A TOXIN-DIRECTED APPROACH TO SELECT LETTUCE RESISTANT TO CORKY ROOT ROT

THE HOST-SPECIFIC TOXIN PRODUCED BY THE CORKY ROOT ROT CAUSAL BACTERIUM PROVIDES US WITH A TOOL TO SELECT THE DISEASE-RESISTANT LETTUCE FROM A MASS POPULATION OF GERMPLASMS. THE MAJOR OBJECTIVES OF THIS PROPOSED RESEARCH ARE: 1) PURIFY THE HOST-SPECIFIC TOXIN. THE TOXIN WILL BE EXTRACTED FROM THE CRUDE CULTURE FILTRATE IN WHICH THE BACTERIUM HAS BEEN GROWN AND REFINED TO ITS MAXIMAL PURITY BY VARIOUS CHROMATOGRAPHICAL SYSTEMS. 2) DEVELOP AN IN VITRO SELECTION SYSTEM THAT WILL IDENTIFY BOTH SPONTANE OUSLY-OCCURING AND CHEMICALLY-INDUCED MUTANTS THAT ARE RE SISTANT TO THE TOXIN. THE SOURCES OF THE TOXIN-RESISTANT MUTANTS WILL INCLUDE BOTANICAL SEEDS OF LETTUCE, SOMACLONAL VARIANTS DERIVED FROM TISSUE CULTURE AND MUTANTS DERIVED MUTAGENIZED CALLUS TISSUE CULTURE. LETTUCE PLANTS DERIVED THE MUTANT SEEDS OR CALLUS TISSUES WILL BE TESTED FOR THEIR RESISTANCE TO INFECTION BY THE BACTERIUM.