| Chromosome location of the "kinky neck" character established
by crossing durum wheat x monosomics of Chinese Spring B. GIORGI Agriculture Laboratory, CNEN, RAD/APPL, Casaccia Nuclear Center, S Marai di Galeria, Roma, Italy The chromosome location of genes in durum wheat is still a difficult task to be overcome, partly because of its tetraploid nature and partly due to the lack of suitable aneuploid lines. So far few attempts have been made in trying to utilize the monosomics of bread wheat (ALLAN and VOGEL, 1960 ; KUSPIRA and MILLIS, 1967 ; BOZZINI and GIORGI, 1971). In durum wheat it happens very often to come across a variety in which the part of peduncle bearing the spike appears to some extent bended and twisted, namely kinky. In a previous work (l. c.) aimed at locating genetic factors in durum wheat the cultivar Capeiti, still widely grown in Italy, was crossed with 14 monosomics lines of Chinese Spring. Obviously, only the chromosomes of the genomes A and B were involved in this kind of monosomic analysis. From the F1's two types of hybrids can be separated by means of chromosome counting in root tips of the seedlings. One type has 35 chromosomes and represents straight way the normal pentaploid hybrid. The other type with 34 chromosomes comprises 14 monopentaploid hybrids in which one chromosome, in turn, is missing. Therefore, in each monopentaploid hybrid one chromosome is represented by a single dose, coming from the durum wheat parent, while the corresponding chromosome of bread wheat is absent. In such a situation the recessive and hemyzigous effective genes carried by the single durum type chromosome can express themselves in F1 generation. The effect of a certain number of genes has been beautifully depicted in this way. Among the parameters studies and rechecked the characters "kinky neck" seems associated with the chromosome 7A. It appears that a major recessive and hemyzygous effective gene controls this characters as evidenced by the spike of CS mono 7A x Capeiti (Fig. 1). From time to time plants of the remaining monopentaploid hybrids show very slightly the "kinky neck" character, thus indicating that minor genes or modifiers can be present, spread throughout the genomes of durum wheat. Literature Cited ALLAN, R.E. and A.O. VOGEL 1960. F1 monosomic analysis involving a smooth-awn durum wheat. Wheat Inform. Serv. 11, 3-4. BOZZINI, A, and B. GIORGI 1971. Genetics analysis of tetraploid and hexaploid wheat by utilization of monopentaploid hybrids. Theor. and Applied Genetics, 41 : 67-74. KUSPIRA, J . and L.A. MILLIS 1967. Cytogenetic analysis of tetraploid wheats using hexaploid wheat aneuploids Can. J. Genet. Cytol. 9 : 79-86. |