EVALUATION OF MEXICAN GUAVA GERMPLASM AGAINST ROOT KNOT NEMATODES

Abstract

Root knot nematodes (Meloidogyne spp.) are one of the main phytosanitary problems of guava orchards in Mexico. At Calvillo, Aguascalientes, almost 90% of the seven-thousand hectares cultivated with guava are infested with nematodes. Although there are chemical and biological strategies to manage this problem, genetic resistance of native guava germplasm under cultivation has never been studied. The purpose of the present study was to determine the degree of susceptibility of a group of guava selections included at the germplasm bank of INIFAP as well as other guava accessions. Air-layering plants of the selections 10, 12, 20, 45, 46, 48, 106, 115, 117, and 118 were obtained, and then placed in pots of 12 kg of capacity. Plants were inoculated with 12 ml J2 plus nematode eggs collected at infested guava orchards of Aguascalientes, Michoacan, and Zacatecas. Results using air-layering plants showed that selections 46, 106, and 45 were more tolerant with 26, 35, and 35% of root damaged, respectively, while the most susceptible was selection 48 with 70% of the roots showing galls. In the group of guava seedlings, four accessions (51, 58, Boyaca, and Brazil) showed the highest gall numbers per centimeter of root, whereas the least affected were selection 42 and a Psidium spp. This study provides evidence that guava genetic resistance to nematodes could be present in the germplasm under study, and could be used as rootstocks or hybridization in future works.