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Fusarium stalk rot (FSR), caused by the Fusarium species complex, is an economic threat to maize cultivation all over the world. We investigated the population structure and genetic diversity of Fusarium species obtained from five major maize-growing regions in India. The Tef-1α locus was used for phylogenetic analysis of geographically distinct isolates of Fusarium verticillioides, F. andiyazi, F. proliferatum, F. nygamai, and F. acutatum causing FSR. A phylogenetic tree showed monophyletic, polyphyletic, and paraphyletic groupings reflecting the complex evolutionary history and genetic diversity within the genus. Monophyletic groupings depicting strong bootstrap support were shown to have a single common ancestor and genetic coherence with limited genetic divergence among sequences. Polyphyletic groupings also presented significant genetic differentiation within the F. verticillioides sequences from diverse ecological niches. Nucleotide diversity of moderate level 0.02471 reflected genetic variations within populations that were attributed to factors such as mutation, genetic drift, or varying selection pressures. The Fst value of 0.98205 is particularly indicative of high genetic differentiation, implying that most of the genetic variance is due to differences between populations rather than within them. F. verticillioides, with 57 sequences, showed low genetic diversity with three segregating sites and a low haplotype diversity of 0.19486, suggesting the founder effect, where a reduced population expands from a limited genetic pool. The total data estimates across all populations for haplotype analysis showed 72 sequences, 44 segregating sites, and 9 haplotypes with a haplotype diversity of 0.48513. The evolutionary dynamics showed genetic differentiations among Fusarium species causing FSR. AMOVA indicated high within-population variations, depicting a substantial genetic diversity within individual populations. The results offer a comprehensive framework for discussing the implications of genetic diversity in pathogen management and the evolutionary dynamics of the Fusarium species causing FSR in maize in the Indian subcontinent. [ABSTRACT FROM AUTHOR]

Certain Trichoderma isolates provide biofertilizer, biocontrol, and other plant-beneficial activities while inhabiting the soil or internal plant tissue, and their use in agricultural systems can contribute to sustainable food production. It is thought that colonization of soil or internal plant tissue is fundamental for biocontrol and biofertilizer applications. Our collective analyses of prior surveys, where the tef1α sequence was almost exclusively used to identify Trichoderma species, showed that isolates from the Harzianum complex clade, the T. asperellum/T. asperelloides group, T. virens, T. hamatum, and T. atroviride were prevalent in soil and/or as endophytes. Population structure and genetic diversity based on the genetic markers tef1α, rpb2, and ITS were investigated, and new lineages with statistical bootstrap support within T. atroviride, T. asperellum, T. hamatum, and T. virens populations were found. The nearest relatives of some of these species were also revealed. Choosing isolates from among more than 500 known Trichoderma species for use in non-targeted evaluation screens for biocontrol or biofertilizer applications is time-consuming and expensive. Preferentially selecting isolates from T. atroviride, T. asperellum/T. asperelloides, T. hamatum, the T. harzianum complex clade, T. virens, and possibly nearest relatives may speed the identification of candidates for commercialization due to the demonstrated ability of these species to successfully inhabit the soil and internal plant tissue. To our knowledge, this is the first report where dominant soil and endophytic Trichoderma species were identified from past survey data and population structure and genetic diversity analyses conducted. [ABSTRACT FROM AUTHOR]

Sclerotinia stem rot (SR) disease emerged as a potential threat in most mustard‐growing regions globally. Sclerotinia sclerotiorum, a necrotrophic pathogen, causes considerable damage to the crop under congenial environments. The sclerotia even under adverse conditions can survive up to 5 years in the soil. The use of resistant sources is the only mean to combat the pathogen. The development of an effective inoculation technique can facilitate the identification of new sources of resistance rapidly. Investigations on resistant sources using Potato Dextrose Agar (PDA) medium for artificial stem inoculation are ongoing under the All India Coordinated Research Project (AICRP) on rapeseed‐mustard for many years but no resistant sources could been identified. In the present study, two non‐injury stem inoculation techniques using sorghum grains and PDA medium as a basal medium were tested on 11 brassica entries for up to three consecutive years. Results revealed that sorghum grain‐based inoculum was found efficient for disease development and lesion formation in brassica entries compared with PDA‐based inoculum. Among the entries, a maximum disease incidence of 42.3% was recorded in entry DRMR 5206 followed by DRMRSJ‐20, DRMRSJ‐22 and DRMR 2017‐8 with 42.1%, 41.8% and 41.3% SR incidence, respectively. In PDA disc inoculation maximum SR incidence of 30.8% was observed in DRMRSJ‐26 followed by DRMR 5206, DRMRSJ‐25 and DRMRSJ‐2017‐18 with 27.5%–24.9%, respectively. Lesion length was more in entries inoculated with fungal mycelium multiplied on sorghum grains compared with the PDA disc inoculation method. The statistical analysis and results of p‐value (<.00001) showed a significant difference between tested methodologies. Thus, the sorghum grain‐based inoculation technique is an appropriate, economic and effective non‐injury inoculation technique for artificial screening against S. sclerotiorum in the mustard crop. This technique can be used to screen a large number of brassica entries more efficiently with less labour and time. [ABSTRACT FROM AUTHOR]

Post flowering stalk rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of phenomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. To investigate the pathogenicity of Fusarium spp. causing PFSR sixty isolates were toothpick inoculated between the first and second node at 55 days after sowing during the tassel formation stage of the crop in Kharif (Rainy season), and Rabi (Winter season) season field trials. Ten most virulent Fusarium isolates, based on the highest observed disease index, were identified by homology and phylogenetic analyses of partial sequences of the translation elongation factor 1 α (Tef-1α). Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into nine clusters. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vivo situations and high disease severity in field experiments. Pathogenicity test during the Kharif season showed 12 isolates with virulent disease symptoms with a mean severity ranging between 50 to 67 percent disease index (PDI) whereas in Rabi season, only five isolates were considered virulent, and the mean severity ranged between 52 to 67 PDI. Based on pathological characterization and molecular identification, 10 strains of Fusarium species namely, Fusarium acutatum (2/10), Fusarium verticillioides (Syn. Gibberella fujikuroi var. moniliformis) (7/10), Fusarium andiyazi (2/10) recorded the highest diseases index. All these species are part of the Fusarium fujikuroi species complex (FFSC). The distribution of virulent isolates is specific to a geographical location with a hot humid climate. Increased knowledge regarding the variability of Fusarium spp. responsible for PFSR of maize occurring across wide geographical locations of India will enable more informed decisions to be made to support the management of the disease, including screening for resistance in maize-inbred lines. [ABSTRACT FROM AUTHOR]

To minimize losses likely to occur due to Corynespora leaf spot, systemic and contact fungicides and formulation of bacterial antagonists like Bacillus subtilis DTBS-5, B. amyloliquefaciens DSBA-11, and Pseudomonas fluorescens DTPF-3 talc-based formulations were evaluated to manage the disease. Though mancozeb has the lowest EC50 value of 1250.54 ppm it was not efficient in the field experiment. In addition, dual culture assay to determine the efficacy of bacterial antagonists against C. cassiicola, B. amyloliquefaciens DSBA-11 effectiovely reduced growth of C. cassiicola. In the field experiments conducted during Kharif 2019 and 2020, two sprays with Azoxystrobin 23 SC@ 0.5 ml lit−1 were found most effective in reducing disease severity by 57.7% and 67.7% respectively during Kharif 2019 and 2020. Azoxystrobin 23 SC treatment resulted in a maximum increase of 281.5 kg in grain yield followed by Pseudomonas fluorescens DTPF-3 264.7 kg and Bacillus subtilis DTBS-5 248.9 kg yield. [ABSTRACT FROM AUTHOR]