Dennis Geoffrey Macedo Valdivia

Onion ( Allium cepa ) is a key crop of high economic importance in the Arequipa region of Peru. In this area, leaf blight caused by Stemphylium spp. is one of the most destructive diseases affecting onion and other Allium crops. Accordingly, this study aimed to identify Stemphylium species associated with leaf blight in onion across production areas in Arequipa, Peru. Plants showing typical symptoms of leaf blight were collected from the provinces of Arequipa, Camaná, Castilla and Islay. A total of 10 isolates were selected and identified. Phylogenetic analyses of the partial calmodulin (cmdA) and glyceraldehyde‐3‐phosphate dehydrogenase (gapdh) gene regions revealed that the following species were associated with leaf blight: Stemphylium vesicarium , S. eturmiunum and S. waikerieanum. Pathogenicity assays in onion demonstrated that all three species caused typical leaf blight symptoms. This is the first in‐depth report of three Stemphylium species causing leaf blight disease in onion in southern Peru. These results provide insights into the etiological agents, enhance our understanding of the disease and support the development of more effective management and control strategies.

Quinoa ( Chenopodium quinoa ) is a nutritious crop expanding in importance worldwide, though its capacity to accumulate cadmium (Cd) can put consumers at risk. The objective of this study was to identify genotypes that vary in Cd uptake and explore how domestication, saponins, and root-associated microbes could influence these differences. Twelve genotypes representing wild ancestors and modern landraces or cultivars from four distinct ecoregions were grown in a greenhouse trial using potting media amended with Cd. Differences in phenological developmental traits were recorded during growth, and plant biomass, microbial derived amino sugars in roots, and concentrations of Cd and other essential elements in grains were quantified at harvest. Phenological development of Ancestors were more adversely affected by Cd than modern genotypes, and Cd concentrations were higher in those developed later near coastal regions in South America and the United States, suggesting that quinoa become more tolerant over domestication and selection. Concentrations of several elements were also lower in the Ancestors vs. modern genotypes in response to Cd, indicating that modern genotypes may not downregulate root transporters as an adaptation to Cd stress. Fungal derived amino sugars were negatively correlated with Cd concentrations in the Coastal ecotypes which had the highest uptake, suggesting that the presence of root-associated fungi could help restrict translocation aboveground. Results of this study will provide breeders with new insights into factors that could aid in selecting for quinoa with low Cd-uptake. Early genotypes selected in the Altiplano region may be most useful in these breeding programs.

Alliaceae crops includes several species of agricultural importance for the Arequipa region, among them the onion is the most produced in the country, however, these crops are affected by phytoparasitic nematodes, including Meloidogyne spp. which causes significant losses in the yield. The aim of the present study was to characterise the root-knot nematode (Meloidogyne spp) and determine the population density of phytoparasitic nematodes in alliaceae crops in the main producing localities of the Arequipa region. Samples of roots and soil were collected in onion, chinese onion, leek and chives crops in the provinces of Arequipa, Castilla, Caylloma and Islay. The identification of nematode genus was found by morphological characteristics and the characterization of Meloidogyne were performed by perineal patterns and electrophoretic pattern of esterase (Est). In the 38 soil samples, different genus of plant-parasitic nematodes was found: Aphelenchus, Dorylaimus, Helicotylenchus, Hemicycliophora, Meloidogyne, Mesocriconema, Mononchus, OGMA, Pratylenchus, Rotylenchus, Tylenchus, Xiphinema and free-living nematodes, in root samples, eight populations of Meloidogyne spp. were found. distributed among three species: (1) M. incognita phenotype Est I1, Rm: 1.0 with 33.33% of frequency and Est I2, Rm: 1.03, 1.07 (50%); (2) M. javanica Est J3, Rm: 1.03, 1.24, 1.37 (16.67%) and an atypical species named Meloidogyne sp. Rm: 0.85 (33.33%). The identification of genus and species phytoparasitic nematodes in alliaceae will allow the adoption of more efficient integrated management measures, because have a distinct parasitism behavior.