Twelve accessions from the Plant Introduction Station, Ames, Iowa and AVRDC, Taiwan were used as female parents in combination with three male testers Saturn, Venus (North Carolina) and Kewalo (Hawaii). All entries reportedly possessed resistance to bacterial wilt. Seedlings of the parents and their hybrids were challenged twice by leaf-clipping and once by stem inoculation with Pseudomonas solanacearum E.F. Sm. at 10^8 cells/ml. Soil inoculation at 27 deg. C using 10 ml of 10^8 cells/ml inoculant/plant gave overkill. Symptoms were rated quantitatively as the infection progressed.
Generally, resistance was increased by combining genes from different parental sources. The order of resistance among male testers was Saturn > Venus > Kewalo; hybrids with the female parent lines collectively showed this same order. Kewalo resistance broke down above 27 deg. C (ambient temperature) and showed poor resistance with soil inoculation.
Accessions L3638, L791, L751 and L1737 (AVRDC source) and accession PI109832 (Ames source) and their hybrids with Saturn, Venus and Kewalo showed low resistance, especially with stem inoculation.
Accessions CL1591-5-0-1-7-0 from AVRDC and Saturn (North Carolina) and their hybrid showed the highest tolerance by all inoculation methods.