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Studies on Plant Parasitic Nematodes Associated with Rice with Emphasis on the Rice-root Nematode Hirschamanniella mucronate (Das, 1960) Luc and Goodey, 1963
Thesis Abstract:
Eight nematode genera were identified in a survey conducted in several rice-growing areas of Laguna, Bicol, Mindanao and Western Visayas, namely: Aphelenchoides besseyi Christie, Hirschmanniella sp., Tylenchorhynchus sp., Helicotylenchus sp., Tylenchus sp., Crisconemoides sp., Trichodorus sp. And Pratylenchus sp. On the other hand, the stem nematode Ditylenchusangustus (Butler) Filipjev was not found in stem samples collected from the six provinces surveyed.
Found in all 11 provinces surveyed, the white-tip nematode A. besseyi was the most prevalent among the genera identified. It had the highest incidence and the most extensive occurrence in Iloilo. The nematode incidence in grains in the province had a mean of 12.7%, with the highest at 32% obtained in the municipality of Pototan. The incidence and distribution was less extensive in Albay but the highest population of 102 nematodes per grain was noted in Tabaco.
The rice-root nematode Hirschmanniella sp. Was less prevalent than A. besseyi.. It was observed in Albay, Camarines Sur, Iloilo and Laguna but not in Mindanao and Negros Occidental. It was most abundant and widely distributed in Laguna where it was found in all 13 municipalities and positively identified in 94% of the root samples collected. The highest population levels were obtained in samples from Calamba, Calauan and Bay.
In pot experiments, population levels of 1,500, 3,000, 4,5000 and 6,000 per pot of the rice-rot nematode H. mucronata inoculated on IR-8, IR-20 and C4-63G rice varieties were not sufficient to induce significant differences in plant response, particularly in yield. However, levels of 10,000, 20,000 and 30,000 were able to reduce significantly the dry-season grain yield of both IR-20 and C4-63G.
All nematode levels did no, however, induce pathological visual symptoms and other plant responses such as tillering and height.