GENETIC VARIABILITY OF Rottboellia cochinchinensis POPULATIONS IN SUGARCANE FIELDS

Abstract

-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.Keywords: Saccharum spp., itchgrass, chemical management, AFLP. (0) RESUMO -Considerando a hipótese de que a dificuldade de controle observada pelos produtores com a espécie do gênero Rottboellia pode ser pela existência de biótipos nas populações, objetivouse estudar a variabilidade genética entre três populações de R. cochinchinensis em regiões de cana-de-açúcar do Estado de São Paulo, utilizando-se da técnica Amplified Fragment Lenght Polimorfism (AFLP). Para a caracterização molecular, seis iniciadores foram utilizados para obtenção dos dados. Os géis de AFLP foram analisados com base na presença (1) e na ausência

Las malezas, plantas incomprendidas

“…Los impactos económicos de las malezas en los cultivos agrícolas incluyen costos y beneficios, monetarios y no monetarios (Cheema & Khaliq, 2000;Sinden et al, 2004). Toda actividad que involucre el manejo de plantas cultivadas debe necesariamente incluir dentro de su presupuesto una considerable inversión para el manejo de la interferencia de malezas con los cultivos (Culliney, 2005;Monaco, Weller, & Ashton, 2002;Schiavetto et al, 2016).…”

Influence of establishment timing on growth and fecundity of two itchgrass (Rottboellia cochinchinensis) biotypes grown in Louisiana

“…], sugarcane, and tobacco (Nicotiana tabaccum L.) crops. Genetic variability among R. cochinchinensis populations across geographic locations in São Paulo, Brazil, as determined using an amplified fragment length polymorphism technique, was 22% and partially explained unsatisfactory control reported with herbicides (Schiavetto et al 2016). Millhollon and Burner (1993) reported two R. cochinchinensis biotypes that infested sugarcane in Louisiana: Louisiana-1 is daylength neutral and Louisiana-2 is a short-day biotype.…”