b'Red baby leaf lettuce. Source: Maraldi SementiOTHER MAJOR BREEDING TARGETSANDsalt tolerance. Schut notes that salty conditions are a long-lasting CHALLENGES issue in the main European production area for winter outdoor Agronomically, Zonneveld believes the main challenge of breed- lettuce, near Cartagena in Spain.ing lettuce lies in ensuring varieties perform well under manyGarca adds that climate change has also caused some dis-environmental conditions. Screening in multiple environmentsease pathogens and insects to move to areas where they have in various places around the world is therefore very importantnever been found before. This makes it necessary to update the for lettuce breeding companies.set of resistances included in each variety, he says. By in-situ For his part, Schut considers breeding to address theselections during the last eight years, we have obtained material dynamics of pathogen development (for example, the continualadaptable to these extraordinary changes.emergence of new Bremia/downy mildew races) to be the most challenging aspect of lettuce breeding. He also lists the majorDISEASES, PESTS AND MOREchallenge of combining a large number of desired traits in oneLettuce is a tender plant and is quite vulnerable, above all, to variety in a short period of time. fungal pathogens. Garca explains that due to market circum-Besides resistance to disease, other agronomic traits ofstances, most lettuce producers grow the same lettuce year after significance for lettuce are bolting tolerance, yield, colour, tip- year on the same fieldand with damp weather favourable to burn resistance, core length and pink vein, as well as optimaldisease, every subsequent crop is at higher risk of funguses and plant size and shape for harvesting and packaging. And all of ourother diseases/pests. breeder experts agree that climate change can potentially affectPrakash explains that soilborne fungi like Fusarium many of these traits. Yes, says Veenstra, in every area we seeoxysporum f.sp. lactucae (Fusarium wilt) Sclerotinia spp. that the weather is less predictable compared to the past, and(lettuce drop) and Verticillium dahlia (Verticillium wilt) are we need to make varieties which can adapt to different circum- generally hard to control once established in the soil. Especially stances. Zaccaria echoes the same thoughts. Response to cli- Fusarium wilt appears to be an increasing problem for lettuce mate is not a negligible detail during the selection process, shegrowers, and resistance breeding is complicated by the fact that says. We are creating new varieties able to perform well duringtwo dominant races (Fol:1 and Fol:4) occur in some important the during the whole cultivation cycle, even if sudden weatherlettuce markets, he says. But by far the most important disease changes occur. And its extremely important to have varietiesof lettuce is Bremia. Its spread by wind, and resistance breeding with uniform high-temperature germination as the springs areis very complex due to the occurrence of many different races. getting warmer, as well as strong tolerance to bolting, with aPrakash reports that seed companies are collaborating via the thick texture and tolerance to Fusarium.International Bremia Evaluation Board (IBEB) to create more Zonneveld notes that much warmer conditions are beingclarity about this disease for the seed industry and its customers. seen in spring in Northwest Europe, so Syngenta now has varie- Schut explains that in response to the emergence of new ties that can handle this. Rijk Zwaan is also using parents suitedBremia strains, several breeding companies including Rijk to the Mediterranean for crossings in its Northern EuropeanZwaan have continually introduced new resistance genes from lettuce breeding programs. ants with higher drought, heat andwild lettuce species. Because of the increased range of available 8IEUROPEAN SEEDIEUROPEAN-SEED.COM'