Impact of phytopathogens on seed quality of tropical grasses in integrated systems

Abstract

This study aimed to identify the main fungal and phytonematode genotypes associated with the main tropical forage seeds used in integrated systems and to distinguish seeds with high physiological and sanitary quality, for which two experiments were conducted. In year 1 (2017/18 crop year), the first experiment (experiment 1) was conducted with seeds produced in the 2017/18 crop year, in a randomized open design with four configurations and four replications. In year 2 (2018/19 crop year), the study (experiment 2) was replicated with the experimental conditions of the first experiment (randomized automatic design, with four sessions and four replications), but using samples from the 2018/19 crop year. The seeds were produced in the 2017/18 and 2018/19 crop years, with the same origin, and were purchased within commercial packages. The treatments of experiments 1 and 2 were the same and consisted of seeds of Brachiaria ruziziensis and the Brachiaria brizantha cultivars Marandu, Xaraés, and BRS Piatã. The same variables were evaluated for each experiment: water content, physical purity, viability, germination rate index, first germination count, germination percentage, crop value, dormancy, accelerated aging, and incidence of fungi and phytonematodes. Cladosporium sp., Fusarium sp., Rhizoctonia sp., Meloidogyne sp., Filenchus sp., Aphelenchus sp., Aphelencoides sp., and Rotylenchulus sp. are the main phytopathogens associated with seeds of the main tropical forage species used in integrated systems. The seeds of B. ruziziensis present high physiological quality, whereas the seeds of the B. brizantha cultivar Xaraés grass present high sanitary quality