38 I SEED WORLD EUROPE I SEEDWORLD.COM/EUROPE | MAY 2026 DISEASE RESISTANCE: FROM HELPFUL TO ESSENTIAL If climate is one pressure, disease is another and the two are linked. Changing climates alter pest dynamics, and restrictions on crop protection narrow the tools available. In that environment, resistance breeding becomes central. Patel lists key viral targets such as tobamoviruses, potyviruses and tospovi ruses, alongside the need to keep up with new races of global pathogens such as Fusarium, anthracnose and powdery mildew. The word “evolving” matters here: resistance is not a one-time victory. Pathogen populations shift, and breeders must keep the package updated. Fernández emphasises that resistance packages depend on target market disease incidence. Fusarium wilt and anthracnose form a common baseline, but grafting prac tices and local conditions shape priorities. Powdery mildew is increasingly important globally, while potyviruses and tobamovi ruses are gaining relevance in certain areas. Emilio Sarria Villada, breeding man ager watermelon, squash and beans at Rijk Zwaan, expands the list, showing how dif ferentiated between countries the threat landscape has become. Root diseases such as Fusarium are among the most challeng ing, tackled through grafting on inter specific rootstocks and through resistance introgression where rootstocks are not yet common. At the plant level, fungal dis eases like powdery mildew and anthrac nose remain significant, while viruses such as SqVYV and various tospoviruses can affect production in specific regions. Some pathogens impact fruit quality directly: CGMMV, acidovorax, and phytophthora. His programme’s objective is to integrate resistance while maintaining high fruit quality, because resistance that produces an unappealing fruit solves only half the problem. “NEW” DISEASES, OR OLD ONES BEHAVING BADLY? When asked about new diseases, Sarria Villada argues that the bigger trend is not brand-new threats, but the resurgence and increased incidence of familiar ones. Aphis gossypii infestations are becoming more frequent. Powdery mildew, once consid ered less critical, is now causing significant damage, particularly where effective chem ical control is not available. The broader message is that disease pressure is rising and breeding must fill the gaps. Lopez Fernandez points to tobamo viruses, especially CGMMV, becoming increasingly prevalent due to mechanical transmission, particularly in certain areas and during procedures such as grafting. He also mentions potyviruses and poleoviruses becoming serious due to vector adaptability under climate change. Again, the thread is consistent: disease dynamics are shifting, and breeding must keep pace. CROP PROTECTION RESTRICTIONS: BREEDING STEPS INTO THE GAP Several breeders describe how restrictions on crop protection products have changed breeding priorities. Less chemistry available means more reliance on genetic solutions and integrated systems. Fernández links restrictions on pes ticide use, lower maximum residue limits, respect for beneficial insects used in biolog ical control, and growth in organic farming to the promotion of hybrids with adapted genetic solutions, i.e. varieties that can deliver yields while meeting sustainability and market requirements. Calvert similarly notes that the loss of crop protection products has increased focus on diseases that were not previously as high a priority. This has intensified research on disease resistance, adaptability, and resilience, maintaining fruit quality in the absence of chemical treatments. She also hints at a broader ecosystem approach, where genetics interacts with other grower solutions beyond seeds. INVESTMENT AND TIMELINES: WHY “QUICK FIXES” DON’T EXIST Watermelon breeding is a long journey even for seeded types, and it stretches further for seedless. Sarria Villada gives a detailed view of the pipeline. It begins with creating parental lines carrying key traits for both male and female components. Even with relatively fast cucurbit cycles, that initial stage takes more than two years. Then come first test crosses and evaluation of hybrids. Promising lines are crossed with multi ple partners over following years to find the best combinations. From hundreds of hybrids, only a small subset, perhaps 10 to 20, moves into multi-environment pheno typing. Then come commercial evaluations, and if everything aligns, a variety may reach the market in two to three years after that phase begins. For seedless programmes, he adds, tetraploid line development adds about two extra years, slowing progress further. Modern breeding also includes marker-as sisted selection, phytopathology testing, hybrid prediction analyses, and scouting genomic selection approaches. He empha sises multidisciplinary collaboration e.g. breeders, assistants, operations, molecular and phytopathology labs, genomic breed ers, working across locations to make the system run. The practical takeaway is simple: when retailers want a new format “next season”, breeding cannot obey that timeline. The seed sector runs on long horizons. STAYING ALIGNED WITH GROWERS: INFORMATION BECOMES A BREEDING INPUT With such long development cycles, align ment with growers becomes critical. If you are breeding for eight to 10 years ahead, you must know where the market is going, without being able to know it perfectly. Fernández describes building as many connections as possible between market and breeders. Teams in contact with farmers, Watermelon variety ‘Tropical Sunshine’. Photo: Rijk Zwaan
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