Introduction to Seed Science: Important Topic for NABARD Grade A and B, FCI AGM

NABARD Grade A and FCI AGM are the most significant exams in the field of agriculture. An aspirant preparing for these exams must not skip the important topics mentioned in the syllabus. One of the important topics in the Agricultural and Rural Development section is Introduction to Seed Science. In this article, we are going to cover the basic introduction to the topic important from the exam point of view. Let’s get started.

NABARD Grade A: WHAT IS A SEED?

A seed is an enclosed structure that holds an embryo or a miniature plant. It is a way of reproduction for all plants. The seeds of gymnosperms are exposed to the environment and are not protected by a structure known as the fruit. In contrast, the seeds of flowering plants are enclosed in a protective structure known as the fruit. It is capable of producing new plants if it is subjected to the proper environmental conditions, such as the right temperature and humidity.

CLASSES OF SEED

The Association of Official Seed Certifying Agencies (AOSCA) has defined these seed classes as follows: 

There are four generally recognized classes of seeds. They are

• Breeder seed
• Foundation seed
• Registered seed
• Certified seed

The basis of seed multiplication of all notified varieties/hybrids is the Nucleus seed.

• Nuclear seed: This is a seed that is 100 percent genetically pure and physically pure, developed by the original breeder/Institute/State Agriculture University (SAU) from simple nucleus seed stock. A pedigree certificate is issued by the producing breeder
• Breeder seed: The progeny of nucleus seed multiplied in a large area as per the directive of Department of Agriculture and Cooperation (DOAC), Ministry of Agriculture, Government of India. It is supervised under a plant breeder/ institute / SAUs. It is monitored by a committee consisting of representatives of state seed certification agencies, national / state seed corporations, ICAR nominees, and concerned breeders. A golden yellow colour certificate is issued for this category of seed by the producing breeder.
• Foundation seed: The progeny of a breeder seed generated by recognised seed producing agencies in the public and private sectors. It is supervised under the seed certification agencies, in such a way that its quality is maintained by defined field ad seed standards. Crop certification organisations grant a white certificate for foundation seed.
• Registered seed is the progeny of foundation seed that has been treated in such a way that its genetic identity and purity are maintained per the standards defined for the specific crop being certified. For this type of seed, a purple certificate is issued.
• Certified seed: The progeny of a foundation seed developed by registered seed growers under the supervision of seed certification agencies to maintain seed quality in accordance with minimum seed certification requirements. The seed certification agency issues a blue certificate for this type of seed.

DIFFERENCE: CERTIFIED SEED AND TRUTHFUL LABELLED SEED

NABARD Grade A: TYPES OF SEEDS ACCORDING TO FREEZING

The two types of seeds according to freezing are:

• Orthodox Seeds
• Recalcitrant Seeds (Unorthodox Seeds)

Orthodox Seeds

Orthodox seeds are long-lived seeds that can be easily dried to moisture contents as low as 5% without harm and can withstand freezing. As a result, orthodox seeds are also known as desiccation-resistant seeds. In addition, low moisture content and freezing temperatures can extend the life of orthodox seeds. Ex-situ conservation of orthodox seeds is not a problem.

Many annual and biennial crops are examples of Orthodox seeds. Citrus aurantifolia, Capsicum annum, Hamelia patens, Lantana camara, guava (Psidium guajava), cashew (Anacardium occidentale), and most grains and legumes are examples of Orthodox plants.

Depending on the species and storage conditions, the lifespan or life cycle of orthodox seeds can range from over a year to several hundreds of years. The case of a 2000-year-old Judean date palm seed that was successfully sprouted in 2005 is a notable example of a long-lived orthodox seed that survived accidental storage followed by a controlled germination. However, the maximum survival time of properly stored orthodox seeds is unknown.

Recalcitrant Seeds (Unorthodox Seeds)

Recalcitrant seeds are remarkably short-lived, unable to be dried to a moisture content of less than 20-30% without injury, and unable to withstand freezing. Recalcitrant seeds are also known as desiccation responsive seeds. Recalcitrant seeds are difficult to store effectively, and ex-situ conservation is difficult.

Because of their high moisture content, they promote microbial contamination and result in faster seed degradation. Second, freezing the recalcitrant seeds allows the development of ice crystals, which destroy cell membranes and cause freezing injury. Therefore, plants that contain recalcitrant seeds must be stored in the growing phase (i.e., as growing plants) and propagated vegetatively.

Recalcitrant species include trees and shrubs from the tropics, as well as moist temperate areas and certain plants that grow in aquatic environments. Avocado, cacao, coconut, jackfruit, lychee, mango, rubber, tea, several horticultural trees, and some plants used in traditional medicine are some common examples of plants that grow recalcitrant seeds.

Recalcitrant seeds have a remarkably short life span. If kept in air, seeds of Acer saccharinum, Zizania aquatica, Salix japonica, and S. pierotti lose viability within a week. Other species’ seeds are only viable for a few weeks, months, or less than a year.

Intermediate Seeds

Many scientists have found that certain seeds do not completely adhere either to the ortho­dox or recalcitrant categories. Some of these seeds may be resistant to desiccation but are vulnerable to freezing temperatures. Citrus and coffee seeds can fall into this intermediate category.

ISOLATION DISTANCE OF SEEDS

The crop raised for seed production should be isolated from other fields of the same crop species by a minimum distance that differs by crop. This is referred to as the isolation distance. Isolation is essential to prevent pollination from unwanted pollen in cross-pollinated and often cross-pollinated plants, as well as to avoid mechanical mixture and the possibility of cross-pollination in self-pollinated species. The isolation distance varies from 3m in self-pollinated crops like wheat and rice to 200m in maize, bajra, and jowar and even 400m in jowar when isolated from Johnson grass (Sorghum halepense).

Minimum Isolation distance of different crops for seed production

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