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- Further Assessment of Rice Yield Loss Due to Bacterial Leaf Blight
Further Assessment of Rice Yield Loss Due to Bacterial Leaf Blight
Thesis Abstract:
The study was conducted to determine the effect of Xanthomonas oryzae (Uyeda et Ishiyama) Dowson on the grain yield of three nonseasonal rice varieties, IR- 8, C4-63(G) and IR-20, the susceptible, intermediate and resistant varieties, respectively during the 1972dry and 1973 wet season. The experimental plants were inoculated at 60, 75 and 90 days after sowing at three disease- intensity levels of 25, 50 and 75%.
Results indicated that bacterial leaf blight could decrease the yield potential of the three rice varieties. Average yield losses of IR- 8 were 10.77 and 25.8% in the dry and wet season, respectively ; C4- 63 (G), 8.01 and 18.76% and IR 20, 3.31 and 13.82%.
The linear regression of yield on disease intensity in the three varieties was statistically signifant in both planting seasons. Average yield decreases of IR 8 were 11.68 and 8.76 g per 0.75 m2 for each unit increase in disease intensity for the dry and wet season, respectively; C4-63 (g), 7.67 and 6.16 g; and IR-20, 3.81 and 4.34 g.
There were appreciable losses in yield due time of inoculation at three stages of plant growth, but statistical analysis showed no interaction between the rice variety and inoculation time. No significant interaction was observed between inoculation time and disease intensity. Except on inoculation 60 days after sowing in the dry season. Significant reaction was oated between disease intensity and all three rice varieties. As the the disease intensity increased the higher was the yields loss.
Yield losses from infected plants were higher during the the wet than during the dry season, indicating that yield reduction was due not only to the susceptibility of the rice plant and severity of infection but also to the season of planting.