A survey of Aphelenchoides besseyi on rice in Louisiana

Abstract

Aphelenchoides besseyi, the causal agent of white-tip disease of rice is one of the plant pathogenic nematodes that causes losses in rice production. This nematode has historically been considered a minor pest in the United States but recently has been found in a number of quarantine samples for overseas shipment in both Arkansas and Louisiana. The objective of this study was determine the current distribution of A. besseyi in Louisiana. A survey was conducted using seed samples obtained from the State Seed Testing Laboratory of the Louisiana Department of Agriculture and Forestry. These seeds represent rice cultivars that were grown in Louisiana or imported from out-of-state for sale to farmers for the years 2015 and 2016. The samples were taken to the nematology lab at LSU and 25 gram sub-sample of each sample was analyzed. The sub-samples were blended in water, placed on a Baermann funnel and counted using a microscope after 24 hours. In total, 189 samples were evaluated, representing 25 different cultivars. Among these samples, 21% were from 4 hybrid cultivars imported from out-of-state. Aphelenchoides besseyi was found in 17 samples belonging to 6 cultivars. Fourteen of the infested samples were from the hybrid cultivars of rice. Approximately 83% of the samples from the rice hybrid cultivar XL 729 were infested with A. besseyi. Populations of the nematode ranged from 2 to 288 per 25g of infected rice seed. Most of the infested seed were from long grain types, but 3 of the infested samples were medium grain types. This study would indicate that most of the rice cultivars produced in Louisiana and released to farmers are relatively free of this pest. Future work will be conducted in order to evaluate more cultivars from Louisiana and test their resistance to white-tip nematode.