Distribution of wild potato species in the north of the Department of La Paz , Bolivia

From 2001 to 2003, field collections of wild potatoes (Solanum Section Petota Solanaceae) were made in the north of the Department of La Paz, Bolivia, with the aim of determining their current distribution in this region. The collection embraced sectors of five provinces: Omasuyos, Larecaja, Camacho, Muñecas and Bautista Saavedra. Five previously described wild species were collected: Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault and S. circaeifolium Bitter, as well as four unidentified species. Some wild potato species in Bolivia, such as S. achacachense, are rare and in danger of extinction because of the destruction of their habitat. In contrast, S. brevicaule, S. candolleanum and S. circaeifolium were recorded in new areas. Some species were affected by pests (Premnotrypes sp.) or the fungus Phytophthora infestans. This is the first time that ‘Lelekoyas’ potatoes (S. tuberosum subsp. andigena) have been detected in the area of influence of Lake Titicaca. In summary, this work reports degrees of genetic erosion for some species, the finding of taxa in new geographical areas, some probable new species, and the presence of P. infestans in some of the species detected. Additional key words: danger of extinction, Phytophthora infestans, rare wild species, Solanum spp.

Both works describe 36 species of potato for Bolivia, although they differ in their descriptions of subspecies and varieties.Between 17 and 19 species (and their variants) are found in the Dept. of La Paz, all of which are represented in potato germplasm collections.Hawkes (1994) indicated some of Bolivia's wild potato species (S. achacachense, S. bombycinum, S. circaeifolium ssp.circaeifolium, S. flavoviridens, S. okadae, S. soestii and S. violaceimamoratum) to be rare1 , and some to be threatened by extinction because of the destruction of their habitat.In addition, Ochoa (1990) reported S. virgultorum to be facing extinction in its type locality2 .These wild species are mainly found in the north of the Dept. of La Paz, where actions over the last few decades designed to achieve rural development, along with other anthropic influences, have led to environmental degradation.The conservation of wild species in situ is important to the food security and economies of different countries worldwide, and certainly, wild potatoes play an important role as sources of resistance to pathogens (Cárdenas, 1966).
Late blight of potatoes3 , caused by Phytophthora infestans, is a disease of world importance, mainly in the temperate to temperate-cold regions (Erwin and Ribeiro, 1996).In the provinces to the north of La Paz, late blight is a common disease in the Interandean valleys (altitude 2,000-3,600 m) and occasionally in areas of higher altitude (3,600-4,500 m).
The aim of the present work was to determine the current in situ distribution of wild potato species in the north of the Dept. of La Paz, and to look for signs of the presence of P. infestans in these species.

Material and Methods
Between January and March (the time of flowering and fruiting in potato species) of 2001, 2002, and 2003, a number of expeditions were made to the type localities of the wild potato species of different provinces belonging to the north of the Dept. of La Paz (Fig. 1).These provinces were: -Omasuyos.Two areas were contemplated, a) the shores of Lake Titicaca (altitude 3,820 m), between the communities of Ajllata Grande and Santiago de Huata to the highlands of Cruz Pata (4,000 m), and b) towards -Muñecas.Including the highlands of Cerro Totoroko (4,350 m) and the area of influence of Timusi.
-Bautista Saavedra.Including the areas of influence of the settlements of Charazani (3,050 m) and Chulina (3,250 m).
In each province, collection expeditions were made to the type localities reported by Cárdenas (1973), Hawkes and Hjerting (1989) and Ochoa (1990), and to new sectors, generally those suggested by local farmers.The altitude, longitude and latitude of each collection point was recorded with the aid of a Global Positioning System receptor (GPS 12, GARMIN).Characteristic specimens of each species at each stage of flowering were collected.Their characterisation and morphological description were undertaken following the descriptors of Ochoa (1990).Whenever signs of P. infestans infection were noted, leaflet or stem samples were taken for laboratory analysis as described by Erwin and Ribeiro (1996).

Results
Between three and five samples of typical plants of the species S. acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault, and S. circaeifolium Bitter were collected at each site where they were found in the different provinces, along with three samples of each of the four undescribed species (Table 1).
-Province of Omasuyos.The most common species in the area of influence of the shores of Lake Titicaca and the communities of Ajllata Grande and Santiago de Huata was S. brevicaule 4 .In these areas, this species was found towards the slopes, between stone walls, species of cactus and native vegetation.Isolated samples of S. acaule 5 were also recorded, as well as 'Lelekoyas' plants, which, according to Cárdenas (1973), correspond to a primitive form of S. tuberosum subsp.andigena.S. acaule was found in the highlands of the community of Cruz Pata; isolated specimens of a taxon that might represent a new species were also found.Towards the Cordillera Real de La Paz (close to Nevado Illampu), in the communities of Murumamani and Chachacomani, plants of S. acaule were collected, quite often affected by the Andean potato weevil (Premnotrypes sp.).
-Province of Larecaja.S. achacachense 6 , and rarely S. acaule were found distributed towards the Cordillera Real (Nevado Illampu), at certain sites along the track between Achacachi and Sorata in the community of Chojchoni Alto in the «La Apacheta» area.In the Valley of Sorata S. circaeifolium 7 was the main species, although its distribution was dispersed.In areas close to this valley (the area of the Hotel Prefectural and neighbouring area) this species was very rare.
Approximately 10 km along the track from Sorata to Millipaya this species was found at Cotaña 8 -a site not reported by Hawkes and Hjerting (1989) or Ochoa (1990).Here, it grows on the high parts of the Cerro Cotaña, between stones and under the protection of bushes; its population density is high.Some plants show prostrate growth (aerial stem length 85 cm).
Towards the foothills of the Nevado Illampu (a sector known as Llust'a), and at certain sites on the track towards Tacacoma (Sorata-Laripata-Tacacoma) in a sector of the community of Paconi (approximately 4,012 m), S. candolleanum was found, as were isolated specimens in the Tacacoma cemetery.'Lelekoyas' potatoes were also recorded in the Cerro Iminapi sector.
-Province of Camacho.Specimens of S. acaule were collected in the highlands of the community of Huallpa Cayu (4,300 m).At the entrance the village of Italaque (on the slopes close to the river), specimens of S. circaeifolium were collected, as well as those of a potentially new species; S. circaeifolium was also collected in the Valley of Moco Moco (2,550 m) (community of Cotusi).
-Province of Muñecas.Specimens of two populations of S. acaule (one with whitish flowers and the other with lilac flowers) were collected on the Cerro Totoroko.Isolated 'Lelekoyas' plants were recorded in the area of influence of Timusi.
-Province of Bautista Saavedra.No wild potatoes were found at all in the areas of influence of the village of Charazani and the community of Chulina.
Four samples (NN-1, NN-2, NN-3 and NN-4), failed to coincide with any of the descriptions provided by Hawkes and Hjerting (1989) or Ochoa (1990), and were recorded as unidentified species (Table 1).Table 2 shows a number of characteristics of three of these species.NN-4, which was collected at the entrance to the village of Italaque (Province of Camacho) in the grassy areas of the slopes, was not classified due to the poor quality and small quantity of specimens collected.
Specimen NN-1 (Table 2) was collected in the high mountains (on the track between Villa Lipe and Santiago de Huata) of the communities with a Lake Titicaca shoreline (Province of Omasuyos), where there are traces of Inca terraces now in decay.This species was rare, and found between stone walls.Its pubescent leaves have a particular shape, and the plant has a semirosetted growth habit.It has never been seen to flower, either in the field or under glass.Some of the samples collected are being characterised in collaboration with the International Potato Center (Peru).
NN-2, collected at «La Apacheta» (Province of Larecaja) along the high parts of the track between Achacachi and Sorata, grew erect, had a rather deep main root (Fig. 2), pubescent leaves, and flowers with a rotaceous corolla.The species appears to be rare; only two specimens were found in the field.
NN-3 was collected in a secondary mountain chain in the highlands of «La Apacheta» (Province of Larecaja), at the altitude of the ENTEL antenna.Sparsely distributed, its main notable characteristic is the form of its leaves (glabrescent and with a long main lobule) and its flowers with a stellate corolla.
Table 3 records the presence of P. infestans on the different species collected.All the species from wet areas (areas with permanent cloud) -S.achacachense, S. candolleanum, S. circaeifolium and S. xjuzepczukii 9were affected by this fungus. 8An Aymaran word meaning «lagoon». 9A species of bitter potato mainly cultivated at altitudes of > -4,000 m.

S. achacachense
This species is only known in the «La Apacheta» sector between Sorata and Achacachi in the highlands of the Province of Larecaja.Nowadays, this locality belongs to the Province of Larecaja, and not Omasuyos as indicated by Cárdenas (1973) and Ochoa (1990).Until the 1970s, the land and the vegetation of the area conserved its natural character, but today they are altered by agriculture and cultivation practices associated with the production of phurejas potatoes 10 ; this is threatening the existence of S. achacachense.Hawkes (1994) indicated the distribution of S. achacachense to be rare; it is now threatened with extinction.P. infestans is only rarely found in this area, and when present it mainly affects the stem (Fig. 3).

S. brevicaule
According to Ochoa (1990), this species is distributed between the Provinces of Manco Kapac and Omasuyos on the high plain north of La Paz.In the present work this species was found to be endemic to the shores of Lake Titicaca sector between Ajllata Grande and Santiago de Huata in the Province of Omasuyos.The finding of 'Lelekoyas' plants in this sector, mainly in the Sorata area, was not reported by earlier authors.

S. candolleanum
This was found in some sectors of the Province of Larecaja, as described by Hawkes and Hjerting (1989) and Ochoa (1990), but it was also recorded in new areas such as the community of Paconi.In all cases its populations were small.

S. circaeifolium
This species was found in the Province of Larecaja, at Cerro Iminapi, in the locality of Laripata, as previously reported (Cárdenas, 1973;Hawkes and Hjerting, 1989;Ochoa, 1990).However, none of these authors recorded the size of the population nor the distribution of this species in this area.It now appears to be very rare and to be found only on the high part of the Cerro Iminapi.
In conclusion, the present results show that, of the species of wild potato recorded in the north of the Dept. of La Paz by Cárdenas (1966), Hawkes and Hjerting (1989), and Ochoa (1990), S. acaule has a distribution greater than originally believed, reaching towards the Cordillera Real, but its survival is affected by a series of factors still to be quantified.The restricted distribution of S. achacachense is conf irmed; its survival also appears to be threatened.S. brevicaule is endemic to the areas around Lake Titicaca.S. candolleanum seems to be most abundant in the foothills of Nevado Illampu, but is very affected by P. infestans.S. circaeifolium is affected in its home environment by a series of factors still to be quantified although it seems to have a wider distribution than originally believed.Morphological variations of some taxa were found as well as four probable new species, three of which are undergoing characterisation.

Figure 1 .
Figure 1.Geographical locations of the areas where the distribution of wild potatoes was investigated.Black dots correspond to study sites, the dashed line to the frontier with Peru, the light blue line to the edge of lake Titicaca, and the red lines to the boundaries of the provinces in the Dept. of La Paz.

Table 1 .
Wild potato species collected in the different provinces of the north of the Dept. of La Paz, Bolivia 1 Metres above mean sea level. 2 Unidentified species.3Unidentifiedspeciesnotundergoingcharacterisationdue to lack of samples.4Known to farmers as «Jamach'i Ch'ogue», an Aymaran word meaning «bird food».5Known to farmers as «Apharu Ch'ogue», an Aymaran word meaning «inedible potato».6Known to farmers as «Achachil Ch'ogue», an Aymaran word meaning «old potato».7Known to farmers as «Monte Ch'ogue», an Aymaran word meaning «country potato».

Table 2 .
Characteristics of potentially new wild species