Cisgenesis Does Not Solve the Late Blight Problem of Organic Potato Production: Alternative Breeding Strategies

Abstract

Average potato yields in Dutch organic farming systems vary from 15 to 29 Mg/ha and are limited by low input of nitrogen and severe late blight attacks caused by the oomycete Phytophthora infestans. Under Dutch late blight regulations it is mandatory to kill the haulm at 7% infestation. The late blight attacks have been so early in the organic potato production of the past few years that its acreage is now gradually decreasing whereas consumer demand is increasing. Agronomic control strategies have limited success. First priority lies in breeding for highly resistant varieties to safeguard organic potato production in the Netherlands. Cisgenesis, however, is not an option for the organic sector. Although the product of cisgenesis does not contain genes from non-crossable species it is a result of a genetic engineering process which is excluded from use in organic agriculture. As the principles and standards of organic agriculture are process-based, cisgenesis does not comply with the norms and standards of organic agriculture. The arguments of the organic sector go well beyond the alleged risks of the gene technology and relate to the technology itself. Breeding at DNA-level, instead of at whole-plant level, violates the integrity of life as described in the concept of naturalness. The Dutch organic sector is now aiming at increasing the traditional breeding activities including the participation of farmer-breeders in close cooperation with the formal breeding companies. Additional selection methods need to be developed to include required traits other than late blight resistance, such as nutrient efficiency. Recently two varieties have been released with high resistance against late blight based on introgressing genes from Solanum bulbocastanum. Organic agriculture can benefit from marker assisted breeding to achieve adequate pyramiding of different, new sources of resistance.