Native durian cultivar as rootstock for the control of Phytophthora palvimora
2010
Anon.
Phytophthora palmivora, the fungal organism causing die back, patch canker, and fruit rot in durian is a big threat to the Philippine durian industry. It affects the plant from seedling to maturity resulting in huge losses. Hence, durian growers are in constant search for possible ways to control the disease. Growers observed that native durian cultivars rarely succumb to P. palmivora such that local nurserymen are encouraged to use native cultivars as rootstocks of more marketable but susceptible varieties. Infante et al. (Department of Agriculture-Southern Mindanao Integrated Agricultural Research Center, Philippines) tested the reaction of rootstocks from five cultivars (Arancillo, Puyat, Native, Graveolens Red, and Graveolens Yellow) to P. palmivora to validate these observations. Seeds were sown in plastic bags and allowed to grow for 5 and 1/2 months before grafting the Puyat cultivar. Four seedlings were used per treatment, replicated three times. The experiment was laid out in completely randomized design (CRD). Grafted seedlings were hardened for 8-10 weeks and then transferred to the feed. The seedlings were inoculated by drenching each with 100 mL of homogenized P. palmivora spore suspension. Plants were monitored weekly while periodic maintenance was observed. Evaluation of disease occurrence based on Frederiksen and Rosenow quantitative scale was used. The scale has 5 scale levels with 1 as highly resistant and 5 as highly susceptible. Diseased plants were sampled and examined in the laboratory to determine the causal organism. Two months after inoculation, flecks were observed on the leaves and 3 months after inoculation, 3 Graveolens Yellow and 1 Puyat died. Disease ratings at seedling stage were as follows: Arancillo, 2.08, Native cultivar, 2.92, Graveolens Red, 5, and Graveolens Yellow, 3. Infected seedlings showed the typical symptoms of P. palmivora infection such as sloughing off, peeling, and rotting of roots, lack of feeder roots, and chlorosis and necrosis of leaves. The researchers cautioned that using resistant rootstocks can not entirely solve the problem brought about by P. palmivora infection because it attacks durian from seedling to maturity. However, using resistant rootstock can give the plants an initial advantage in overcoming the disease. It should, therefore, be taken as an additional tool in the integrated disease management system in durian production.
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