The cowpea, Vigna unguiculata (Fabeaceae) is widely cultivated in semi-arid regions, such as northeast Brazil. Due to the low crop yields in this region, it would be useful to develop cultivars adapted to these climate conditions. Landraces are seen as an important source of germplasm to be used in breeding programs of this species due to their good adaptation to the environment, but for this strategy to be viable, their genetic variability must be studied. To this end, we evaluated the genetic diversity, using ISSR molecular markers, of 52 samples of cowpea landraces collected mostly from small producers from all over the state of Ceará, Brazil. The DNA of the genotypes was extracted and analyzed using 25 primers. Based on the electrophoresis profiles of the bands, a genetic dissimilarity matrix was prepared, and a cluster analysis made using the UPGMA and modified Tocher methods. Fourteen primers amplified 80 bands, of which 61 were polymorphic, generating a polymorphism rate of 76%. The selected markers were efficient in identifying genetic variability among the varieties under evaluation, providing a large amount of information. The polymorphic information content varied from 0.13 to 0.66 and the band frequency ranged from 0.01 to 1.00. The two clustering methods agreed in the number of groups formed (n = 6), with the genetic distances ranging from 0.05 to 0.31, values considered low, suggesting a narrow genetic base for the landraces of this species in Ceará state.

Melon is one of the most important vegetable crops in the world. With short cycle in a system of phased planting, phytosanitary control is compromised, and a great volume of agricultural chemicals is used to control vegetable leafminer. Genetic control is an ideal alternative to avoid the damage caused by this insect. Thus, the aim of this study was to evaluate Cucumis accessions in regard to resistance to leafminer and correlate the variables analyzed. Fifty-four accessions and four commercial hybrids of melon were tested. The study was divided into two experiments: with and with no choice. The following characteristics were evaluated: with choice, in field - subjective score based on the infestation and the number of mines per leaf; and with no choice, in cage - number of mines per leaf, chlorophyll content, and leaf colorimetry. The results showed variability among the accessions and some genotypes showed favorable results for resistance in both experiments. There was correlation between the two variables in the experiment in the field. The accessions CNPH 11-282, CNPH 06-1047, and CNPH 11-1077 are the most recommended for future breeding programs with aim on introgression of resistance to vegetable leafminer in melon.