Somatic embryogenesis in Coix aquatica Roxb.

--G. Chandel and S. K. Katiyar

Protocols for the in vitro production of plants through somatic embryogenesis from cultured immature, unemerged inflorescence segments of Coix aquatica genotype C-21, C-27 and C-65 have been developed.

Out of various concentrations of 2,4-D (2,4-dichlorophenoxy acetic acid) and sucrose tested for callusing, N6 media with 1-2mg/l 2,4-D and 3% sucrose concentration gave good response.

Table. Mean relative chromosome length, arm ratio and centromeric index (CI) in Coix and maize.
 
  Relative Chromosome Length Arm Ratio Centromeric Index
Chromosomes Coix aquatica Coix lacryma jobi Z. mays Coix aquatica Coix lacryma jobi Z. mays Coix aquatica Coix lacryma jobi Z. mays
  (2n=10) (2n=20) (2n=20) (2n=10) (2n=20) (2n=20) (2n=10) (2n=20) (2n=20)
1 24.01 12.96 11.90 1.24 1.24 1.22 44.55 44.38 44.90
2 21.84 11.88 11.90 1.27 1.40 1.88 44.29 41.65 34.64
3 20.08 11.28 11.66 1.41 1.21 1.33 41.29 45.18 42.84
4 18.32 10.53 10.71 1.40 1.22 1.19 42.07 44.86 45.46
5 16.36 9.89 10.71 1.36 1.20 2.00 42.63 45.63 33.29
6 - 9.51 10.71 - 1.40 1.66 - 42.23 37.28
7 - 9.10 8.80 - 1.31 1.54 - 41.30 39.35
8 - 8.91 8.56 - 1.32 2.29 - 43.51 30.32
9 - 8.14 8.32 - 1.31 1.69 - 43.38 37.08
10 - 7.65 6.66 - 1.46 1.27 - 40.75 44.03

Coix aquatica - overall mean of 20 collections.

Coix lacryma jobi - overall mean of 8 collections.

The frequency of callus induction from genotype C-27 was up to 80%. Differences in callusing were found to be due to genotypes rather than the concentrations of 2,4-D. The length of the explant at the time of inoculation was also found to be critical for callusing.

Out of two different types of calluses subcultured, compact callus produced embryos when transferred to liquid MS medium with various combinations and concentrations of NAA, BAP and KIN. The maximum number of plantlets were regenerated on MS medium supplemented with 0.5mg/l BAP+0.01mg/l NAA and 3% sucrose in 25-30 days after subculturing. The combination of BAP+NAA was found to be better than the combination of KIN+NAA. Vigorous regenerated plants were transferred to sterile soil after 1-3 days of hardening treatment, kept in the glasshouse for 15-20 days, and later transferred to the field. In vitro regenerated plants showed normal flowering and seed set. This is the first time that complete reproducible in vitro regeneration protocols in Coix aquatica have been developed and plants taken to maturity. The seeds obtained are viable. This is a very significant step and opens up avenues for the application of plant genetic engineering methods.


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