Resistência do sorgo (Sorghum bicolor (l.) Moench) a Colletotrichum graminicola (CES.) wils

A inoculacao na nervura central, de 2 folhas bem abertas a partir do topo de duas linhagens de sorgo: SC-326-6 e 7509010 revelou que a reacao daquelas e proporcional a idade das plantas. A reacao e menor nas folhas mais novas. A linhagem SC 326-6 mostrou-se resistente e a 7509010 suscetivel ao patogeno. A inoculacao de 46 linhagens e variedades de sorgo permitiu-lhe a distincao em 3 categorias: altamente resistentes, com resistencia intermediaria e suscetiveis. Das 12 progenies F 3 de sorgo inoculadas, 5 mostraram-se adequadas para a selecao por apresentarem lesoes menores e maior variabilidade genetica. Com relacao as reacoes apresentadas pelos cruzamentos reciprocos, os resultados sugerem uma heranca citoplasmatica para resistencia a C. graminicola . Os meios de cultura preparados com extratos de folhas de linhagens resistentes e suscetiveis e, variando na concentracao mostraram que a esporulacao de C. graminicola foi diretamente proporcional a concentracao. Isso, independente da reacao do hospedeiro, mas meios com extratos de folhas de linhagens resistentes induziram a maior esporulacao. Abstract The inoculation into the mid ribs of two wiede opened leaves of two sorghum inbred lines: SC-326-6 and 7509010 revealed that the reaction of the leaves to C. graminicola is proportional to plant age, being lesser on newer ones; the inbred line SC 326-6 was resistant and the inbred line 7509010 was susceptible to the pathogen. The inoculation of 46 inbred lines and varieties of sorghum permitted three categories of resistance to be distinguished: highly resistante, intermediate resistant and susceptible. From 12 F 3 progenies of sorghum inoculated, 5 were suitable for resistance selection because they presented smaller lesions and greater genetic variability. Concerning the reactions presented by the reciprocical cross, the results suggested a citoplasmic inheritance for resistance of C. graminicola . Artificial media prepared with extracts of leaves from resistant and susceptible inbred in different concentrations, showed that the sporulation of C. graminicola was directly proportional to the concentration. The media with extracts of leaves from resistance inbred lines inducer higher sporulation.