RESUMO A cultura da goiabeira tem sido severamente atacada pelo fitonematóide Meloidogyne enterolobii (Sin.: M. mayaguensis), que tem causado drástica redução de produtividade e, em alguns casos, até morte de todas as árvores do pomar cultivado. Devido à sua ampla gama de potenciais hospedeiros e fácil disseminação, M. enterolobii representa um perigo constante e tem se mostrado um dos maiores limitantes para o cultivo da goiabeira no Nordeste brasileiro. Objetivou-se com esse trabalho avaliar a reação de genótipos de goiabeira e araçazeiro ao parasitismo de M. enterolobii em condições de casa de vegetação. Foram avaliados 44 genótipos de araçazeiros oriundos de populações naturais do Estado de Pernambuco e seis genótipos de goiabeiras. Os genótipos foram avaliados segundo os seguintes parâmetros: índice de galhas (IG), fator de reprodução (FR), número de ovos por grama de raiz (OGR) e redução do fator de reprodução (RFR). Considerando os critérios avaliados, os genótipos de araçazeiros REC-DI-A02 e REC-DI-A04 alcançaram os melhores resultados, podendo ser indicados como fonte de resistência à M. enterolobii e também como genótipos promissores para testes de enxertia em goiabeira.
Root-knot nematodes are a group of endoparasites species that induce the formation of giant cells in the hosts, by which they guarantee their feeding and development. Meloidogyne species infect over 2000 plant species, and are highly destructive, causing damage to many crops around the world. M. enterolobii is considered the most aggressive species in tropical regions, such as Africa and South America. Phytonematodes are able to penetrate and migrate within plant tissues, establishing a sophisticated interaction with their hosts through parasitism factors, which include a series of cell wall degradation enzymes and plant cell modification. Among the parasitism factors documented in the M. enterolobii species, cellulose binding protein (CBP), a nematode excretion protein that appears to be associated with the breakdown of cellulose present in the plant cell wall. In silico analysis can be of great importance for the identification, structural and functional characterization of genomic sequences, besides making possible the prediction of structures and functions of proteins. The present work characterized 12 sequences of the CBP protein of nematodes of the genus Meloidogyne present in genomic databases. The results showed that all CBP sequences had signal peptide and that, after their removal, they had an isoelectric point that characterized them as unstable in an acid medium. The values of the average hydrophilicity demonstrated the hydrophilic character of the analyzed sequences. Phylogenetic analyzes were also consistent with the taxonomic classification of the nematode species of this study. Five motifs were identified, which are present in all sequences analyzed. These results may provide theoretical grounds for future studies of plant resistance to nematode infection. HIGHLIGHTS• CBPs are remarkably conserved between Meloidogyne species • CBPs exhibit two to three functional domains related to signal binding and cellulose hydrolase activities Menezes, A.M.F.; et al.
Psidium guajava (guava) is an important crop and economic resource in many tropical countries and Brazil stands out as one of its major commercial producers. The guava crop has been severely attacked by the plant parasitic nematode Meloidogyne enterolobii which has caused drastic reduction of productivity and, in some cases, even total loss of cultivated areas. The use of resistant rootstocks that are tolerant to these soil pathogens can be a low-cost solution to this pathogen, which has established itself as one of the major constraints for the cultivation of guava in Northeast Brazil. The objective of this work was to evaluate the reaction of P. guajava and P. guineense to M. enterolobii infection under greenhouse conditions, with an infection period of 60 days. 12 P. guineense, and 4 P. guajava were evaluated. The host response to the nematode infection was evaluated according to the following parameters: gill index (GI), reproductive factor (RF), and reduction of reproductive factor (RRF). Considering the RRF criteria, the P. guineense genotypes, AR1, AR3, AR4 and AR10 were considered resistant. The RF index was considered inadequate to evaluate resistance in the 60 days period, due the slow development of the parasite in P.guineense.
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