Disease Note: First Records of Potato Late Blight Caused by Phytophthora infestans in Bolivia

Late blight, caused by the oomycete Phytophthora infestans Mont. de Bary, is historically one of the most destructive of all potato (Solanum tuberosum L.) diseases. In the Bolivian Andes, it causes important potato losses at altitudes of 2000-3500 m, between which the climatic conditions are suitable for its development. The traditional potato-growing area of the Department of Cochabamba is commonly affected (Figure 1). If control measures are not taken (mainly the use of fungicides), losses can be severe. In recent times it has shown the reemergence of this disease by finding new more aggressive populations, for example, resistant to fungicides fenilalamides as Ridomil (MetalaxylMefenoxam) [1,2]. The Andean countries, including Bolivia, have significant value in studies related to the biology and epidemiology of P. infestans and its implications at local, regional and global levels for the management of late blight of potato (S. tuberosum L.) and tomato (Solanum sculentum L.). During part of the nineteenth and twentieth centuries, expeditions and botanical collections of cultivated and wild potato species for different regions of the Andean area of Bolivia, with the purpose of taxonomic studies and other scientific interest were made. The question remains, however, as to when late blight first appeared in Bolivia. Though it is certainly a serious pathogen in the country today, it is unclear when it first arrived. The present work reviews the historical literature to provide a record of potato late blight in Bolivia.


Introduction
Late blight, caused by the oomycete Phytophthora infestans Mont. de Bary, is historically one of the most destructive of all potato (Solanum tuberosum L.) diseases. In the Bolivian Andes, it causes important potato losses at altitudes of 2000-3500 m, between which the climatic conditions are suitable for its development. The traditional potato-growing area of the Department of Cochabamba is commonly affected (Figure 1). If control measures are not taken (mainly the use of fungicides), losses can be severe. In recent times it has shown the reemergence of this disease by finding new more aggressive populations, for example, resistant to fungicides fenilalamides as Ridomil (Metalaxyl-Mefenoxam) [1,2]. The Andean countries, including Bolivia, have significant value in studies related to the biology and epidemiology of P. infestans and its implications at local, regional and global levels for the management of late blight of potato (S. tuberosum L.) and tomato (Solanum sculentum L.). During part of the nineteenth and twentieth centuries, expeditions and botanical collections of cultivated and wild potato species for different regions of the Andean area of Bolivia, with the purpose of taxonomic studies and other scientific interest were made. The question remains, however, as to when late blight first appeared in Bolivia. Though it is certainly a serious pathogen in the country today, it is unclear when it first arrived. The present work reviews the historical literature to provide a record of potato late blight in Bolivia.

Materials and Methods
During the 19th and 20th centuries, many botanical expeditions to the Andes were undertaken, and collections made of wild and cultivated potatoes from different parts of Bolivia. An exhaustive review was made of the scientific literature from this period to the present, and any mention of potato blight recorded.

Results
The historical literature was found to contain little information on potato late blight in Bolivia.

1800-1900
No 19th century record of potato late blight was found. The oldest information on potato collection from this period records the botanical expeditions of Alcides D'Orbigny [3]. Among the forms collected was a wild potato from near the town of Chuquisaca, which was later  [4]. However, he makes no mention of late blight either [2]. Finally, in 1891, Miguel Bang, who spent several years in Bolivia at the end of the 19th century, collected a wild potato species near Cochabamba that was later classified as S. brevicaule Bitter (described by Bitter) [5]. But just like those before him, Bang makes no mention of late blight.
beginning of the present year, a rare epidemic affected the potato crop in Mizque (Figure 1). In but a few days it destroyed the plants of this important tubercle. The Beltsville Research Station of the Department of Agriculture in Washington D.C. confirmed the problem to be caused by Phytophthora infestans (Mont.) de Bary". This identification is supported by the work of May and Ristaino [5], who detected haplotypes of P. infestans in herborized specimens from the same area deposited (in 1944, by Cárdenas) in the United States Department of Agriculture National Fungus Collection in Beltsville Maryland (BPI 1944). Indeed, in 1944 Cárdenas [16] reported (again in the Revista de Agricultura) the disease to have affected the area anew, as well as other areas of Bolivia and Peru (around Cuzco). Outbreaks then appear to have become more common. In 1949, a botanical collection expedition organised by the Comunidad de Choro (Ayopaya, Cochabamba) reported that "the El Choro Estate hardly produces some thousand 'cargas' [1 'carga'=approx. 100 kg] of potatoes, and is infested by Phytophthora, Rhizoctonia, Spongospora and viruses" [16] (Figure 1). Observations made in April 1960 further support an increasing presence of the disease. During an expedition to the Provinces of North and South Cinti (Department of Chuquisaca), Cardenas [10], noted the following concerning an estate in the Cuplina area: "… the local headsman spoke of the state of abandonment in which that part of the Republic found itself, and he showed me some potatoes infected by Phytophthora … the only clones cultivated in the area were an ordinary variety of Solanum andigenum known as Malkachu and a potato imported from Argentina, possibly Kathadin, both of which are sensitive to late blight" [10]. However, the disease did not spread rapidly everywhere. Though the presence of P. infestans around Lake Titicaca has been a matter of scientific debate for years, but it was not until 2004 that a few isolated Santa Cruz). The observation was made in a damp forest in the region known as "Siberia" (Figure 1). Cardenas [10], writes: "… we discovered another white-flowered wild potato that showed lesions reminiscent of Phytophthora infestans infection." This potato was later classified as S. cevallos-tovarosii [7], but was later understood by Ochoa [3] to be a synonym of S. microdontum Bitter. In the other instance, Coca Morante et al. [8] recorded late blight caused by P. infestans affecting the wild species S. achacachense Card. and S. circaiefolium Bitter in the area of Sorata-La Paz area ( Figure 2).

Cultivated potatoes:
Many different varieties of potatoes are cultivated in Bolivia, yet in his work "Clasificación de la papa de Bolivia" (Classification of the Potato in Bolivia), the first to examine the diversity of potatoes cultivated in this country, Cevallos-Tovar makes no mention of late blight [11]. In March 1954, Bell and Alandia [12] indicated that "in a data-collecting expedition to gather information on late blight attack in the extensive cultivated area around Lake Titicaca, no such attack was recorded. Similarly, in 1954, mentioned by Bell and Alandia [13] researchers at the Estación Experimental del Altiplano del Servicio Agrícola Interamericano (High Plains Research Station of the Interamerican Agriculture Service), reported "there are no known instances of late blight attack in these areas [around Lake Titicaca], perhaps because the temperature is too low for infections to be successful. But, in 2004, is mentioned by first time the presence of late blight symptoms in northern Altiplano Experimental Station [14]. (Figures 2A and 2B).
Earlier, however, in 1943, Cardenas [15] had published what would appear to be the first official report of P. infestans infection in Bolivia. Writing in the journal Revista de Agricultura he noted: "at the In conclusion potato late blight caused by P. infestans in Bolivia is little mentioned in the historic literature, the first record stemming from 1943 in cultivated potatoes. It would appear that before this time P.infestans was not an important pathogen of potato plants in this country, but gradually took hold among cultivated crops.