Exotic genes for solving emerging peach production challenges

Abstract

Peach, a major fresh-market and processing tree crop world-wide, is entering a period of transformation driven by changes in climate, production methods and market trends but where future breeding progress is severely limited by its very narrow genetic base. Peach rootstocks, which are also of global importance, have a long history of utilizing interspecies hybridization to successfully incorporate needed traits for disease, pest and environmental stress resistance. Interspecies hybridizations resulting in commercially successful rootstocks have been made between cultivated peach and its close wild peach relatives, as well as the more distantly related cultivated almond and its numerous and ecologically diverse wild relatives. Hybrids between peach and plum as well as apricot species have also been successful, though more difficult. Recent efforts to further introgress such exotic germplasm for peach cultivar improvement have successfully transferred not only disease and pest resistance but also improved fruit and tree quality as well as greater tolerance to environmental stresses. Associated genetic and genomic studies provide useful information on trait heritability and, in many cases, have identified putative linkage group and possible candidate genes. Heritability of most traits derived from exotic germplasm, however, remains poorly studied, though early research suggests genomic and epigenetic modifications may sometimes be involved in addition to more traditionally studied genetic changes. While exotic gene introgression has the potential for transferring novel traits of value for rootstock and cultivar improvement, undesirable but undetected changes can also occur that, because of the long-lived and high-value nature of peach orchards, can ultimately result in severe economic losses.