Quality seed maintenance of pulses in view of resource conservation agriculture

Murleedhar Aski , S.K. Chaturvedi and Neelu Mishra

Indian Institute of Pulses Research, Kanpur 208 024

Introduction:The Food and Agriculture Organization (FAO) recognizes 10 primary and 5 minor pulses, which are cultivated worldwide over 105 countries. From the standpoint of production, dry beans (19.7 m t), fieldpea (10.4 m t), chickpea (9.7 m t), cowpea (5.7 m t), lentil (3.6 m t) and pigeonpea (3.5 m t) are the most important (FAO, 2010). Globally, pulses are the second most important group of crops after cereals. In 2009, the global pulses production was 61.5 million tons from an area of 70.6 million ha with an average yield of 871 kg/ha. Dry beans contributed about 32% to global pulses production followed by dry peas, chickpea, broad beans, lentils, cowpeas and pigeonpea. (Nadarajan, 2011). Developing countries contribute about 74% to the global pulses production and the remaining comes from developed countries.

Pulses Diversity in India: India grows such a variety of grain legumes which none of the countries in the world grows.  There are nine major grain legumes (chickpea, pigeonpea, urdbean, mungbean, horse gram, moth bean, lathyrus, lentil and peas) which together account for more than 95% of the total area under pulses.  There are 11 minor grain legumes viz. cowpea, broad bean, dry bean, rice bean, winged bean, adzuki bean, hyacinth bean, lima bean, jack bean, zombie pea and pillipesera, which are grown sporadically in isolated pockets. India is the largest producer (18.09 million tonnes in 2010-2011) and consumer of pulses in the world has low average annual productivity growth rate for most of the pulses. Grain legumes are an important source of dietary protein for many people in developing world with a protein content meanly twice as high as that in cereals. They are the cheap source of quality protein that complements the protein in cereals and thus enhances the nutritional value of cereal dominated diets.  Green pods of many legumes, tender shoots and leaves and roots in few legumes are consumed as vegetables.  The green stalks and dry straw form nutritious animal feed.  Through symbiotic nitrogen fixation, legumes play significant role in low-input agriculture by reducing the dependence on nitrogen fertilizers.  Thus, contribution of pulses to soil fertility is a key factor in sustaining the production of cereals in the rainfed dry areas in the developing world.

Seasonality of pulses in India: The pulses are grown in three distinct seasons viz., winter or Rabi season (November to April), rainy or kharif season (June to October) and spring/summer or zaid season (March to June).  Some to these crops are also grown in temporal niches overlapping two seasons partly or completely.  For example, late maturing pigeonpea covers both kharif and rabi seasons (June to April), some cool season grain legumes grown in plains during rabi season viz., peas, lentil, chickpea and dry bean (Rajmash) are cultivated during summer season in the low temperature regions of Himalayas.  The area under grain legumes during rabi season is larger than that during kharif season. The country may be divided into two major regions viz., northern and southern according to spread of growing season and the temperature variations available.  In northern region, the grain legumes cover larger area during rabi season (about 70%) than during kharif season (about 30%).  On the other hand, in southern region there is larger area under these crops during kharif season (about 75%) than during rabi season (about 25%).

These pulses are grown during rabi (chickpea, lentil and fieldpea: northern India, mungbean and urdbean: coastal India), kharif (mungbean, urdbean and pigeonpea) and spring/summer (mungbean and urdbean) in different parts of the country. The productivity of Rabi pulses is more than the kharif pulses as many more insect pests and weeds limit their production potential. Chickpea has made tremendous progress in terms of production and productivity increase over years. However, mungbean has made rapid advances in irrigated areas of north India as spring/ summer crops under intensive crop rotations and urdbean in rice fallows of southern and coastal states. Rising prices of pulses and government policies have motivated farmers to grow more pulses with care. As a result, there is increasing demand of quality seed of these crops. With the development of high yielding and diseases resistant varieties for different seasons and cropping systems and support from government policies, the demand for quality seeds is likely to increase considerably in future.

 Pulses statistics: In India, pulses were grown on 25.51 million ha area producing 18.09 million tonnes of the grain during 2010-11. Usually these crops are grown as rainfed on marginal soils. Since, less than 25% area is irrigated, the productivity of pulses remain less than 800 kg per ha at national level. The major producers of pulses in the country are Madhya Pradesh, Uttar Pradesh, Maharashtra, Rajasthan, Andhra Pradesh followed by Karnataka which together share about 77% of total pulse production while remaining 23% is contributed by Gujarat, Chhattisgarh, Bihar, Orissa and Jharkhand.

 Constraints in Quality seed production of pulses:  Among major production constraints, availability of quality seed of improved varieties has been a major constraint in enhancing production and productivity of pulses in India.  Despite a target of 10% of seed replacement rate we could not achieve even more than 7% at country level.  This is primarily due to lack of organized seed production programme for pulses. Still we do not have a proper medium term (4-5 years) seed rolling plan for major pulses producing states. The indent for breeder seed is quite low in many cases and that too is for old varieties. There is poor conversion of breeder seed to foundation and certified seed. Even true picture of conversion of breeder seed to foundation and certified seed is not available for most the states.  To insure timely availability of quality seed, capabilities of seed production must be enhanced with introduction of contractual obligation component by involving seed societies, farmers, private sectors and NGO’s besides SAU’s, IIPR and  State Seed Corporations. Participation of growers in seed production should be encouraged by way of simplifying the registration and seed certification procedures.

 Chickpea: Chickpea is grown on about 8.75 million ha covering almost all agro-ecological zones of the country and the maturity period varies (95-170 days) among zones. Therefore, it is imperative to produce the seed of a particular variety in its area of recommendation or in nearly states. The production levels and quality of seed produced is usually better in central and northern India than the coastal areas of the country. The fields free from weeds, diseases, salinity and water logging ensure better quality of nucleus and breeder seed of high yielding varieties.

 Mungbean: Since, mungbean can mature just in 60-70 days in most of the seasons and area, area is increasing in northern India as summer/ spring season crop between wheat and rice or after potato and rapeseed-mustard. The Overall demand for breeder seed of mungbean has increased considerably. For example, mungbean has tremendous potential for cultivation in Rajasthan and it has shown impressive area coverage from 3.66 lakh ha in 1991-95 to more than 9.80 lakh ha in 2009-10. Uttar Pradesh has shown positive growth rate for area under spring/summer whereas Maharashtra has also shown a significant increase in area in kharif season in during last 10 years.

 Urdbean: Urdbean is the third most important pulse crop of India cultivated over a wide range of agro climatic situations. The major urdbean growing states of the country are Maharashtra, Andhra Pradesh, Madhya Pradesh and Tamil Nadu. Development of short duration, photo-thermo-insensitive and disease resistant varieties has led to its cultivation as a sole or intercrop during spring season in north India and as a sole relay crop during rabi season in the rice fallows of the coastal peninsular India. Uttar Pradesh has shown progressive increase both in area and production. This occurred mainly due to the popularization of high yielding varieties and improved production technology. The demand for quality is increasing in most of the states.

 4. Pigeonpea:  Pigeonpea is a hardy, widely adapted and drought tolerant crop with a large temporal variation (90–300 days) for maturity. These traits allow its cultivation in a wide range of environments and cropping systems. In India, pigeonpea area and production have increased about 70% and 75%, respectively since 1950-51. However, productivity (~ 8 q ha^-1) has remained almost the same. During the period, traditional long-duration types (mostly grown in north-eastern plains) have been continually replaced by short- (northwest plains, central and southern India) and medium duration (mostly central and southern India) varieties. These varieties although improved in per day productivity are low yielder compared to long-duration types. This is one of the reasons why no breakthrough has been realized in the productivity of pigeonpea. The indirect impact of these improved early and medium varieties has been on enhancement of overall crop intensity. Bihar ranks first in productivity (12-12.5 q/ha). South and central zones which account for nearly 2/3^rd of the total area have productivity even lower than the national average yield. Since, pigeonpea crop is often cross pollinated (6-35% cross pollination), it becomes difficult or almost impossible to maintain genetic purity of seed at farm level.  Therefore, systematic seed production programme for high yielding varieties involving farmers and other stakeholders is of paramount importance for this crop because it may not be possible for government agencies to produce and supply quality seeds every year for huge area.

Seed multiplication ratio in pulses

Multiplication ratio helps in planning of breeder to foundation and certified seeds. The multiplication ratio of chickpea, lentil, fieldpea, mungbean, urdbean and pigeonpea is given below:

Crop	Multiplication ratio	Seed Rate
Chickpea	1:15	55-60 kg/ha: desi; 80-90 kg/ha : kabuli chickpea
Lentil	1:15	40 kg/ha : small seeded, 50 kg/ha: large seeded or for rice fallow/utera
Fieldpea	1:20	85-90 kg/ha
Mungbean/ urdbean	1:30	Kharif (12-1 kg/ha5) Summer/spring (20-25 kg/ha)
Pigeonpea	1:40	12-15 kg/ha

Best practices to ensure quality seed production: Production of high-quality seed is fundamental to modern agriculture. Most annual crops are established each season from seeds, and seed quality can have a major impact on potential crop yield. Seeds can serve as the delivery system not only for improved genetics but also for new planting and production methods and crop protection strategies that improve the overall efficiency of agriculture and reduce its environmental impact. The purity of any commercial product propagated by seed begins with the genetic purity of the seed planted. Genetic purity standards have been established by state seed laws and seed certification agencies to assure growers that the seed they buy is accurately labelled with the correct crop and variety. Seed purity standards also specify the percentage of contamination by seeds or genetic material of other varieties or species. The physical purity of seed refers to the presence and identity of weed seeds, and the percentage of other materials such as dirt or plant residues. In addition, the germination capacity of the seed in a standard test must be shown on the label. In some cases, seeds must also be tested for the presence of seed-borne diseases, and hybridity tests are conducted to confirm parentage in hybrid seed. Production of high quality seed is an exacting task. Seed producers take many steps to protect genetic integrity, including ensuring the integrity of their planting seed, properly identifying and labelling plants and fields, planting seeds on clean land which has not been used to grow the same crop in the recent past, removing rogue plants, or plants which are not true to the variety’s characteristics, and employing physical isolation – via net houses, distance isolation, time isolation or hand pollination – to ensure that pollination only occurs among plants of the desired variety.

1.Maintaining Genetic Purity: Genetic purity refers to the percentage of contamination by seeds or genetic material of other varieties or species.  The genetic purity of any commercial agricultural product propagated by seed begins with the purity of the seed planted. In general, the genetic purity of the seed planted must equal or exceed the final product purity standard required, as purity generally decreases with each subsequent generation of propagation. It is virtually impossible to assure that no off-type plants or pollen is present in the seed production field and that all handling and conveyance equipment and storage facilities are completely free of contamination. As a result, commercial planting seed is seldom 100% pure. In practice, practical seed genetic purity standards have been established by state seed laws and by seed certification agencies to ensure that the purchaser receives seed that is within certain purity tolerances. These tolerances are established based on the biology of the species (i.e., self- or cross-pollinated), the type of variety (i.e., open-pollinated, hybrid, synthetic), and market-driven standards for final product quality. Earlier generations of seed (e.g., foundation or breeder seed) have stricter standards in order to be able to meet the certified seed purity criteria. The main sources of contamination of a seed crop are the prior crop grown in a field, transfer of pollen from a nearby field, and mixtures during harvesting and handling.

2. Maintaining  proper isolation distance (mainly in hybrid pegionpea): To ensure that pollination occurs only among plants of the desired variety, fields must be isolated either by distance or flowering time from potentially contaminating pollen sources. 
The isolation required depends on flower characteristics, sexual compatibility with neighbouring crops, pollen quantity and viability, mode of pollen dissemination and purity standard required for specific class of seed. Self-pollinating crops such as rice or wheat require relatively small isolation distances of 0 to 30 feet because their flower characteristics limit movement of pollen among plants.

Isolation is primarily to prevent mechanical mixtures during harvesting. 
Cross-pollinating crops, on the other hand, can require distances greater than 1 mile (1.6 km) of isolation from sexually compatible plants to prevent out-crossing, depending upon the flower structure, the mode of pollen transfer, the duration of pollen viability, and the type of seed being produced (e.g., foundation versus certified or hybrid versus open-pollinated). Recommended isolation distances may need to be increased depending upon the economic impact of contamination.

For example, hybrid seed production or production of seeds in which contamination would be readily apparent (e.g., contamination of seeds for white onions with seeds of red onions) often requires greater isolation to achieve purity standards expected in the marketplace. Similarly, greater isolation is required reduce the likelihood that pollen from outside the field will introduce undesired traits intro the crop, such as biotech traits into an organic field. Isolation can also be achieved by planting crops at different times such that their flowering periods do not overlap. Border rows around the field that are not harvested with the seed crop can also be employed to intercept stray pollen and reduce contamination of the remainder of the field. Related weeds and volunteer crop plants or home gardens can also be sources of pollen contamination. Certifying agencies inspect fields and the surrounding areas to ensure that isolation standards are met.

3. Hybridity and varietal purity tests (mainly in hybrid pegionpea): Hybrid seed is seed produced by cross-pollinating plants in a controlled environment. Hybrids are bred to improve the characteristics of the resulting plants, such as better yield, greater uniformity, improved vigour, colour, disease resistance, and so forth. Today, hybrid seed is predominant in agriculture and home gardening, and is one of the main contributing factors to the dramatic rise in agricultural output during the last half of the 20th century. . Hybrid seed cannot be saved for replanting without losing the benefits of the original variety as these traits randomly segregate among the saved seed, not reliably producing true copies of the original variety.  New seed must therefore be produced for each planting.As genetic purity is a function of seed production, each hybrid seed lot must be testedfor parentage and purity. To achieve this, hundreds of seeds from each seed lot are planted and observed for uniformity in field tests. Protein and DNA molecular marker analyses are also widely used for hybrid purity testing. Protein analysis is often prefered because it is less expensive, but DNA tests are becoming increasingly affordable. Similar tests are applied to open-pollinated and synthetic varieties to assure varietal purity.

4. Seed enhancement: Seed quality or seed enhancement refers to various technologies used to increase the consistency in performance of the seed with respect to its vigour, leading to improved crop yield and quality of produce. In recent times with the availability of scientific information of various physiological aspects of the seeds and seed enhancement technologies in ensuring better protection against   diseases and insect pests at seed or seeding stage, improve seed vigour and modify seed emergence capabilities, it has become easier to enhance seed quality before its sowing to ensure higher yield with better quality produce. We all are aware of the pulses seed treatment with recommended fungicides and insecticides besides inoculation with rhizobium or PSB culture. Some of the other technologies becoming popular are listed below.

a. Seed coating: The application of materials on the seed surface to minimize diseases and insect pest incidence is mainly related to seed coating. The chemicals or bio-agents such as fungicides, insecticides, Trichoderma etc. are normally used for seeds coating of seeds of pulse crops. In developed countries film coating, in which the active ingredient is applied in a quick-drying polymer film around the seed, has gained popularity. A major advantage of film coating of the seed is that it ensures reduced loss of active material from the seed during seed transport and handling. This can be of value for rajmash and soybean seed in India, where losses in germination has been observed during transportation.

b. Seed pelleting: The technology is used to alter the seed surface properties to enable more precise seed singulation during sowing through seed drills and placement in the soil through other means. This helps in ensuring proper plant populations and avoids clustering of seedlings. Seed pelleting can also be used to deliver a range of beneficial additives like micro-organisms, micronutrients and plant protection agents e.g. trichoderma for pulses seeds. This technology can be of immense value for the crops like mungbean, urdbean, mothbean, clusterbean, cowpea, lentil, etc.

c. Seed priming: Seed priming is being used to enhance germination at fast rate and overcome seed dormancy. In seed priming, seeds are hydrated in a controlled manner to provide enough water to initiate the physiological processes of germination (imbibitions), but not enough to allow germination. After soaking of the seeds in desired or recommended solution these are allowed to dry and sowing is done in usual way. These primed seed ensure rapid and uniform germination from the soil compared to non-primed seed of the same seed lot. These differences are greatest under receding soil moisture or poor moisture retentive soils. Seed priming can be of utmost importance in lentil or chickpea when sowing is to be done as utera/paira or under late sown conditions as zero tillage. Even under late sown condition, primed seeds of chickpea and lentil helps in good growth and development of biomass.

5. Proper storage conditions for quality seeds: The storage of seeds in coastal or high humid area is a difficult task. For most of pulses, high quantity of seed is required for sowing in unit area; it becomes further difficult to store seeds in humid areas. Therefore, government should take initiative to develop infrastructure for safe storage of seeds and also maintains minimum stock for regular as well as contingent plan.

6. Human resource development: Human resource development programmes for maintenance of genetic purity, seed production procedures, safe storage and seed testing with minimum parameters of quality seed must be launched to ensure quality seed supply of pulses locally.

7. A formal seed supply system: A formal seed supply system characterized by a vertical organized production and distribution of improved and high yielding varieties, using strict quality control can further maximize the pulses productivity and it is estimated that quality seed can increase the yield levels by 15-25% in comparison to the yield of local seed available with farmers. The share of formal seed sector is about 3% as against the desired level of 10-15%. Visualizing the importance of pulses in human and soil health, it is utmost importance to stream line the seed multiplication chain of these crops.

 Protocol for quality seed production

A. Nucleus seed production (Mandal et al., 2010)

1.      Basic seed is required to be grown in a minimum area of 200 m² areas for base population for selecting true to the type single plants. The field should be uniform in terms of topography, moisture availability and fertility. The recommended inter and intra row spacing at 45 cm and 10 cm for mungbean and urdbean, and 90-120 cm and 20-25 cm for pigeonpea, respectively should be maintained. Weed free conditions should be maintained for quality seed production. Standard agronomic practices must be followed to raise the basic population.

2.      Select 1000-1200 true-to-type plants before flowering for mungbean and urdbean, and 100-120 plants for pigeonpea. The selected plants should be tagged and observed throughout the growing period and any plant showing variation should be rejected and uprooted before flowering.

3.      The selected tagged plants should be harvested separately.

4.      The seeds of individual plant should be table examined and if the seed of any plant does not confirm to the seed characters of the variety, it should also be rejected.

5.      Seed should be properly dried, treated with insecticide before storage.

6.      In the next cropping season, the individual plant progenies should be grown in rows following recommended inter and intra row spacing in a well prepared, homogeneous and disease free field having no water logging and salinity problems. An isolation distance of 5 m and leaving 1.5 m space after each bed in mungbean and urdbean seed production fields for a regular visit by the breeder and the monitoring team is desired for maintaining varietal purity. Similarly, 400 m isolation distance and 3 m space after each bed in pigeonpea for a regular visit by the breeder and the monitoring team is desired for maintaining varietal purity in pigeonpea.

7.      The reoriented package of practices for cultivation should be followed for getting higher seed to seed ratio.

8.      The individual plant progenies should be regularly visited and observed by concerned breeder right from germination to different growth stages. Any plant progeny deviating from the characters of the original variety or showing disease incidence in the field should be completely removed. In case of presence of even single off-type or diseased plant in the progeny, the entire plant progeny should be removed rather than rouging out single plant.

9.      The true to type single plant progenies should be harvested and threshed separately.  Due care should be taken at the time of harvesting and threshing to avoid any kind of physical mixture of progenies.

10.    The seed lot of individual progeny should be examined with reference to seed size, shape and colour etc. Any progeny showing deviation from the varietal seed characteristics should be rejected.

11.    The seeds of true to type progenies left after rejection both at pre and post-harvest stages should be bulked to be designated as nucleus seed.

12.    The seed should be dried to 10% moisture level and stored after treating with insecticide to avoid losses during storage.

13.    A grow out test can be carried out in the green house, if available or in the field to confirm the genetic purity of the seed lot. In grow out test, observations at vegetative, reproductive and maturity stages should be recorded which would help in identifying the genetic purity of the seed lot.

B. Breeder seed production

1.      The agency for breeder seed production is required to have the nucleus seed of the variety from the concerned breeder/Institute along with a list of specific characteristic/features of the variety.

2.      The nucleus seed is planted in a disease free, well prepared and homogeneous plot having recommended isolation distance from other field having same crop. The planting should be done as per sowing time prescribed for each zone and indicated in the text.

3.      Planting is done with the required seed rate leaving sufficient space after each bed for easy monitoring of the field. The plot should be managed as per the recommended package of practices of chickpea cultivation.

4.      The breeder should visit the plot at regular intervals to rogue out off-type plants before flowering.

5.      Harvesting should be done at the proper maturity. Precautionary measures should be taken at the time of harvesting and threshing to avoid mechanical mixtures. The simultaneous threshing of the two varieties should not be done.

6.      The seeds should be dried to 10% moisture level before storage, if required.

7.      Grow out test should be carried out as per the standard procedure, after taking samples from different lots to confirm the purity of the seed.

8.      The seed should be treated with insecticide to protect it from the store pests and be packed in properly labelled gunny bags.

9.      All the prescribed BSP Performa (except BSP I: allocation) should be sent to Project Coordinators, ADG (Seeds) ICAR; and Seed Division of DAC at the scheduled timings so as to complete the process effectively.

Perspectives: Pulses are the integral component of dry land farming system. Therefore, these crops are very popular as mixed crops, intercrops etc. Being the crops with short maturity duration they fit well under varying farming systems. There is need to established seed banks for difficult areas or where seed storage is difficult. Such areas are usually warm and humid (coastal) or prone to drought (Bundelkhand tracts of Uttar Pradesh, Madhya Pradesh and Vidarbha region of Maharashtra etc.) or flood (Assam, Bihar, Orissa and part of West Bengal). Most of the time performance of locally adaptive cultivars is stable hence farmers have more reliance upon these cultivars. There is need to insulate present day high yielding varieties against weather vagaries and major diseases and pest attack.

References

FAO, 2010. (Websitehttp://faostat.fao.org/)

N. Nadarajan (2011) Vision 2030.  Indian Institute of Pulses Research (IIPR) Kanpur-208024. PP 1-2.

A. B. Mandal, A. K. Sinha and S. Natarajan (2010) Nucleus and breeder seed production manual. Directorate of seed research (DSR) Kushmaur, Mau- 275101 (UP).  PP 66-70.