description
- In a world experiencing major environmental upheaval and population growth it is widely predicted that food security will be a major area of concern for the foreseable future. Increasing the resilience of crops is an area of active research, as scientists aim to increase food production on less land using fewer resources. Part of the toolbox of scientists and plant breeders are the use wild relative species of the crop to introduce new traits into crops to produce enhanced and more resilient varieties. Such approaches have worked successfully in some crops such as banana, barley, beans, cassava, chickpeas, maize, lettuce, oats, potato, rice, sugarcane, sunflowers, tomatoes and wheat. One important global food crop for which there has been insufficient understanding of wild relatives for the use of this approach, is the sweetpotato (Ipomoea batatas). However, recent published research has made significant progress in understanding the phylogenetic relationships between sweetpotato and the species most closely related to it. Objective 1: Describe the wild form of the sweetpotato and define a set of morphological descriptors that allow sweetpotato breeders to distinguish it from cultivated Ipomoea batatas and from other materials of interest to them. Objective 2: Assemble a high-quality genome of wild sweetpotato. This will allow us to conduct comparative genomic studies with the already available genomes of other species of Ipomoea. These comparative studies are essential to understand the evolution of the crop species and how polyploidization affected its genome. In addition, it will constitute a high-quality reference for assembling the genome of the hexaploid cultivar. Objective 3: Document phenotypic variation within and between wild sweetpotato populations, across its entire distribution. This will provide a comprehensive comparative framework for understanding the distribution of traits between the wild form, the crop and all other wild relatives. Objective 4: Determine genetic variation in wild sweetpotato. We will conduct whole genome sequencing of 96 samples from different populations of wild sweetpotato across Ecuador, taking into account geographical and phenotypic variation as identified in Objective 3. This analysis will allow us to not only quantify genetic variation in the wild form of the sweetpotato compared to the cultivated form, but also to assess the genetic processes underlying sweetpotato domestication and to investigate adaptive evolution of 'domestication genes'. Objective 5: Identify genes under positive selection during the adaptation of sweetpotato to cultivation. Plant domestication is often associated with selection of specific traits in the wild plants that make them suitable for cultivation. We will look for a signature of this selection by comparison between the wild form and several sweetpotato cultivars. This type of sister-lineage comparison will allow us to identify differences in synonymous and non-synonymous substitutions and to determine whether polymorphism is due to positive selection or neutral drift. Further, this information will allow us to understand in detail the adaptive mutations that were important during the evolution of the crop compared to its wild form. Objective 6: Clarify the origin, route to polyploidy and domestication of the sweetpotato and what role domestication had in the origin and evolution of the edible storage root.