Molecular and biochemical characterization of a potato collection with contrasting tuber carotenoid content

Maria Sulli,Giuseppe Mandolino,Gianfranco Diretto,Giovanni Giuliano,Monica Sturaro,Chiara Onofri,Bruno Parisi,Hiroshi Ezura

doi:10.1371/journal.pone.0184143

Abstract

After wheat and rice, potato is the third most important staple food worldwide. A collection of ten tetraploid (Solanum tuberosum) and diploid (S. phureja and S. chacoense) genotypes with contrasting carotenoid content was subjected to molecular characterization with respect to candidate carotenoid loci and metabolic profiling using LC-HRMS. Irrespective of ploidy and taxonomy, tubers of these genotypes fell into three groups: yellow-fleshed, characterized by high levels of epoxy-xanthophylls and xanthophyll esters and by the presence of at least one copy of a dominant allele of the β-Carotene Hydroxylase 2 (CHY2) gene; white-fleshed, characterized by low carotenoid levels and by the presence of recessive chy2 alleles; and orange-fleshed, characterized by high levels of zeaxanthin but low levels of xanthophyll esters, and homozygosity for a Zeaxanthin Epoxidase (ZEP) recessive allele. Novel CHY2 and ZEP alleles were identified in the collection. Multivariate analysis identified several groups of co-regulated non-polar compounds, and resulted in the grouping of the genotypes according to flesh color, suggesting that extensive cross-talk exists between the carotenoid pathway and other metabolite pathways in tubers. Postharvest traits like tuber dormancy and weight loss during storage showed little correlation with tuber carotenoid content, with the exception of zeaxanthin and its esters. Other tuber metabolites, such as glucose, monogalactosyldiacyglycerol (a glycolipid), or suberin precursors, showed instead significant correlations with both traits.

Highlights

With a worldwide annual production higher than 300 million tons, potato (Solanum tuberosum) ranks third, after wheat and rice, as a staple crop for human nutrition (FAOSTAT 2013)
A core collection of 10 genotypes with contrasting flesh color was selected for further analysis, including five tetraploid S. tuberosum (Fontane, Laura, E60/1, Melrose and Daifla), four diploid S. phureja (Mayan Gold, Andean Sunside, Papapura and ISCI 105/07-8) and one diploid S. chacoense clone
Tubers could be grouped into three categories: a first group with yellow flesh and high levels of epoxy-xanthophylls and xanthophyll esters, comprising tetraploid Fontane, Laura, E60/1, Melrose and diploid Mayan Gold; a second group with white flesh and very low tuber carotenoid content; and a third group, with orange flesh and high levels of non-esterified zeaxanthin, which included diploid Papapura, Andean Sunside and ISCI 105/07-8

Summary

Introduction

With a worldwide annual production higher than 300 million tons, potato (Solanum tuberosum) ranks third, after wheat and rice, as a staple crop for human nutrition (FAOSTAT 2013). Most early cultivated potatoes were diploid [1], while the greatest part of the commercial varieties are autotetraploid (2n = 4x = 48) [2], highly heterozygous and suffer from acute inbreeding. Potato carotenoid content decision to publish, or preparation of the manuscript

Methods

Results

Discussion

Conclusion