Peronospora hyoscyami f. Sp. tabacina. Variabilidad de las poblaciones en Cuba (I)

the germination capability of peronospora hyoscyami f. sp. tabacina was assessed along the incubation period and latency. sporulation and infective capability and the sporulated area on different blue mold sensitive and resistant tobacco varieties were also assessed by floating leaf discs method. isolates originated from the provinces of holguín, ciego de ávila, pinar del rio, cienfuegos and la habana showed the highest germination capability. a significant variability was observed among the different isolates, which was particularly evident due to the occurrence of short incubation and latency periods; specially in the isolates obtained from ciego de ávila and one specific isolate obtained from la habana with a five days period, 100% sporulated area and infective capability, and a high sporulation capability even on blue mold resistant varieties. isolates from pinar del río and some others obtained from la habana were the following ones with incubation and latency periods of six and seven days, and sporulated area and sporulation capability on blue mold susceptible and resistant varieties. the isolate obtained from matanzas and one from la habana were less aggressive, with incubation and latency periods of eight and ten days. a lower infective and sporulation capability and sporulated area was also registered for these isolates on blue mold resistant varieties. the holguin isolate showed a low aggressiveness on the blue mold resistant varieties, with latency and incubation periods of eight and ten days, a low infective and sporulative capability and also a low sporulation and infective capability and sporulation area on resistant varieties although it was much more aggressive on the susceptible ones.