GrainGenes

II. 12. Fertility of microspore derived plants over three successive generations.

B. Foroughi-Wehr, G. Mix and W. Friedt. Department of Plant Genetics, Gesellschaft fur Strahlenund Umweltforschung mbH., 8059 Grünbach, FRG.

In the period between April 1976 and March 1977 as many as 202 plants recovered from the anther callusses of seven different barley varieties reached maturity. They comprise the first generation of anther plants (A1 generation). Out of this A1 70 plants were completely sterile (0% seed set, Tables 1 and 2). These individuals were grass-like, with narrow leaves, many tillers and short stature. There were on average about 60 tillers per plant, although one with 232 was observed (Mix et al., 1978). Scoring fertility was complicated by the fact that plants with more than 20 fully formed sterile spikes would spontaneously produce a fertile one. Within the Al-generation plants of a total different phenotype as compared with the donor plants occurred such as small plants with narrow twisted leaves, or extremely wide leaves and chlorophyll-deficient plants.

Table 1. Sterile and fertile plants derived from microspore callus over a one-year period (Al-generation).

Table 2. Fertility of microspore derived plants of 'Mutina' and 'Dissa' over three successive generations as compared to the donor varieties grown under field conditions at Grünbach, FRG, 1978.

In spring 1977 the seeds obtained from the more or less fertile A1individuals were planted in the field at Grünbach. Nearly 90% of this A2-generation appeared similar to the donor plants in growth and habit. Seed set was high (90-100%) and the plants were therefore classified as diploids. Approximately 10% of the A2 of the varieties 'Mutina' and 'Dissa', however, showed deviating phenotypes. The development of the plants was delayed, they showed wider leaves, fewer tillers and poor growth in general. Most of these individuals resembled tetraploid barley plants. This portion of the A2 was harvested separately and the fertility of each individual scored (Table 2). It is obvious that the majority of the A2 plants from 'Dissa' and almost 50% of the 'Mutina' A2 show predominantly sterile florets.

A number of A2- plants with varying degree of partial sterility were selected for A3- planting in 1978; plants with extremely low fertility were excluded. Nevertheless, in the A3- generation again a number of individuals with extremely low seed set as well as completely sterile plants appeared. Since most of the partially sterile A2- plants had been classified morphologically as tetraploids the occurrence of completely sterile progeny was not expected (such sterile plants are usually not observed in tetraploid barley populations).

One explanation for the observed phenomenon could be that in the course of the culture period in vitro, gene as well as chromosome mutations may have occurred, which cause the segregation of sterile genotypes in the successive generations. This view is supported by the observation of chromosome breaks, etc., in root-tip cells of microspore derived plants (Mix et al., 1978) as well as by the very recent evidence for reciprocal translocations in PMCs of microspore derived progeny (Friedt, unpublished).

The cytological status of several A3- plants has been investigated in their root-tip cells. There was still a great variation of chromosome numbers between different plant progeny. Even within single plants haploid and diploid as well as tetraploid and aneuploid cells have been observed.

The possible causes of the cytological instability described have to be studied in more detail in the future.

Reference:

Mix, G, H.M. Wilson, and B. Foroughi-Wehr. 1978. The cytological status of plants of Hordeum vulgare L. regenerated from microspore callus. Z. Pflanzenzüchtg. 80:89-99.

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