This was likely to be due to the great extension AZD3965 of diseased tissue with symptoms of chlorosis;

however, the cells were obviously not protected efficiently against X translucens pv. undulosa colonization. Rodrigues et al. (2005) found that the accumulation of LTGA derivatives was biphasic in rice cultivars Katy and M201 inoculated with an isolate of P. grisea that resulted in an incompatible and a compatible interaction, respectively, regardless of whether the plants from these cultivars were supplied or not with Si. Indeed, the rate of accumulation of LTGA derivatives accumulation appeared slower on leaves from plants of cultivar M201 supplied with Si. Regarding the activity of the enzymes evaluated on this study, CHI was high at the most advanced stages of X. translucens this website pv. undulosa infection on leaves from plants supplied with Si and possibly had a negative effect on bacterial population on leaf tissue. By contrast, Rodrigues et al. (2003a) showed that CHI was not an important mechanism of defense in rice against P. grisea because the pattern of chitin localization over fungal cell walls in tissues of plants supplied or not with Si was very similar in terms of uniformity and density. Indeed, Rodrigues et al.

(2005) found weak induction of CHI transcripts on rice leaves of a susceptible cultivar to blast, supplied or not with Si, suggesting that this enzyme is not important for resistance. Considering that X. translucens pv. undulosa nutrition and successful invasion are prerequisites for the development of water-soaked lesions with massive bacterial exudation on wheat leaves, cell wall degradation through the action of lytic enzymes is conceivably one of the most harmful events associated with the colonization process of many bacteria including the X. translucens pv. undulosa (Duveiller and Maraite, 1993) Rodrigues et al. (2005) showed that POX transcripts increased during the course of infection by P. grisea

in both incompatible and compatible interactions on rice plants supplied or not with Si. In the susceptible cultivar supplied with Si, a higher Interleukin-3 receptor level of POX transcripts accumulated during the time course studied. Accumulation of POX transcripts was associated with an increase in resistance of rice plants to blast, presumably due to the participation of POX in the biosynthesis of lignin (Rauyaree et al., 2001). This finding is not in agreement with the results from the present study, which showed that POX activity following infection by X. translucens pv. undulosa was not increased by Si, but can somehow be linked with the highest concentration of LTGA derivatives obtained at 12 d.a.i. of plants supplied with Si. The PPO activity had no apparent effect on wheat resistance to leaf streak regarding the Si treatments. Methods used to protect economically important crops such as wheat against devastating pathogens like X.