This paper reports the efficacy of burning and heat-treating pistachio branches and twigs as a means of disposing of prunings from trees infected with Xanthomonas translucens pv. pistaciae (Xtp). Burning of pistachio wood, naturally infected with Xtp, was conducted twice under field conditions. Viable Xtp was detected in some non-burned wood, but not in charcoal, ash or partially burned wood. Controlled laboratory experiments were conducted with pure cultures of Xtp and naturally and artificially infected pistachio wood. In liquid culture, 65°C was lethal to Xtp, whereas survival at 60°C or less varied with culture medium and duration of exposure. Xtp survived in infected wood exposed to 40-55°C for at least 60 min but was killed by exposure to 60°C for 15 min or more. Overall, the results of burning and heat treatment were consistent, and confirmed that burning was a reliable eradication technique to dispose of infected wood, such as prunings, providing the pathogen was exposed to a temperature of 60°C or greater for at least 15 min.

Aims: Piper nigrum L. (black pepper) is an economically important commodity plant in Malaysia, which generated RM 200.95 million from pepper export in the year of 2018. However, the increase in pepper production is restricted by diseases. Fusarium wilt is one of the major diseases of P. nigrum L. The objectives for this study were to isolate Fusarium spp. associated with Fusarium wilt of P. nigrum L. from selected pepper farms in the northwestern region of Sarawak and to characterize the Fusarium spp. isolated morphologically and molecularly. Methodology and results: Fusarium spp. were isolated from diseased root samples. The pathogen was grown on potato dextrose agar (PDA) under dark condition at circa (ca.) 25 °C for morphological characterisation. Molecular characterisation was done by using internal transcribed spacer (ITS). Phylogenetic tree was constructed to study the genetic relationship of the isolates. Fusarium solani, Fusarium oxysporum, Fusarim proliferatum were the three Fusarium species identified. There were variations in morphological characters observed between and among the species, including the colony form, margin, elevation, surface appearance and pigmentation. No distinctive morphological characteristic was specific to a location. In addition, growth rate, macroconidia sporulation rate, and microconidia sporulation rate of the isolates were not correlated. In molecular phylogeny, the three Fusarium species were separated into three distinct clades representing the three identified species. The genetic relatedness between isolates within each species was depicted in the tree. Conclusion, significance and impact of study: Variations were observed among isolates in this study based on morphological and molecular characterization. This study would contribute information on the variations of Fusarium spp. associated with Fusarium wilt of P. nigrum L. from the northwestern region of Sarawak.

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