The initial interaction of vesicle and the target membrane prior to their fusion is called vesicle tethering, a process mediated by an octameric protein complex called the exocyst. The exocyst connects vesicles and binds them to phosphatidylinositol 4, 5-biphosphate (PI (4,5) P2), located on the plasma membrane. The exocyst complex is located at the target site, helping to prepare the soluble N-ethylmaleimide-sensitive fusion protein attachment protein (SNAP) receptor (SNARE) for docking and subsequent release of vesicular contents after fusion. The importance of the exocyst in cellular processes is inevitable since it performs central roles in exocytosis thereby inducing SNARE-mediated membrane fusion. The study presented here is concentrated on the role of exocyst genes during the defense response in Glycine max (soybean) against the plant- parasitic nematode Heterodera glycines known as the soybean cyst nematode (SCN). Using developmental genomics analysis, G. max root cells that have been induced by H. glycines through their pathogenic activities to develop into nurse cells known as a syncytium have been isolated by laser capture microdissection (LCM). RNA isolated from these cells undergoing resistant reactions in two different G. max genotypes have been used in gene expression profiling experiments that have led to the identification of the genes employed in this analysis. The results demonstrate the involvement of exocyst components in the defense process that G. max has toward H. glycines. Related studies also show the involvement of RPM1-INTERACTING PROTEIN 4 (RIN4) functioning in this defense process.

Cotton (Gossypium hirsutum) growth, development, and yield can be limited due to reniform nematode and bacterial blight infestation. Studies were conducted in 2016 and 2017 to evaluate the profitability of a soil fumigant application, seed treatments, and inurrow nematicides to protect cotton from nematode infestation as well as inoculation of bacterial blight at various growth stages in cotton to determine effects on yield. Research was conducted by applying various combinations of nematicides to cottonseed at planting and a fumigant prior to planting. Bacterial blight was conducted by inoculated on cotton at multiple growth stages throughout the year. Based on the results of these studies, a seed treatment plus inurrow application should be applied at planting in nematode infested fields to increase yield and economic returns in cotton. Bacterial blight infestation was greatest when inoculated at pinhead square in cotton.

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Plant parasitic nematodes cause billons of dollars in annual crop losses. One of the most damaging is the root-knot nematode, Meloidogyne incognita, which is known to attack more than 3000 plants. This research will contribute to the understanding of host-plant resistance through characterization of the early infection processes of Meloidogyne incognita race 3 in susceptible (Lahontan) and resistant (Moapa) alfalfa cultivars by light microscopy and transmission electron microscopy. Neither differential penetration of M. incognita J2 into Lahontan, nor migration of J2 from Moapa, played a significant role in the resistance mechanism(s). Coiled nematodes in the cortex were observed in greater numbers in the Moapa 48 hours after inoculation. This position was interpreted as a sign of disorientation and starvation. By 96 hours after inoculation, no coiled nematodes were observed in Lahontan. In Moapa, resistance probably depends not only on the failure of the J2 to identify a suitable feeding site and initiate giant cells, but also on its inability to maintain the giant cells, once they are initiated. At the ultrastructural level, 48 hours after inoculation, the most evident change in both cultivars was the appearance of a uniform interstitial material (IM) between the nematode cuticle and the root cell wall. At 96 hours, IM in Moapa was completely agglutinated while in Lahontan it was still uniform or only slightly agglutinated. Due to these clear differences between both cultivars I propose that the IM plays a role in the resistance of Moapa to M. incognita. Immunolabeling techniques were employed to determine if the distribution of the nematode's surface coat, deposited in host tissues, differs in resistant and susceptible alfalfa cultivars. At 72 hours after inoculation, labeling of surface coat epitopes in Moapa was stronger than at 24 and 48 hours after inoculation. Labeling was observed on the nematode's cuticle, the plant cell wall, and the IM. In Lahontan, 72 and 96 hours after penetration, labeling of the surface coat epitopes was observed on the nematode's cuticle, the root cell walls, and the cell wall junctions of cells near the nematode, but not in direct contact with the cell.

O gênero Eucalyptus possui diversas espécies que apresentam grande valor comercial, sendo utilizado principalmente para produção de energia (carvão e lenha) e celulose-papel. Na literatura, entretanto, existem poucas informações acerca de nematoses nessa cultura. Além dessa carência e de sua importância econômica, o eucalipto é comumente cultivado em locais de alta incidência de Pratylenchus brachyurus e Meloidogyne incognita, além de ser consorciado com diversas outras culturas intolerantes, como por exemplo a soja. Dessa forma há uma necessidade de conhecer a reação das espécies de eucalipto a estes nematoides. Dito isso, o presente trabalho teve por objetivo testar a reação de algumas espécies de eucalipto a P. brachyurus e M.incognita. Foram realizados 6 experimentos, 5 envolvendo o nematoide das lesões e 1 com o nematoide de galhas. Os tratamentos foram inoculados com uma população inicial de nematoides e, após 90 dias, estimava-se o fator de reprodução (FR) e nematoides por grama de raiz (Nem/g). Adotou-se o critério baseado em Oostenbrink (1966), onde a espécie foi considerada suscetível quando apresenta FR >= 1 e resistente quando FR < 1. Dos eucaliptos testados, 6 apresentaram reação suscetível e 4 reação resistente para P. brachyurus. As espécies com maiores FR estão entre as mais utilizadas no Brasil, exceto E. saligna. Ressalta-se que estas não necessariamente são resistentes, necessitando apenas de um período maior para o estabelecimento do patógeno. Observou-se indícios de que E. saligna e E. camaldulensis sejam intolerantes a P.brachyurus. Para M. incognita raça 3 todas as espécies testadas foram resistentes. Aconselha-se a realização de experimentos com períodos superiores a 100 dias para uma correta classificação da reação de hospedeiro. O eucalipto é uma opção para aproveitamento de áreas infestadas com M. incognita raça 3, porém seu uso mostra-se um risco em áreas infestadas com P. brachyurus. / The Eucalyptus has several species with high commercial value and is used mainly for energy purpose (Charcoal and firewood) and paper. In the literature, however, there is little information about plant parasitic nematodes in this woody specie. In addition to this lack and its economic importance, eucalypts is also commonly cultivated in areas with high incidence of Pratylenchus brachyurus and Meloidogyne incognita, and consorted with several intolerant crops, such as soybean. Thus, there is a need to know the host status of the eucalypts species to these nematodes. With that, this work aimed to test the reaction of some Eucalyptus species to P.brachyurus and M. incognita. For this purpose six experiments were performed, five to test the lesion nematode and one to test the root-knot nematode. The treatments were inoculated and, after 90 days, it was estimated the reproduction factor (FR) and nematodes per gram of root (Nem/g). The present work adopted the criteria based on Oostenbrink (1966), where the species was considered susceptible when presenting FR >= 1 and resistant when FR < 1. Of species tested, six were susceptible hosts and four resistant host to P. brachyurus. The species with highest FR are among the most used eucalypts in Brazil, except E. saligna. It is emphasized that those species with FR < 1 are not necessarily resistant, requiring only a longer period for the pathogen establishment. There was some evidence that E. saligna and E. camaldulensis are intolerant hosts to P. brachyurus. To M. incognita Race 3 all tested species were resistant. It is advisable to perform experiments for periods longer than 100 days to a correct classification of host status. Eucalyptus is an option for utilization of areas infested with M. incognita race 3, but its use appears to be a risk in Pratylenchus brachyurus infested areas.