Caracterización de poblaciones de phytophthora infestans (mont, de bary) obtenidas de solanum transgénicas y de híbridos somáticos resistentes

In the Toluca Valley, México, in the summer of 2003, clones obtained by genetic engineering and somatic hybridization between Solanum tuberosum and S. bulbocastanum were exposed to natural infection by Phytophthora infestans in order to quantify their resistance to the oomycete, previously proven under different conditions. The objective was to identify was to identify the P. infestans genotypes that selectively and progressively infected the potato clones. Most clones were resistant in the early growing stages, although gradual infection showed up later in the cycle. Twenty two P. infestans variants were identified on the basis of mating type (MT) and on the allozymatic multilocus profiles for glucose-6-phosphate isomerase (GPi) and peptidase (PEP). Six weeks after planting the first infections by five isolates were obtained in the non transformed control (H6, cv. Katahdin). A week later, other five P. infestans genotypes were isolated in the same host, four of which were different to the ones obtained the previous week. At the same time, other four genotypes were obtained in another clone that did not acquire the transgene (H4). Both clones died at midseason. The P. infestans genotypes infecting most frequently all the clones, mainly at the end of the cycle, were A1, 100/100, 100/100 (MT, GPi, PEP; 19%), and A2, 100/100, 100/100 (14%). The A1:A2 ratio for all the population was 1:1 (86:77; 52.7%:47.3%). It is concluded that a great P. infestans genetic diversity was present; the transgenes conferring resistance worked well in young plants early in the cycle, and no host-pathogen specificity was observed.