Genetic variability and resistance of cultivars of cowpea [Vigna unguiculata (L.) Walp] to cowpea weevil (Callosobruchus maculatus Fabr.).

The cowpea weevil (Callosobruchus maculatus Fabr.) is the most destructive pest of the cowpea bean; it reduces seed quality. To control this pest, resistance testing combined with genetic analysis using molecular markers has been widely applied in research. Among the markers that show reliable results, the inter-simple sequence repeats (ISSRs) (microsatellites) are noteworthy. This study was performed to evaluate the resistance of 27 cultivars of cowpea bean to cowpea weevil. We tested the resistance related to the genetic variability of these cultivars using ISSR markers. To analyze the resistance of cultivars to weevil, a completely randomized test design with 4 replicates and 27 treatments was adopted. Five pairs of the insect were placed in 30 grains per replicate. Analysis of variance showed that the number of eggs and emerged insects were significantly different in the treatments, and the means were compared by statistical tests. The analysis of the large genetic variability in all cultivars resulted in the formation of different groups. The test of resistance showed that the cultivar Inhuma was the most sensitive to both number of eggs and number of emerged adults, while the TE96-290-12-G and MNC99-537-F4 (BRS Tumucumaque) cultivars were the least sensitive to the number of eggs and the number of emerged insects, respectively.

Genetic variability of Dactylopius opuntiae (Hemiptera, Dactylopiidae) on forage cactus in northeast Brazil.

The carmine cochineal Dactylopius opuntiae is a key pest in productive fields of forage cactus in Pernambuco, Brazil. Species identification by means of molecular markers assists in understanding the genetic profile, underpins morphological characterization, and supports the monitoring of populations in integrated management programs designed to control this pest. We evaluated the genetic variability of natural populations of D. opuntiae. Genetic variability was analyzed with ISSR and RAPD primers in 24 populations from 12 municipalities of Pernambuco State in Brazil. Morphological characterization confirmed that D. opuntiae was the only cochineal species present in all samples. Nine ISSR primers and six RAPD produced a total of 62 and 58 polymorphic fragments, respectively. Both types of markers showed an average genetic similarity of 80% regardless of the geographic origin of samples. The low genetic variability demonstrates a high degree of relatedness among these D. opuntiae populations.

pelB gene in isolates of Colletotrichum gloeosporioides from several hosts.

Colletotrichum gloeosporioides is an important pathogen for a great number of economically important crops. During the necrotrophic phase of infection by Colletotrichum spp, the degradative enzymes of plant cell walls, such as pectate lyase, clearly increase. A gene pelB that expresses a pectate lyase was identified in isolates of C. gloeosporioides in avocado pathogens. Various molecular studies have identified a kind of specialization of C. gloeosporioides isolates with specific hosts; however, there have been no studies of this gene in isolates from hosts other than avocado. The same is true for other species of Colletotrichum. We examined genetic variability in order to design primers that would amplify pelB gene fragments and compared the products of this amplification in C. gloeosporioides isolates from different hosts. Genetic variability was assessed using ISSR primers; the resultant data were grouped based on the UPGMA clustering method. Primers for the pelB gene were designed from selected GenBank sequences using the Primer 3 program at an annealing temperature of 60 degrees C and product amplification of nearly 600 bp. The ISSR primers were efficient in demonstrating the genetic variability of the Colletotrichum isolates and in distinguishing C. gloeosporioides, C. acutatum and C. sublineolum species. The gene pelB was found in C. gloeosporioides, C. acutatum and C. sublineolum. Amplified restriction fragments using MspI did not reveal differences in pelB gene structure in isolates from the three different host species that we investigated.

The FML (Fucose Mannose Ligand) of Leishmania donovani. a new tool in diagnosis, prognosis, transfusional control and vaccination against human kala-azar.

The Fucose-Mannose Ligand (FML) of Leishmania donovani is a complex glycoproteic fraction. Its potential use as a tool for diagnosis of human visceral leishmaniasis was tested with human sera from Natal, Rio Grande do Norte, Brazil. The FML-ELISA test, showed 100% sensitivity and 96% specificity, identifying patients with overt kala-azar (p < 0.001, when compared to normal sera), and subjects with subclinical infection. More than 20% apparently healthy subjects with positive reaction to FML developed overt kala-azar during the following 10 months. In the screening of human blood donnors, a prevalence of 5% of sororeactive subjects was detected, attaining 17% in a single day. The GP36 glycoprotein of FHL is specifically reconized by human kala-azar sera. The immunoprotective effect of FML on experimental L. donovani infection was tested in swiss albino mice. The protection scheemes included three weekly doses of FML, supplemented or not with saponin by the subcutaneous or intraperitoneal routes and challenge with 2 x 10(7) amastigotes of Leishmania donovani. An enhancement of 80.0% in antibody response (p < 0.001) and reduction of 85.5% parasite liver burden (p < 0.001) was detected in animals immunized with FML saponin, unrespectively of the immunization route.