Genetic analysis of selected PSB rice varieties for resistance to bacterial blight (Xanthomonas oryzae pv oryzae ex Ishiyama)
2004
Abalos, M.C.(Philippines Rice Research Inst., Science City of Munoz, Nueva Ecija (Philippines). Plant Breeding and Biotechnology Div. | Tabien, R.E. | Alfonso, A.A. | Dela Cruz, Q.D.
Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae ex Ishiyama is a serious disease and one of the major constraints in rice production in many Asian countries. Effective chemical-based control measures are not available against BB and the use of resistant varieties remains the most important ecological control method. More than 25 genes are available for resistance (R) to BB in rice including the Xa21, Xa7, Xa4, xa8, xa5, Xa13, Xa10 and Om gene. It was in this light that this study aimed to analyze BB resistance observed in some PSB rice varieties possibly caused by new resistance genes. Seven BB isolates were used in the inoculation using a clipping method for introducing the bacteria into the plant leaves. Six modern rice varieties were subjected to genetic analysis for resistance to BB. These included the PSB Rc2, PSB Rc34, PSB Rc56, PSB Rc64, PSB Rc80 and PSB Rc82 varieties. The PSB Rc2 variety was found to contain the Xa-4 gene ; PSB Rc34 had 4 genes effective against races 1,6 and 9; PSB Rc56 had Xa-4, Xa-14 and an unknown gene found to be very effective for race 8; PSB Rc64 had Xa-4, Xa-14, Xa-7 and a putative new gene that was effective against race 6; PSB Rc80 contained Xa-4 gene found effective against races 1 and 7; and PSB Rc82 had at least nine different genes that made it resistant to Xoo races 1,6,7,8 and 9 based on the analysis of two population (PSB Rc82 x IR24 and PSB Rc82 x IRRBB5). Furthermore, knowledge on the properties of BB resistant genes, its effectiveness to specific races and to the bacteria itself would help us deploy the suitable verieties for specific locations prevalent to this disease.
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