Chromosome associations and seed fertility in five strains of hexaploid triticale¹⁾²⁾

T. TSUCHIYA

Department of Agronomy, Colorado State University, Fort Collins, Colorado. 80521., U.S.A.

Chromosome associations and fertility were studied in five advanced strains of hexaploid triticale. The materials used in the experiment are shown in Table 1.

Chromosome associations were analyzed at metaphase I of meiosis in the materials grown in the experimental field of the University of Manitoba, Winnipeg, Canada, in the summer of 1966. The materials were fixed with 1 : 3 acetic alcohol solution and preparations were made by acetocarmine squash technique. Fertility was shown by the percentage of seed set in the primary florets (the first and second florets of a spikelet) of two to three spikes collected from each plant.

The number of closed and open bivalents and the number of univalents per sporocyte are shown in Table 2 with seed fertility in some plants.

These results indicated that meiotic association of chromosomes are almost normal with high average number of bivalents (20.1) per sporocyte in combination with low number of univalents (1.78 per sporocyte) on an average. The variation of the number of bivalents and univalents per sporocyte was not great in different plants within a variety with a few exception (6316-9, 6408-1). The chromosomal associations in 6250 were slightly lower than the other four strains. The average seed fertility was, however, even higher in 6250 than the other strains studied as partly shown in Table 2.

These results shown in this brief note suggest that the chromosome association may not be the only factor affecting the seed fertility expressed by the seed set percentage in the primary florets. However, as shown in 6316-9, the abnormal meiotic behaviour may be directly reflected to the lower seed fertility when the abnormality is beyond some points, though more data should be obtained to give definite conclusion about the relationship between meiotic abnormalities and the seed set reduction.

At any rate, the results obtained suggest that the selection should be made in triticale breeding towards at least two directions: Selection of the plants or strains with high fertility and selection of materials with regular meiotic behaviour of chromosomes.

(Received March 5, 1971)