Grober, K.
An X-ray induced chlorophyll mutant of Lycopersicon esculentum (variety "Condine Red") proved lethal when forming cotyledons under normal greenhouse conditions. Progenies of heterozygous plants showed normal Mendelian ratios, the two phenotypes (white and green) being clearly discernible.
Contrary to this a segregation in germ-dish was not observed after sowing seeds of heterozygous plants at constant temperatures above 26 deg. C. The cotyledons as well as the primary leaves were green. Differences in tallness become obvious after three weeks, allowing the possibility of distinguishing the homozygous recessive genotype because of slightly disturbed growth after this time.
Before this genotype, which is lethal under normal conditions, was cultivated at constant high temperatures above 26 deg. C, more than one hundred plants were obtained after grafting on a normal root-stock in 1958 and 1959. Grafting was carried out in March and for this reason grafting-combinations were exposed partly to temperatures below 15 deg. C. The result was a relatively strong green-white variegation of the primary leaves, which decreased with increasing light intensity and temperature during mid-summer. Seeds from variegated as vell as green sectors gave faint seedlings exclusively with temperatures below 22 deg. C and green seedlings with temperatures above 26 deg. C, thus rendering improbable a mutational basis for reversions to green.