Breeding and Seed Production of Ornamental Crops (2+1)

Procedure of Hybridization (Contd..)

Procedure of Hybridization

Techniques of emasculation

i) Hand Emasculation:

• It is the commonest method of emasculation in most of the floricultural crops. In species with relatively large flowers e.g. lilium, rose, aster, antirrhinum etc., stamens or anthers are removed with the help of forceps. The exact details of the procedure, however, varies from one crop species to the other.
• Emasculation is done before the anthers are mature and the stigma has become receptive. It is done to ensure any possibility of self-pollination. Usually, stigma receptivity is at its peak during the morning hours when the flowers open, but different crop species show considerable variation in the duration for which their stigmas remain highly receptive.
• After some experience, the breeder should be able to select such flowers without much difficulty. Generally, it is desirable to remove the older and the younger flowers located close to the flower to be emasculated in order to avoid confusion in the identification of crossed pods/fruits etc. For example, in antirrhinum emasculation is started when the lowermost flower is tight lipped but has started showing colour. Further, emasculation is done on successive days along with opening of the florets on the spike. Uppermost 1/2 to 1/3^rd portion of the spike is cut with a sharp scissors and not used for hybridization
• A general procedure for hand emasculation is as follows: The corolla of the selected flowers is opened and the anthers are carefully removed with the help of fine-tip forceps. Care must be taken to remove all the anthers from the flowers without breaking them and, the most important, the gynoecium must not be injured.
• An efficient emasculation technique should prevent self-pollination and produce high percentage of seed set on cross-pollination i.e. viability of the stigma should be judged critically.
ii) Suction Method:

• This method is useful in species with small flowers. Emasculation is done in the morning just before or immediately after the flowers open. The petals are generally moved with forceps exposing the anthers and the stigma.
• A rubber or glass tube attached to a suction- hose is used to suck the anthers from the flowers. The tube is also passed over the stigmas to suck any pollen grains present on their surface. The suction may be produced by an aspirator attached to a water tap, or by a small suction pump. The amount of suction used is very important.
• The suction should be enough to suck the stamens and pollen grains, but not the flowers or the gynoecium. With suction method, considerable self-pollination (up to 15 per cent) is likely to occur. Washing the stigma with a jet of water may help in reducing self-pollination. However self-pollination cannot be eliminated in this method.
iii) Hot Water Emasculation:

• Pollen grains are more sensitive than the female reproductive organs to both genetic and environmental factors.
• In the case of hot water emasculation, the temperature of water and the duration of treatment varies from crop to crop, and must be determined for every species. The hot water is generally carried in thermos flasks and the whole spike is immersed in the water. Emasculation with hot water is generally highly effective in killing all the pollen grains provided the correct temperature and treatment duration are used.
iv) Alcohol Treatments:

• It is not a commonly used method of emasculation. The method consists of immersing the flower or the inflorescence in alcohol of a suitable concentration for a brief period, followed by rinsing it with water.
v) Cold Treatment:

• Cold treatment, like hot water treatment, kills pollen grains without damaging gynoecium. Cold treatment is less effective than hot water treatment. The amount of self-pollination is generally greater in cold treatment than in the case of hot water treatment.
vi) Genetic Emasculation:

• Genetic or cytoplasmic male sterility is one of the most efficient attributes that can be utilized to eliminate the necessity of emasculation. Many species are self-incompatible. In such cases, emasculation is not necessary because self-fertilization will not take place. Many lilium species are self incompatible, and hence there is no need for emasculation.
• However, for commercial hybrid seed production, male sterility is the most feasible and efficient method of emasculation. Male sterility is commercially being exploited for the hybrid seed production in marigold and zinnia.