Submitted to: Central Alfalfa Improvement Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 1999
Publication Date: N/A
Technical Abstract: The root-lesion nematode (RLN; Pratylenchus penetrans) can reduce alfalfa seedling establishment and lead to rapid thinning of stands when present at high population densities. In an effort to develop multiple-pest resistant germplasm, we introduced genes for rice proteinase inhibitors into alfalfa and evaluated the plants for resistance to the RLN. The genes for oryzacystatin I (OCI) and oryzacystatin II (OCII) were introduced into alfalfa under the control of the potato pin2 promoter. To establish if this promoter is active in alfalfa, we also introduced the pin2 promoter fused to the marker gene beta-galacturonase (GUS). Alfalfa plants containing the pin2-GUS gene showed two patterns of expression; either expression was observed in root tips, leaf pulvinus, and leaf mesophyll at cut edges or expression was seen in just roots tips and in root and leaf vascular tissue. In both groups, mechanical wounding of leaves resulted in a 2-3 fold increase in GUS activity after 24 hours. Plants containing the pin2- OCI and pin2-OCII genes were inoculated with 300 root-lesion nematodes and the number of nematodes in the fibrous roots was determined after 12 weeks. Control plants supported an average of 23,120 RLN/g dry fibrous roots. Of the 23 lines tested, 9 lines had significantly fewer nematodes in roots than control plants (P=0.05) with an average of 5,971 RLN/g dry fibrous roots. On average, these 9 lines supported 74% fewer nematodes than control plants, approaching the control obtainable in resistant varieties. Experiments to detect the inhibitors in roots and dried foliar material, and to evaluate resistance to the root-knot nematode are underway.