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Subject: Plant Pathology × Author: Bag, Dipanjali × Start date: 2000 × Thesis Type: Ph.D ×
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    Pathogenic and genetic diversity in Fusarium species causing rice Bakanae in Punjab and its management
    (Punjab Agricultural University, 2023) Bag, Dipanjali; Hunjan, Mandeep Singh
    Bakanae disease, primarily caused by Fusarium fujikuroi has been reported from nearly all ricegrowing countries across the world, especially in Asian countries like India and is known to cause high yield losses. The disease incidence is especially high on Basmati rice cultivars Pusa Basmati 1121 and Pusa Basmati 1509. Studies on cultural and morphological characters of 25 isolates showed that, the isolates produced milky white, to cream colored and cottony to fluffy colonies. The size of the spores also varied from 3-21µm X 1-5µm for non-septate micro-conidia and 13-18µm X 2-7µm for macroconidia with 3-5 septa. Molecular identification and characterization of the isolates were carried using TEF-1α gene, ITS gene and RPB2 genes. All the isolates showed amplification, and these genes from four representative isolates from different districts of Punjab were sequenced. The BLAST and phylogenetic analysis of three isolates i.e., FR4, FR14, and FR24 showed 99-100% similarity with Fusarium fujikuroi, and one isolate (FR11) with Fusarium sacchari. Pathogenic diversity analysis of these isolates revealed that they produced typical Bakanae symptoms in the different basmati cultivars. The most virulent isolate of Fusarium was FR8 from Ropar, and the least virulent was FR7 from Badshahnagar (Patiala), with the highest disease incidence recorded in the most susceptible varieties Pusa Basmati 1121 and Pusa Basmati 1509. In molecular diversity analysis revealed, all the isolates showed positive amplification for FUM1 gene for Fumonisins production loci and 24 isolates for des gene (Gibberellic acid production loci). Sequence analysis of representative isolates showed 99-100% similarity with Fusarium fujikuroi. Genetic diversity of the isolates resolved using twenty SSR primers revealed high degree of polymorphism (PIC value ranging from 0 to 0.89) inferring intra- and interspecific genetic variation, clustering the pathogen population into two major clusters. It was observed that the pathogen does not survive in soil; infected seeds being the source of primary inoculum. The level of seed infection and age of nursery plays a very important role in development of Bakanae in both nursery and field. Maximum disease was observed when the level of seed infection was 30 per cent and when 35 days old seedlings were transplanted. The mitigation studies demonstrated that presowing seed treatment with either Sprint 75WS or Trichoderma harzianum greatly reduced the disease during Kharif 2021 and 2022. Fungicide sprays in field could also curb the seed infection in succeeding crop, however, these mitigation strategies were adaptable only upto a certain level of seed infection.