54. Tissue culture responses of calli from different explants of rice

Tetsuo Mikami and Toshiro Kinoshita

Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo 060, Japan


A total of 108 rice varieties were examined for their callus growth responses. The sources of explants for callus induction were dehusked seed, radicle and coleoptile sections from 5-6 day-old seedlings and anthers at the uninucleate stage of microspore development (Mikami and Kinoshita 1986).

Callus growth from seed, radicle and coleoptile became visible after 7 to 10 days on MS medium. The frequency of callus initiation in seed and radicle cultures was almost 100% in all genotypes examined, whereas the percentage of coleoptile explants which developed calli varied from 0 to 80% among the varieties. Most of the genotypes were also able to produce anther-derived callus with frequency of 5-55% on N\6\ medium within 20 days of culture.

Small pieces of callus of known initial fresh weight (40 to 50 mg) were plated on the appropriate medium. Callus growth was expressed as the ratio of the increase in weight after 50 days incubation to the initial fresh weight and was designated as the "fold fresh-weight increase". In seed culture, for example, genetypes differed significantly in the ability to develop vigorously growing callus: fold fresh-weight increase ranged from 1.9 to 14.4 (Table 1). Japonica varieties generally showed a higher capacity for callus growth than Indica genotypes, a pattern that agrees with the observation of Abe and Futsuhara (1986). Similar results were also obtained when testing radicle-, coleoptile- or anther-derived callus (Table 1). In addition, the fresh weight grains of seed (a), radicle (b) and coleoptile calli (c) were intercorrelated (r\ab\=0.714; r\ac\=0.710; r\bc\=0.541, all being significant), but were not correlated with that of anther callus (d) (r\ad\=0.172; r\bd\=0.084; r\cd\=- 0.169). Further studies are in progress to determine whether the difference in callus growth response between anther and the other cultures may be due to the higher proportions of haploid cells involved in the anther callus tissues.


Table 1. Callus growth response in seed, radicle, doleoptile and anther cultures. The experiments were scored 50 days after inoculation.

=============================================================================
Culture    Type        Fold fresh-weight increase                     No. of
                    2   4   6   8   10   12   14   16   18   20   22  lines
=============================================================================
Seed    Japonica    1   2   5  19   12    7    3                        49
        Indica      1   4   6   8    6    3                             28
        Japonica        1   1   2    2    1                              7
         x Indica
        Total       2   7  12  29   20   11    3                        84
=============================================================================
Radicle Japonica        1   6  19   27    5    3    1         1         63
        Indica      5   7   4   1    4    2                             23
        Japonica            1   2    4    1    1                         9
         x Indica
        Total       5   8  11  22   35    8    4    1         1         95
=============================================================================
Coleoptile    
        Japonica        2   4   6    2    4    2    1                   21
        Indica          2   1   3    3    1    1    1                   12
        Japonica                3    1                                   4
         x Indica
        Total           4   5  12    6    5    3    2                   37
=============================================================================
Anther  Japonica        1   4   8   10    8    3    1    1              36
        Indica              6   1    2    1    2    1    1         1    15
        Japonica                1    1    2                              4
         x Indica
        Total           1  10  10   13   11    5    2    2         1    55
=============================================================================


References

Abe, T. and Y. Futsuhara, 1986. Genotypic variability for callus formation and plant regeneration in rice (Oryza sativa L.). Theor. Appl. Genet. 72: 3-10.

Mikami, T. and T. Kinoshita, 1986. Inhibitory effect of streptomycin on rice tissue cultures and the selection of resistant callus clones. Euphytica (in press).