A new study by Texas A&M AgriLife scientists has identified zebra chip resistance among some wild potato species. Phys.org. The article "Identification and Characterization of Potato Resistance to Zebra Chip Among Wild Solanaceae" recently appeared in the journal Frontiers in Microbiology.
Zebra chip is a complex disease of potatoes, the causative agent is the bacterium Candidatus Liberibacter solanacearum, the carriers of the disease are insects. The disease was first identified in Saltillo, Mexico, in the mid-90s. Then the disease was fixed in many regions of the world where potatoes are grown. The disease affects harvest volumes and can potentially lead to loss of potato crops (up to 94%). Symptoms include purplish discoloration of young leaves, curling of upper leaves, air tubers, wilting, stunted growth, and plant death.
The bacteria that causes this disease can also infect other vegetable crops. Current zebra chip control strategies involve vector control, either with insecticides or by changing planting dates.
The study by Texas scientists used wild potato varieties grown from seeds obtained from the U.S. National Plant Germplasm System in Wisconsin.
New sources of resistance to zebra chip have been identified among a wild collection of tuberous Solanum species. This group of wild potatoes is a taxonomically well-characterized and diverse collection from which valuable characters can be extracted.
Several of the 52 accessions studied were susceptible to moderately susceptible, showing slight leaf curl, chlorosis and stunting. After screening, phenotypic evaluation and quantification of the bacteria in bacteria-infected samples, the scientists identified one zebra chip resistant species, Solanum berthaultii, along with three other samples that were moderately resistant. The three accessions identified in the study as moderately resistant to zebra chip were S. kurtzianum, S. okadae and S. raphanifolium.
Mandadi's team found that S. berthaultii has dense, glandular leaf trichomes, and this structural modification of the leaves may be one of the factors responsible for much of the observed resistance to the disease.
The spread of the wild potato S. berthautii occurred in Bolivia, which is adjacent to Peru and is historically considered the original "homeland" of the cultivated potato. Perhaps S. berthautii can be used in breeding new potato varieties.
Similar approaches to identifying new genetic resistance and tolerance in wild plant species could help in the fight against other dangerous crop diseases such as late blight. potato, citrus gardening and banana wilt.