The hypersensitive reaction to bacterial canker in Mirabilis jalapa is simply inherited

Abstract

The four o’clock plant (Mirabilis jalapa) displays a hypersensitive reaction to the causal agent of bacterial canker, Clavibacter michiganensis subsp. michiganensis. Two lines of M jalapa were crossed with one another and a local weed accession not showing the same reaction. All F1 progeny displayed the hypersensitive reaction within 48 h of inoculation with suspensions of Clavibacter michiganensis subsp. michiganensis. Selfed F2 progenies of the two hypersensitive parents were shown to be hypersensitive. F2 populations derived from crosses between either hypersensitive parent and the local non-hypersensitive line displayed Mendelian segregation ratios, 3 hypersensitive: 1 non-hypersensitive. There were no maternal effects. This demonstrates that the trait is under the control of a single dominant gene. Morphological traits including flower colour and cotyledon colour were under more complex genetic control.