Non Technical Summary
Potato relatives offer a more diverse and accessible germplasm resource than is found in any other crop. Potato and wild species relatives grow from sea level to 4300 m and are found in a tremendously wide array of environments. Most of these wild relatives cross readily with cultivated potato, producing offspring with acceptable tuber yield and type that can provide the genetic diversity to needed for potato production in stressful environments, including those with heat stress and disease pressure. One diploid species that was central in the domestication and improvement of potato was Solanum microdontum with clear association of adaptive traits present in modern cultivars that can be traced to introgressions during the movement of cultivated potatoes from Peru/Bolivia to southern Argentina. To build on germplasm resources for a diploid potato breeding approach, in this project, we will phenotypically characterize available S. microdontum germplasm for key agronomic traits that can be readily incorporated into breeding material. We will also generate a chromosome-scale reference genome and catalogue genetic diversity in this species to understand the underlying genetic diversity that contributes to phenotypic diversity. Through the identification of loci and alleles linked to late blight resistance and heat tolerance, we will address not only the major disease pressure in potato production but also position potato breeding such that it can address concerns associated with climate change.
Animal Health Component
Research Effort Categories
Goals / Objectives
Wild species relatives of potato provide a more diverse and accessible germplasm resource compared to any other crop as they grow from sea level to 4300 m and are found in a wide array of environments including cold high grasslands, hot semi-deserts, seasonally dry habitats, humid subtropical to temperate mountain rainforests, and coastal beaches. Most wild relatives cross readily with cultivated potato, producing offspring with acceptable tuber yield and type that can provide the genetic diversity required to adapt potato production to stressful environments, including those with low water availability, seasonal frost, heat stress, and disease/pest pressure. One diploid species that was central in the domestication and improvement of potato was Solanum microdontum in which a clear association of adaptive traits in modern North American cultivars can be traced to introgressions from S. microdontum during the movement of cultivated potatoes from Peru/Bolivia to southern Argentina. To build towards genomic and germplasm resources for a diploid potato breeding approach, in this project, we will interrogate the diversity of S. microdontum at the sequence and phenotype level to provide germplasm, sequence, and molecular resources that will enable efficient breeding of potato varieties with resistance to late blight, the major pathogen of potato, as well as tolerance to heat associated with global warming.Our specific objectives are:Objective 1. Phenotype a S. microdontum diversity panel for late blight resistance, heat tolerance, and resistance to late blight under elevated temperature to address challenges in potato production due to climate change.Objective 2. Generate a chromosome-scale long read-generated S. microdontum reference genome sequence, characterize allelic diversity within the species S. microdontum, and provide single genotyped and phenotyped clones to the USDA Potato Genebank.
Objective 1. Phenotype a S. microdontum diversity panel for late blight resistance, heat tolerance, and resistance to late blight under elevated temperature to address challenges in potato production due to climate change.All independent S. microdontum PIs will be ordered from the USDA GRIN Genebank and maintained in tissue culture on Murashigi and Skoog media. Cuttings from each tissue culture plant will be planted into SureMix Perlite Mix along with four control clones known to be resistant or susceptible to late blight; plants will be grown in a controlled growth chamber with a 22 ?C day/18 ?C night with 12 hr day length. Five isolates of P. infestans which represent a large portion of the clonal diversity in the US and Canada will be used to score late blight resistance using a detached leaflet inoculation as described by previously. The severity of late blight on foliar tissue will expressed as the Relative Area Under the Disease Progress Curve.We will perform a replicated experiment to determine extent of the impact of heat stress on vegetative fitness, reproductive fitness, and late blight resistance. Cuttings from tissue culture plants will be planted into SureMix Perlite Mix and grown under permissive temperatures and allowed to establish for 3 weeks. Plants will then be transitioned to the two selected heat stress conditions or control conditions and grown till maturity; three phenotypes will be scored. Vegetative Fitness: Plant vigor at harvest [a 1-5 scale where 1 represents the weakest plants based on above-ground biomass and 5 represents the most vigorous plants], total above-ground biomass at harvest, and below-ground biomass (tuber number, tuber yield) at harvest will be determined. Reproductive fitness: We will determine the impact of heat stress on inflorescence number and pollen viability. Late blight resistance under heat stress will be tested under heat stress.Objective 2. Generate a chromosome-scale long read-generated S. microdontum reference genome sequence and characterize allelic diversity within the species S. microdontum.We will use the Oxford Nanopore Technology to generate a chromosome-scale assembly of theS. microdontum clone that has exhibited the highest level of disease resistance and heat tolerance to be the reference genotype. The genome will be annotated using robust transcriptome evidence generated through RNA-sequencing. Whole genome shotgun libraries from the S. microdontum diversity panel will be constructed and sequenced; allelic diversity will be determined from single nucleotide polymorphisms and small insertions/deletions.The S. microdontum reference genome sequence, annotation, gene atlas expression data and allelic diversity data will be made available via deposit in the National Center for Biotechnology, publication, and through SpudDB, an on-line resource for potato genome, sequence, and diversity data (http://solanaceae.plantbiology.msu.edu/).