Avena spp: reação a nematoides-das-galhas, atividade nematicida e alelopática

Abstract

The assessment of phenotypic traits of the white oat (Avena sativa) and black oat (A. strigosa) germplasm do not routinely comprise the reaction to the root-knot nematodes (Meloidogyne spp.), nematicidal activity and the allelopathic action. The use of this attributes, in the pre-breeding stage, would create the possibility of the development of cultivars for distinct conditions and cultivation systems. This work evaluated the reaction of Avena spp. to M. javanica and M. incognita, the nematicidal and allelopathic activities through bioassays, which results are presented and discussed separately in this document, in three chapters. Chapter 1: Reaction of Avena spp. to Meloidogyne javanica and M. incognita. The white oat genotypes (UPFPS Farroupilha, UPFA Ouro, IPR Afrodite, AF1345 Ucraniana) and black oat ones (Agro Quaraí, Agro Esteio, Embrapa 139, Iapar 61 Ibiporã, UPFA 21 Moreninha, AF 12202) were tested for nematode reaction in two inoculum concentrations (M. javanica: 1,500 and 5,000 eggs and second-stage juveniles (J2); M. incognita: 1,500 and 2,900 eggs and J2). The genotypes that presented resistance reaction to the two inoculum concentrations of M. javanica were: IPR Afrodite, AF1345 Ucraniana, UPFA Ouro, UPFPS Farroupilha, UPFA 21 Moreninha, Embrapa 139; for M. incognita: IPR Afrodite, AF1345 Ucraniana, UPFA Ouro, UPFPS Farroupilha, UPFA 21 Moreninha, AF12202, Embrapa 139. Chapter 2: Nematicidal activity of extracts of Avena spp. to Meloidogyne javanica and M. incognita. Crude aqueous extracts were prepared in three concentrations (5, 10 and 20% w/v), with dry plant material from the aerial part of white oats (UPFPS Farroupilha, AF 1345 Ucraniana) and from black oats (Agro Quaraí, Agro Esteio, Embrapa 139 and AF 12202). The suspension with nematode eggs and extracts were incubated in the Petri dishes with incubation in a growth chamber for 10 days. For M. javanica, the most efficient extracts, in descending order, are Embrapa 139, UPFPS Farroupilha, Agro Quaraí, AF 1345 Ucraniana, AF 12202, Agro Esteio. For M. incognita: Agro Quaraí and AF 1345 Ucraniana, UPFPS Farroupilha, Agro Esteio and AF 12202, Embrapa 139. Chapter 3: Allelopathic activity of Avena spp. extracts. Twenty-seven crude aqueous extracts made from the aerial part of white oats (UPFPS Farroupilha and AF 1345 Ucraniana) and from black oats (Agro Quaraí, Agro Esteio, Embrapa 139, AF 12104, AF 12109 , AF 12202 and AF 12209) were tested in three concentrations (5, 10 and 20% w/v), over the germination and growth of lettuce seedlings (Lactuca sativa L.). The experiment was conducted on a germination chamber for 15 days. There was total inhibition of germination at the maximum concentration of the extract and partial inhibition at 10% w/v. The genotypic difference was better evidenced at the concentration of 5% w/v, being observed, in descending order of effective allelopathic action in germination and root and hypocotyl elongation (inhibition >50%) the extracts from UPFPS Farroupilha, AF 12104, AF 1345 Ucraniana, Agro Quaraí, Embrapa 139, AF 12209, Agro Esteio and AF 12202. The genotypic variability in Avena spp. in relation to the reaction to root-knot nematodes, nematicidal and allelopathic activities can be explored in breeding programs in order to add value and offer additional elements to be chosen by the rural producer.