Avaliação dos contaminantes de lotes de sementes de arroz irrigado (Oryza sativa L.) produzidos na fronteira oeste do Rio Grande do Sul

Abstract

The Fronteira Oeste seed production fields in the state of Rio Grande do Sul produce high quality seeds in relation to all their attributes; therefore, they are highly sought after by irrigated rice producers, to be sown in their production areas. This work aims to evaluate the quality of the seeds produced and delivered by the seed companies to the final consumer (producer), as well as to verify certain problems that end up causing the disapproval of seed lots, coming from these production fields. For that, data from seven harvests from 2014 to 2020 were used, totaling 17,477 lots analyzed in the seed laboratories of the IRGA (Rio-Grandense Institute of Rice) located in the cities of Cachoeirinha, Rosário do Sul and Uruguaiana. Samples were collected in the processing units of the seed producing companies in the Western Frontier and sent for analysis in the IRGA Laboratory network, by a sampler with RENASEM active, maintaining all the criteria determined by MAPA, for the certification of seed lots. . The germination percentage, presence of red rice seeds, black rice and seeds of harmful tolerated plants were evaluated. With the results, it was possible to conclude that these fields of seed production have a tendency of reduction in the general failures of the lots due to the presence of seeds of black rice, red rice and, disapproval for germination outside the standard of the produced category. Already, the disapprovals for the presence of tolerated harmful seeds have been increasing every year. Of the total lots analyzed, there was an average failure of the years in 15%, the main reason for failures being the presence of red rice, followed by germination below the standard, by the presence of seeds of harmful tolerated plants and, finally, with the presence of black rice seeds. Regarding the presence of red rice seeds, it was found that long thin red rice has been predominant in the analyzed samples, causing the vast majority of failures of seed lots from the region. This increase in contamination of the seed production fields by long thin red rice raises a great concern for certifying entities, as well as for breeders, breeders and seed producing companies, as their identification in the field is very difficult, mainly due to the phenotype is very similar to cultivated rice. Another alternative would be the advent of new technologies to control this contaminant, which could solve this serious problem and, consequently, reduce the contamination rates in commercial crops in Rio Grande do Sul, which has depreciated the final product, reducing productivity and causing large financial losses in the rice production chain.