One seed source of Jeffrey pine shows resistance to dwarf mistletoe

Abstract

Four seed sources of Jeffrey pine (Pinus jeffreyi) were selected for testing through controlled inoculation for resistance to dwarf mistletoe (Arceuthobium campylopodum). The pines were 7 years old and part of a progeny test planting established by the USDA Forest Service's Institute of Forest Genetics, Placewille, California. One of the seed sources {Foresthill) was considered from previous studies to be highly resistant. It was also found to be resistant in this study. Test trees were inoculatedin 1980 and 1981 with about 13,500 seeds of dwarf mistletoe. A high proportion of the seeds were lost before germination, but branches covered with bird-proof and insect-proof mesh lost significantly fewer seeds. Mean percentage infection based on remaining seeds was significantly lower on trees from the Foresthill seed source than any of the other sources. Similarly, mean percentage of trees infected was significantly lower for the Foresthill source than for the three others. Development of the endophytic system, as indicated by length of branch sweIling, and mistletoe shoot development were not significantly different among the seed sources. However, significantly fewer brooms developed on the Foresthill trees than on trees from two of the other sources.

Citation

Scharpf, Robert F.; Kinloch, Bohun B.; Jenkinson, James L. 1992. One seed source of Jeffrey pine shows resistance to dwarf mistletoe. Res. Paper PSW-RP-207. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 8 p.