of zinc was higher in uninoculated plant organs than in the inoculated counterpart. Our findings thus suggest that rhizobacterium strain RL9 could be exploited for bacteria-assisted reduction of zinc toxicity in zinc-contaminated soils due to its intrinsic abilities of expressing growth-promoting substances and reduction of the toxic effects of zinc

Cadmium, chromium and copper in greengram plants

Soils contaminated with heavy metals including cadmium, chromium and copper present a major concern for sustainable agriculture. We studied the effects of cadmium, chromium and copper used both separately and as mixtures, on plant growth, nodulation, leghaemoglobin, seed yield and grain protein in seeds, in greengram inoculated with Bradyrhizobium sp. (Vigna). Cadmium at 24 mg kg$^{-1}$ of soil reduced the dry matter accumulation and number of nodules by 27 and 38%, respectively. Chromium at 136 mg kg$^{-1}$of soil increased the dry phytomass and nodule numbers by 133 and 100%, respectively. The average maximum increase of 74% in seed yield occurred at 136 mg Cr kg$^{-1}$ of soil. Cadmium and copper at 24 and 1338 mg kg$^{-1}$ soil decreased the seed yield by 40 and 26%, respectively. Chromium at 136 kg$^{-1}$ of soil increased the root and shoot N and leghaemoglobin content by 42, 31% and 50%, respectively. In contrast, the root and shoot N decreased by 22% at 24 mg Cd kg$^{-1}$ of soil, while a maximum decrease of 50% in leghaemoglobin content occurred at 12 and 669 and 24 and 1338 mg Cd with Cu kg$^{-1}$ of soil, relative to the control. The average maximum grain protein (283 mg g$^{-1})$ was observed at 136 mg Cr kg$^{-1}$ of soil, while minimum grain protein (231 mg g$^{-1})$ was recorded at 24 and 1338 mg kg$^{-1}$ of cadmium with copper. The metal accumulation in roots and shoots at 50 days after sowing and in grains 80 days after seeding differed among treatments. The degree of toxicity of heavy metals to the measured parameters decreased in the order Cd $>$ Cu $>$ Cr

Morpho-Cultural and Pathogenic Variability of <i>Sclerotinia sclerotiorum</i> Causing White Mold of Common Beans in Temperate Climate

The present systematic research on cultural, morphological, and pathogenic variability was carried out on eighty isolates of Sclerotinia sclerotiorum collected from major common bean production belts of North Kashmir. The isolates were found to vary in both cultural and morphological characteristics such as colony color and type, colony diameter, number of days for sclerotia initiation, sclerotia number per plate, sclerotial weight, and size. The colony color ranged between white and off-white with the majority. The colony was of three types, in majority smooth, some fluffy, and a few fluffy-at-center-only. Colony diameter ranged between 15.33 mm and 29 mm after 24 h of incubation. The isolates took 4 to 7 days for initiation of sclerotia and varied in size, weight, and number per plate ranging between 14 and 51.3. The sclerotial arrangement pattern on plates was peripheral, sub peripheral, peripheral, and subperipheral, arranged at the rim and scattered. A total of 22 Mycelial compatibility groups (MCGs) were formed with seven groups constituted by a single isolate. The isolates within MCGs were mostly at par with each other. The six isolates representing six MCGs showed variability in pathogenicity with isolate G04 as the most and B01 as the least virulent. The colony diameter and disease scores were positively correlated. Sclerotia were observed to germinate both myceliogenically and carpogenically under natural temperate conditions of Kashmir. Germplasm screening revealed a single resistant line and eleven partially resistant lines against most virulent isolates

Metabolic-GWAS provides insights into genetic architecture of seed metabolome in buckwheat

Abstract Background Buckwheat (Fagopyrum spp.), belonging to the Polygonaceae family, is an ancient pseudo-cereal with high nutritional and nutraceutical properties. Buckwheat proteins are gluten-free and show balanced amino acid and micronutrient profiles, with higher content of health-promoting bioactive flavonoids that make it a golden crop of the future. Plant metabolome is increasingly gaining importance as a crucial component to understand the connection between plant physiology and environment and as a potential link between the genome and phenome. However, the genetic architecture governing the metabolome and thus, the phenome is not well understood. Here, we aim to obtain a deeper insight into the genetic architecture of seed metabolome in buckwheat by integrating high throughput metabolomics and genotyping-by-sequencing applying an array of bioinformatics tools for data analysis. Results High throughput metabolomic analysis identified 24 metabolites in seed endosperm of 130 diverse buckwheat genotypes. The genotyping-by-sequencing (GBS) of these genotypes revealed 3,728,028 SNPs. The Genome Association and Prediction Integrated Tool (GAPIT) assisted in the identification of 27 SNPs/QTLs linked to 18 metabolites. Candidate genes were identified near 100 Kb of QTLs, providing insights into several metabolic and biosynthetic pathways. Conclusions We established the metabolome inventory of 130 germplasm lines of buckwheat, identified QTLs through marker trait association and positions of potential candidate genes. This will pave the way for future dissection of complex economic traits in buckwheat

Delineating Marker-trait Associations for Fusarium Wilt in Chickpea using Axiom® Cicer SNP Array

Fusarium wilt (FW) caused by the Fusarium oxysporum f. sp. ciceri is a devastating disease of chickpea (Cicer arietinum L.). To identify promising resistant genotypes and genomic loci for FW resistance, a core set of 179 genotypes of chickpea was tested for FW reactions at seedling and reproductive stages under field as well as controlled conditions in the greenhouse. Our results revealed that at seedling stage, most of the genotypes were found resistant whereas, at the reproductive stage majority of the genotypes were found susceptible. Genotyping using a 50K Axiom®Cicer SNP Array and trait data of FW together led to the identification of 26 significant (p≤E-05) marker-trait associations (MTAs) for FW resistance. Among 26 MTAs, 12 were identified using trait data recorded in the field (3 at seedling and 9 at reproductive stage) and 14 MTAs were identified using trait data recorded under controlled conditions in the greenhouse (6 at seedling and 8 at reproductive stage). The phenotypic variation explained by these MTAs varied from 11.75 to 15.86% with an average of 13.77%. Five MTAs were classified as major, explaining more than 15% phenotypic variation for FW and two MTAs were declared stable, being identified in either two environments or at two growth stages. One of the promising stable and major MTAs (Affx_123280060) detected in field conditions at reproductive stage was also detected in greenhouse conditions at seedling and reproductive stages. The stable and major (>15% PVE) MTAs can be used in chickpea breeding programmes