Production of disomic haploids by anther culture of a series of trisomic plants in Nicotiana sylvestris.

Abstract

In order to investigate the genic imbalance caused by addition of an extra chromosome to normal diploid and haploid complements, an experiment was carried out on the production of trisomic (2n+1) and disomic haploid (n+1) plants in Nicotiana sylvestris (n=x=12). F1 plants between triploid and diploid were backcrossed with the diploid plants. By the examination of chromosome number, 61 trisomic plants were selected from the B1 progenies. These trisomic plants were grouped into 12. types by the leaf shape and flower morphology. The anther culture was perfrmed using the 12 types of trisomic plants. The frequencies of androgenetic plantlet production varied greatly among the types of trisomic plants. This result indicates that the variety of the extra chromosome in the trisomic plants effects the frequency of plantlet production. In this anther culture, disomic haploids were obtained from 7 types of trisomic plants. No disomic haploid was obtained in the other 5 trisomic types. Besides the production of euhaploids and disomic haploids, several kinds of polyploids and mixoploids. were also obtained. The frequencies of androgenetic plants derived from the pollen grains with 12 chromosomes were apparently higher than those of plants derived from the pollen grains with 13 chromosomes, except for 2 trisomic types, B220 and Q480, in which the frequencies of plants with and without the extra chromosomes were almost the same. These 2 trisomic types tended to produce at a high frequency the androgenetic plants with no extra chromosome in early stages of buds, and those with the extra chromosomes in late stages of buds. This was assumed to be due to unsynchronized development of pollen grains with and without the extra chromosome. Among the disomic haploids obtained, 5 types of plants developed flower organ. The flower of disomic haploid derived from B 220 trisomic plant was conspicuously small and malformed, while the corresponding trisomic plant produced normal and remarkably larger flowers than the normal diploid. The mechanism of reversed effects caused by the addition of the same extra chromosome on diploid and haploid level, however, was not clarified in this study.