Abstract

RODRIGUEZ, Dorian; ALCALA DE MARCANO, Dylcia  and  ESCALONA, Fernando. Introductory selection of potato clones for resistance to late blight and yield. Bioagro [online]. 2008, vol.20, n.1, pp.29-35. ISSN 1316-3361.

Late blight, caused by Phytophthora infestans, is still the most important potato disease in the world. To select clones with horizontal resistance from 14 families of the Population B of International Potato Center, a test was conducted in a screen house with 190 clones. Plants were inoculated with a mixture of six isolates of P. infestans collected from different Venezuelan regions which had shown differences in susceptibility to metalaxil. Late blight severity was evaluated eight times and values in percentage were used to calculate the area under disease progress curve (AUDPC). In addition, tuber production per plant was evaluated, and a second trial was taken in the field with selected clones to observe their behavior. Significant differences (P<0.01) were found among families and among clones within families. Most of the clones showed low disease severity, with AUDPC values from 0 to 10,000. Likewise, very susceptible clones were found within some families, with values above 50,000. Kennebec, the susceptible control, showed a mean value over 100,000. Results indicated that the potato families 392636, 392634, 393258 and 391048 had the highest levels of disease resistance and the lowest variabilites. With regard to tuber production, clones from these families, besides 393194-1, demonstrated to be potentially competitive with local varieties. Those clones with low disease severity and high productivity are still being evaluated in the field to select the most outstanding and stable ones in their resistance to the pathogen.

Keywords : Phytophthora infestans; horizontal resistance; area under the curve.