Mechanisms of moderate resistance in rice varieties to the brown planthopper Nilaparvata lugens (STAL) / by Dang Thanh Ho

By: Contributor(s): Material type: TextTextLanguage: English Publication details: Los Baños, Laguna : 1981. Cavite State University- Main Campus,Description: 223 pages : illustrations ; 28 cmContent type:
  • text
Media type:
  • unmediated
Carrier type:
  • volume
Subject(s): DDC classification:
  • 633.18  H65 1981
Online resources: Abstract: DANG, THANH HO, University of the Philippines at Los Banos, January, 1981. Mechanisms of Moderate Resistance in Rice Varieties to the Brown Planthopper, Ntlaparvata_lugens (Stal). Major Professor: Dr. Elvis A. Heinrichs. The mechanisms of resistance involved in moderately resistant (MR) rice varieties to the brown planthopper (BPH), Nrlaparvata lugens were studied. Moderate resistance is found quantitatively expressed and polygenically controlled with minor genes having a small, cumulative effect. Minor gene recombination occurred in the F. and F. accumulatively. MR varieties have a low level of resistance at the seedling stage but can tolerate a high BPH population under field conditions at the vegetative stage. The most important component in MR varieties is tolerance. A MR variety continued photosynthetic activity in spite of suffering heavy damage caused by BPH feeding. Yield reduction in a MR variety was significantly less than in a susceptible variety under high insect infestation. Therefore, in epidemics, tolerance operates as a major component of MR varieties to maintain acceptable yields. The second most important component operating in moderate resistance is antibiosis which affects growth and development of the insect population. Although a MR variety allows high feeding activity, it reduces the food utilization for body biomass and egg formation and eventually the insect population growth rate is reduced. With the cumulative effects of minor genes in MR varieties, insect survival is higher but development is slower compared to the highly vertical resistant varieties with oligogenic resistance. Moderate resistance expresses a compromising mechanism, allowing high insect survival but reducing the food assimilation and utilization for growth, development, and reproduction of the hoppers and ultimately decreasing the population growth rate; moderate resistance, thus exerts less selection pressure on the BPH population as compared to polygenically varietal resistance. A MR variety hence reduces the adaptability of the BPH by decreasing the rate of selection, speciation, and adaptation processes in biotype development. BPH egg parasitism and predation on vertically resistant varieties was less at high N fertilizer rate while in the MR varieties, egg parasitism was not affected by the rate of N fertilizer. The study indicated that MR varieties could be considered as potentially promising genetic sources in the breeding of longer lasting and more stable BPH resistant varieties.
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Thesis (Ph.D. - - Entomology) University of the Philippinesm College, Laguna.

Includes bibliographical references.

DANG, THANH HO, University of the Philippines at Los Banos, January, 1981. Mechanisms of Moderate Resistance in Rice Varieties to the Brown Planthopper, Ntlaparvata_lugens (Stal). Major Professor: Dr. Elvis A. Heinrichs.

The mechanisms of resistance involved in moderately resistant (MR) rice varieties to the brown planthopper (BPH), Nrlaparvata lugens were studied. Moderate resistance is found quantitatively expressed and polygenically controlled with minor genes having a small, cumulative effect. Minor gene recombination occurred in the F. and F. accumulatively. MR varieties have a low level of resistance at the seedling stage but can tolerate a high BPH population under field conditions at the vegetative stage.

The most important component in MR varieties is tolerance. A MR variety continued photosynthetic activity in spite of suffering heavy damage caused by BPH feeding. Yield reduction in a MR variety was significantly less than in a susceptible variety under high insect infestation. Therefore, in epidemics, tolerance operates as a major component of MR varieties to maintain acceptable yields. The second most important component operating in moderate resistance is antibiosis which affects growth and development of the insect population. Although a MR variety allows high feeding activity, it reduces the food utilization for body biomass and egg formation and eventually the insect population growth rate is reduced. With the cumulative effects of minor genes in MR varieties, insect survival is higher but development is slower compared to the highly vertical resistant varieties with oligogenic resistance. Moderate resistance expresses a compromising mechanism, allowing high insect survival but reducing the food assimilation and utilization for growth, development, and reproduction of the hoppers and ultimately decreasing the population growth rate; moderate resistance, thus exerts less selection pressure on the BPH population as compared to polygenically varietal resistance. A MR variety hence reduces the adaptability of the BPH by decreasing the rate of selection, speciation, and adaptation processes in biotype development.

BPH egg parasitism and predation on vertically resistant varieties was less at high N fertilizer rate while in the MR varieties, egg parasitism was not affected by the rate of N fertilizer.

The study indicated that MR varieties could be considered as potentially promising genetic sources in the breeding of longer lasting and more stable BPH resistant varieties.

Submitted to the University Library 01/07/1994 T-1497

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