Phytotron ecology of mutant genes

This paper is the first in a series dealing with intra- and interlocus hybrids of mutant genes in phytotron cultivation. Two allelic earliness mutations from different parental backgrounds were crossed inter se and with their parents. Nine genotypes were tested in two photoperiods, one long-day and one short-day, as well as in three different thermoperiods, with high, medium and low temperatures. Eight traits (characters, phenes) were studied in six different types of climate. Mutant gene heterosis was especially evident under short-day conditions, to which the mutant homozygotes, but not the basic parental strains, are adapted. Also under long-day cultivation heterosis of generative traits was pronounced, but less so of semigenerative and vegetative traits. Definite regularities were found with regard to the stimulating action of heterozygous mutant alleles in two monohybrid materials and one mutant-variety outcross. These regularities correspond to genotype, photoperiod and phene differences of reaction. Yielding ability is highest applying long-day (20 hours of light) and low temperature (15–10°C), lowest at short-day (12 hours of light) and high temperature (20–15°C).