Recent Wild Species Collections from Chile

Roger T. Chetelat¹ and Ricardo A. Pertuzé²

¹C.M. Rick Tomato Genetics Resource Center, Dept. of Plant Sciences, University of California, Davis, CA  95616, USA

²Depto. de Producción Agrícola, Universidad de Chile, Casilla 1004, Santiago, Chile

            Our ex situ collections of the four wild tomato spp. native to Chile – L. chilense, L. peruvianum, S. sitiens and S. lycopersicoides – were vastly improved by several collecting expeditions made in the 1980’s (Rick and Holle 1989).  However, even with the newly acquired accessions, there were still significant gaps in the geographic representation of each species. 

To address these deficiencies, two expeditions to northern Chile (Regions I and II) were sponsored by the USDA Plant Exchange Office in 2001 and 2005.  In addition to the authors, the participants were Elaine Graham (UC-Davis) and Pedro León (INIA, Chile) on the first trip, Carl Jones (UC-Davis) on the second, and Luis Faúndez (Univ. de Chile) on both trips.  The primary goal of the 2001 expedition was to obtain additional populations of S. sitiens and S. lycopersicoides, species that at the time were represented by only a handful of accessions each.  The objectives of the 2005 jaunt focused on collecting new populations of L. chilense from the arid coast ranges.  Our combined observations from both trips regarding the ecology and distribution of each species, and characteristics of selected accessions, are summarized below.

L. chilense  – 2004/2005 was a dry year along the coast of Chile, and few actively growing populations were found in this region.  One notable exception was a population from Quebrada los Zanjones (LA4339), located about 15 Km further south and in a different drainage system than previous collections near Taltal.  The Zanjones population represents the southern limit of the distribution of L. chilense.  In the opposite direction, we collected a population from Estación Puquio (LA4324), located near the border with Peru, and the northernmost accession ever collected from Chile.  Previously known only from an herbarium specimen made in the 1950’s, the Estación Puquio population grows in an extremely arid, desolate, and inaccessible region.  Several other new accessions (LA4117, LA4329, LA4330, LA4332) were collected in the Andes near Calama and San Pedro de Atacama, an area from which few collections had been previously made.  These new accessions link the populations to the southeast – a distinctive race once recognized as a separate species (L. atacamense) – with those to the northwest and the center of the distribution.  Interestingly, the population from below Paso Jama (LA4117) grows at up to nearly 3,600m elevation, extremely high, possibly the highest, for any Lycopersicon species.  Considering its lower latitude, which is over 12 degrees further from the equator than the high altitude L. hirsutum’s for instance, this L. chilense accession would likely be a good source of cold tolerance. 

L. peruvianum – We collected two populations (LA4317 and LA4325) growing in agricultural fields near the coast.  At both locations, but especially the first, large ‘metapopulations’ extended from sea level up to mid elevations in the river valleys.  As expected for large populations of an obligate outcrosser, we noted abundant morphological variation between plants, hinting at a relatively high level of genetic diversity in this material.  We also made new collections from the upper Río Lluta and Río Camarones drainages (LA4318 and LA4328).  The latter population, of which we could find only one plant with fruit, was morphologically distinct from our existing accessions of L. peruvianum, but unfortunately could not be regenerated at Davis.  Another high elevation population was collected at Camiña (LA4125) which is the southern limit of this species’ distribution.  This population proved to be entirely self-compatible (Graham et al. 2003), a situation similar to that of L. hirsutum and L. pennellii, both of which are mostly SI but include Sc races on their southern geographic margins.

S. sitiens – Our recent collections of S. sitiens nearly triple the number of accessions of this species maintained by the TGRC, and greatly expand the geographic range preserved ex situ.  A population found near Mina La Escondida (LA4105) is located over 100 Km to the south of any other known S. sitiens populations, and is morphologically distinctive.  Another interesting accession was collected from Cerro Quimal (LA4331), located further to the east than any other known population of this species.  It survives close to a mountaintop bordering the Salar de Atacama, in an extremely arid environment, and probably subject to periodic frosts.  Tests of soil samples taken at several S. sitiens collection sites indicated high levels of salinity – up to 500 meq/L Na⁺ at Estación Cere (LA4113) – which suggests this species could also be a source of salt tolerance for tomato improvement.  Like the existing accessions of S. sitiens, the new populations are all SI.

S. lycopersicoides – We collected two small populations (LA4320 and LA4326) at 1200 - 1400m elevation, lower than any previously known population of this species, which generally prefers high elevations (up to nearly 3,800m).  Additional accessions (LA4123 and LA4126) were collected from  the Río Camiña drainage, near the location of an earlier collection (LA2951) noteworthy for producing hybrids with cultivated tomato that are unusually fertile, a feature that facilitates introgression (Canady et al. 2005).  In addition, we collected the first accessions of this species from the Río Camarones canyon (LA4130, LA4131).  The physical barriers – arid ridges and coastal plain, distance, etc. – that separate neighboring river valleys in this part of Chile likely result in reproductive isolation and genetic differentiation of local populations.  This underscores the importance of a thorough geographic sampling for conservation of these species ex situ.

Our two expeditions afforded an opportunity to observe ecological preferences and evaluate changes in the status of individual populations from one visit to the next.  By far the most widespread in Chile, populations of L. chilense were generally robust and healthy.  Nonetheless, some popoulations have been impacted by human activities, such as road construction and heavy grazing, which in some cases precluded viable seed collections.  Grazing is a serious concern with S. lycopersicoides, a relatively rare plant to begin with, whose preferences for more mesic, high elevation sites places it in prime territory for herds of goats, sheep, llamas and alpacas.  This situation is exacerbated by low seed production, a long fruit ripening phase, and lack of fruit abscission, all of which increase vulnerability to herbivory.  Populations of S. sitiens appear to avoid this threat thanks to the lack of vegetation in its hyperarid habitat.  On the other hand, many populations grow in the vicinity of active mines.  The Mina Escondida population, for instance, is threatened by construction of a nearby pipeline.  In light of these concerns, we recently filed petitions to add S. lycopersicoides and S. sitiens to the IUCN red list of endangered species in Chile.

Detailed passport information on each accession can be obtained at our website, http://tgrc.ucdavis.edu.  After multiplication of seed at Davis, samples will be provided, upon request, to interested researchers (check website for current availability).

 

Literature cited:

Canady M.A., Meglic V., and Chetelat R.T. (2005) A library of Solanum lycopersicoides introgression lines in cultivated tomato.  Genome 48: 685-697.

Graham E.B., Shannon S.M., Petersen J.P., and Chetelat R.T. (2003) A self-compatible population of Lycoperisicon peruvianum collected from N. Chile.  TGC 53: 22-24.

Rick C.M., and Holle M. (1989) Recent collections in northern Chile.  TGC 39: 30.