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Unlocking resistance: Harnessing wild potato relatives to improve late blight protection

This article was written by Jorge Luis Alonso G., an information consultant specializing
in the potato crop.

Improving potato late blight (LB) resistance is essential for ensuring food security, particularly using wild relatives endemic to Phytophthora infestans-prone regions. However, reproductive barriers can impede the transfer from potato wild relatives (PWR) to the cultivated genepool.

A research team from the International Potato Center (CIP) undertook a study seeking to incorporate potentially novel LB resistance from wild diploid accessions of Series Piurana (Solanum chiquidenum, Solanum paucissectum, and Solanum piurae), Tuberosa (Solanum cajamarquense), and Megistracroloba (Solanum sogarandinum) into tetraploid potato.

The study, titled “A case study of potato germplasm enhancement using distant late blight resistant wild relatives” was published in the journal Crop Science. This article is a summary of the study.

Cultivated potatoes, a ubiquitous food and cash crop, are severely affected by late blight (LB) — a disease responsible for significant yield losses. Historically, early LB resistance initiatives were based on genes derived from wild species, although many of these strains have since succumbed to virulent pathogens.

More recently, new resistance genes have been discovered in several wild potato species (PWR), providing new potential sources of resistance. Technologies such as genetic engineering and marker-assisted introgression are being used to integrate these resistance genes into cultivated varieties. However, genetic barriers such as ploidy and endosperm balance number sometimes pose challenges to the incorporation of PWR into breeding.

Some PWRs have been used in potato variety development, but others remain largely untapped. The International Potato Center is actively screening these species for LB resistance and has identified several species with moderate to high levels of resistance. The most resistant of these have been selected for further testing.

A major focus of this research is a systematic attempt to introduce novel LB resistance from underutilized PWRs into cultivated potatoes. This will be achieved using techniques such as rescue pollination and sexual polyploidization.

The study also presents a method used by the CIP pre-breeding program to create new potato stocks resistant to LB. This method involves incorporating resistance from underutilized wild potato relatives into advanced tetraploid backgrounds. Of eight promising selections tested with Andean farmers, two emerged as top performers. One of these was subsequently named “CIP-Matilde” and is recommended for use in Peru’s tropical highland conditions.

Using rescue pollination, the research transferred beneficial traits from wild potatoes to cultivated potatoes, resulting in the creation of 699 rare sexual hybrid combinations. These hybrids, characterized by desirable traits such as high dry matter and LB resistance, provide a promising basis for future breeding strategies.

The study revealed considerable variation in the success of crosses between different wild potato relatives, highlighting the importance of species-specific compatibility in the transfer of resistance traits. In addition, the research has resulted in the production of a large number of tetraploid hybrids, a portion of which have demonstrated promising yields.

However, further research is needed to validate the novelty of the resistance observed in these hybrids. While the use of wild relatives has resulted in the transfer of some undesirable traits — such as poor tuber attractiveness — these issues will need to be addressed in subsequent breeding efforts.

In conclusion, the study culminated in the development and characterization of promising sexual and tetraploid hybrids. These hybrids represent valuable resources that can be used in future potato breeding strategies.

Source: Ordoñez, B., Aponte, M., Lindqvist-Kreuze, H., & Bonierbale, M. A case study of potato germplasm enhancement using distant late blight resistant wild relatives. Crop Science. https://doi.org/10.1002/csc2.21038
Photo: Credit Prince Abid on Unsplash

Editor & Publisher: Lukie Pieterse


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