Preliminary evaluation of guava selections for guava wilt disease resistance in South Africa
South African Journal of Plant and Soil
Agricultural Research Council-Institute for Tropical and Subtropical Crops, Nelspruit, South Africa; Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa
Guava wilt disease (GWD), caused by Nalanthamala psidii, is a serious disease occurring in the guava-producing areas of the Mpumalanga and Limpopo provinces of South Africa. Two resistant guava rootstocks, TS-G1 and TS-G2, were developed by the ARC-ITSC in 1995. In 2009, a renewed outbreak of GWD was reported, which also affected the resistant TS-G2 cultivar, placing the guava industry under threat again. The aim of this study was to seek resistant guava selections by means of in vitro screening of guava seedlings and subsequently testing the most promising selections in inoculation studies with N. psidii. A culture filtrate of N. psidii was used to screen guava seedlings in vitro. Promising selections were multiplied in tissue culture, hardened-off and planted in bags before inoculation with the GWD fungus in a shadehouse trial. The number of plants surviving nine months after inoculation was recorded. Although none of the selections showed complete resistance, selection MS44 showed some tolerance against the G2 isolate of the pathogen obtained from diseased TS-G2 trees, whilst selection MS70 showed some tolerance against the G1 isolate obtained from diseased TS-G1 trees. These selections were also resistant to the original Fan Retief isolate of the pathogen. © 2014 © Southern African Plant and Soil Sciences Committee.
cultivar; disease resistance; fruit; inoculation; pathogen; seedling; wilt; Limpopo; Mpumalanga; South Africa; Fungi; Nalanthamala psidii; Psidium