Lipoxygenase activity in Brazilian rice cultivars with variable resistance to leaf blast disease

Eight rice lines viz. CNA 8983, IAC-1732, IAC-1733, IAC-1748, IAC-1736, IAC-201, Volano and Arborea were evaluated in greenhouse for resistance against the leaf blast disease caused by Magnoparthe gracea. Lines CNA 8983, IAC 1732, IAC 1733 and IAC 1748 showed satisfactory resistance against the blast fungus while IAC 1736 and IAC 201 were intermediate and Volano and Arborea susceptible. All lines did not have lipoxygenase activity increased by methyljasmonic acid, however enzyme activity showed a positive relationship with resistance. Oito linhagens de arroz (CNA 8983, IAC-1732, IAC-1733, IAC-1748, IAC-1736, IAC-201, Volano e Arborea) foram avaliadas em casa de vegetação para a resistência contra a brusone causada por Magnoparthe gracea. As linhagens CNA 8983, IAC 1732, IAC 1733 e IAC 1748 foram satisfatoriamente resistentes contra o fungo; IAC 1736 e IAC 201 foram intermediárias e Volano e Arbórea, suscetíveis. Em todas as linhagens não ocorreu atividade de lipoxigenase aumentada pela exposição ao ácido metiljasmônico, no entanto, a atividade enzimática mostrou correlação positiva com a resistência.