ARS | Publication request: Persistence of Gliocephalotrichum spp. causing fruit rot of rambutan (Nephelium lappaceum L.) in Puerto Rico

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2011
Publication Date: N/A

Technical Abstract: Worldwide, fruit rot of rambutan is an important problem that limits the storage, marketing and long-distance transportation of the fruit. A complex of pathogens has been reported to cause fruit rot of rambutan and significant post-harvest economic losses. During 2009 and 2011 rambutan fruit rot was observed on trees at the USDA-ARS Tropical Agricultural Station in Mayaguez, Puerto Rico. Infected fruit sections (1mm2) were surface sterilized, rinsed with sterile deionized-distilled water and transferred to acidified potato dextrose agar (APDA). Using light and scanning electron microscopy, a total of 27 isolates of Gliocephalotrichum spp. were obtained and preliminarily identified morphologically into two species (Gsp and Gsp1). Pathogenicity tests were conducted on healthy superficially sterilized fruits that were inoculated with 5-mm mycelial disks of 8-day-old pure cultures grown in APDA. Untreated controls were inoculated with APDA disks only. Fruits were kept in a humid chamber for eight days. Five days after inoculation (DAI), white mycelial growth for Gsp and yellowish mycelial growth for Gsp1 were observed on rambutan fruits. Eight DAI, fruit rot symptoms were observed on both Gsp and Gsp1 isolates. Fruits changed in color from red to brown, and, on average, mycelia of Gsp and Gsp1 covered 50 and 60% of the fruit, respectively. Conidiophores were observed on spintems (hair-likes-appendages on fruit surface). Both species were re-isolated from diseased plant tissue, thus fulfilling Koch’s postulates. To identify the species of the isolates obtained from the surveys on both years, PCR amplifications of the ITS rDNA region are being conducted. Gliocephalotrichum spp. have already been associated with rambutan fruit rot in Costa Rica, Hawaii, Sri Lanka and Thailand.