Title: Field survey and fungicide screening of fungal pathogens of rambutan (Nephelium lappaceum) fruit rot in Hawaii Authors
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2011
Publication Date: May 1, 2011
Repository URL: http://handle.nal.usda.gov/10113/56503
Citation: Keith, L.M., Matsumoto Brower, T.K., Nishijima, K.A., Wall, M.M., Nagao, M. 2011. Field survey and fungicide screening of fungal pathogens of rambutan (Nephelium lappaceum) fruit rot in Hawaii. HortScience. 46:730 - 735. Interpretive Summary: Unfortunately, a number of fungal diseases attack rambutan and will affect quality and quantity of this fruit. The objectives of this study were to: (i) identify the causal agent(s) of commonly observed symptoms of fruit rot of rambutan in Hawaii; (ii) compare fungal isolates by studying pathogenicity, morphological, cultural and molecular characteristics; (iii) examine the effect of temperature on growth of the pathogens; and (iv) determine the in vitro efficacy of fungicides currently registered for use on rambutan in Hawaii.
Technical Abstract: Rambutan (Nephelium lappaceum Linn.) is a tropical fruit in Hawaii that has increased in value in the niche market of exotic fruits. The primary limitation to pre-harvest and post-harvest quality is the occurrence of fungal diseases of the fruit. A survey of rambutan disease was conducted in Hilo, Hawaii and at the surrounding farms to determine the main fungal pathogens affecting fruit quality. Rambutan fruit (rind and spinterns) were affected by brown to black lesions that progressed to blackening and drying of the fruit that frequently became totally mummified. Four fungi consistently isolated from symptomatic fruit included Lasmenia, Pestalotiopsis, Phomopsis and Colletotrichum spp. Over the 2 year sampling period, disease incidence from more than 300 fruits sampled was 84.6%. Nine rambutan cultivars were evaluated for disease incidence under field conditions. Twelve fungal isolates from infected fruit were selected for further characterization (six Lasmenia isolates and two isolates each of Pestalotiopsis, Phomopsis and Colletotrichum). Morphology, colony characteristics, and pathogenicity of the isolates were examined. Molecular methods were used to confirm the identity of the fungi. The fungal isolates were evaluated for in vitro baseline sensitivities for mycelial growth for fungicides registered for use in Hawaii (Abound® and Trilogy®). This is the first report where traditional and molecular methods were used to identify and characterize fungal pathogens of rambutan in Hawaii. Potential control methods were also investigated.