Diversidade, agressividade e patogenicidade de Meloidogyne spp. em cana-de-açúcar e prospecção da resistência genética em genótipos adaptados ao sul do Brasil

Abstract

Among the problems affecting sugarcane crop, plant-parasitic nematodes can result in potential crop damage. The present study was carried out in in three chapters. In the first, Meloidogyne spp. populations sampled in sugarcane location of Rio Grande do Sul state, were characterized through the esterase (Est) activity where part of them were evaluated as the physiological races. Subsequently, 35 populations of Meloidogyne spp. from this study and the work of Bellé (2014) were molecularly characterized by SCAR and RAPD markers. In the second chapter, efforts were done to evaluate the aggressiveness of different populations of M. javanica and M. incognita in different sugarcane genotypes. The last step of this study aimed to evaluate the reaction of 25 sugarcane genotypes to M. incognita and M. javanica. Additionally, the effects of two root-knot species was monitored based on the development of inoculated plants(a); the response of parasitized plants by M. incognita, M. javanica and M. arenaria on the Meloidogyne spp. reproduction, vegetative development, shoot production, content sugars and components of the shoot cell wall of sugarcane plants. Finally, the pathogenicity of low-frequency Meloidogyne species were quantified. Meloidogyne spp. was detected at 92.6% of the collected samples and M. incognita Est I2 was the most frequent species (51.3%). Among M. incognita populations physiologically characterized, the races 1, 2, 3 and 4 were identified; however, it was not possible to correlate them with the respective esterase phenotypes. The use of SCAR markers allowed to differentiate most of the Meloidogyne populations by amplifying species-specific fragments for M. javanica (670 bp), M. incognita (399 bp), M. arenaria (420 bp) and M. javanica (670 bp), M. morocciensis (420 bp), M. ethiopica (350 bp) and M. enterolobii (520 bp). By RAPD analysis, 234 and 394 reproducible fragments were amplified, whose the percentage of amplified polymorphic bands ranged from 21.0 to 31.5%, respectively. By the phylogenetic analysis, four groups were formed: in the first one, 16 populations of M javanica were grouped; in the second, M. arenaria and M. morocciensis; in the third, M. incognita and Meloidogyne sp. Est. SC1; and, M. ethiopica, M. luci and M. enterolobii were grouped separately. Evaluating the aggressiveness of the populations of Meloidogyne spp., there was a significant interaction between sugarcane genotypes and nematode populations for the variables related to nematode reproduction and damage caused in the roots, as well as growth plant parameters, fiber digestibility, sugars content and cell wall components. Considering the sugarcane reaction to M. javanica and M. incognita, all genotypes were susceptible in different degrees; these nematode species interfered on the development of the plants. Evaluating the pathogenicity of M. luci, M. enterolobii, M. morocciensis, M. hapla, M. arenaria and M. ethiopica, all species reproduced (10.2> RF <50.5) on sugarcane and affected negatively the vegetative development of this crop.