Variabilidade Genética Em Populações De Rottboellia Cochinchinensis Na Cultura Da Cana-de-açúcar

The hypothesis assumed was the existence of biotypes within populations, which has been the cause of difficulties in itchgrass control by farmers. For that, the genetic variability of three populations of Rottboellia cochinchinensis in sugarcane fields in the state of São Paulo was investigated by using the Amplified Fragment Length Polymorphism (AFLP) technique. Six primers were used to obtain molecular characterization data. AFLP gels were analyzed based on marker presence (1) and absence (0). Using NTSYs (Numerical Taxonomy and Multivariate Analysis System) software, the genetic similarity was calculated by the Jaccard coefficient and, from that, a dendrogram was built through the UPGMA (Unweighted Pair Group Method Arithmetic averages) method, besides determining the isopolymorphic marks. The average genetic similarities seen in the region was 0.742 for Igarapava, 0.793 for Mococa and 0.808 for Piracicaba. Between regions it was 0.730 (Igarapava vs Mococa), 0.735 (Mococa vs Piracicaba) and 0.694 (Igarapava vs Piracicaba). In line with the dendrogram, it is possible to detect the formation of two groups, one with 8 plants from Igarapava and Mococa and the other with 21 plants from Igarapava, Mococa and Piracicaba, as well as the presence of 1 discriminant individual from Piracicaba. It can be concluded that the genetic similarity among itchgrass populations from the state of São Paulo was high (72%), which denotes that the difficulties in chemical management are not only due to different biotypes but also due to other characteristics linked to tolerance of the species to herbicides. However, biotype existence cannot be discarded because of the polymorphic marks generating 22% average genetic variability. © 2016, Sociedade Brasileira da Ciencia das Plantas Daninha. All rights reserved.34347548

Seletividade do imazapic para dois cultivares de amendoim (Arachis hypogaea) cultivados na ausência e na presença de palha de cana-de-açúcar

Neste trabalho, objetivou-se estudar a seletividade de imazapic a dois cultivares de amendoim (Tatu Vermelho e IAC-5), em condições de ausência e de presença de palha de cana-de-açúcar. O experimento foi instalado em vasos, em delineamento inteiramente casualizado, com os tratamentos dispostos em esquema fatorial 3x2, com quatro repetições. Constituíram os fatores principais três doses de imazapic (0, 98 e 140 g ha-1), aplicadas em pré-emergência sobre duas condições de palha de cana-de-açúcar (0 e 15 t ha-1). Constatou-se que a camada de palha possui potencial em reter o herbicida, especialmente sob períodos de pouca precipitação ou irrigação; as plantas de amendoim sob esta condição apresentaram menos sintomas de intoxicação. Entretanto, na ausência da palha, as plantas, independentemente do cultivar, apresentaram maiores injúrias visuais e redução na altura, massa seca da parte aérea e raiz.This research aimed to evaluate imazapic selectivity for two peanut cultivars (Tatu Vermelho and IAC) with and without sugarcane straw. The experimental design was completely randomized arranged in a3x2 factorial scheme with four replicates. The experiment was set in plastic pots and the treatments consisted of a combination of three rates of imazapic applied in pre-emergence (0, 98, and 140 g ha-1), and two levels of sugarcane straw (0 and 15 ton ha-1). The straw layer retained the herbicide, mainly under little precipitation or irrigation periods; under these conditions, peanut plants showed fewer intoxication symptoms. However, without the straw,the plants showed larger visual injuries and reduction in height, aerial parts and root dry mass for both peanut cultivars and herbicide rates