Abstract
Thailand is the leading producer and exporter of durians worldwide. Serious diseases in durians include root rot, stem rot, and fruit rot, which are caused by Phytophthora palmivora, P. nicotianae, and Pythium cucurbitacearum, respectively. Thai farmers have applied fungicides for more than 20 years to control rot, but it remains difficult to control. Thus, the monitoring of fungicide-resistance development in pathogens is important for disease management. Pathogens were isolated from naturally infected durians between 2016 and 2017 in southern Thailand. The sequences of the internal transcribed spacer (ITS) and 5.8S regions of rDNA were used for the identification of their species. Seventeen out of twenty isolates were confirmed to be P. palmivora. All the isolates were tested for mycelium-growth sensitivity to metalaxyl, azoxystrobin, and dimethomorph. The results showed that nine isolates were resistant to metalaxyl with the 50% effective concentration (EC50) higher than 100 mg L−1. By contrast, all the isolates were sensitive to both azoxystrobin and dimethomorph, with EC50 < 1 mg L−1. Metalaxyl-resistant isolates were not controlled (−25.6% to 22.2%) by the treatment of the detached leaves of ‘Monthong’ durian with 100 mg L−1 metalaxyl prior to inoculation, but all the metalaxyl-sensitive and moderately metalaxyl-resistant isolates were better controlled (33.0% to 62.6%). These results clearly indicate that metalaxyl-resistant strains are present in the populations of P. palmivora in Thailand.
Highlights
The durian (Durio zibethinus), known as the “king of Thai fruits”, is one of the most popular fruits in the region and attracts a premium price
Root rot, stem rot, and fruit rot diseases, which have been shown to be caused by several Phytophthora species, including P. palmivora, P. nicotianae, and Pythium cucurbitacearum, are the key limiting factors for durian production [5,6]
Commercial formulations of the following fungicides were used in the experiments: metalaxyl (a.i., 25%), azoxystrobin (a.i., 25%), and dimethomorph (a.i., 50%)
Summary
The durian (Durio zibethinus), known as the “king of Thai fruits”, is one of the most popular fruits in the region and attracts a premium price. Eighty percent of the durians in Thailand are an important export commodity [2,3,4]. Root rot, stem rot, and fruit rot diseases, which have been shown to be caused by several Phytophthora species, including P. palmivora, P. nicotianae, and Pythium cucurbitacearum, are the key limiting factors for durian production [5,6]. They are serious pathogens because the crop losses and control costs are estimated to be in the range of 20–25% of production [5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
