Reação de genótipos de Psidium spp. ao fitonematóide Meloidogyne enterolobii e análise in silico de fatores de parasitismo

Abstract

The guava crop has been severely attacked by the phytonematode Meloidogyne enterolobii (Sin.: M. mayaguensis), which has caused drastic reduction of productivity and, in some cases, even total loss of cultivated areas. Due to its wide range of potential hosts and easy dissemination, M. enterolobii represents a constant danger and has been shown to be one of the major limitations for the guava cultivation in the Brazilian Northeast. Caltreticulin (CRT), a highly conserved excretion protein in animals and plants, has been identified in the secretions of several parasites indicating that they are associated with suppression of plant immunity. Bioinformatics has provided valuable information on biomolecules and, through in silico analysis, has provided structural and functional characterization data of genomic sequences, structural prediction and protein functions, as well as comparisons of biological sequences of several species. The objective of this research was to evaluate the parasitism of M. enterolobii in P. guineense and guava genotypes for future compatibility studies for rootstocks of commercial guavas and to characterize the sequence of the calreticulin protein (CRT), to verify their phylogenetic conservation, identifying functionality, subcellular localization and presence of conserved domains, as well as, develop a tertiary structure model with in silico computational homology modeling tools. 44 P. guineense genotypes from natural populations of the State of Pernambuco and 6 guava genotypes were evaluated under greenhouse conditions. The genotypes were evaluated by the following parameters: gall index (GI), reproduction factor (RF), number of eggs per gram of root (OGR) and reduction of the reproductive factor (RFR). Considering the evaluated criteria, the P. guineense genotypes REC-DI-A02 and REC-DI-A04 achieved the best results and can be indicated as a source of resistance to M. enterolobii and also as promising genotypes for grafting tests in guava. In the in silico analysis of the CRT protein, 15 proteins sequences from free-living, plant and animal parasitic nematodes, present in genomic databases were characterized. The results also indicated the presence of five functional domains. The analysis of the physical-chemical parameters showed hydrophilic CRTs with low activity at acidic pH. The cluster analysis showed consistency with the taxonomic classification of the evaluated species. We also developed a stable CRT 3D model which may help the understanding of the structure of this protein. The results obtained on CRT may provide insights for future resistance studies in plants against nematode attacks. The obtained results point out perspectives for understanding of the parasitism factors of M. enterolobii and, as well as the search for resistant rootstocks in guava commercial crops, especially in the Northeast region of Brazil, which is of fundamental importance for the agribusiness, in view of the losses occurred in the plantations with the cultivars "Paluma" and "Pedro Sato".