Dioscorea, commonly known as yam, is an economically, socially, and culturally-relevant tuber crop in many tropical countries. This study aimed to characterize the genetic diversity of Dioscorea alata L. and related species from Colombia (42 D. alata L., 6 D. bulbifera L., 3 D. rotundata Poir., and 3 D. trifida L. f.) through seven intersimple sequence repeat (ISSR) markers. The plant material was collected in five departments of Colombia. The seven ISSR generated 164 bands that showed high polymorphism (83.62%). Nei-Li genetic diversity coefficient (0.66) and Shannon information index (0.2636) revealed a high level of genetic diversity. The 54 genotypes were grouped into six groups according to geographic location but not by species. We found moderate genetic differentiation (Gst = 0.13) and high gene flow (N m = 2.7367). The analysis of molecular variance (AMOVA) showed higher variation (86%) within groups than among groups (14%). Our results suggest that the high genetic diversity in yam in Colombia can be exploited in future work on crop improvement.

Selenicereus megalanthus H. is a tropical fruit belonging to the family Cactaceae, is rich in essential nutrients, antioxidants and bioactive components. It presents wide variability in different characteristics and a great demand in the market; however, genetic studies in Colombia are scarce. The main of this study was to characterize the genetic diversity of 76 yellow pitahaya genotypes with eight ISSR markers. Genetic parameters expected average heterozygosity (He), percentage of polymorphic loci, genetic distances and Fst were estimated with TFPGA. The analysis of the population genetic structure was carried out with the STRUCTURE 2.3.4. As a result, 225 alleles were generated and the number of polymorphic loci ranged 85 (CT, AG) to 90 (GT). High genetic diversity was found, with an average value of heterozygosity was 0.34 with a genetic differentiation coefficient (Fst) of 0.26, indicating that there was a great genetic diversity, similar values than those reported in other studies of pitahaya genetic diversity in Colombia. The 76 genotypes were grouped into K=3 according to geographic location, however, in some groups a mixture of individuals from different origins was observed. The analysis of molecular variance (AMOVA) showed higher variation (75%) within groups than among groups (25%). These results provide information that can be used to develop conservation strategies for dragon fruit and breeding programs to obtain more productive pitahaya genotypes with superior quality, high yield and with resistance to biotic and abiotic factors.

RESUMEN

The root-knot nematode Meloidogyne spp. causes yield losses of up to 68% on tomato (Solanum lycopersicum L.) crops. Genetic resistance in the host plant makes the crop sustainable and it can breakdown when there is a high population density of the pathogen. The objective of this study was to determine the nematode population density that allow determining the resistance potential of tomato germplasm associated with the Mi-1 resistance gen. The Mi-1 gene was evaluated with the molecular marker SCAR Mi-23 and specific primers in the genotypes COLY007, IAC1687, LA0445, IAC1622 and two commercial controls (susceptible and resistant). The damage scale and the number of individuals recovered (eggs and juveniles) were assessed, with different population densities of the pathogen inoculated (0, 1000, 2000, 3000, 4000 and 5000 individuals plant -1 ), in a split plot design, with six replicates and a plant as the experimental unit. The genotype IAC1687 and the resistant commercial control presented the resistance allele of the Mi-1 gene and were classified as moderately resistant to a density of 1000 individuals plant -1 . Despite having the Mi-1 gene, the COLY007 genotype was classified as moderately susceptible and with densities greater than 1000 individuals plant -1 can break resistance in all genotypes evaluated. Additionally, it is necessary to correlate the genotypic and phenotypic responses to guarantee the success of the selection supported by molecular markers such as SCAR Mi-23 and identify promising genotypes that could be included in a long-term breeding and also used as rootstocks in an integrated management of root-knot nematode.

Quinoa (Chenopodium quinoa Wild.) is an Andean crop that originated from the Andes of South America, with great agronomic, industrial, pharmaceutical potential and also a great capacity to tolerate adverse environmental factors. In Colombia, more accurately in the Department of Nariño, Cauca, Cundinamarca and Boyacá. Shows great genetic variation, both molecular and morphological, which organization remains poorly documented. In Boyacá, there are few studies on the morphological characterization of cultivated materials, and there is no certified planting material, with farmers planting a mixture of materials. Qualitative and quantitative descriptors and principal component and cluster analyses were used to characterize the structure of the intra-population phenotypic variation in Blanca de Jericó quinoa materials grown in the Department of Boyacá. The principal component analysis explained more than 70 % of the observed variation, with the AP, LP, DP, LHS, and AHS characteristics being more variable. The cluster analysis showed grouping by characteristics, such as AP, panicle color, and the presence of pigmented axillae. Results show that the variance in morpho-phenological traits was concentrated at the intra-population, due to high variation at the inter-individual level. A more efficient selection process should be carried out to find materials or "pure" varieties with higher yields, resistance to biotic and abiotic factors, and adaptation to local conditions, which make quinoa an economically profitable crop in the Boyacá department.