Thesis (BS Biology) -- University of the Philippines Mindanao, 2008

This study was conducted to confirm the reactions of different durian cultivars to Phytophthora fruit rot under field conditions. Three durian farms with areas of not less than one hectare or with at least one hundred fully bearing trees of durian each within Tugbok District, Davao City were chosen. The study showed that Brunei, Lacson 2 and SKF2 manifested high susceptibility to the disease. Rated moderately susceptible were Chanee, Kob and Soriano, D101, D24, Indonesian Native, Karnyao, Latayan, Oboza, Puyat, SKO and UP1616 were rated low in susceptibility. Alcon Fancy, Arancillo, Lacson 1 and Monthong were variable from moderate to high; while Native Hybrid varied from low to moderate susceptibility and Shurot was variable from low to highly susceptible. Indonesian Native was free from infection during the 2 year period, basing on data from a sole tree. The performance of some of the varieties such as Indonesian Native, Karnyao, SKO, and UP1616 needs to be further monitored considering that these cultivars were either found in one farm and not in the other farms or the observations were based on one tree alone. Infection was low during first month, becoming intense two or three months after the initial monitoring, then declining until harvest. The presence of the shot holes caused by the shot hole beetles, age of the tree and the distance of the spines of the fruit are quite persistent in the different farms over the two-year period. Waterlogged areas, canopy type, border planting and distance of planting seem to predispose the trees to the disease. The model however, accounted for less than 60% of the variability on the incidence of the disease. The F tests revealed that the presence of shot holes, waterlogged areas, distance of planting, border planting, type of canopy, distance of spines, and age of the tree were critical in the severity of disease incidence.