HISTOLOGICAL AND CYTOLOCICAL SELECTION OF SOMACLONAL AND INDUCED VARIANTS OF ASPARAGUS DERIVED FROM CALLUS CULTURES

Morphogenic lines established from meristem explants of asparagus spears of female (XX), male (XY) and supermale (YY) genotypes have been selected on appropriate media and maintained for more than 10 years in continuous subculture.
The differentiation of shoot initials is closely correlated with a protein deposition in the vacuoles of callus cells and with the subsequent formation of meristematic cell clusters.
Cytophotometric measurements of the nuclear DNA in callus cells revealed a predominant occurrence of 2c-nuclei in cultures with high regeneration potency, whereas in non-morphogenic callus the 4c and 8c phases increased significantly.
Screening for genome mutations has been carried out by means of guard cell length measurements as a ploidy marker.

Exclusively diploid regenerants were found in male callus cultures.
From female callus lines which contain greater genome variation about 10% of the callus-derived plants were polyploid.
Treatment of meristematic explants with colchicine and caffeine as chemical mutagens and subsequent regeneration from callus cultures from 400 tested plants 6% yielded 2x, 80% 4x and 14% had intermediate chromosome numbers.
The protein content of the tetraploids was double that of the diploids.
Protein compounds in 4x samples had larger and deeply-stained electrophoretic bands.

I International Symposium on In Vitro Culture and Horticultural Breeding

G. Reuther

https://doi.org/10.17660/ActaHortic.1990.280.63