|Grauke, Larry - L J|
Submitted to: Journal of American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2000
Publication Date: N/A
Interpretive Summary: Aphids are insects that feed on leaves of almost all kinds of plants. In pecan, scientists have discovered that some types of trees (cultivars) are more resistant to these pests than others. We call this type of resistance "host plant resistance" since it exists in the host. In this paper, we show that some cultivars are much more resistant than others. This is valuable information for growers, since the culture of resistant trees is an effective way of minimizing aphid problems. 'Pawnee' is a pecan cultivar released by the USDA in 1984. This research shows it to be somewhat resistant to this yellow aphid. Pecan growers will be more likely to grow this cultivar now that they know it has resistance. We also conduct a breeding program in which we select resistant cultivars. By knowing more about the inheritance of resistance, parents can be selected to cross to produce more resistant progeny that will eventually be released das new USDA cultivars.
Technical Abstract: The blackmargined aphid is a major insect pest of pecan. Host plant resistance to this insect was tested in two NPACTS (National Pecan Advanced Clone Testing System) tests in California. 'Pawnee,' which had been shown to be resistant to this insect in Texas and Georgia, showed resistance in California also. Other cultivars with high levels of resistance were 'Navaho,' 'Kiowa,' Cape Fear,' 'Caddo,' 'Shoshoni,' and 'Maramec.' Severa unreleased clones under evaluation in other NPACTS tests also showed high levels of resistance. Level of host plant resistance was generally unpredictable, based upon parentage. In pecan breeding programs, this makes clonal testing imperative, since predictability of performance based on pedigree has limitations. Commercial production on clonally propagated trees is also an advantage, since genetic variability among trees is eliminated.