The Potato Late Blight Caused by <i>Phytophthora infestans</i> Mont de Bary as Selection Factor of Phurejas Potatoes (<i>Solanum phureja</i> Juz et Buk) in Endemic Areas of the Bolivian Andes

Abstract

Phurejas potatoes ( Solanum phureja Juz et Buk) are cultivated in very restricted areas of the Bolivian Andes. Late blight caused by Phytophthora infestans is a destructive, endemic disease that affects the survival and cultivation of this crop. The aim of this study was to determine the resistance characteristics of phurejas potato varieties to P. infestans in a traditional area of cultivation. An experimental plot was prepared in the locality of Chojchoni (3200 m) and planted with different phurejas varieties: 1 ) Chojllu Phureja ( Sste ) ; 2 ) Phureja Amarilla ( Sphu ) ; 3 ) Polo Phureja ( Sphu ) ; 4) Phureja Roja ( Sphu ) ; 5 ) Phureja Negra ( Sphu ) and 6 ) Waych’a Pacena ( Sadg ), a susceptible control. Severity was assessed according to the criteria of the Centro Internacional dela Papa , determining the area under the disease progress curve (AUDPC). Regression analysis (log N disease severity against time) was performed usi ng the logistic mod el [ln(y/1 - y)] to determine infection rates. The different varieties showed different levels of resistance. The disease progress curve, the AUDPC and the linear regression results revealed the varieties Chojllu Phureja, Phureja Amarilla and Polo Phureja to likely have larger copy numbers of minor resistance genes against P. infestans than Phureja Roja or Phureja Negra. Late blight caused by P. infestans could cause the long-term loss of some phurejas varieties through farmers selecting others less severely affected by the disease.