DEVELOPMENT OF A TECHNIQUE FOR EVALUATING THE WEIGHT OF CROWN GALLS ON APRICOT STEMS

The weight of galls due to Agrobacterium tumefaciens was selected as an objective criterion for the evaluation of the disease when comparing apricot descents produced in breeding programs.
The detachment of the galls from the infected stem is impossible in most cases, thus making the evaluation very difficult.
To overcome the difficulty, it was assumed that the shape of a segment of stem is that of a cylinder or a truncated cone, whose weight could be calculated from its thickness and its length, and then subtracted from the weight of the diseased portion of stem.
Estimates of gall weight can be obtained, assuming that the density of galls is identical to that of stems, by determining the density of the later in a sample of healthy stem pieces similar to those attached to the galls.
This technique was tested on two hybrid ‘families’ of apricot, one resulting from the cross of two cultivars showing some degree of resistance (‘Stella’ and ‘Stark Early Orange’(SEO)), and another produced by self-pollinating a susceptible cultivar (‘Bergeron’). No statistically significant differences were found between the mean gall weights of the two ‘families’ of hybrid genotypes, ‘Stella’ × ‘SEO’ being as a rule less susceptible than ‘Bergeron’ × ‘Bergeron’ (average of the former 4.83 g, contrasting with 8.34 g of the later). Evidence for genetic segregation in the descent could be found.

XII International Symposium on Apricot Culture and Decline

J. Tsiantos, P. Psallidas, J.M.S. Martins

Prunus armeniaca, Agrobacterium tumefaciens, disease, susceptibility, testing procedure

https://doi.org/10.17660/ActaHortic.2006.701.81