A line with a deletion on the long arm of chromosome 6B isolated in Triticum aestivum cv. Chinese Spring.

B. GIORGI

Agriculture Laboratory, CNEN, RAD/APPL, Cas accia Nuclear center, S. Maria di Galeria, Roma, Italy

A wide range of aneuploid lines, nullisomics, monosomics, telosomics, isosomics, trisomics, tetrasomics and nulli-tetrasomics compensating stocks have been developed in T. aestivum cv. Chinese Spring by SEARS (1954). Other aneuploids and naeuploid derivatives involving other varieties have been intensively searched during the past 25 years.

So far, homozygous deletions which might be exstremely useful for genetic analyses, either have not been sought, or have been overlooked for various reasons. However, an interstitial and small deletion involving the Ph gene located on the long arm of chromosome 5B seems to have occurred following radiation treatment both in bread (SEARS, 1977) and in durum wheat (GIORGI, 1978).

In a routinary work based on chromosome counting of monosomic lines of Chinese Spring a spontaneous heterozygous deletion involving the long arm of chromosome 6B was noticed. It was easily recognizable because such a deletion deals with a statellited chromosome in which about 2/3 of the long arm is lacking. In the progeny of a selfed heterozygote plant, 3 out of 18 carrying deletion homozygote plants were recovered. All of them have spikes with shrot awans just like CS ditelo 6BS.

Morphologically this lines (henceforth called CS Df 6BL) is quite similar to the ditelo 6BS, being however a little more vigorous. Yield and yield components of this line, CS ditelo 6BS, CS ditelo 6BL and Chinese Spring euploid were analyzed and compared in a field experimental based upon a single plant randomisation.

The results reported in Table 1 show that the absence of the distal part of the 6B long chromosome arm affects as much severely the overall growth as the lack of the entire long arm.

The presence of awns in the spikes of CS Df 6BL proves that the awn inhibitor B2 must be located in the distal part of the long arm of the chromosome 6B.

In addition, the above cytologically marked lines show a different picture as to types, structure and distribution of cuticolar waxes.

This is an interesting aspect which deserves further investigation.

Fig.1

Literature Cited

GIORGI, B. 1978. A homoeologous pairing mutant isolated in Triticum durum cv. Cappelli. Mutation Breeding Newsletter n. 11 : 4-5.

SEARS, E.R. 1954. The aneuploids of common wheat. Missouri Agric. Exp. Sta. Res. Bull. 572 : 1-59.

SEARS, E.R., 1977. An induced mutant with homoeologous pairing in common wheat. Can. J. Genet. Cytol. 19 : 585-593.