Bakanae disease is a major rice disease caused by Fusarium fujikuroi. Infected plants show slender and hyper elongated internodes due to the over-production of gibberellic acid. Application of Trichoderma spp. as biocontrol agent is gaining attention due to high capability in hyperparasitize the soil borne pathogen. The studies aimed to screen and evaluate the bio-efficacy of Trichoderma spp. with antagonistic activities against F. fujikuroi and plant growth-promoting properties. All the 65 Trichoderma isolates were isolated from healthy rice rhizosphere soil. Thirty eight out of 65 Trichoderma isolates exhibited more than 45 Percentage of Inhibition Radial Growth (PIRG) against F. fujikuroi in dual culture plate testing. All selected Trichoderma isolates were further in vitro screened for antagonistic testing: volatile compounds production and hydrogen cyanide production and plant growth-promotion properties: IAA production and phosphate solubilization. Twelve Trichoderma isolates were selected for further evaluation on antagonistic activity against F. fujikuroi, germination rate, plumule and radical lengths and vigor index. Finally, seven of the most potential Trichoderma isolates were selected for greenhouse evaluation. The bakanae disease incidence and disease severity in rice plant treated with respective selected Trichoderma isolates were significant reduced as compared with untreated plant. However, there was no significant increase in plant height between Trichoderma inoculated and uninoculated plants. Moreover, rice plant treated with Trichoderma T61 showed significantly increase in total plant dry biomass as compared to untreated plants. The selected Trichoderma isolates have potential to be developed as biological control agent against F. fujikuroi and also as an alternative for bakanae management.
In aerobic rice cultivation systems, compost mulching and incorporation are important to rehabilitate the soil. Microbial-fortified compost is increasingly accepted as a safe approach in agro-waste management to recycling of crop residuals in agriculture soil and also to promote growth and suppress disease. This study aims to examine the stability and viability of the selected plant growth-promoting microorganisms (PGPM) in rice straw compost (RSC) over incubation period and its bio-efficacy in promoting rice (Oryza sativa) plant growth, productivity, soil health, and controlling of Pyricularia oryzae in aerobic cultivation conditions. Six selected PGPM: Pseudomonas aeruginosa (UPMP1), Corynebacterium agropyri (UPMP7), Enterobacter gergoviae (UPMP9), Bacillus amyloliquefaciens (UPMS3), Trichoderma harzianum (UPMT1), and Trichoderma virens (UPMT2) were used as a consortium of microbial inoculants to develop the microbial-fortified rice straw compost (MRSC). The MRSC was incorporated into mineral soil used for aerobic rice cultivation and its bio-efficacy was evaluated at harvest. The viability of Trichoderma spp. found stabilized at 6.78-6.00 log cfu/g and declined for all the bacterial isolates. At harvest, soil amended with MRSC significantly increased in plant height, leaf area index, 1000 grain weight, and productivity. The MRSC amended plots had significant low in rice blast disease severity with area under disease progress curve (AUDCP) of 748.22 unit/square, as compared to control (1782.67 unit/square). The physicochemical and microbiological properties of soil amended with MRSC were improved at harvest. The application of MRSC has potential to improve plant growth, productivity, rice blast disease management, and soil health of rice under aerobic cultivation systems.
Metarhizium anisopliae Metchnikoff (Hypocreales: Clavicipitaceae) is a fungal pathogen that causes disease in various insect pests, and it can be exploited and developed as a biological control agent to combat the red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Dryophthoridae). The study on indigenous isolates is crucial especially for development of bioinsecticides in the future. The M. anisopliae strain called MET-GRA4 was tested for pathogenicity against adult red palm weevil and treated in vitro with different spore viabilities. The isolates exhibited pathogenicity with 100% mortality 21 d postinfection. The median lethal time (LT50) for 85% viable spores was 8.6 d, while 39% viable spores had an LT50 value of 21.37 d, with 92 and 16.6% mycosis, respectively. The species MET-GRA4 strain was molecularly characterized using ITS1 and ITS4 from pure culture (Isolate A), mass-produced spores (Isolate B), and infected red palm weevil cadavers (Isolate C). The DNA sequences obtained matched M. anisopliae sequences, with 99% similarity. This new isolate of M. anisopliae has potential as a targeted bioinsecticide for management of red palm weevil.
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