SEED SCIENCE AND TECHNOLOGY
SEED PRODUCTION PRACTICES FOR BEAN (Phaseolus vulgaris)
Bean (Phaseolus vulgaris) belonging to the family Leguminosae is a commercially important vegetable variety. It is one of the widely cultivated vegetable varieties. The seed production of this crop can be taken up in July – September and January – February.
Method of seed production
Bean is a self-pollinated crop. Cross-pollination occurs very rarely since self-pollination takes place before the opening of the flowers. To maintain the varietal purity an isolation distance of 25 metres for certified and 50 metres for foundation seed production is necessary from the fields of other varieties and of the same variety not conforming to the varietal purity requirements of certification.
Seed production stages
Breeder seed Foundation seed Certified seed
Land selection
The land selected should not be cultivated with other variety of the same crop in the previous season and should be free of volunteer plants. The land should be fertile with neutral pH. The soil should be light with proper drainage facility.
Seed selection and sowing
Certified seeds of good quality should be obtained from an authentic source. Seeds should be healthy with good germination percentage. Remove the off coloured and out sized seeds. The seed rate varies depending on the variety. It is 26 kg/acre (65 kg/ha) for bushy variety and 10 – 14 kg/acre (25 - 35 kg/ha) for pole varieties. Treat the seeds with powder form of Trichoderma viride @ 4 gms/kg or Pseudomonas @ 10gms/ kg of seeds. Seed treatment with Trichoderma or Pseudomonas protects the crops from disease causing microorganisms. Seeds can be soaked in diluted panchagavyam for 20 minutes and dried before treating with Trichoderma or Pseudomonas. After treating the seeds with these bio-control agents treat them with biofertilizer Rhizobium @ 600 gms/acre of seeds 24 hours before sowing to facilitate natural nitrogen fixation by plants. Mix Rhizobium in rice gruel and then mix it with seeds. Seeds should be dried under the shade for 15 minutes and then sown. Treated seeds are sown in double row of 30 cm apart with 1.5 metre distance between each pair of rows in a land prepared to fine tilth. Seeds should be sown in line method at a depth of 4 – 5 cm. A spacing of 60 x 10 - 30 cm should be followed for getting high yield and quality seeds.
Nutrient management
Farm yard manure @ 10 – 20 tonnes/acre (25 - 50 tonnes/ha) should be applied at the time of land preparation incorporated into the soil. Neem cake @ 30 kg/acre (75 kg/ha) and vermicompost @ 250 kg/acre (600 kg/ha) should be applied as basal manure. Enriched vermicompost (2 kg Azospirillum, 2 kg Phosphobacterium and 2 litres Panchagavya mixed with 250 kg vermicompost and kept covered for a week and then used) @ 250 kg/acre (600 kg/ha) should be applied 20 – 25 days after sowing as first top dressing. Second top dressing should be done 40 – 45 days after sowing using neem cake 15 kg and vermicompost 250 kg mixed with 200 gms ofasafoetida per acre (35 kg neem cake + 600 kg vermicompost mixed with 500 gms of asafoetida per hectare). During flower initiation stage 10% tender coconut solution (1 litre tender coconut water + 9 litres of water) should be sprayed. For rainfed cultivation replace the neem cake with pungam cake and apply all the above mentioned inputs only when the soil is wet.
Weed management
The first hand weeding is done in 20 days after sowing followed by the second weeding in 40 days after sowing. Weeding is not required after 60 days of sowing. If needed, then manual weeding should be done.
Irrigation
Irrigation is very important factor for good yield of seeds with high quality. The first irrigation is done immediately after sowing and the second irrigation is done 2 – 3 days after sowing. After this, the field is irrigated once in 8 – 10 days. Irrigation during flowering and pod filling stages are very critical.
Important operations
The shoot apex of the plants should be nipped off in 65 days after sowing in pole variety to increase the seed yield. * Pest and disease management: The pests and diseases like aphids, pod borer, yellow mosaic virus, stem blight, root rot and powdery mildew affects the bean crop at different growth stages. The management techniques for these pests and diseases are provided in Appendix – 1. * Roguing: Roguing should be done from vegetative stage to harvesting stage. The off-types and volunteer plants are removed based on the morphological characteristics like plant type, leaf, flower and pod colour etc. Off-types and diseased plants affected by leaf spot, stem blight, yellow mosaic virus should be removed from the seed field to maintain healthy crops. Plants of early and late flowering types should also be removed. * Field inspection: A minimum of two inspections should be done from flowering to fruiting stage by the Seed Certification Officer. The first inspection is done before flowering followed by the second during flowering and fruiting stage to determine isolation, off-types, volunteer plants and diseased plants etc.
Harvesting
The crop reaches the physiological maturity in 80 days after flowering. Harvesting takes place soon after the maturation of the seeds. Physiological maturation of the pods can be identified by change of colour from green to yellow. Matured pods should be harvested in two to three pickings. Harvest should not coincide with rains, because it will result in off coloured and dimpled seeds. Delay in harvesting will result in shattering of pods.
Threshing and processing
Harvested pods are dried under the sun light to attain a moisture content of 15 – 18%. Then the dried pods are beaten with pliable bamboo stick to separate the seeds. The seeds should then be cleaned by winnowing. Seeds are graded using 19/64” round perforated metal sieve. Seeds of different colour and sizes should be removed.
Drying and storage
Processed and graded seeds are further dried for 2 – 3 days under the mild sun light between 9 – 11 am and 2 – 4 pm to attain a moisture content of 8 – 10% for safe storage. Coating seeds with edible oil will prevent weevil infestation during storage. Seeds can also be treated with activated clay @ 1 kg/100 kg of seeds to control bruchid infestation. Under appropriate storage conditions, bean seeds can be stored for three years.
Seed standards
The percentage of maximum physical purity of foundation and certified seeds should be 98% with minimum germination capacity of 75%. The maximum moisture content should be 9%. The presence of inert material should not exceed 2%.