Progresso da brusone nas folhas no plantio direto e convencional de arroz de terras altas

portugais. Foram estudados o progresso da brusone (Pyricularia grisea) e o conteúdo de clorofila nas folhas em experimentos de campo, com arroz (Oryza sativa) de terras altas, nos sistemas de plantio direto (PD) e convencional (PC), durante as safras de 1998/1999 e 1999/2000. As taxas aparente de infecção da brusone nas folhas na primeira safra no PC e no PD formam de b = 0,099 (r = 0,97**) e de b = 0,066(r = 0,90**), respectivamente. Na segunda safra foram de b = 0,054(r = 0,99**) no PC e no PD de b = 0,055(r = 0,99**). Entretanto as taxas de progresso da brusone nas folhas não diferiram estatisticamente nos dois sistemas de plantio. Foi observada uma relação linear, positiva e significativa entre conteúdo de clorofila e a severidade da brusone nas folhas.

anglais. The disease progress of leaf blast (Pyricularia grisea) and chlorophyll leaf content in upland rice (Oryza sativa) were studied under direct drilling (DD) and conventional drilling (CD), in field experiments during 1998/1999 and 1999/2000. The apparent infection rates of leaf blast for CD and DD were b = 0.099 (r = 0,97**) and b = 0.666 (r = 0,90**) respectively, in the first growing season. In the second season, the rates for CD and DD were b = 0.054 (r = 0,99**) and b = 0.05 (r = 0,99**). However, there was no significant difference in the rates of leaf blast progress in these two tillage systems. A linear, positive and significant relationship was observed between the chlorophyll content of the leaf and leaf blast severity.