ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
RESISTANCE TO THE BIRCH LEAFMINER (FENUSA PUSILLA) WITHIN THE BETULA SECTION COSTATAE IS RECESSIVE AND DISPLAYS A GENE DOSAGE EFFECT |
| Authors: | W.A. Hoch, B.H. McCown |
| Keywords: | Betula alleghaniensis, Betula costata, Betula turkestanica, polyploidy, larval antibiosis, Messa nana, cost of resistance |
| Abstract:
The birch leafminer (Fenusa pusilla) is a common and often serious pest of ornamental birches throughout much of the temperate regions of North America. Of the five Betula species resistant to this insect pest, none possess ornamental white bark. Interspecific hybridization promises to combine leafminer resistance and ornamental white bark in a single genotype. Twenty-two interspecific crosses within the genus Betula were performed and the progeny assayed for resistance to F. pusilla. Two leafminer resistant species within the section Costatae, B. alleghaniensis and B. costata, were successfully hybridized to white-barked species. All progeny resulting from diploid x diploid crosses of highly resistant individuals of B. costata with white-barked species were susceptible to leafminer. Offspring of the diploid x hexaploid cross B. turkestanica x B. alleghaniensis displayed a broad range of resistance levels. While the progeny of this cross closely resemble the hexaploid B. alleghaniensis parent in most phenotypic characters, the majority of individuals in this population displayed leafminer resistance that is intermediate between the two parents, with some plants possessing the susceptibility of the diploid B. turkestanica. These data suggest segregation of alleles contributed by the hexaploid parent. The results of this study indicate that the leafminer resistance mechanism utilized by these members of the Betula section Costatae is inherited as a recessive trait with gene dosage effects. No relationship was found between plant growth rate and resistance to F. pusilla. Resistance to F. pusilla was also not correlated to oviposition preference and/or survival of Messa nana, a birch leaf-mining sawyfly belonging to the same family as F. pusilla. | |
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