Indian Institute of Pulses Research

Diosgenin, a steroid with multiple pharmacological properties such as anti-cancerous, anti-microbial, anti-inflammatory, cardioprotective, etc., is primarily derived from Dioscorea species, and represents an important component of steroidal medications. Due to its economic importance and rising demand, identifying sustainable alternative sources of diosgenin is imperative. Endophytes, a group of plant-associated microbial communities inhabiting the internal tissues of plants, have been reported to produce a wide range of bioactive compounds, including host metabolites. The study is aimed at bioprospecting of bacterial endophytes from Dioscorea bulbifera (air potato), an underutilized tuber crop collected from Chhattisgarh for the production of diosgenin. Eleven bacterial endophytes were isolated from the bulbs of D. bulbifera, and based on 16S rRNA gene sequencing, were identified as belonging to five genera: Enterobacter, Pseudomonas, Bacillus, Priestia, and Staphylococcus. Subsequently, a preliminary screening of their crude extracts for diosgenin production was performed using Fourier transform infrared spectroscopy (FTIR). The Pseudomonas aeruginosa D3 crude extract was found to have FTIR spectra similar to that of standard diosgenin. The endophyte-mediated diosgenin production was further confirmed by High-Performance Liquid Chromatography (HPLC) and Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) analysis. This is the first report of diosgenin production by a bacterial endophyte of D. bulbifera, and highlights the potential of exploring endophytes as a promising alternative source for plant metabolites.

BACKGROUND:Pigeonpea is an important legume crop, serving as a major source of dietary protein for the predominant vegetarian Indian population. Breeding for short duation and higher yield remains a key focus of pigeonpea improvement programs in the country. Identifying QTLs and genes governing key plant ideotype traits is crucial for accelerating genetic gain through marker-assisted selection, genomic selection and systematic breeding programs. In this study, association analysis was performed using 93 diverse pigeonpea genotypes evaluated over two years (2016-17 and 2017-18) for phenotypic data and genotyped with 63 pigeonpea-specific polymorphic simple sequence repeat (SSR) markers. METHODS:The mapping panel was screened for various plant ideotypic traits over two consecutive years, and the panel was genotyped with 63 polymorphic SSR markers. The genotypic data were utilized to study the population structure following the admixture model. Phenotypic and genotypic data, along with population structure information, were used to identify marker-trait associations (MTAs) using both the GLM and MLM methods. Candidate genes were then searched in the genome near the positions of the associated markers. RESULTS:A total of 11 and 22 MTAs were identified using GLM (with Q) and MLM (with Q + K) models, respectively, for six traits viz., days to initial flowering (IFL), days to 50% flowering (DFF), days to maturity (DM), plant height (PH), no. of primany branches (PB), and seeds per pod (SPP) at a corrected p-value of < 0.05. The phenotypic variation explained by these MTAs ranged upto 30.76%. Among these, markers HASSR28, HASSR30, and HASSR199 were consistently associated with IFL, accounting for > 12%, > 16%, and > 4.9% of the phenotypic variation, respectively. In addition, flowering traits related candidate genes, such as Glycosyltransferase, cold-responsive protein kinase 1, NRT1/PTR family 5.4, and Root phototropism protein 2, were identified in the vicinity of significant markers. CONCLUSIONS:The present study identified MTAs for flowering time, days to maturity, and plant height, and also revealed few potential candidate genes linked to these traits. Validation of MTAs and understanding the functions of candidate genes will pave the way for the development of short-duration, and high-yielding pigeonpea cultivars.

Chitinases can contribute to plant defence against fungal pathogens and insect herbivores, but their family organization, inducible deployment, and putative ligand-recognition behaviour remain poorly resolved in chickpea. We combined genome-wide identification, field expression profiling under controlled Helicoverpa armigera infestation, hormone treatments, and structure-guided comparison of representative proteins to prioritize defence-associated chickpea chitinases. We identified 28 chickpea chitinase loci (Car_Chits), comprising 22 glycosyl hydrolase family 18 (GH18) genes and 6 GH19 genes. Local duplication, especially tandem duplication within GH18, was the main contributor to family expansion, and interpretable duplicate pairs were retained mainly under purifying selection. Promoter scans indicated broad enrichment of defence- and hormone-associated cis-elements. Field quantitative real-time PCR (qRT-PCR) profiling of 11 candidate genes in field-grown plants subjected to controlled H. armigera infestation and hormone treatments showed treatment-specific temporal regulation. Car_Chit-4 (GH19) was strongly induced by salicylic acid (7.81-fold at 0.5 h; q < 0.05) but transiently repressed shortly after H. armigera feeding (0.15-fold at 0.5 h; q = 0.030). Car_Chit-19 (GH18) was the clearest herbivory-responsive gene, with late induction at 8 h (1.62-fold; q = 0.050) and 48 h (1.85-fold; q = 0.050). Jasmonic acid caused broad early repression across several genes, followed by delayed induction of Car_Chit-4 at 24 h. Seven Car_Chit-(GlcNAc)₄ complexes were modelled, docked, and simulated for 100 ns. GH18 proteins generally showed more favourable predicted MM-PBSA binding energies than GH19 proteins, but the structural metrics were interpreted as relative ligand-recognition indicators rather than direct evidence of anti-herbivore function. Car_Chit-17 had the most favourable predicted binding energy (ΔG_bind = − 18.51 ± 6.75 kcal/mol), whereas Car_Chit-14 and Car_Chit-27 retained the most stable ligand poses and Car_Chit-19 displayed the most stable protein scaffold. Chickpea chitinases show differentiated temporal responses to herbivory and hormone signalling. The study supports a working model in which GH19 Car_Chit-4 marks a rapid salicylic-acid-responsive arm, whereas GH18 Car_Chit-19 marks a delayed herbivory-responsive arm. A tiered prioritization framework separates expression-deployed candidates from structure-guided biochemical candidates, explaining why different genes emerge from qRT-PCR and molecular modelling analyses. The structural analyses provide complementary prioritization of Car_Chit-17, Car_Chit-14, and Car_Chit-27 for biochemical characterization. Together, these results provide a resource for dissecting chitinase-mediated defence in chickpea and for selecting candidates for functional validation.

Common bean (Phaseolus vulgaris L.) exhibits significant susceptibility to heat stress during its reproductive phase. However, the physiological and reproductive traits underlying heat tolerance remain inadequately characterised across diverse bean germplasm. In this study, 56 accessions were assessed under controlled heat stress conditions (32/22 °C day/night) and optimal conditions (25/15 °C) during the flowering-to-podding stage over a seven-day period across two consecutive growing seasons (2023 and 2024). Seventeen traits encompassing phenological, growth, physiological, reproductive, and yield categories were evaluated. Heat stress resulted in severe and consistent yield reductions across both seasons, with the extent of these reductions varying significantly between the tolerant and sensitive accessions. Single seed weight decreased by approximately 8% in tolerant accessions compared to approximately 34% in sensitive accessions, whereas total seed weight decreased by approximately 50% and 71%, respectively, with differences that were highly reproducible across both growing seasons. Pollen viability, pollen germination, stigma receptivity, and ovule viability were the most pronounced differentiators between the groups. Pollen viability decreased by 55–59% in tolerant accessions compared to 64–72% in sensitive lines, and pollen germination decreased by 59–65% and 71–79% across both years, respectively. In addition, tolerant accessions exhibited substantially lower electrolyte leakage and smaller declines in stomatal conductance, chlorophyll content, and photosynthetic efficiency. Two-way ANOVA revealed significant effects of accession, treatment, and their interaction for the key reproductive and yield traits. Regression analysis identified total seed weight ratio (R² = 0.876 and 0.801) and single seed weight ratio (R² = 0.522 and 0.523) as the traits most strongly associated with heat tolerance, whilst pollen viability (R² = 0.449 and 0.488), pollen germination (R² = 0.428 and 0.460), ovule viability (R² = 0.438 and 0.387), and stigma receptivity (R² = 0.428 and 0.366) showed moderate associations. Cluster and principal component analyses consistently identified IC-14912, EC-106613, IC-545783, and IC-16906 as heat-tolerant and IC-545792, EC-100098, EC-121013, and IC-362075 as heat-sensitive in both seasons. The identified heat-tolerant accessions represent priority genetic resources for heat tolerance breeding programmes in common bean.

Chickpea (Cicer arietinum L.) is a vital pulse crop that contributes significantly to global nutrition and food security. However, its narrow genetic base limits improvement for tolerance to abiotic and biotic stresses. Wild relatives of chickpea, comprising 44 species across the primary, secondary, and tertiary gene pools, represent an invaluable reservoir of genetic variation that can help overcome these limitations. This review synthesizes current knowledge on the role of wild Cicer species in enhancing chickpea resilience. Annual species such as C. reticulatum, C. echinospermum, and C. pinnatifidum confer drought and cold tolerance, while the recently described C. turcicum shows adaptation to heat stress. Perennial species, including C. microphyllum and C. anatolicum, thrive in extreme environments and contribute traits for drought and cold tolerance. Several wild accessions also exhibit resistance to major biotic stresses such as Fusarium wilt, Ascochyta blight, and nematodes. Advances in molecular genetics and genomics have accelerated the discovery of quantitative trait loci, single-nucleotide polymorphisms, and candidate genes associated with these adaptive traits, facilitating their use in pre-breeding, marker-assisted selection, and comparative genomics. Nonetheless, challenges such as cross-incompatibility, linkage drag, and limited pre-breeding efforts persist. Innovative techniques, including embryo rescue, tissue culture, and genome editing, offer promising solutions to these barriers. Harnessing the genetic potential of wild Cicer species is therefore crucial for developing climate-resilient, high-yielding cultivars. Integrating genomics, advanced phenotyping, and pre-breeding will be key to realizing this potential and ensuring sustainable chickpea production for future food and nutrition security.