Characterization of Fusarium spp. Associated to Fusarium Wilt Symptom on Piper nigrum L. in North-western Region of Sarawak

Wan Joo, Tan (2023) Characterization of Fusarium spp. Associated to Fusarium Wilt Symptom on Piper nigrum L. in North-western Region of Sarawak. Masters thesis, Faculty of Resource Science and Technology.

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Abstract

Fusarium wilt is one of the major diseases in Sarawak pepper plantation. Fusarium spp. had been identified as the causal agent for the disease. Hence, further understanding on the causal agent, Fusarium spp. is essential in the initial step to design a sustainable disease control strategies such as development of disease resistance varieties to curb the disease. The objectives for this study were: 1. To isolate and characterise morphologically and molecularly Fusarium species associated with Fusarium wilt of Piper nigrum L.. 2. To study the growth performance of Fusarium solani isolates on different pH and nutrient media. 3. To study the genetic relatedness of Fusarium solani isolated in Malaysia as well as those across Asia. Ten F. solani, three Fusarium oxysporum and eleven Fusarium proliferatum were isolated from diseased root samples collected from fifteen pepper farms in Northwestern region of Sarawak and identified based on Internal Transcribed Spacer (ITS) sequence. Variations were found on the colony morphology, growth, sporulation rate and ITS sequence of the Fusarium spp. isolates. The isolates also showed morphological variations within each species. Nine isolates of F. solani were further characterised for their colony morphology and growth on Potato dextrose agar at pH 5-9. Their morphology and growth were also recorded on five different types of nutrient media. The isolates displayed variation of colony morphology across the pH and showed better growth performance when cultured under pH 7-8 compared to other pH of PDA media. F. solani isolates also portrayed variations in colony morphology when cultured on different nutrient media. Isolates cultured on PDA media showed the most colony variations in terms of morphological appearance. Five out of nine isolates were more favourable to grow on Carnation Leaf Agar media. ITS sequence ranged from 517 bp to 525 bp was used for genetic relatedness study. It was found that F. oxysporum and F. proliferatum isolates are genetically closer with each other as they iv shared the same common recent ancestor. Both the phylogenetic analysis of local Fusarium isolates and F. solani isolates from Asia region highlighted their genetical relationship was not based on the geographical distribution of the isolates. Besides that, the analysis showed similarity of colony appearance of the isolates also does not related with their genetical relationship. In conclusion, the objectives of this study were achieved where three Fusarium spp. associated to Fusarium wilt of Piper nigrum L. were successfully isolated. The colony morphological variations of all the isolates were studied and documented. Different pH and nutrient media were found to affect the colony appearance and growth performance of the F. solani isolates. Genetic relatedness of the isolates were found to be not related to their geological distribution. Keywords: Fusarium spp., Piper nigrum L, morphological characterisation, growth, genetic relatedness

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