Interrelations of Reproductive Stages of Timothy 1

THE relations that occur between and among various stages of meiosis are of interest in cytological studies, and the effect of inbreeding upon such divisions may be of significance. It was the purpose of this investigation to examine these relations in hexaploid timothy (Phleum pratense L.). While a number of workers have suggested relations among irregularities at various stages of meiosis, and between cytological stages and seed fertility, relatively little information based on actual study of this problem is available for perennial grasses, particularly inbred populations. Evidence that chiasmata frequency was negatively related to univalent occurrence at metaphase I and positively associated with quadrivalent frequency in Dactylis glomerata L. was obtained by Myers (1). Similarly, a positive relation was found between univalents at metaphase I and lagging chromosomes at anaphase I (1). Myers and Hill (2) reported an increase in the amount of irregularity that occurred at certain stages of meiosis in first-generation inbred orchardgrass when these were compared with their parents. Rees (5) showed that lines of rye inbred more than 20 generations were essentially true-breeding. When progeny of hybrid combinations of these lines were inbred, and chiasmata frequencies and premeiotic errors compared in different inbred generations, positive relations were obtained. Comparisons were made between the F3 and F4, and the F4 and F5 generations (6).