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United States Department of Agriculture

Agricultural Research Service

Research Project: Alfalfa Germplasm Enhancement for Blue Aphid and Stem Nematode Resistance

Location: Plant Germplasm Introduction and Testing

2011 Annual Report


1a.Objectives (from AD-416)
Screen dormant alfalfa germplasm for resistance to blue alfalfa aphid (Acyrthosiphon kondoi) and stem nematode (Ditylenchus dipsaci) and release germplasm.


1b.Approach (from AD-416)
Plant selected dormant germplasm in greenhouse for determination of resistance to blue aphid. At the same time, screen large numbers of plants from Columbia Basin College germplasm for selection purposes. Score resistance reaction according to standard tests using known non-dormant resistant varieties as resistant checks. If dormant resistant plants are identified, cross in greenhouse, test and reselect. If no resistance is identified in dormant germplasm, cross with resistant non-dormant germplasm in the greenhouse. Screen seed from dormant germplasm for resistance and plant in the field to select for class four dormant plants. Recombine in greenhouse for germplasm release.

Standard tests developed for screening and testing for stem nematode have failed to produce resistant varieties that will perform well in the field. Recurrent field selection is a good indication that field selection may be better suited than standard screening procedures that have been in use for over 30 years with little or no progress. Columbia Basin College (CBC) will plant experimental varieties selected from infested fields for stem nematode to evaluate progress for resistance. Additional selections will be made from the field for seed increase and testing. Germplasm will be released based on test results. At the same time a greenhouse screening procedure will be developed that will allow more time for infection of all plants. More precision is necessary for progress toward higher levels of resistance. Documents SCA with Columbia Basin College.


3.Progress Report

The objective of this study was to develop a new screening procedure for germplasm resistant to the pink biotype of the green pea aphid. The study involved using 34 entry variety test for the pink biotype of the pea aphid. The test included resitant and susceptible checks. Twelve resistant germplasm were identified during the first year of the study. The second objective of this project was to develop a new screening procedure and germplasm resistant to stem nematode. This study was conducted using 35 experimental lines, commercial varieties, and resistant and susceptable check varieties. Screening requires 10 to 12 months in a stem nematode infested medium. Entries will be evaluated for their response to stem nematode infestation.

This study is in progress and contributes to objective 1 of the parent project.

The project was monitored by phone and email contact with the cooperators.


Last Modified: 10/30/2014
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