Resistance to Sclerotinia, Stem Nematode and Foliar Fungal Diseases in Red & White Clover
Introduction
The importance of both red and white clover in low input grassland systems as nitrogen sources is well established. Furthermore they are both vital, and red clover particularly so, in building and maintaining fertility in stockless organic arable and vegetable farming. However, there is a reluctance to rely on clover in many situations because of fears about persistence and productivity. Resistance to pests and diseases is extremely important in these situations, since both pest and disease problems are major causes of loss of clover plants. Sclerotinia trifoliorum is a serious disease of red and white clover. It has been recorded throughout the UK, and is often particularly serious where winter faba beans, which are also susceptible, have been grown for horse feed in the past. Resistance to the pathogen is a National List character. However, in recent years, no information has been produced due to a lack of trial records. Though the stated importance of Sclerotinia in clover and the absence of records from trials may at first seem contradictory, it is important to realise that a) distribution is patchy and b) initial infection in the autumn is very difficult to see, and the consequent loss of clover the following spring is often attributed to other factors since infected plants have disappeared.
 |
Loss of plants may also be caused by the stem eelworm organism, Ditylenchus dipsaci, which is regarded as a severe pest of both red and white clover. Differences in cultivar resistance are known to exist, but information on white clover and new red clover material is not available. Knowledge of resistance would contribute to efficient grassland farming in both organic and conventional systems. |
Results
Sclerotinia trifoliorum
Both red and white clover varieties differed significantly in the degree of petiole rotting observed. Overall, seedling test results correlated relatively well with previous field scores where extensive data existed.
Ditylenchus dipsaci
In white clover, several varieties were as resistant to eelworm as Pronitro, which was included as a resistant control. In red clover, two varieties showed a clear improvement over Britta, which was the most resistant variety based on historical data.
The financial support of DEFRA is gratefully acknowledged.