QUALITY SEED PRODUCTION

Seed may be defined as fertilized mature ovule that possesses an embryonic plant stored food material covered by a protective coat or coat which is viable and has capacity to germinate under favorable environmental conditions. Seed quality is the possession of seed with required genetic and physical purity that is accompanied with physiological soundness and health status.

Seed is a primary input in crop production, whether agriculture is practiced at commercial or subsistence levels, by large or small-scale producers, or in favorable or less favorable environments. It is also a means for delivering new agriculture-based technologies to farmers. Since seed quality is one of the main factors that affects crop production potential it should reach farmers in a good quality state. ‘High quality seed’ can be broadly defined as‘ seed of an adapted variety with high genetic varietal, species, and physical purity; high germination and vigor; free from seed-borne pests (fungi, bacteria, viruses, insects, nematodes, parasitic weeds); and properly cleaned, treated, tested and labeled’. Seed quality is a multiple. QUALITY SEED PRODUCTION351concept comprising of several components each with a relative importance under assets of circumstances. In general, seed quality comprises many aspects where four key attributes maybe explicitly identified:1. Genetic quality—the inherent genetic make up of the variety contained in the seed which provides the potential for higher yield, better grain quality, and greater tolerance to biotic or abiotic stresses;2. Physiological quality—the viability, germination and vigor of seed which deter-mines the potential germination and subsequent seedling emergence and crop establishment in the field;3. Physical quality—freedom from contamination with other crops, common and particularly noxious and parasitic weed seeds, seed size, seed weight and seed lot uniformity;4. Health quality—absence of infection/infestation with seed-borne pests (fungi, bacteria, viruses, nematodes, insects, etc).However, seed quality can be affected by environmental conditions under which the crop is grown, the cultural practices used for production such as soil conditions, nutrient deficiency, water stresses, extreme temperatures and pests as well as the handling operations.

REQUIREMENTS FOR SEED PRODUCTION

Seed is a living biological product that requires special attention and care to ensure the varietal, physical, physiological and health quality. Maintaining seed quality is essential if the variety is to meet the expectation of farmers and consumers. Seed producers should be quality oriented and aware of the legal and administrative requirements for growing a crop for seed, and ensure that all operations are carried out strictly under specific guidelines in a timely fashion. The quality of the seed can be ensured only by following the combination of key regulatory control, administrative measures, and technical procedures. The regulatory measures include a framework of:

(1) establishing variety release systems to allow only superior varieties enter commercial seed production,

(2) defining the category for seed production by limiting the number of generation to minimize contamination,

(3) setting appropriate field and seed standards that need to be met during seed multiplication, and

(4) establishing a mechanism or agency to oversee the enforcement of regulatory framework.

The quality control agency by establishing administrative guidelines and technical procedures plays a supervisory role for smooth operation and implementation of the program and for enforcing the regulatory measures to maintain the quality of seed produced. The administrative measures may include the registration of seed growers, producers, processors, and suppliers as well as the implementation of the certification scheme through field inspection and seed testing through a robust quality assurance system. Seed production should be strictly monitored throughout the entire crop growth period, from planting through harvesting, cleaning, storage and marketing. Key technical components for producing quality seed may include:

(i) selection of production sites to avoid high risk environments;

(ii) selection of clean field to eliminate volunteer plants from preceding crops (previous cropping) and to avoid build-up of noxious weeds and soil-borne pests;

(iii) isolation from sources of contamination (genetic or physical);

(iv) rouging to remove off-type contaminants;

(v) maintaining the cleanliness of farm machinery during planting, harvesting and transportation;

(vi) maintaining the cleanliness of processing machinery to avoid admixtures during cleaning, treatment,

(vii) provision of adequate storage facilities to protect against damage from insect pests and maintain quality;

(viii) production arrangements by selecting specialized contract seed growers.

The following sections deal with variety release and variety maintenance as well as techniques in seed multiplication, seed cleaning, seed treatment, seed storage, and seed quality assurance.

VARIETY TESTING AND RELEASE

New and potential promising variety, once identified by agricultural research institutes, it is customary to release and make it available to farming communities. The term ‘variety release’ encompasses several broadly interrelated activities from identifying promising lines and submission for further testing by a competent authority to releasing a new variety to end users by making available the breeder seed for further multiplication. It is a mechanism to safe guard against release of varieties with uncertain performance to protect the farmers and the industry. Consequently, new lentil varieties must pass through a series of simultaneous evaluation i.e. registration and performance testing before they are officially released to enter large-scale commercial seed production and supply.

Variety Testing Performance testing are often referred to as ‘variety trials’ which focus on the value for cultivation and use (VCU) of the variety, i.e. the benefit of the new variety to crop producers (farmers) and end users (industry, consumers). Performance trials are conducted at multi-locations in different agro-ecological zones with at least minimum of over two years to assess the adaptation and performance of the variety. The effects of different crop management practices are also assessed.

QUALITY SEED PRODUCTION

New varieties are compared with existing standard commercial varieties to measure their merits. Performance trials are usually run for three consecutive years. In some countries, however, the variety is further tested in on-farm verification trials underfarmer management conditions before final release (e.g. Ethiopia).A registration testing is a descriptive assessment, establishing the distinctness, uniformity and stability (DUS) of the variety. Morphological, physiological, cytological, chemical characters or presently molecular techniques are used to establish the varietal identity by assessing the distinctness, uniformity and stability. In these tests, new varieties are compared with a wide range of existing varieties. At the end, the variety description is prepared and differences with other varieties established. The registration testing is usually conducted for a minimum of two consecutive seasons in at least one location where the variety will be released and commercialized. The International Union for the Protection of Plant Varieties(UPOV) has published test guidelines (http://www.upov.int) for morphological description of lentil (UPOV, 2003).4.2. Variety Release Variety release is a culmination of several interrelated activities where a decision could be taken to approve a new variety for commercial use based on the results of registration and performance tests. Almost all countries have a variety release procedure in place whether that is done by an ad hoc committee or legally sanctioned independent authority. The varieties that meet the requirements for registration and performance are officially released and the owner of the variety makes breeder seed available for commercial seed multiplication and marketing. The way variety release procedures and protocols are organized and conducted and extent the breeders are involved is described as compulsory or voluntary system. In a compulsory system (e.g. EU), the governments strictly regulate the introduction of new varieties, prohibiting seed production and marketing until the variety is tested and meet all the requirements by a competent government agency and approved by the release committee (Gisselquist and Srivastava, 1997). In a voluntary system (e.g. USA), the responsibility of releasing a variety is at the discretion of the breeders or breeding institutions which introduce and commercialize the variety. The breeder will be responsible to provide supporting data to prove the merit of the variety on voluntary basis.4.3. Variety Registers The new variety, upon approval, will be listed in a variety register to inform the stakeholders i.e. seed producers, farmers and the industry. The list could be informative or recommendatory. The register is periodically updated removing obsolete varieties and defining varieties that are currently eligible for commercial seed production at national or regional levels. Many countries have a national variety register (e.g. Crop Variety Register in Ethiopia) whereas the OECD has a 354BISHAW ET AL. common variety catalogue (http://www.oecd.org) which enables the variety to be produced and marketed in all member countries participating in the OECD Seed scheme.

Harmonizing Variety Release System

Variety release procedure is a collective term that refers to the release type, the attached terms and conditions, the protocols and administrative procedures used in releasing a new variety for seed production and distribution to farmers (Delouche and Gomaa, 1999). In many developing countries the NARS receive almost similar breeding lines supplied through a network of IARCs. Despite certain similarities in the agroecology, farming system and germplasm there is no mechanism for sharing of data in making decisions for variety release even among neighboring countries. In principle the procedures for variety testing, registering, and releasing are essentially similar in most countries. This provides an opportunity for developing testing protocols, sharing data and developing flexible and harmonized variety release schemes within regional or international contexts to make available a wider choice of varieties to farmers. In Turkey, foreign registered varieties from member countries of EU, OECD and UPOV are exempted from DUS testing and accepted as part of the variety release procedure. It is highly desirable for policy and regulatory frameworks to encourage countries to move from mandatory to voluntary and from single-to multi-country lists in variety release system (Gissel quest, 1997); this will increase the choice and movement of varieties to harness the impact of plant breeding research at national and/or international levels.

CONTAMINATION OF VARIETY

Seed production follows a generation system where a small quantity of ‘parental material’ or ‘nucleus seed’ received from breeders is systematically multiplied into larger quantity of certified seed for distribution to farmers. In the process the seed is prone to several deteriorative factors reducing the genetic, physical and health quality due to progressive increase in the degree of contaminants over the years. Generally three types of contamination can be distinguished, viz: (i) genetic contamination, (ii) mechanical contamination, and (iii) pathological contamination. Genetic contamination arises from residual segregation, spontaneous mutations or undesirable natural out-crossing with other varieties, species or wild relatives as the case may be. Self-fertilizing crops like lentil often have small percentages of cross-pollination resulting in genetic contamination of the seed crop, whereas undesirable cross-pollination is a common feature in all cross-fertilizing crops, unless fields are adequately isolated. The spontaneous mutation rate is generally low, usually recessive and often difficult to detect. Mechanical contamination results from a very wide range of sources but is mainly due to insufficient cleanliness of fields (cropping history, crop rotation)and equipment (planters, combines, cleaners, vehicles, bags, stores) and inadequate measures to avoid such contamination (field selection, physical isolation, cleanliness). Pathological contamination occurs through infection particularly with seed-borne diseases which are exclusively transmitted by seed. Pathological contamination is usually caused by pathogens from the same variety, other varieties, other crops or weeds which spread the disease to normal plants or contaminate the seed lot. It could also happen due to gradual loss of tolerane of the variety to plant diseases.

CONCLUSION
In this way quality seed can be produced.

Writer: RAJAN KOIRALA (STUDENT, BSC AG 4th SEMESTER, PAKLIHAWA CAMPUS)