Meiosis in diploid and tetraploidPrimula sinensis

Crosses Between Digitalis Purpurea and Digitalis Ambigua

“…Since the tetraploid is intermediate between its diploid parents in seed production, as it would be expected to be in ovule production, its generational fertility may be taken to be as high as theirs. Since the diploid was, as a diploid, absolutely sterile, this is another example of the rule that there is an inverse correlation between the fertility of a diploid and that of the tetraploid to which it may give rise (Darlington, 1928). Infertile diploids, fertile tetraploids 1 Primula kewensis (Newton and Pellew, 1929) 2 Raphanus-Brassica (Karpechenko, 1927) 3 Nicotiana digluta (Clausen and Goodspeed, 1925) (Levitsky and Benetzkaia, 1929) 13 Triticum turgidum x T. villosum (Tschermak, 1930) 14 Galeopsis pubescens x G. speciosa (Muntzing, 1930) This rule seems to be equally applicable to the newer cases.…”

“…None of these conditions is universal^ but since they are all nearly so the principle ' The first condition might not apply to certain structural hybrids; the second condition would not apply with a localisation of chiasmata (Darlington, 1932), and the third condition is less important in high polyploids.…”

Double reduction at the mid locus in Lythrum salicaria

“…In the mating between a triplex and a nulliplex, one recessive in 28 could be expected on this hypothesis. Darlington (1931), however, showed that cytologically there were a number of restrictions to Haldane's theory, and concluded that intermediate conditions between random segregation of chromatids and diploid segregation were to be expected, and had in fact been observed by Lawrence. In four crosses involving one triplex with four different nulliplex, Lawrence (ig) observed double reduction at the Y locus in tetraploid Dahlia. He obtained 7 recessives out of 385 plants and explained this as "probably due to chromatid segregation ".…”

Cytological Studies in the Genus <i>Fragaria</i> (Rosaceae)

“…For example, in an induced autotetraploid Primula sinensis (2n= 4x=48), the mean number of quadrivalents was 10.4 per cell (Darlington 1931), but in an autotetraploid Lycopersicon esculentum (2n=4x=48) derived from a haploid, and therefore having four identical sets of chromosomes, the majority of the chro mosomes were associated as bivalents (Lindstrom and Humphrey 1933). A range of intermediate types has been reported between these two extremes of chromosome behaviour.…”

“…Some of this variation can therefore be attributed to either cytological or gene tical factors. Irregular disjunction of chromosomes at meiosis and therefore numerically unbalanced gametes can result in reduced fertility in autotetraploids (Darlington 1931). Bremer and Bremer-Reinders (1954) reported that an increase in fertility in autotetraploid Secale cereale selected over several generations was correlated with a decrease in the frequencies of univalents and multivalents and an increase in the frequency of bivalents at meiosis.…”