|Samac, Deborah - Debby|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/14/1996
Publication Date: N/A
Technical Abstract: The root lesion nematode Pratylenchus penetrans is a migratory endoparasite that can damage most crop species. We have analyzed mRNA levels of known defense response genes in 3 susceptible and 3 resistant alfalfa (Medicago sativa) clones challenged with nematodes. Resistant clones support from 6 to 10 fold lower levels of nematodes than susceptible clones in growth chamber assays. Three cm root segments from two week old vegetative cuttings were incubated with or without (controls) 50 nematodes/cm root on water agar. RNA was purified from roots at 0, 6, 12, 24, and 48 hr. At 0 hr, northern blot studies with alfalfa cDNA probes for phenylalanine ammonia lyase, chalcone synthase, isoflavone reductase, and caffeic acid O methyl transferase showed that the corresponding mRNA levels (quantitated by densitometry) were 2 to 3 fold higher in control roots of resistant as compared to susceptible clones. Overall, mRNA levels declined over 48 hr in both susceptible and resistant control roots. However, challenge with nematodes increased mRNA levels in susceptible roots to levels from 2 to 3 fold higher than mRNA levels in resistant roots at the same time. These elevated phenylpropanoid pathway enzyme mRNA levels in nematode challenged susceptible roots approximated those in 0 hour resistant control roots. Preliminary results have shown differences in alfalfa B-1,3-glucanase and chitinase mRNA levels in susceptible and resistant roots challenged with nematodes. Northern blot studies with cDNA probes for defense response genes of pea, potato, and tomato have been unsuccessful.