Ana Panta

Molecular and physiological adaptation to prolonged drought stress in the leaves of two Andean potato genotypes

Responses to prolonged drought and recovery from drought of two South American potato (Solanum tuberosum L. ssp. andigena (Juz & Buk) Hawkes) landraces, Sullu and Ccompis were compared under field conditions. Physiological and biomass measurements, yield analysis, the results of hybridisation to a potato microarray platform (44 000 probes) and metabolite profiling were used to characterise responses to water deficit. Drought affected shoot and root biomass negatively in Ccompis but not in Sullu, whereas both genotypes maintained tuber yield under water stress. Ccompis showed stronger reduction in maximum quantum yield under stress than Sullu, and less decrease in stomatal resistance. Genes associated with PSII functions were activated during recovery in Sullu only. Evidence for sucrose accumulation in Sullu only during maximum stress and recovery was observed, in addition to increases in cell wall biosynthesis. A depression in the abundance of plastid superoxide dismutase transcripts was observed under maximum stress in Ccompis. Both sucrose and the regulatory molecule trehalose accumulated in the leaves of Sullu only. In contrast, in Ccompis, the raffinose oligosaccharide family pathway was activated, whereas low levels of sucrose and minor stress-mediated changes in trehalose were observed. Proline, and expression of the associated genes, rose in both genotypes under drought, with a 3-fold higher increase in Sullu than in Ccompis. The results demonstrate the presence of distinct molecular and biochemical drought responses in the two potato landraces leading to yield maintenance but differential biomass accumulation in vegetative tissues.

Genetic identity in genebanks: application of the SolCAP 12K SNP array in fingerprinting and diversity analysis in the global in trust potato collection

Breeders rely on genetic integrity of material from genebanks; however, admixture, mislabeling, and errors in original data can occur and be detrimental. Two hundred and fifty accessions, representing paired samples consisting of original mother plants and their in vitro counterparts from the cultivated potato collection at the International Potato Center (CIP) were fingerprinted using the Infinium 12K V2 Potato Array to confirm genetic identity of the accessions and evaluate genetic diversity of the potato collection. Diploid, triploid, and tetraploid accessions were included, representing seven cultivated potato taxa (based on Hawkes, 1990). Fingerprints between voucher mother plants maintained in the field and in vitro clones of the same accession were used to evaluate identity, relatedness, and ancestry using hierarchal clustering and model-based Bayesian admixture analyses. Generally, in vitro and field clones of the same accession grouped together; however, 11 (4.4%) accessions were mismatches genetically, and in some cases the SNP data revealed the identity of the mixed accession. SNP genotypes were used to assess genetic diversity and to evaluate inter- and intraspecific relationships along with determining population structure and hybrid origins. Phylogenetic analyses suggest that the triploids included in this study are genetically similar. Further, some genetic redundancies among individual accessions were also identified along with some putative misclassified accessions. Accessions generally clustered together based on taxonomic classification and ploidy level with some deviations. STRUCTURE analysis identified six populations with significant gene flow among the populations, as well as revealed hybrid taxa and accessions. Overall, the Infinium 12K V2 Potato Array proved useful in confirming identity and highlighting the diversity in this subset of the CIP collection, providing new insights into the accessions evaluated. This study provides a model for genetic identity of plant genetic resources collections as mistakes in conservation of these collections and in genebanks is a reality. For breeders and other users of these collections, confirmed identity is critical, as well as for quality management programs and to provide insights into the accessions evaluated.