This technique commonly starts with breeding either through conventional or molecular approaches. The use of resistant varieties remains the most effective and economical control against bacterial leaf blight of rice (Chukwu et al., 2019). Previous reports showed that climatic conditions (temperature at 25 – 30 ☌, strong winds, rainfall, and high air humidity) accompanied by inappropriate cultural management (use of susceptible varieties and excessive application of nitrogen) are among the major factors that favour the development of the disease and epidemic spread (Exconde et al., 1973 Horino et al., 1982 Reddy and Nayak, 1984 Ou, 1985 Diekmann and Bogyo, 1992 Savary et al., 1995). Lesions that result from infection still occur on resistant varieties but to a lesser extent, as the pathogen is enveloped by plant polymers making the bacteria unable to colonise the intercellular spaces (Cottyn and Mew, 2004). Longer-range spread is associated with strong winds and typhoons, which both disperse inoculum and cause wounds that make the plants susceptible in infection (Mundt et al., 1999). It multiplies in intercellular spaces and bacterial ooze is produced on the leaf which can be passed to other plants by direct contact of foliage and through irrigation water (Mundt et al., 1999 Cottyn and Mew, 2004 White and Yang, 2009). The pathogen infects wounds and water pores in the plant. Xanthomonas oryzae is short-lived outside of its host and so does not survive well in the soil and there are contradictory reports of its survival on seed. It survives between seasons on rice stubble and on weeds, considered the primary sources of inoculum. Infections at the later booting stage, do not have such a significant effect on yield but result in poor quality grains and a high proportion of broken kernels. oryzae can result to more than 70% yield loss owing to reductions of physiological (photosynthetic rate, stomatal conductance to CO 2, water use efficiency, and leaf transpiration rate) and agronomic components of rice (1000 grain weight and percent filled spikelets Rao and Kauffman, 1977 Reddy et al., 1979 Reddy and Nayak, 1984 Ou, 1985 Mew et al., 1993 Kumar et al., 2013). It is destructive to high-yielding varieties in both temperate and tropical regions, especially in Asia. oryzae (Ishiyama, 1922) is one of the most important diseases of rice (Choi et al., 1998 Savary et al., 2000a Savary et al., 2000b). As the season progressed, we observed an emerging short-range (1.6 m–4 m) spatial structure suggesting secondary spread was predominantly short-range, particularly where the resistant variety was grown.īacterial leaf blight caused by Xanthomonas oryzae pv. Primary infection was characterised by spatially-random observations of disease incidence. In fact, we found site to be a greater determinant of the number of infection attempts suggesting that other environmental and management factors had greater effect on the disease than climate. Likewise, we found spread in the dry season can be substantial and should therefore not be ignored.
Despite secondary spread being attributed to splash dispersal which is exacerbated by wind and rain, the wetter sites of Pila and Victoria in south Luzon tended to have lower infection rates than the drier sites in central Luzon. However, we found no evidence that the primary infection efficiency was lower in resistant varieties, suggesting that differences were largely due to reduced secondary spread. Disease incidence was generally lower in the resistant variety. To explore this, we analysed data on the disease progress on resistant and susceptible varieties of rice grown at four sites in the Philippines across five seasons using a combination of mechanistic modelling and statistical analysis. local site conditions and season), management, and in particular, variety resistance. infection efficiency, and spatial spread) change according to environment (e.g. To better control the disease, it is important to understand its epidemiology and how key aspects of this (e.g. oryzae) is a serious disease in rice across the world.
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