Thumbnail Image

Thesis

Browse

20191
Reset filters
Subject: Plant Pathology × Author: Choudhary, Ajay Kumar × End date: 2019 × Start date: 2010 × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    ThesisItemRestricted
    DEVELOPMENT OF EFFECTIVE STRAINS OF Trichoderma SPECIES FOR THE MANAGEMENT OF FOOT ROT OF CITRUS
    (Punjab Agricultural University, Ludhiana, 2019) Choudhary, Ajay Kumar; Narinder Singh
    Foot rot of citrus is caused by Phytophthora spp. and is one of the most important disease of kinnow crop. Soil samples were collected from foot rot infected citrus orchards from Abohar and Fazilka areas. Three isolates of Phytophthora spp. were isolated by using leaf-disk baiting on PARPH-CMA medium and were characterized morphologically and at molecular level. For molecular analysis genus (Ph2–ITS4) and species (Pn5B–Pn6) specific primers were used and all three isolates were identified as Phytophthora parasitica var. nicotianae. Soil samples from healthy citrus orchards of Abohar and Fazilka regions were collected and total 25 isolates of Trichoderma were isolated and screened in vitro for antagonistic activity against Phytophthora parasitica var. nicotianae. Among the twenty five isolates, T20 isolate had maximum mycoparasitism, volatile and non-volatile metabolites activity i.e. 74.81 per cent, 65.61 per cent and 75.93 per cent, respectively. T20 parent isolate also had maximum cellulase and gulcanase activity i.e. 1.98 unit/ml and 1.31 unit/ml respectively. Seven parent isolates of Trichoderma (T2, T3, T4, T16, T20, T21 and T25) were selected on the basis of superiority in bioassay and biochemical studies. Molecular identification was done by using ITS1 and ITS4 universal primers and sequencing of all the seven parent isolates of Trichoderma revealed six isolates as Trichoderma asperellum and one as Trichoderma harzianum. These seven parent isolates were used to develop seven mutant strains of Trichoderma through different mutantgens like EMS (Ethyl Methane Sulfonate) and UV rays. The enzymes production was increased significantly for both glucanase and cellulase from 2.6 to 4.3 and 2.03 to 3.05 times, respectively as compared to parents strains that lead to increased antagonistic activity against Phytopathora parasitica var. nicotianae under in-vitro and vivo conditions. T20 mutant (Trichoderma asperellum) isolate had maximum mycoparasitism, volatile and non-volatile metabolites production i.e. 83.70, 79.26 and 81.11 per cent respectively. Among all the Trichoderma isolates, T20 mutant (T. asperellum) showed maximum enzyme activity of 3.62 unit/ml and 6.19 unit/ml for β-1,3-glucanase and β-1,4-glucanase enzyme, respectively. These seven parent and mutant isolates of Trichoderma were tested against foot of citrus pathogen i.e. Phytopathora parasitica var. nicotianae under green house and field conditions. All the Trichoderma mutant isolates performed better than their respective parents under green house and field conditions. T20 mutant (Trichoderma asperellum) isolate was the best and had minimum diseases incidence (13.33) per cent, maximum germination percentage (93.30), feeder root density (0.023 cm3) and recovery of lesion size (95.82 per cent). Maximum number of fruit and yield per plant was also noticed in T20 mutant (Trichoderma asperellum) i.e. 988 and 164 as compare to control which was 500 and 87kg. Cloning and Sequencing of cellulase (1, 4 β-glucanase) gene from T20 T. asperellum (parent and mutant) and T16 T. asperellum (parent and mutant)) exhibited 98 per cent homology to the endo-β-1,4-glucanase genes from T. asperellum KJ188168.1. Study of shelf life of bioformulations revealed that antagonists T. asperellum T20 (parent and mutant) and T. asperellum T16(parent and mutant) can remain potent at ambient temperature for 300 days, while at freezing temperature storage (0oC) these can remain potent up to one year.