Progresso espacial e temporal da antracnose a partir de diferentes niveis de inoculo inicial em sementes de feijoeiro

Abstract

Seeds are efficient ways ofdissemination ofplant pathogens such as the species of Colletotrichum. Most Colletotrichum species associated to seeds, are able to cause disease on plants, including C. lindemuthianum. When transmission to susceptible plant occurs, it will constitute the initial focus ofthe disease, and from it, depending on environmental conditions, the epidemics will progress in space and in time. Initially studies were conducted to veriry the progress of antracnose of bean in the drought (04/03/1998) and in the rainy (15/12/1998) seasons, when different leveis of infection of seeds (0; 0,5; 1,0; 2,0 and 4.0%) for C. lindemuthianum were tested. Only in the drought season the área under of disease progress curve of the incidence (AUDPCI) and of severity (AUDPCS), were influenced by different leveis of inoculum. The analysis of the space standard and of the gradient using 0,5% ofseeds as source of inoculo allowed to observe greater incidence ofthe disease in the drought season. In the drought season the standard of distribution of anthracnose was aggregate. In the rainy season the standard of distribution was aggregated, except for the two fírst evaluations. In the both cultivation season there were a better adjustment to the exponential model. In other experiments in the drought (15/03/2001) and inthe rainy (15/12/2001) seasons the progress ofanthracnose of the beans with three leveis of infection of seeds (0;1,0 4.0%) were studied using mixtures of susceptible and resistant lines (0, 25, 50 and 75% of the resistant line) and in the rainy season included 100% resistant. The leveis of inoculo 1,0and 4.0% provided greater intensity of the disease in relation to free inoculum plots in both seasons. In the drought season the mixture was not efficient in reducing the AUDPCI and the AUDPCS. Lower values of the healthy leafárea duration (HAD) and ofthe healthy leafárea absorption (HAA) occurred when leveis ofinoculum 1,0 and 4,0% were used.