Articles
BREEDING FOR RESISTANCE TO YELLOW DISEASE OF HYACINTHS
The use of resistant cultivars would be a promising method of control.
Testing for resistance was carried out under controlled climate conditions in the greenhouse.
The plants were, just after blooming, inoculated with yellow disease.
The degree of leaf infection was taken as selection criterion.
Using this method the cultivars ‘King of the Blues’ and ‘Pink Pearl’ show a high degree of resistance while ‘Blue Giant’ and ‘Carnegie’ appear to be very susceptible.
This leaf infection corresponds with differences in resistance known in practice.
In order to estimate combining ability and heritability for yellow disease resistance, a range of cultivars, varying in resistance, was used as parents in an incomplete diallel design.
Significant general combining ability (GCA) component for resistance to yellow disease was found.
The late flowering cultivars ‘King of the Blues’ and ‘Marconi’ and the early flowering H. orientalis were found to be the best combiners for yellow disease.
Within a cultivar, the degree of earliness itself was not associated with degree of resistance.
Correlation coefficients of leaf characters and degree of resistance showed that hyacinths with short and/or narrow leaves are generally more resistant than those with long and/or broad leaves.
Tetraploid cultivars with few, large stomata tend to be susceptible, diploid ones with many small stomata tend to be the more resistant.
In 1983 the first yellow disease resistant cultivar out of this programme, Nestor, originating from a cross with H. orientalis, was released to 5 hyacinth growers in the Netherlands.