An anatomy of the bacterial blight epidemics in the Philippines

Mew T.W., . and Vera Cruz C.M., . and Medalla E.S., . (1990) An anatomy of the bacterial blight epidemics in the Philippines. [Proceedings Paper]

Bacterial blight BB of rice has been reported in the Philippines since 1950's. It was considered a major constraint to rice production in the 50's and became increasing in importance in the 60's when the semi-dwarf high-yielding cultivars were introduced to the farmers. Consequently resistance to BB has been undertaken as an important breeding objective. Currently most of the improved rice cultivars planted to about 80 percent of rice land possess of the resistance gene Xa-4. The disease is caused by Xanthomonas campestris pv. oryzae which appears to be highly variable. When cultivars with the Xa-4 for resistance was released in early 70's shortly it was found susceptible in some parts of the country. The race which was virulent to the resistance gene Xa-4 designated as race 2 was found to exist in the pathogen population in the early 60's. Race 1 which was predominant until early 70's is virulent to Xa-10 Xa-11 and Xa-14 before improved modern rice cultivars highly responsive to nitrogen fertilizer and management were widely cultivated. Later when the cultivars with the Xa-4 gene was introduced race 1 declined but the emergence of races 2 and 3 throughout the country was quite evident. By late 70's race 2 has occupied 80 percent of the pathogen population which corresponded well to the total rice land area planted to rice cultivars possessing the Xa-4 gene. The population trend has maintained until 1988 so was the area of cultivated rice. There are six races four of which are often detected during the past 20 years. Besides race 2 which has a narrow spectrum of virulence other 4 races appear to have distinct geographical distribution. Race 1 continues to be detected in low lands where traditional cultivars are planted or cultivars with Xa-4 have not been extensively cultivated. Race 3 one time most predominant in the southern Philippines was low in the population; so with race 4 which was found only in Palawan. Race 5 exists as a high land race and has dominated the bacterial population in Banaue the Mountain Terraces more than 3000 feet above sea level. A very minute population of race 6 was also detected

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Abstract

Bacterial blight BB of rice has been reported in the Philippines since 1950's. It was considered a major constraint to rice production in the 50's and became increasing in importance in the 60's when the semi-dwarf high-yielding cultivars were introduced to the farmers. Consequently resistance to BB has been undertaken as an important breeding objective. Currently most of the improved rice cultivars planted to about 80 percent of rice land possess of the resistance gene Xa-4. The disease is caused by Xanthomonas campestris pv. oryzae which appears to be highly variable. When cultivars with the Xa-4 for resistance was released in early 70's shortly it was found susceptible in some parts of the country. The race which was virulent to the resistance gene Xa-4 designated as race 2 was found to exist in the pathogen population in the early 60's. Race 1 which was predominant until early 70's is virulent to Xa-10 Xa-11 and Xa-14 before improved modern rice cultivars highly responsive to nitrogen fertilizer and management were widely cultivated. Later when the cultivars with the Xa-4 gene was introduced race 1 declined but the emergence of races 2 and 3 throughout the country was quite evident. By late 70's race 2 has occupied 80 percent of the pathogen population which corresponded well to the total rice land area planted to rice cultivars possessing the Xa-4 gene. The population trend has maintained until 1988 so was the area of cultivated rice. There are six races four of which are often detected during the past 20 years. Besides race 2 which has a narrow spectrum of virulence other 4 races appear to have distinct geographical distribution. Race 1 continues to be detected in low lands where traditional cultivars are planted or cultivars with Xa-4 have not been extensively cultivated. Race 3 one time most predominant in the southern Philippines was low in the population; so with race 4 which was found only in Palawan. Race 5 exists as a high land race and has dominated the bacterial population in Banaue the Mountain Terraces more than 3000 feet above sea level. A very minute population of race 6 was also detected

[error in script]

Item Type:	Proceedings Paper
Additional Information:	1 ill. 4 tables; 7 refs. Summary En
AGROVOC Term:	ORYZA SATIVA
AGROVOC Term:	RESISTENCIA A LA ENFERMEDAD
AGROVOC Term:	TIZON
AGROVOC Term:	FILIPINAS
AGROVOC Term:	XANTHOMONAS CAMPESTRIS
AGROVOC Term:	PODER PATOGENO
AGROVOC Term:	VARIEDADES
Geographical Term:	MALAYSIA
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:26
URI:	http://webagris.upm.edu.my/id/eprint/14880

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