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Plant introductions, including the movement of seeds across international borders, significantly contribute to the emergence of viral pathogens, which account for approximately half of all emerging plant diseases. Among plant virus families, the Potyviridae stand out as the largest and most economically impactful. The potyvirus genus with 201 species widespread across various crops, causes substantial crop losses globally. These viruses are primarily transmitted by aphids in a nonpersistent manner, with some also capable of transmission through seeds. Global food security is significantly impacted by the crucial part that seed transmission plays in the epidemiology and spread of different plant viruses. With transmission rates varying greatly between viruses and host plants, over 231 viruses were discovered to be capable of spreading through seeds, including 20 seed-transmitted potyviruses. The seed transmission efficiency of potyviruses such as maize dwarf mosaic virus (MDMV), cowpea aphid-borne mosaic virus (CABMV), and bean common mosaic virus (BCMV) ranges from 3% to 95%. Other notable viruses include soybean mosaic virus (SMV) (58% transmission) and pea seed-borne mosaic virus (PSbMV) (100% transmission). The diversity in seed transmission efficiency among viruses demonstrates the important role that seeds play in the propagation and dissemination of viral pathogens. In addition, seed transmission permits viruses to survive in unfavorable environments, promotes long-distance spread via international seed exchange, and acts as the main point of infection for viruses that have vertical transmission. The complex dynamics of seed transmission and the complex relationship between viruses and their host plants highlight the significance of strict phytosanitary measures in protecting global agriculture from the destructive effects of viruses transmitted through seeds. This review focuses on potyvirus seed transmission, with an emphasis on determining the significance of this mode and understanding the potential role of seed transmission in potyviruses.

Papaya is widely grown in tropical and subtropical climates due to its high yield potential and high returns. The vital hormone melatonin, regulating various biological processes in plants, is eco-friendly and less harmful to humans than other chemicals. This study aims to enhance the quality and antioxidant enzyme activities and lessen postharvest senescence in papaya cv. CO 8 fruits during both ambient (32 ± 2 °C and 55 ± 5% RH) and cold storage (10 ± 2 °C and 90–95% RH) as exogenous melatonin (EMT) is applied in varying concentrations. An optimum melatonin dose of 1.5 mM was applied as a pre-harvest spray 15 days before harvest and a postharvest dip proved effective in prolonging shelf life (under ambient it prolonged to day 9 and under cold storage up to 28 days) and delaying ripening and softening. Exogenous melatonin application enhanced antioxidant activity, reduced weight loss, maintained firmness, delayed ripening enzymes, and lowered ethylene and CO2 levels. For instance, control fruits had weight losses between 7.42% and 10.09%, while fruits treated with 1.5 mM melatonin showed 5.74% and 9.06% weight loss under ambient and cold storage, respectively. In conclusion, applying EMT (1.5 mM) could be an economically viable and environmentally benign way to lessen senescence after harvest and preserve the qualities of the papaya fruit during ambient and cold storage.

This study aims to increase Bacillus and Streptomyces antagonistic activity against the root rot and wilt diseases of pulses caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. udum, respectively. To increase antagonistic action, Bacillus subtilis BRBac4, Bacillus siamensis BRBac21, and Streptomyces cavourensis BRAcB10 were subjected to random mutagenesis using varying doses of gamma irradiation (0.5–3.0 kGy). Following the irradiation, 250 bacterial colonies were chosen at random for each antagonistic strain and their effects against pathogens were evaluated in a plate assay. The ERIC, BOX, and random amplified polymorphic studies demonstrated a clear distinction between mutant and wild-type strains. When mutants were compared to wild-type strains, they showed improved plant growth-promoting characteristics and hydrolytic enzyme activity. The disease suppression potential of the selected mutants, B. subtilis BRBac4-M6, B. siamensisi BRBac21-M10, and S. cavourensis BRAcB10-M2, was tested in green gram, black gram, and red gram. The combined inoculation of B. siamensis BRBac21-M10 and S. cavourensis BRAcB10-M2 reduced the incidence of root rot and wilt disease. The same treatment also increased the activity of the defensive enzymes peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. These findings suggested that gamma-induced mutation can be exploited effectively to improve the biocontrol characteristics of Bacillus and Streptomyces. Following the field testing, a combined bio-formulation of these two bacteria may be utilised to address wilt and root-rot pathogens in pulses.

Clonostachys rosea, an ascomycetous, omnipresent, cellulose-decaying soil fungus, has been reported to be a well-known mycoparasitic biological control agent. In this study, we isolated C. rosea, a mycoparasitic fungus for the first time in India from sclerotia of the notorious plant pathogen Sclerotinia sclerotiorum, causing head rot disease in cabbage. A total of five mycoparasitic fungi were isolated from the sclerotial bodies of S. sclerotiorum (TNAU-CR 01, 02, 03, 04 and 05). All the isolates were tested under morpho-molecular characterization. Among them, TNAU-CR 02 showed the greatest mycelial inhibition of 79.63% over the control. Similarly, the SEM imaging of effective C. rosea isolates indicated the presence of numerous conidia destroying the outer cortex layers of sclerotia. Metabolite fingerprinting of C. rosea TNAU-CR 02 identified 18 chemical compounds using GC-MS analysis. The crude antibiotics of C. rosea TNAU-CR 02 were verified for their antifungal activity against S. sclerotiorum and the results revealed 97.17% mycelial inhibition compared with the control. Similarly, foliar application of TNAU-CR 02 at 5 mL/litre on 30, 45 and 60 days after transplanting showed the lowest disease incidence of 15.1 PDI compared to the control. This discovery expands our understanding of the biology and the dissemination of C. rosea, providing a way for the exploitation of C. rosea against cabbage head rot pathogens.

Ashwagandha (Withania somnifera), enriched in alkaloids, steroidal lactones and saponins, is a valuable herb in Indian Ayurvedic medicine. During December 2023, Va-1 (Vallabh Ashwagandha-1) plants at ICAR -Central Tobacco Research Institute, Vedasandur, Tamil Nadu (10.53717ºN, 77.9507°E) were noticed with anthracnose-like disease symptoms, characterized by irregular necrotic lesions on stem, leaves and pods. Infected plants dried entirely in the advanced stage and had pin-head-shaped fruiting bodies. In the assessment of 185 plants, 42 were symptomatic, while five were dried, and the disease severity varied between 17 to 22%. Pathogen was isolated from infected leaf and stem tissues (3 to 5 mm2) using a potato dextrose agar (PDA) medium amended with streptomycin sulphate (20 mg/l). Infected tissues were surface sterilized using 1% sodium hypochlorite, and the PDA plates were incubated at 27°C for three days. The pathogen was purified, and two cultures, AVCT01 and AVCT02, were used for the downstream characterization. Colonies on the PDA medium were initially pale white and later turned to dark grey, with an average growth of 42.6 mm (diameter) on the 7th day after inoculation (DAI). Conidia were smooth, hyaline, aseptate and curved, with a tapering end and truncate base. The conidial dimensions (n=30) were 22.8 ± 1.32 × 3.4 ± 0.29 µm (20.6 to 25.8 × 2.9 to 4.2). Acervuli were scattered, containing dark brown conidiomata with septate, pointed setae and measured 119 ± 16.6 × 4.2 ± 0.5 µm (81 to 148 × 3.1 to 5.3) in dimension. Morphological and cultural characteristics were identical to Colletotrichum truncatum described by Damm et al. (2009). Further, the molecular characterization was executed with primers targeting ITS (ITS1/ITS4) and three housekeeping genes; act (ACT-512F/ACT-783R), tub2 (Bt2a/Bt2b) and gapdh (GDF1/GDFR1) (Kim et al. 2020). The amplified products were sequenced bidirectionally and in BLASTn analysis, sequences revealed 100% identity with C. truncatum [(NCBI GenBank OM327672 (ITS), OR147336 (act), MG214130 (tub2) and MK675260 (gapdh)]. In the maximum likelihood phylogeny of concatenated alignments, these cultures clustered with CBS119189. All sequences were deposited in NCBI GenBank (ITS: PP919605 and PP919606; act: PP921525 and PP921526; tub2: PP921527 and PP921528; gapdh: PP921529 and PP921530). Pathogenicity was done by spraying conidial suspension of AVCT01 (1 × 106/ml) on leaves of three plants (two months old). Non-injury technique of Gupta et al. (2020) was conducted for stem inoculation. The inoculated and control plants (sprayed with sterile distilled water) were maintained separately at 25°C with 90% relative humidity. Necrotic lesions were observed on leaves and stems of inoculated plants on 8th DAI confirming Koch's postulates and the pathogen re-isolation was also done. Disease severity was assessed using the scale of Yang and Hartman, 2015. Previously, leaf spots caused by C. gloeosporioides and C. dematium were reported in ashwagandha from West Bengal (Sarkar and Dasgupta, 2017) and Uttar Pradesh (Wijeskara et al. 2005) states of India. However, our study marks the first report of C. truncatum in ashwagandha, alerting the adaptation of multiple Colletotrichum species to this highly valued medicinal herb. Elucidating the etiology of newly adapted pathogen species paves the way for rapid disease diagnostics to implement effective disease management strategies.

Tomato (Solanum lycopersicum) and chilli (Capsicum annuum) are globally significant vegetable crops susceptible to damping-off disease caused by Pythium aphanidermatum, leading to substantial yield losses. The study aimed to document the biocontrol and plant growth promotion potential of Streptomyces rochei against damping-off disease in tomato and chilli. The actinobacterial isolates ACS18 followed by ACT30, and AOE12 were accomplished as the most effective antagonists against P. aphanidermatum in vitro. Molecular characterization confirmed these isolates as members of Streptomyces genus, with ASH 18 the top performer identified as S. rochei isolate. Analysis of biomolecule through GC-MS during ditrophic interaction between pathogen and S. rochei showed the presence of various antifungal metabolites which were directly related to suppression of the pathogen. Subsequently, S. rochei was formulated into a talc-based preparation and used as seed treatment and soil application against damping-off. In greenhouse trials, significant reductions in damping-off incidence were observed, Furthermore, seedlings treated with S. rochei displayed enhanced root and shoot lengths compared to the uninoculated controls. These benefits potentiate S. rochei as a promising biocontrol agent and demonstrating its dual benefits of disease suppression and promotion of seedling growth., (© 2024 Wiley‐VCH GmbH.)

Glory lily ( Gloriosa superba ), an ornamental climbing plant, contains the bioactive compound colchicine, attracting attention from the pharmaceutical industry. However, soilborne pathogens have emerged as a serious threat to the cultivation of glory lily, leading to substantial economic losses in the southern parts of India. Among these, the three major pathogens are Macrophomina phaseolina , Fusarium oxysporum , and Agroathelia rolfsii , causing dry root rot (also referred to as charcoal rot), wilt, and stem rot, respectively. Here, we characterized these pathogens using morphological characteristics and phylogenetic analysis of DNA sequences related to the internal transcribed spacer of ribosomal DNA, calmodulin ( CAL ), and translation elongation factor 1-alpha ( TEF-1α ). Furthermore, in the pathogenicity tests, the inoculation of M. phaseolina alone resulted in lesions measuring 7.54 ± 0.01 mm on tubers and 90% seedling mortality. This severity was comparable to the simultaneous inoculation of all three pathogens, indicating the prominence of dry root rot among soilborne diseases. This study marks the first detailed investigation of soilborne pathogens combined infection in G. superba , contributing to the understanding of fungal disease complexity in medicinal plants., Competing Interests: The author(s) declare no conflict of interest.