Avaliação de doenças em híbridos de Urochloa spp.

Abstract

In Brazil, pastures are the main and most economical source of feed for livestock. Urochloa spp, commonly known as brachiaria, is a genus of forage plants native to Africa that have been extensively introduced in Brazil. These grasses are widely cultivated in pastures, integrated crop-livestock systems, and other agricultural applications, especially in the country's tropical and subtropical regions. They demonstrate excellent adaptation to different soil types and climatic conditions, playing a key role in animal production. The objective was to identify phytopathogenic fungi, as well as quantify the incidence, severity, and plant response to diseases in Urochloa spp. hybrids cultivated in the Cerrado region. The experiment was conducted in an experimental field at the Federal University of Mato Grosso, Campus Universitário do Araguaia II, located in Barra do Garças - MT (15º52'26" S 52º18'52 W). The experimental area consisted of 19 treatments, with four replications arranged in a randomized block design. Evaluations were carried out at intervals of 14 to 33 days (15 days was the chosen interval for evaluations during the rainy season in the region, and up to 33 days during the dry season), totaling 20 evaluations over one year of the experiment. For precise assessment of pathogens observed in the field, visualizations were conducted using a light microscope. Three pathogens were observed during the experiment: Pyricularia sp., Curvularia sp., and Bipolaris sp. The Pyricularia fungus was endemic throughout the experiment, being present in all evaluations, initially appearing in the first evaluation conducted 15 days after Urochloa sowing. Curvularia incidence occurred in late february, remaining in the field for several months with no incidence between June and midnovember. Bipolaris first appeared in mid-march, with higher incidence and severity during the dry periods of the region. These latter two pathogens are characterized as saprophytic. The highest incidence and severity were caused by the Bipolaris genus pathogen, followed by Curvularia and Pyricularia. The hybrids 9 and 16 exhibited better health, according to the statistical analyses.