DEVELOPING A TEST METHOD FOR SELECTION ON RESISTANCE TO DRY-ROT DISEASE (STROMATINIA GLADIOLI) IN GLADIOLUS

J.P. van Eijk, A. van Zaayen, W. Eikelboom
Cultivation of gladiolus in the Netherlands - and other regions with a temperate climate - is seriously threatened by the dry-rot disease, caused by Stromatinia gladioli.

Sclerotia develop on roots and stems of infected plants. These sclerotia may infest soils for many years.

Therefore, in cooperation with LBO, possibilities are being investigated to develop dry-rot resistant cultivars in order to prevent a further spread of the disease, to keep a sufficiently large area available for cultivation, and to diminish the use of fungicides.

In 1983, at IVT research into the development of a test method was started. Based on the results of preliminary experiments at LBO, the following inoculation procedure is now applied: sclerotia of S. gladioli are added to the soil on a level just below the planted material, at a glasshouse temperature of 16–19°C.

Corms, cormlets or seeds of the species Gladiolus italicus showed a high degree of resistance when planted or sown in soil infested with sclerotia. This species will be taken into account as parent in breeding programs. However, it is almost not related to the small- or large-flowered gladioli of the current assortment and crossing barriers exist. So far, from crosses between G. italicus and large-flowered cultivars, only a small number of flowering hybrids could be obtained. Therefore, attention was also paid to commercial large-flowered cultivars like 'Oscar' and 'President de Gaulle', with a lower level of resistance. Resistance of those cultivars was expressed, when corms (12–14 cm circumference) were planted in infested soil, but not when 'pits' or cormlets were planted in a similar medium.

When testing progenies from crosses between large-flowered cultivars and species, there was only a low correlation between percentages of healthy seedlings from seeds sown in infested soil and percentages of healthy corms from seedlings planted in infested soil. This result indicates that the reaction of germinating seedlings differs from that of corms.

To accelerate testing roots of germinated seeds of different progenies were inoculated with sclerotia in Petri dishes. After three weeks, sclerotia were observed. Under these circumstances, G. italicus was found to develop new roots after infection,

van Eijk, J.P., van Zaayen, A. and Eikelboom, W. (1990). DEVELOPING A TEST METHOD FOR SELECTION ON RESISTANCE TO DRY-ROT DISEASE (STROMATINIA GLADIOLI) IN GLADIOLUS. Acta Hortic. 266, 365-374
DOI: 10.17660/ActaHortic.1990.266.48
https://doi.org/10.17660/ActaHortic.1990.266.48

Acta Horticulturae