Comparação de métodos de extração e reação de genótipos de alho a Ditylenchus dipsaci, aspectos produtivos e primeiro relato de ocorrência de Meloidogyne ethiopica em alho no Brasil

Abstract

Among the phytosanitary problems that affect the culture of garlic (Allium spp.) in Brazil, the stem and bulb nematode (Ditylenchus dipsaci) is one of the most important and responsible for economic losses mainly due to the management difficulties and limitations for available methodologies in the detection and quantification of this pest. Considering the control measures, in general, the use of resistant or tolerant genotypes is the most recommended alternative. However, information about the reaction of garlic to D. dipsaci is scarce under field conditions. In addition, the efficiency of the recommended methods for D. dipsaci extraction and detection in samples of seed garlic or green material is highly variable; and other plant parasitic nematodes not reported in A. sativum until now can parasitize this vegetable. Therefore, this study aimed: a) to evaluate the efficiency of different extraction methods about to D. dipsaci detection in garlic and soil samples; b) to evaluate the resistance of garlic genotypes by nematode reproduction factor (RF=Final population / initial population) at greenhouse and field conditions; c) to report the occurrence of Meloidogyne ethiopica in garlic plants in Brazil and around the word for the first time. Comparing different soil nematode extracting methods, Jenkins (1964) and Baermann (1917) and their variations, the first one was the most efficient in recovering specimens of D dipsaci from the infested soil, regardless of density (400 or 600g of sucrose/L water). The percentage of mobile and immobile nematode specimens recovered (extracted) from the samples was influenced by the origin of the infected plant material (fresh or dry). For garlic fresh material, the nematodes remained actives (mobile) until 120 hours after extraction regardless of the method; and, for garlic dry material (bulbs) they remained actives only in the first 24 hours, who’s the most efficient method was the petri dish. Considering the resistance of garlic genotypes to D. dipsaci, ‘AMPC Farias’, ‘Quitéria’, ‘Hozan’, ‘Peruano’, ‘Chonan’ and ‘Moz 114’ were the most resistant at greenhouse (RF<0,88) and field (RF<10,77); experiments; and, ‘Araguari’, ‘AM-Erenice’, ‘Amarante’, ‘Cateto Roxo’ and ‘Gravatá’, susceptible. Evaluating the production of garlic in an area infested with the stem nematode, 'AM-PC Farias', 'AM-Erenice' and 'Quitéria' were the most productive and least negatively affected genotypes in terms of the volume harvested compared to the production obtained in D. dipsaci free area. However, considering all associated parameters, the lowest rates of multiplication, damage and impact caused by the nematode on productivity in an infested area, 'AM-PC Farias', 'Quitéria' and 'Hozan' were the most suitable genotypes for planting. Characterizing the species of the root-knot nematode detected in garlic, Meloidogyne ethiopica was identified. It is the first report of this nematode parasitizing Allium sativum in Brazil and around the world.