INTRAGENIC RECOMBINATION IN MAIZE: POLLEN ANALYSIS METHODS AND THE EFFECT OF PARENTAL Adh1 + ISOALLELES

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Abstract
The ability to stain mature pollen grains for the presence of alcohol dehydrogenase (ADH) activity permits the quantitation of ADH+ gametophytes at frequencies below 10-6. This resolution allows reversion and genetic fine structure analyses. The rationale of pollen analysis follows Nelson's prototype studies with waxy. As with the waxy gene, revertant frequencies for seven Adh1-deficient (Adh1 -) alleles appear to be in excess of microbially derived expectations. Each of the seven Adh1 - alleles were derived from one of three naturally occurring isoalleles. Based on Schwartz's protein level characterizations of the mutants' products, it was anticipated that the seven Adh1 - alleles should recombine to yield ADH+ cistrons in certain pairwise combinations. This expectation was not met. The parental "wild-type" isoalleles from which the mutants were derived appear to be structurally divergent. The discussion interprets these data in view of understanding naturally occurring cistronic variation.