Authors: Madhu Choudhary*, Ravi Kumawat, Kana Ram Kumawat and Mamta Bajya
Department of Plant Breeding and Genetics, S.K.N. Agriculture University, Jobner-303329, Jaipur (Rajasthan), India
*Corresponding Author E-mail: anamikaz0129@gmail.com
Introduction
The primary objective of plant breeding is to develop superior varieties. The benefits from such varieties can only be realized when they are grown by the farmers on a large scale. Therefore, seeds of improved varieties must be produced in sufficient quantities to make them available to the farmers. According to an estimate, seed contributes up to 15-20% to the total crop production and with efficient input management practices it may contribute up to 45%. Clearly, seed of new varieties should reach the farmers in a pure and healthy state. To ensure this, elaborate seed programmes exist in most of the countries. India also has a well organized seed production programme through National Seeds Corporation (NSC), State Seeds Corporations (SSC) and State Seed Certification Agencies (SSCA) which are responsible for seed multiplication, certification and distribution of high quality seed. Quality seeds are produced at Nucleus, Breeder, Foundation and Certified levels.
Definition
Seed- Botanically seed is the ripened ovule in the ovary of a flower. It contains the embryo which has developed after fertilization of the male and female gametes in the embryo sac of the ovule. In Seed Science, the seed is any part or organ of the plant which has capability to regenerate a new plant. The seed has potentiality to maintain the intrinsic qualities through generations of the variety or species to which it belongs.
Quality Seed Production
Production of high quality seed requires considerable technical skill since a number of rigid requirements must be fulfilled to ensure the high purity and germination requirements. Seed production requires improved cultural practices; efficient weed, disease and pest control; optimum irrigation and fertilizer application and some other operations specific for seed crops. Seed production is described under the subheads, (1) isolation and (2) seed crop cultivation
- Isolation The crop raised for seed production should be separated from other fields of the same crop by a minimum distance called isolation distance, which varies from one crop to the other. Isolation is essential to prevent pollination by unwanted pollen in the case of cross-pollinated and often cross-pollinated species and to avoid mechanical mixture and chance cross-pollination in self-pollinated species. In any case, it is necessary to plant a variable number of border rows of the male parent in case of hybrid seed production to ensure a sufficient supply of pollen on the edges of the field. It may be seen that the minimum isolation distance required for foundation seed crops is markedly greater than that for certified seed crops in the case of all those crops where pollen contamination is feared. In most cases, the isolation needed for foundation seed crop is twice as much as or even more than that for certified seed crop. Only in the case of strict self-pollinators like wheat, rice, soybean etc. the isolation requirement for the two classes of seeds are identical (3m). Table: Minimum isolation distance for seed certification in some crops
| Crop | Minimum isolation distance (m) | Isolation distance modified by | |||
| Foundation seed | Certified seed | Area of seed field | Additional border rows of the pollinator parent | Differential planting dates | |
| Maize inbred | 400* | - | |||
| Hybrid maize | 400* | 200 | Yes | Yes | Yes |
| Maize (OP/ Synthetic) | 400 | 200 | |||
| Hybrid sorghum | |||||
| a) From other sorghum | 300 | 200 | No | No | Yes |
| b) From johnson grass | 400 | 400 | No | No | Yes |
| Sorghum (OP) | 200 | 100 | |||
| Hybrid pearlmillet | 1000 | 200 | No | No | Yes |
| Pearlmillet (OP) | 400 | 200 | |||
| Wheat | 3 | 3 | |||
| Hybrid wheat | 200 | 100 | |||
| Rice | 3 | 3 | |||
| Hybrid rice | 200 | 100 | |||
| Barley | 3 | 3 | |||
| Triticale | 3 | 3 | |||
| Cotton (Op/hybrid) | 50 | 30 | |||
| Soybean | 3 | 3 | |||
| Sunflower (OP) | 400 | 200 | |||
| Rapeseed and mustard | 50** | 25** | |||
| Castor (OP/hybrid) | 600 | 300 | |||
| Groundnut | 3 | 3 | |||
| Sesame | 100 | 50 | |||
| Pigeonpea | 250 | 100 | |||
| Peas | 10 | 5 | |||
| Cowpeas, rajma | 10 | 5 | |||
| Tomato | 50 | 25 | |||
| Hybrid tomato | 200 | 100 | |||
| Okra | 400 | 200 | |||
| Sweet pepper | 500 | 250 | |||
| Potato | 5 | 5 | |||
| Brinjal | 300 | 150 | |||
| Carrot | 1000 | 800 | |||
| Cucurbits | 1000 | 500 | |||
| Hybrid cucurbits | 1500 | 1000 | |||
| Radish, turnip | 1600 | 1000 | |||
| Cauliflower | 1600 | 1000 | |||
**For self compatible genotypes.
- Seed Crop Cultivation Improved cultural practices and recommended levels of fertilizer and irrigation must be provided to raise a healthy seed crop so that the minimum yield of high quality seed is obtained. The following important points should be observed for raising a good seed crop.
- Land Requirement The land should be level, fertile and free from noxious weeds specified for the crop. In some cases like pearlmilliet and sorghum, the field to be used for seed production should not have been used for growing the same crop in the previous year. If the same crop were grown in the previous year, the field should be irrigated three weeks before sowing and ploughed just before sowing. This is done to allow the seeds that might have dropped in the field from the previous crop to germinate and to destroy the seedlings (volunteers) by ploughing. Table: Modification of the minimum isolation distance for hybrid maize certified seed production by area of the seed field and by border rows of pollinator (male) parent
| Area (ha) of the seed field | Minimum number of border rows of the male parent | |||
| 4 | 8 | 12 | 16 | |
| Isolation distance (m) from maize | ||||
| 200 | 190 | 180 | 170 | 1 |
| 175 | 165 | 155 | 145 | 3 |
| 150 | 140 | 130 | 120 | 5 |
| 87.5 | 77.5 | 67.5 | 57.5 | 10 |
| 50 | 40 | 30 | 20 | 13 |
- Cultural Practices Recommended improved cultural practices must be followed and recommended dose of fertilizers and irrigation water must be applied for high yields of high quality seed. Poor cultural practices would give lower yields and seeds of smaller size, which would be rejected at the time of grading and reduce the profits to seed growers.
- Plant Protection Adequate measures must be taken to protect the seed crop from diseases and pests that may cause considerable damage to crop reducing the yield and quality of seed. Further, incidence of some diseases may lead to the rejection of seed crop by the certifying agency. For example, the maximum permitted incidence of head smut and grain smut in sorghum (seed parent only) is one head in 10000 and one head in 2500, respectively, at the time of last field inspection. This rigid requirement is prescribed to prevent the occurrence of disease epidemics in the commercial crops due to contaminated seed.
- Weed Control Effective weed control is a must for good seed production. Weeds reduce crop yields and their seeds contaminate the crop seed. Certain weeds are classified as objectionable weeds by the seed certification agency and the seed field is generally required to be free from such weeds. For example in case of hybrid pearlmillet, no objectionable weeds should be present at any field inspection.
- Rouging Rouging is the removal of plants of the same crop species, which are off-type, i.e., phenotypically different from the plants of variety under certification. It is an important aspect of seed production and is necessary to prevent out-crossing and mechanical mixture. The off-type plants are regularly removed from seed fields either by uprooting or by cutting at ground level. The off-type plants may differ in plant height, leaf characters, flowering time, maturity etc.
- Special Operations Seed production in certain crops may require some special operations. For example, hybrid maize seed production may require detasseling of plants of the female parent before they shad pollen. Further, in hybrid seed production, the rows of male parent are harvested before those of female parent to avoid mechanical mixture.
- Harvesting
References:
1. Allard, R.W. (1960). Principles of plant breeding. John Wiley and Sons, Inc., New York.
2. Sen, S. and Ghosh, N. (2012). Seed science and technology. Second Revised and Enlarged Edition, Kalyani Publishers, New Delhi.
3. Singh, B. D. (2015). Plant breeding principles and methods. Tenth Revised Edition, Kalyani Publishers, New Delhi.
About Author / Additional Info:
I have completed M.Sc. (Ag.) degree from S.K.N. Agriculture University, Jobner.