Some details and effects of the premeiotic controls of recombination frequencies inNeurospora crossa

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Abstract
SUMMARY: Recombination data from crosses made at a single constant temperature of incubation were compared with those from crosses transferred to a different temperature at either the time of conidiation of protoperithecia by the strain of opposite mating-type, or after fertilization when crozier stages were first visible. Results were also compared from reciprocal crosses, from crosses made in different ways and from crosses in which protoperithecia were conidiated at different stages of maturity.Different temperature regimes during vegetative growth and proto-perithecial development had highly significant effects on subsequent meiotic recombination, while temperature differences during later premeiotic stages (between conidiation of protoperithecia and the crozier stage) had no or little effect. It was found that premeiotic controls could have as great, or greater, effects on meiotic recombination than those operating directly during meiosis. The possible adaptive significance of this is discussed.Recombination frequencies were affected by the method of making a cross (joint-inoculation of strains of opposite mating-type, or conidiation of protoperithecia), and by protoperithecial age at the time of conidiation by the opposite mating-type. Differences in recombination between reciprocal crosses were obtained and were dependent on temperature of incubation and age of protoperithecia at the time of conidiation. Recombination was not affected by different lysine concentrations in the medium. Genetic differences in premeiotic effector-production between the strains used were inferred.