THE ASSOCIATION OF A GENE FOR CHLOROPHYLL PRODUCTION WITH A SPECIFIC CHROMOSOME IN <i>AVENA SATIVA</i>

Chlorophyll mutants of various types have been observed and described in common oats, Avenn sntiva L., several times since Nilsson-Ehle (1913) first reported finding albinos. Most of the literature on this subject has been thoroughly revlewed and presented cl~ronologically by Froier (1946) so only the most pertinent literature will be included here. The most strilting chlorophyll mutant is the albino which is conlpletely devoid of pigment. In addition to the one found by Nilsson-Ehle (1913), albinos have been reported by only a few other worlters (Zllegalov, 1920; Philp, 1935; Smith, 1938; and Tegenltamp and Finltner, 1954). There is general agreement that there are polymeric genes governing chloropl~yll production. Pllilp (1935) reported the presence of at least two independently inherited pairs of genes and suggested, since oats are hexaploid, that very liltely three loci on different chromoson~es are involved. Since a single gene is as effective in producing cl~lorophyll as when all are present, there is no selection against a recessive mutation of these genes until all loci are involved. Consequently there are in existence oat varieties having various numbers of thcse genes in their genotype. In varieties having only a single pair of genes for chloropl~yll production, a plant nullisomic for the c l~ro~noso~ne carrying this gene is albino. The first such case was reported by Philp (1935) who found that aibino plants had only 40 cl~ro~~~osornes, whereas the parent plants of albinos were monosomic having 41 chromosomes. The albinos were present in a very high frequency of nlonosomic progeny. It was shown cytologically that during meiosis of pollen mother cells of monosomic plants the univalent (the V, cllromosome) was included in only about 7 per cent of the pollen grains. Thus, most often deficient gametes were involved in fertilization. Earlier, Nishiyama (1931) found that the C chromosome (fatuoid cl~romosome) was included in 10.1 per cent of the pollen grains and an even lower frequency (6 per cent) was reported by Philp (1938) for the L cl~romosome (chron~osome for broad leaves). A considerable variation (from 2.1 per cent to 46.0 per cent) was found in the frequency of nullisomics in progeny of five oat rnonosornics by Costa-Rodrigues (1954). A/luc11 of the variation was attributed to non-survival of 40-chromosome zygotes. Philp (1938) was able to show that the C, L and V cl~romoson~es were different from one another but could not actually identify the respective cl~romosoines. Recently a ltaryotype study of Avenn species was conducted by Rajhathy and Morrison (1959). With the aid of their idiogram it maltes possible the identification of many of the chromosomes involved in aneuploidy and subsequently the association of the attending phenotypic change with a