Potato Diversity and Its Genetic Enhancement

Abstract

Potato is the world’s third largest food crop after rice and wheat widely grown across all continents. It belongs to the genus Solanum and section Petota that contain approximately 2000 species that are distributed from the South-western United States (38°N) to Chile (41°S) between 2000 to 4000 m altitudes. Potato has 6 cultivated species, 225 wild relatives and 110 wild tuber-bearing species. The main cultivated potato species Solanum tuberosum L., a tetraploid (2n = 4x = 48) originated from Andes of Peru and Bolivia in South America over 10,000 years ago. The ploidy of potatoes varies from diploid (2n = 24) to hexaploid (2n = 72) with majority being diploids. Potatoes were introduced to Europe in 1570s and by beginning of seventeenth century they spread to the other parts of the world. Systematic potato breeding started in 1807 in England followed by other parts of Europe, North America, India, International Potato Centre, Peru and China. There are two basic approaches to conserve potato genetic resources, viz. in situ and ex situ. Currently, cryo-conservation is being tapped for long-term conservation. Seven major potato gene banks are present worldwide to conserve existing diversity. Although more germplasm are being evaluated, the use of genetic resources has been much poorer to their evaluations mainly due to undesirable tuber traits of the wild species and crossability barriers. This has led to narrow genetic base of the cultivated potatoes. The ‘Irish famine’ of 1840s depicts the devastating effect of growing large areas under a single variety. Cultivated potato exhibits complex tetrasomic inheritance and high heterozygosity. Dihaploids of tuberosum cross readily with many diploid species thus providing opportunity for introgression of useful traits from alien sources to cultivated background. The other well-exploited techniques in potato breeding, viz. somaclonal variations, somatic hybridization, molecular markers, genetic transformation and RNAi approaches. Potato is one of the rare crops where maximum tissue culture and genetic engineering interventions have been connoted. Today, potato genome is sequenced and it opens up new vistas for developing tailor-made varieties in future.