Education - Rice Cultivation Manual for Experiments

Seeding	Transplantation	Artificial crossing	Emasculation
Pollination	Harvest	Seed preservation

Seeding

• Seed disinfection:

Before sowing the rice seed, the surface of the seed should be sterilized by using a 1 in 1000 Benlate hydrate solution. For small quantity of seed, they may be placed in a petri-dish and keep the seed dipped in the above mentioned solution until germination.

• Germination:

For safety of germination, seeds are separately placed in petri-dish of appropriate size according to their kind. Place a filter paper on the bottom of petri-dish, arrange the seed on it, pore water until the seed is just covered. Put the dish into an incubator adjusted at 30C, or keep under room temperature. Ordinary seed are treated with their glumes but for the case with special care, the glume may be removed. After two to three days, they will start to germinate and almost complete within a week.

• Sowing the seed and a portable seed bed.

Sow the germinated seed on to the seed bed which may be an open box or a planting pot prepared with soil. When many strains are dealt, it is convenient to sow the seeds in rows. Place the germinated seeds with forceps onto a marked line on the soil with 1.5 to 2cm apart, then cover the seeds with surrounding soil. Rows will be 5 to 6cm apart. Each strain will be marked with a label at the top of row or area. Seed bed may be a reasonable size of not too big or heavy in view of handling convenience, for instance, a wooden or plastic box of 33cm x 57cm with 10cm depth.

Transplantation

• Though you may sow the seed on a plant pot from the beginning, it is recommendable to sow the seed on a seed bed separately according to the strains and then transplant the seedlings into plant pots or a paddy field around 30 days old. This is particularly convenient when many strains are dealt . When pots used, the soil is filled up to 2-3 cm below the rim of a pot so that water is kept on the surface of soil at the time of irrigation. The cylindrical plastic pots of one-five thousandth are (1/5000 a, 16cm diameter) or one-two thousandth are (1/2000 a, 25.5cm diameter) are available, but if it is not for a quantitative physiological experiment but simply to grow rice plants, approximately equivalent size of plastic pails (16cm or 25.5 cm diameter) can be used instead. In NIG, plastic water pails of 24 cm diameter and 17-18cm depth with a handle are used conveniently since they are of economical price and of easy handling for moving from one place to another.

• Fertilizer:

Nitrogen (N) 10kg, Phosphate (P2O5) 12kg, and Potassium (K2O) per 10 are.

Artificial crossing

• At anthesis (flowering), as soon as a rice flower opens its spikelet (lemma and palea) and its anthers become ripen and split, and then the pollen are shed on a stigma of own pistil for fertilization. So the self-pollination occurs. For crossing, the anthers of mother plant should be taken out (emasculation) before anthesis to avoid self-pollination. Then the pollen of father plant should be placed on to the stigma of mother plant.
  

• Adjustment for common anthesis date.

When the flower of mother plant opens, the pollens are taken from the father plant and pollinated on the stigma of the opened mother flower. For this purpose, both the flowers of mother and father plants should be adjusted to be at an anthesis at the same time. The most effective method is to apply a short day treatment, but it needs special facility. Otherwise it is so laborious to be not recommendable. If the rice strains which is able to flower in the area, flowering date may be changed to some extent by different sowing dates. So, sow the seed at different dates and choose the flowers of mother and father plants coincidentally at an anthesis.

• Keep the mother plant in a pot.
  

If the rice plants are grown in a paddy field, take the mother plants out and keep each of them in pots one day before the crossing.

Emasculation

• Removing the anthers:
  

In the previous afternoon of flowering, remove the anthers of flower which will open the next morning. For this work, cut the tip of spikelet about one-third off, remove the anthers with forceps carefully through the cut end, so that no damage on the sigma. All six anthers should be removed. Except the treated flowers, all of the other flowers (spikelets) are removed. Then the panicle is covered by a paper bag until the next morning avoiding the natural contamination of other pollen. Next morning, the anthesis starts when it becomes clear. It is recommendable to keep the materials in a dark room and take them out just before crossing operation.

• Hot water emasculation method:
  

Dip the rice panicle in to the hot water of 43 C for 5 to 7 min. , then the anthers in a flower ready to anthesis on the morning are killed and at the same time the flower becomes open by the stimulation of the hot water. Remove all of the flowers except the opening flowers. Pollinate the pollen of father plant during the treated flowers are open.

Pollination

Cut the panicles of father plants before anthesis in the morning, and keep them in a flask with water to make ready for crossing. When the emasculate flowers of mother plants become open, sprinkle the pollen of opening father flowers on to them. If the pollen is not enough, take the anthers just before splitting from opened father flowers and splinkle the pollen by splitting the anthers over the stigma of mother flowers.

Harvest

Harvest the seeds after 40 to 50 days from anthesis, by this time the color of spikelets become yellow and seeds become hard.

Seed preservation

Store the seed under dry and low temperature conditions. Generally the seeds are stored in a desiccator in a cool place. For long preservation, the seeds are stored under -1 C with 30% relative humidity.