Screening rice lines with various resistant genes and combinations against Xanthomonas oryzae pv oryzae strains from Malaysian rice granaries

Kogeethavani, R.¹*, Fatin, N. A.¹, Nurshamiza, M. Y.¹ and Muhammad Rusydi, S.¹

Abstract
Bacterial blight caused by Xanthomonas oryzae pv oryzae is the most destructive disease of rice in Malaysia due to its
high epidemic potential. Therefore, the most effective solution for disease management, considering both environmental
safety and production costs, is the utilisation of resistant rice varieties. This study evaluated the performance of 10
near-isogenic lines and 16 pyramided lines carrying known bacterial blight resistance genes against 12 different
Xanthomonas oryzae pv oryzae pathotypes collected from Malaysian rice granaries. Lesion length percentage was
measured 21 days after inoculation and converted into various disease reaction categories. The study revealed that single
resistance genes, xa5 and Xa7, found in IRBB5 and IRBB7, respectively, were effective against Malaysian strains of
Xanthomonas oryzae pv oryzae. Furthermore, the combination of these genes with Xa21 (IRBB21) in pyramided lines
IRBB54, IRBB60, IRBB64, IRBB65 and IRBB66 exhibited strong resistance against Malaysian Xanthomonas oryzae
pv oryzae strains. This information supports the use of resistant cultivars in Malaysia as part of a gene deployment
strategy to manage the disease.

Keywords: bacterial blight, resistance gene, near-isogenic lines, rice, Xanthomonas oryzae pv oryzae

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