Identificação de marcadores moleculares associados à resistência à Meloidogyne exigua em cafeeiro

Abstract

One of the limiting factors for the growth and high productivity in coffee are phytonemtodes. This work was done with the objective of identifying microsatellite and AFLP markers associated with the resistance of M. exígua in coffee under the filed and greenhouse condition, that can be used in the future genetic improvement programs. Under the greenhouse condition 82 F5 progenies of coffee seedlings derived from the crossing of Híbrido de Timor and Catuaí Amarelo IAC 86 were planted and the measurements (reproduction factor and index of galls) were evaluated after 320 days of nematode inoculation. It was verified that among the 44 SSR markers tested 11 primers became polymorphic between parents. In the progenies studied, it was observed 4.5 polymorphic alleles per primer. The clustering analysis of the progenies based on the polymeric alleles grouped the progenies into three groups and these groups have relation with the nematode reaction. The markers SSRCafé 20 allelo 3 (100bp), SSRCafé 40 allele 2 (250bp), and SSRCafé 15 allele 3 (100bp) are associated with the resistance of nematodes M. exigua in the progenies. The AFLP marker was used with the objective of realizing association mapping in 22 F4 progenies of coffee and identify the AFLP markers associated with resistance to nematode M. exigua. The population of M. exigua per grams of root, M. exigua per 100 cc of soil, number of galls and vegetative vigor were evaluated in January and July. For the molecular analysis eleven AFLP primer combinations were used and 14.4 polymorphic alleles per primer combination were observed among the progenies. The clustering analysis based on the molecular data and the phenotypic data grouped the progenies into 4 cluster groups. Based on the population structure analysis the progenies were grouped into 2 groups (K=2), being the 90 percent of the resistant progenies included in the same group. The Mixed Linear Model (MLM) model was used for association mapping analysis and identified AFLP markers associated with the resistance of nematode M. exigua.