Caracterizacion morfologica, patogenica y molecular de hongos asociados a frutales exoticos tropicales, rambutan (Nephelium lappaceum L.) y longan (Dimocarpus longan L.) en Puerto Rico

Rambutan, Nephelium lappaceum L. and longan, Dimocarpus longan L., are exotic tropical fruits that have great importance in the international market, attracting great interest from farmers in Puerto Rico. However, it is common to find lesions in the different organs and diseases that occur during fruit storage. Ignorance of the pathogens that affect exotic fruits in Puerto Rico is a limiting aspect in the management of orchards and fruit post-harvest. To identify the causative agents of diseases in exotic tropical fruit in field and storage, different organs were collected from symptomatic and asymptomatic trees of rambutan and longan during the period from August to September 2008 and April to May 2009. Samples were taken from exotic fruit trees USDA-ARS 'Tropical Agriculture Research Station' (TARS) in Mayaguez, Agricultural Experiment Stations, University of Puerto Rico, commercial and private farms located at the northwest, west, central and southwest of the island. Plant tissue was superficially disinfected and transferred to potato dextrose agar acidified (APDA) to promote the development of fungi associated with injuries. A total of 765 fungal isolates were obtained from plant tissue examined. Seventy five percent of isolates were from Rambutan and 24.83% to longan. Eighty percent of the isolates were characterized morphologically and 20% of the isolates were characterized molecularly by amplification of the rDNA ITS region. Eighty one DNA sequences of fungi associated with exotic tropical fruit were obtained. Twenty seven genera of fungi, 17 Ascomycetes and 10 mitosporic fungi were identified. Of the 27 genera identified, 9 were pathogenic to rambutan and 5 to longan. Botyosphaeria rhodina was the most pathogenic fungus, affecting both exotic tropical fruits, causing lesions on leaves, flowers and fruits. Albonectria rigidiuscula and Phoma spp. were also pathogenic to both exotic tropical fruit, with similar symptomatology in inflorescences, rachis wilt and mummification respectively. Lasmenia sp. was pathogenic to rambutan leaves, flowers and fruits. Calonectria pseudospathiphylli, Fusarium chlamydosporum, Glomerella cingulata, Leuconectria clusiae, Pestalotiopsis virgatula, Phomopsis longicolla were pathogens causing necrosis of rambutan's fruits. Fusarium culmorum and Pestalotiopsis clavispora were pathogens affecting longan, flowers and fruits, respectively. Calonectria Pseudospathiphylli, Leuconectria clusiae and Lasmenia sp. species are first reports for Puerto Rico.