Sustainable control of soil-borne pathogens in dryland taro cropping systems

Abstract

In Hawai'i, taro (Colocasia esculenta) is an important part of cultural, nutritional, and agricultural traditions. Soil-borne pathogens are responsible for significant losses in taro production systems. Meloidogyne javanica and Pythium aphanidermatum are pathogens found in dryland taro production systems that attack taro in Hawai'i. A sustainable method to control these pathogens in dryland taro cropping systems is warranted. Combining phytochemical producing green manure cropping systems that are toxic to pathogens with resistant cultivars can provide sustainable control of these pathogens. Ten green manure crops that produce pathogen toxic phytochemicals were screened for host status to M javanica. Interactive affects of M javanica, Pythium aphanidermatum, and 22 green manure crop species were also evaluated. Tagetes spp. were not hosts of M javanica, and were not affected by P. aphanidermatum, inoculating both pathogens concurrently reduced growth. Brassica spp. were good hosts to M javanica, and P. aphanidermatum. Sorghum X sudangrass varied in host status, but produced copious amounts of biomass in the presence of either pathogen alone or combined. The best candidate was Sorghum X Sudangrass Graze All ST. It had a low reproduction factor (Rf = 0.19) and grew well inoculated with M javanica and Pythium aphanidermatum combined and individually. Taro gerrnplasm were screened for resistance to M javanica in the greenhouse. Of the 54 taro gerrnplasm screened, resistance remained elusive. Thailand accession 035 and hybrid 40 from a Hawaiian Palauan cross are candidates for tolerance evaluation. In comparison to Bun Long, the most widely grown variety of dryland taro produced in Hawai'i, 23 accessions had superior growth and 20 accessions supported less reproduction.