VARIATION IN THE SUSCEPTIBILITY OF PEAR SEEDLINGS TO DAMAGE BY THE LARVAE OF THE SAWFLY (CALIROA CERASI)

Pear slug, the larva of the sawfly Caliroa cerasi, can be a serious pest of pears in New Zealand orchards under organic management and, if left uncontrolled, can cause leaves of susceptible cultivars to become skeletonised.
In December 1999, this pest reached high levels of natural infestation in two breeding blocks of pear seedlings involving full-sib inter-specific crosses.
These seedlings were scored for damage, and heritability estimates computed from variance components were obtained by fitting a random effects model.
The heritability estimates were high (= 0.5 and above). In one population, this was largely due to a single Pyrus bretschneideri family which had a mean infestation score of less than 2 (compared to >5.5 for all other families). In the other population, families with Huobali (P. Bretschneideri) as a grandparent on both sides tended to be more resistant.
Wherever ‘Max Red Bartlett’ was used as a grandparent families tended to be more susceptible.
The pattern of damage on resistant seedlings suggested that the resistance mechanism was related to deterring larval feeding, although there was some evidence that variation in adult egg deposition may also have been involved.

VIII International Symposium on Pear

L.R. Brewer, P.A. Alspach, A.G. White

pear slug, Pyrus bretschneideri, heritability estimates, genetic correlation

https://doi.org/10.17660/ActaHortic.2002.596.99