The Use of Fungal Endophytes in Suppressing Fusarium Wilt Pathogen in Cavendish Banana Plants in Sarawak

Norhayati, Binti Ahmed Sajali (2019) The Use of Fungal Endophytes in Suppressing Fusarium Wilt Pathogen in Cavendish Banana Plants in Sarawak. PhD thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Fusarium wilt disease caused by Fusarium oxysporum f. sp. cubense (Foc), tropical race 4 (TR4) was confirmed responsible for the damage of the acreage of Cavendish plantation in Landeh, the only identified Panama disease infested area in Sarawak. The only recovered causal pathogen from the infected banana is Fusarium oxysporum f. sp. cubense (Foc) as vegetative compatibility group (VCG) complex 01213/16. It is similar with one of reported isolates from Peninsular Malaysia and Indonesia as the nearest countries, from where it was possibly introduced. Tissue culture method stands as an effective means to control the disease. However, the tissue culture tissue culture derived banana plants were claimed more susceptible to pest and disease problems. This might be due to elimination of important microbes during the tissue culture process. Therefore, in this present study, the fungal endophytes collected from the roots of wild, planted commercial bananas and from the roots of non-infected banana plants were isolated and screened for their use as beneficial microbes in the banana plantlets. It was found that 77 out of 157 isolated fungi exhibit their potential to inhibit FocR4 with percentage of inhibition of radial growth (PIRG) more than 50%. Further field assessment demonstrated that Trichoderma harzianum isolated from planted commercial banana roots, Rasthali providing plant growth regulator (PGR) effect. At the first four month, the T. harzianum-treated banana plants showed a significant stimulating effect on monthly mean increment in plant height and diameter at 3.85 cm and 4.50 cm respectively compared to the untreated control plants at 2.53 cm and 3.80 cm in height and diameter respectively. Reisolation of the T. harzianum-treated banana plants from the roots after 450 days of inoculation indicated that the fungus colonization was successful. The fungus was present at the roots and corm tissues. Furthermore, reisolation indicated that diverse group of other microbes were present, and the community was different from the control treatment. In other experiment, the T. harzianum is able to enhance host resistance through higher production of defense related compounds such as total phenolic compound (TPC) and Phenylalanine Ammonia Lyase (PAL) enzyme compared to untreated control. TPC was higher when inoculated with T. harzianum compared to the plant treated with fungicide (BenomylTM) at 12 hrs exposure times, indicating a strong respond to the pathogen infection. Following to the results obtained in this study, preventive and control of the Fusarium wilt disease can be achieved through artificially introduced T. harzianum on the tissue culture banana at the plantlets stage and thus plays an important strategy in the management of Fusarium wilt disease. Keywords: Fusarium wilt, Fusarium oxysporum f. sp. cubense, Trichoderma harzianum, Phenylalanine Ammonia Lyase, total phenolic content.

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