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.

ABSTRACT The guava crop has been severely attacked by the phytonematode Meloidogyne enterolobii, which has caused drastic reduction in productivity and, in some cases, even the death of all trees in the cultivated orchard. Due to its wide range of potential hosts and easy dissemination, M. enterolobii represents a constant threat and has established itself as one of the major constraints for guava cultivation in Northeast Brazil. The objective of this study was to evaluate the reaction of guava and “araçá” genotypes to M. enterolobii parasitism under greenhouse conditions. Forty-four “araçá” genotypes from natural populations in Pernambuco State were evaluated, as well as six guava genotypes. The genotypes were evaluated according to the following parameters: gall index (GI), reproduction factor (RF), number of eggs per gram of root (OGR) and reproductive factor reduction (RFR). Considering the evaluated criteria, the “araçá” genotypes REC-DI-A02 and REC-DI-A04 had the best results and can be recommended as a source of resistance to M. enterolobii, also constituting promising genotypes for grafting tests in guava.

ABSTRACT: Stylosanthes capitata Vogel and Stylosanthes macrocephala M.B.Ferreira & Sousa Costa are two forage leguminous species of agronomic importance for animal husbandry in tropical environments. The physical mixture of both species (80 % S. capitata and 20 % S. macrocephala) comprises the commercial cultivar “Estilosantes Campo Grande”. However, proximity of fields for seed production may contaminate seed lots, compromising seeds quality. The combined use of dominant and co-dominant molecular markers is an appropriate strategy to certificate genetic purity and perform diversity studies of cultivars. In this research, a set of ISSR (Inter-Simple Sequence Repeat polymorphic DNA) and SSR (Simple Sequence Repeat polymorphic DNA) molecular markers were standardized to characterize S. capitata and S. macrocephala species and evaluate the genetic purity of commercial samples. Four ISSR markers (UBC 2, 864, 885, 886) and SSR marker SC18-01 G4B showed precise species-specific electrophoretic fingerprints for both species. Electrophoretic patterns of ISSR molecular markers should be displayed first to confirm the sample identification. The structure analysis showed that the less contaminated sample was S. capitata with 97 % of its genetic composition assigned to a single genetic cluster vs. 95 % for S. macrocephala. S. capitata has greater genetic diversity (ISSRHe:0.292; SSRHe:0.57) than S. macrocephala (ISSRHe:0.285; SSRHe:0.16); however, this difference was only significant with SSR molecular markers. As these genetic resources have considerable ecological, agronomic and economic importance, tools for accurate species identification and genetic studies are essential for further seed multiplication, as well as for improvement and conservation of cultivars.

Abstract 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.