Contributors to this page: T.T. Chang Genetic Resources Centre-IRRI, Philippines (Ruaraidh Sackville Hamilton, Ken McNally, Flora de Guzman, Renato Reaño, Soccie Almazan,Adelaida Alcantara, Elizabeth Naredo); WARDA, Cotonou (Ines Sánchez); UPLB-University of the Philippines at Los Baños (Teresita Borromeo).
Provides guidelines and recommendations about the best practices for the daily management of genebanks, describing when and how field genebanks should be used for rice. Best practices are shown in a pale blue color with bullets. Justification for each best practice is given within brackets (…).
When should be used?
Rice field banks conserves rice as live plants in the field or screenhouses.
- When cultivated rice seeds have low viability or low seed stocks.
- When wild rice or related genera do not produce enough seeds for storage (this is the case of O. longistaminata, O. neocaledonica and related genera such as Leersia at IRRI).
- When wild rice or related genera do not flower in the conditions of the genebank (this is the case of O. schlechteri and related genera such as Potamophila and Zizaniopsis at IRRI).
- When wild rice relatives have special needs, where different species require different cultural practices (Oryza granulata and Oryza meyeriana for example, need partial shading and special soils, because they are originally from forest regions, whereas most of the other species need to be kept soaked because they are originally from swampy areas).
There are more than 20 different species of wild rice scattered across tropical Asia, Africa, Latin America and the Caribbean that need to be well conserved. These species are from a rich pool of diversity from different habitats, from sunny open lands to shady forests.
At the IRRI genebank there are more than 3000 potted wild rice specimens being conserved in a large screenhouse.
How should be done?
- It recommended that distinct and completely independent areas are used for cultivated and wild types (to avoid the risk of mixtures with the highly invasive wild species).
- It is advisable to grow them in individual pots or special propagation beds, inside quarantine screenhouses.
- Perennial species should be maintained as living plants when seeds are difficult to produce.
- (look for more recommendations)!!
Sample and storage specifications
Field bank for cultivated rice:
- Seeds should be germinated in flat seed boxes and transplanted to concrete beds after 21 days or when seedlings are vigorous enough and can withstand stress upon transplanting.
- The concrete beds can be small ‘field-like’ lowland plots constructed inside the screenhouse, about 2.5m wide and 11m long, like the ones used at IRRI.
- Soil preparation can be done by a mechanical mini-hydrotiller after re-shoveling manually.
- Use 500g of complete fertilizer mixed well with the soil as basal fertilizer application before final soil leveling and lay-out.
- Transplant 2-3 seedlings per hill using 25cm spacing between hills and between rows, leaving one row vacant between entries in the lay-out.
- For insufficient seedlings (1-3 seedlings), transplanting should be done in pots to ensure the continuous growth of the plant.
- In these cases, additional care should be extended in plant maintenance, such that daily monitoring of plant health.
Field maintenance and management
- Spray a pre-emergence herbicide and a granular insecticide applying a day after transplanting.
- Do a top dressing at 30 and 45 days after transplant with 350g and 300g of ammonium sulfate, respectively, for the indica and javanica types.
- For the japonica types, top dressing should be done earlier at 10 and 20 days after transplanting because spikelet fertility is highly affected.
- Maintain the water level until panicle initiation. For the upland types, water should be withheld 30 days after transplant to provide drier soil conditions.
- Regular monitoring of pest and disease incidence should be coordinated with the plant health experts and specific control measures applied when needed.
- Panicle harvesting is observed for easy handling and verification.
- Harvested panicles should be dried and kept in the drying room for 2 weeks before finally hand-threshing.
Field bank for wild rices:
Choice of environment
- Most accessions of wild rices require different cultural management practices for seed increase compared to those of the cultivated rices.
- Most of them are strongly photoperiod-sensitive so that the best time to grow them is during a season with short daylength to induce panicle initiation.
- Several species such as O. meyeriana, O. granulata, O. ridleyi, and O. longiglumis grow better under partial shade, while others grow well under full sunlight.
- Consequently, they need to be grown in 30cm wide-mouthed pots without holes.
- Wild species are also known to have stronger dormancy than the cultivated species.
- Plant the germinated seeds 1-2cm apart, in a seed box containing moist, fine, clean (preferably sterilized) soil mixed well with appropriate amount of ammonium sulfate.
- Apply a granular insecticide (e.g. Furadan) 3-4 days after planting to protect the seedlings from ants and other insects.
- Water the seedlings carefully with a fine spray, and grown them under partial shade until a week before transplanting.
- Transplant the seedlings 30 days after sowing to water- tight pots with good quality soil mixed with about 5g of complete fertilizer.
- Maintain the water level to at least 1cm depth.
- For species of the O. meyeriana complex, the seedlings should be transplanted into pots with light soil and good internal drainage to prevent water logging as they thrive best in mesophytic conditions.
- For the highly stoloniferous species, such as O. schlechteri and some related genera like Luziola, Leersia, and Hygroryza, a modified flat bed should be constructed and used for growing and maintaining a single accession.
- The pots should be laid-out at least 100cm apart to provide sufficient ventilation between plants and enough space for plant management.
- All species of the genus Oryza grow well under full sunlight except members of the O. meyeriana complex and O. ridleyi complexes which are best maintained in partial shade.
Field maintenance and management
- A granular insecticide (e.g. Carbofuran) should be applied 7 and 14 days after transplant to protect the plants against hoppers and defoliators.
- Top dressing is recommended at 30 and 45 days after transplant with 5g ammonium sulfate per pot.
- For O. meyeriana complex, 2g of ammonium sulfate should be applied weekly during 3 weeks, 30 days after transplant.
- Plants should be watered daily.
- Plant health should be monitored regularly.
- Appropriate control measures should be applied to specific pest and diseases once symptoms appear.
- Maintaining the cleanliness of plants also helps preventing the spread of diseases.
- When purelines are to be developed, only 1 plant per pot should be maintained and spaced widely, preferably alternating species of different complexes.
- If a bulk population of seeds is required, 2-3 seedlings per pot should be transplanted and all the plants should be maintained.
- At the late vegetative stage, (about 60 days after transplant) the tillers should be tied loosely with for example an abaca twine to a bamboo stake (5cm x 2m) to prevent plants from encroaching from one pot to another, at the late reproductive stage, to facilitate panicle bagging.
- Panicle bagging is necessary for handling wild rices to minimize outcrossing, to prevent seed loss due to shattering, and to prevent mixtures at harvesting.
- Panicles should be bagged a week after full panicle emergence using nylon net bags which provides ample ventilation to facilitate anther dehiscence and prevent mold formation on glumes.
- For species with shorter panicles, glassine bags are a good substitute.
- The net bag should be pinned to the bamboo pole.
- Prior to bagging, labels should be prepared using shipping tags written with plot number and date of bagging with indelible ink.
- The labels must be attached inside the net bags.
- The panicles should be harvested 30 days after bagging or when most of the seeds have shattered.
- If sufficient seeds are obtained, the plants should be discarded and disposed through burning.
- However, for species with low seed set like O. rufipogon and O. longistaminata, the plants should be ratooned by cutting about 20-25 cm from the culms base, a little amount of ammonium sulfate should be applied and plants should be maintained until the next flowering to maximize seed production.
- After harvesting, the panicles should be dried and kept inside the drying room for 2 weeks, before carefully hand-threshing and cleaning the seeds.
Disposal of contaminated materials
To ensure plants do not spread by seeds or rhizomes, specific measures should be followed:
- Do the seed multiplication of all wild rices inside the screenhouse in pots.
- Designate a disposal area (a pit about 3-4 meters deep from the surface ground) for burying discarded and burnt samples.
- Provide a modified incinerator or burning facility to accommodate burning activities especially during the rainy season.
- Cover all drainage canals inside the screenhouse with fine-mesh screens to further control dissemination of seeds through water.
- Waste materials from the canals should be regularly hauled, burned, and buried.
- If sufficient seeds are obtained, old plants should be discarded, burned and buried into the pit.
- Excess planting materials (seeds, seedlings, rattooned tillers) should be collected, burned and buried after seeding, transplanting and/or replanting.
- Discarded soil used in growing should be treated with herbicide and buried in the designated area.
- Before filling up all the discarded materials, the disposal area should be treated with a non-selective herbicide (e.g. glyphosate).
- Screenhouse staff should be advised to change their working clothes to minimize dispersal of seeds when they leave.
- Hand threshing and seed cleaning should be done in a specified room in the Seed Processing Area.
- All dried leaves/straws, unfilled grains, mixtures and off-types must be collected, burned and buried.
- The access to screenhouses should be regulated depending on the nature/importance of the visit.
Note: These protocols were defined for the conditions at IRRI in Los Banos. Modifications and adjustments should be done (and re-adjusted regularly) to determine the best conditions for individual species. Screenhouse facilities should also be continuously upgraded to suit their specific needs. However, understanding plant morphology and knowledge on the natural growing habitat of the different species are significantly important in the initial seed multiplication of this germplasm. These will provide the necessary information on how to properly manage the species.
Routine monitoring methods
- Survival rates.
- Plant vigor.
- Pests and diseases.
- Replacement by other weeds.
System for tracking materials/inventory system during field bank storage
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Recording information during field bank storage
References and further reading
International Rice GeneBank Operations Manual
Rice Knowledge Bank