Rick, C. M. and Dora Hunt
For many years tomato workers have been plagued with poor seed germination of certain wild forms. The problem is pirticularly acute with accessions of Galapagos tomatoes, in some of which none of the seeds will germinate without artificial aid. Careful excision of of the seedcoat has been recomended, but, at best, this treatment causes only slight improvement. After testing a galaxy of treatments we found a gratifying response to exposures to sodium hypochlorite, thanks to a kind hint from our agronomic colleagues. It has been found effective for breaking dormancies in seeds of guayule and various range grasses.
All germination tests were made on blotting paper inside plastic sandwich boxes. Various intensities of exposure have been found effective, but we have found a useful standard to be half-strenght Clorox or other household bleaches of the same composition (5.2% sodium hypochlorite). After treatment the seeds are washed thoroughly and placed in the germinators at room temperature. It is evident from the appearance of the seeds that the treatment digests avay part of the seed coat. The response to such exposure with seeds of the Galapagos accessions is dramatic: LA317 (var. minor) jumped from the control level of 1% to 81% and LA166 from 0% to 52%. More stubborn lots required repeated treatments alternated with periods in the germinators. Following these repeated treatments the radicles literally pop out of the seed coats within minutes as if they had been simply unable to break through the seed coats.
A similar response was observed in other materials. Seeds of S. lycopersicodes, which are notoriously difficult to germinate, respond well and similarly those of S. pennellii and certain difficult accessions of L. chilense and L. peruvianum. About 40% of the seeds of F1 L. esculantum x S. pennellii germinate without treatment, but the percentage is about doubled after hypochlorite treatment.
Seeds of Galapagos accessions have also been found to respond favorably to digestion by the Galapagos tortoises. Various aspects of this problem have been investigated and a manuscript summarizing results is in press.