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Correlation between Grape maturity & seed germination.

Written by Søren Larsen.& Mark ????

Agroscope Changins-Wädenswil ACW is a research station that conducts applied research in plant science. Areas of study include field crops, pastures, viticulture, arboriculture, horticulture, berries and aromatic and medicinal herbs. I got permission to bring the pictures from the original report, that is written in German. You can find it here:  Zusammenhang zwischen Beerenreife, Traubenkernreife und Keimfähigkeit

Katharina Hintermann, Werner Koblet und Irma Roth, had harvested seeds from 2 varieties during the last 2 month before normal harvest. The seeds were investigated for the germ ability compared to the sugar level .( Oechsle or Brix levels) Varieties were "Riesling x Silvaner" and Blauburgunder.

Storage and seed

After the seed were separated from the berries, the juice were pressed, filtered and analysed. (Sugar, total acid, apple and tartaric acid). The seeds were washed until they were clean. All floating seeds were removed. The stratification (seeds are stored several months with damp and cool conditions) was accomplished after Balthazard (1979). Ref

After washing the seeds were air-dried over night, and stored afterwards in the refrigerator (8 °C). The seeds were put in a nylon bag and covered with damp sand. The storage in the freezer (minus 1-1,5 °C) took 3 weeks. Before sowing the seed, the seeds were carefully thawed at 2 °C.

On the 19 February 96 the seeds were sawed in rearing earth in a greenhouse. (100 seeds on 80 cm2) The set-up got a heating plate, cause the trail would proceed according to the principle of Balthazard (1979), which suggests an alternating temperature. As soon as the cotyledons were unfolded, the seedling was accomplished. The first counting took place after 16 days, the latter after 53 days.

"Riesling x Silvaner" Sugar level [Oe] development, and the seed germ ability in %

Keimungstotal = Germination %   ---   Oechle = sugar level  (4 Oe = app. 1 brix )   ---   Erntedatum = Harvest date

The figure show some interesting numbers. The germination % is not higher than 50, but most interesting is that this is also the case 6 weeks before harvest !!! A drop in sugar development on the 26'th of september gives lower germination a week later.

A more or less correlation between the sugar level and the germination % was observed in the Riesling x Silvaner seeds. The maximum germination value was at 75,9 °Oe and were reached on the harvest date. The germ ability was always below 50%. The Riesling x Silvaner vine is an early ripe variety, and this could be the explanation for the bad development of the seed.  

Early ripe varieties do not ripe the seed fast enough to get mature seeds at harvest. At “Varaision” the growth of the embryo is slowed down and even stopped finally, which has as a consequence that it does not reach the minimum length of 1 mm. This is main reason, why early ripe varieties show usually bad germinating ability, even if the environmental condition is good.

 Germination representation of the harvest date

This diagram shows the germination process during the 8 weeks trail. It also shows a that sprouting & the first growth of the Cotyledons is minimum 3 weeks. The best seed-lot is from the 24 October and even though there is germination after 7 weeks. Not a ideal process here.

Blauburgunder Sugar level [Oe] development, and the seed germ ability in %

This figure shows even more interesting number, Blauburgunder got a germination % peak 5 weeks before harvest !!! Her is the germination more than 70% and decreasing to the end of trail. At normal harvest time, the germination is only 30%. This is not good, and this shows clearly that the seeds is going into an other kind of dormancy. At least that is what I think. A normal stratifying is not waking-up the very mature seeds. A 70% germination is good, and this shows that the seeds is ready to be harvested at 15-17 Brix. After the 19'Th of september the seed is starting a kind of after-ripening, and this cause another kind of stratification process.

Reference:

Balthazard J, Contribution a l'amelioration de la germination des graines de vigne 1979

The author studies the factors affecting the lifting of dormancy and the germination of vine seeds. Tegmentary inhibition plays a much less important role than psychrolabile embryonic dormancy. This dormancy is lifted during low temperature (1 ° C) stratification for several months. The optimum temperature for germination is 30 ° C. Temperature alternations (3 hours at 30 ° C, 9 hours at 20 ° C) increase the germination percentage. Light, of whatever type, does not have any effect on germination. Seeds whose embryos are less than 1 mm long are unsuitable evaluate the germination ability of a seed batch. The author shows that the cause of bad germination of the seeds of early varieties is due to the fact that embryonic growth is arrested at berry ripening, at a time when they have not yet reached the limiting length of 1 mm.(Pouget, R.; Pont-de-la-Maye) 

 Editor Søren Larsen