Potato landraces: description and dynamics in three areas of Ecuador

This thesis aims to fill the gap of information on the potato landrace diversity present in farmer fields of Ecuador. Passport data from previous collections (1970’s and 1980’s) were used to identify Carchi, Chimborazo and Loja as representative areas of potato diversity. The status of on-farm conservation in these three selected areas is covered in Chapter 2. Microsatellites (SSRs) helped us to describe the genetic relationships among the landraces found in these areas (Chapter 3). The characterization of potato landraces with respect to late blight resistance (Chapter 4) and quality traits (Chapter 5) complement the description. Previous reports suggested loss of potato diversity (genetic erosion) in Ecuadorian farmer fields, but our collection of a total of 174 landraces showed that these areas still hold a substantial amount of potato landrace diversity (Chapter 2). More potato landraces were found in Chimborazo and Loja than previously sampled in the 70’s and 80’s. A comparison between the two collections, in each of the three areas, indicated only a small overlap in landrace names suggesting that the sampling of local landraces was far from exhaustive, both during the 70’s and 80’s and during the present collection trips. This is further supported by the fact that the diversity fair, which was organized after our collection trips in Chimborazo, resulted in many new landraces. Surveys and farmer meetings in the study areas were used to describe the landrace-holders and the characteristics of the farming system they use. Mostly elderly people and small-scale farmers are currently maintaining potato landraces. These farmers look for income alternatives besides agriculture, resulting in migration. The vulnerability of the potato conservation varies among our study areas. In Carchi younger farmers demonstrate a lack of interest in cropping potato landraces. In Loja farming is not seen as the only sustainable source of income and there is a perceived lack of support from the government for the activities necessary to maintain local landraces. In Chimborazo farmers are culturally more attached to their land and see agriculture as a family activity, rendering the potato landrace conservation less vulnerable. Externally driven on-farm conservation interventions, such as diversity fairs or re-introduction of landraces, were highly appreciated by the farmers and could help to conserve the potatoes. Diploid, triploid and tetraploid potato landraces are found in farmers fields. The material sampled at the three areas shows a high allelic diversity. At the tetraploid level (the most abundant) this was comparable to the variation present in an European collection of more than 800 varieties. More alleles are expected to be found when more material from other areas will be screened. There was no clear grouping of material collected according to study region, suggesting extensive movement of seed potatoes all over Ecuador. A comparison of the application of variety names with the genetic relationships among potato landraces can result in either under- or over-estimation of the variability present in farmer fields (Chapter 3). In a number of cases landraces with identical common names proved to be genetically different or individual collection samples were actually a mixture of two landraces, pointing at under-estimation of diversity present. On the other hand, cases that might lead to over-estimation were also evident, e.g. genetically identical material was present under different names. Our sampling of genetically different landraces for late blight (LB) resistance characterization (Chapter 4) confirmed that there was some variation for this trait among the landraces. Most of the landraces were susceptible to moderately resistant, but also some landraces with field resistance were identified. The observed field resistance was comparable to that in the widespread improved variety Fripapa. Possible strategies to improve late blight resistance in potato in Ecuador could include the identification of accessions with resistance among the local landraces, although only a few accessions may be expected to present field resistance. The introduction of new sources of resistance from other origins is a more viable alternative. One could attempt to introduce novel R-genes in material that already contains some level of quantitative resistance. We found varying levels of dry matter, total polyphenol and total carotenoid contents among Ecuadorian potato landraces, some were comparable to the improved varieties. Based on the dry matter content most of the Ecuadorian landraces evaluated were suitable for processing as French fries or chips. The total polyphenol content of these potatoes were quite similar to those reported by the International Potato Center (Peru) for a set of accessions representing more than 60% of the variability in their potato collection. The total carotenoid content values of the Ecuadorian potatoes included in our study were similar or lower compared to previous studies on improved or Andean potatoes. The identified outstanding potato materials could be used to develop new potato varieties through plant breeding. In Chimborazo and Loja farmers select landraces mainly based on their nutritional characteristics. However, in Carchi farmers prefer commercial improved varieties. Farmers´ preferences include empirical valuation of potato-quality rather than specific knowledge on nutritional characteristics of these potatoes. This thesis provides important knowledge about the potato landraces in Ecuador. Our results can serve as the basis for further description and use of Ecuadorian native potatoes by breeders and local communities.