Plant Research International has proven the existence of a Fusarium strain that can break the resistance of a number of tulip cultivars previously judged non-susceptible. This Fusarium strain may possibly one of the reasons for the increasing problems caused by the disease. Plant Research International, working in partnership with Applied Plant Research (PPO), will investigate how widespread this strain is and whether it is indeed partly responsible for the increasing Fusarium problems. In addition, they will attempt to track down new resistances in order to enhance the selection available to growers.
The disease caused by the pathogen Fusarium oxysporum f.sp tulipae is a major problem in tulip growing. One of the ways to reduce its impact is to use resistant varieties, which have been effective for decades. In recent years, however, the Fusarium problem has dramatically increased, which in practice has meant that a number of resistant cultivars have been affected more often and to an increasing extent by Fusarium.
Plant Research International has isolated a Fusarium strain from a diseased batch of Yokohama bulbs; this strain can quickly and totally affect the bulbs of the resistant varieties Monte Carlo, Kees Nelis, Christmas Marvel, Yokohama and Bellona. This means that the resistance of Monte Carlo and Kees Nelis, which has been stable for many years, can be broken by this new strain. And should this strain become widely spread in the Netherlands, then the impact on the current varieties will be far more dramatic in the years ahead.
Plant Research International will conduct research into the extent to which new resistance sources are available within the currently available cultivars or in botanical selections which are not affected by the new strain. Such new resistances can then be introduced into the newly developed cultivars via cross-breeding.
Furthermore, the institute is cooperating with the Bulb Sector of Applied Plant Research in Lisse (South Holland) to investigate how widespread this new strain is in practice and to what extent it is responsible for the increase in the Fusarium problem. For this purpose, affected bulbs are currently being collected from various cultivars that have proven to be either susceptible or resistant in practice. The Fusarium strains that can be isolated from these bulbs will be tested to see whether they can affect susceptible and resistant cultivars.
List of press releases for 2002