Field bank for wild rice and related genera genetic resources

Contributors to this page: T.T. Chang Genetic Resources Centre-IRRI, Los Baños, Philippines (Ruaraidh Sackville Hamilton, Ken McNally, Flora de Guzman, Renato Reaño, Soccie Almazan, Adelaida Alcantara, Elizabeth Naredo); WARDA, Cotonou, Benin (Ines Sánchez); UPLB-University of the Philippines at Los Baños (Teresita Borromeo).

When are field banks (in vivo collections) used

• For wild rice species or related genera that produce recalcitrant seed or no seed.
  • This is the case of O. longistaminata, O. neocaledonica, O. granulalta, O. meyeriana and related genera such as Leersia at IRRI, that do not produce enough seeds for storage.
  • Porteresia coarctata has recalcitrant seeds.
• When wild rice or related genera do not flower in genebank conditions.
  • 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 screen house as living plants.

Establishment of field genebanks (in vivo collections)

• Perennial species should be maintained as living plants when seeds are difficult to produce.
• Plants must only be grown inside contained facilities (e.g. glasshouse or screen house), in compliance with national biosafety regulations, to prevent their escape as a weed.

Sample processing and viability in field banks (wild rice and related genera)

Contributors to this page: T.T. Chang Genetic Resources Centre-IRRI, Philippines (Ruaraidh 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 the most important procedures for sample processing and viability in field genebanks for wild rice and related genera. Best practices are shown in a pale blue color with bullets. Justification for each best practice is given within brackets (…).

Cleaning propagules/seeds in field banks

Source of planting materials in field banks

• Use seeds treated with additional care to assure germination and survival.

Visual inspection of plant materials

• Check the materials carefully for pest or disease contamination.
• Consult the health diagnosis menu for specific details about pests and diseases.

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.

Routine monitoring for field banks

Methods and frequency

• Survival rates - Check survival monthly (some germplasm that have to be maintained in a field genebank are perennial and regular monitoring is important to ensure survival).
• Vigor - Record vigor monthly.
• Pests and diseases - Inspect for pests and diseases monthly (this is sufficient to identify any pests or diseases and rescue the plants in case of problems).
• Replacement by other weeds - Rogue plants of other species regularly and at flowering time. Check taxonomy at least once in a year.

Recording information during sample processing and routine monitoring in field banks

The following information should be recorded for each step:

• Accession number (an ID number).
• Genus (genus name of the plant, entered in full).
• Species (species name of the plant, entered in full).
• Field bank site name (a code to indicate the site of seed production).
• Plot number (the plot number at the production site).
• Date of monitoring (date when data is collected).
• Name of staff (name of staff recording the data).
• Damage [a score of 1-5 (where 5 is damaged) on amount of damage (insect, disease etc)].
• Vigor [assessment of vigor of the plants on a scale of 1-5 (where 5 is high)].
• Details of plants removed or destroyed (due to type mixtures or pests or diseases contamination).

Regeneration guidelines for wild rice and related genera

Contributors to this page: T.T. Chang Genetic Resources Centre-IRRI, Los Baños, Philippines (Ruaraidh Hamilton, Ken McNally, Flora de Guzman, Renato Reaño, Soccie Almazan, Adelaida Alcantara, Elizabeth Naredo); WARDA, Cotonou, Benin (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 the most important procedures to regenerate wild rice and related genera. Best practices are shown in a pale blue color with bullets. Justification for each best practice is given within brackets (…).

Storage specifications

Choice of environment and planting season

Climatic conditions

Preparation for regeneration

When regenerate?

• When stocks are below??

Pre-treatments

• Apply .... to break dormancy??

Method of regeneration

Sowing method

• Plant the germinated seeds 1-2 cm 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.

Transplanting

• Transplant the seedlings 30 days after sowing to water-tight pots with good quality soil mixed with about 5 g of complete fertilizer.
• Maintain the water level to at least 1 cm depth.
• A granular insecticide (e.g. Carbofuran) should be applied 7 and 14 days after transplant to protect the plants against hoppers and defoliators.
• 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 100 cm 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.

Different varieties of rice being grown inside an IRRI green house (photo: IRRI)

Crop management

Fertilization

Irrigation

Pest and disease control

• 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.

Thinning

• 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.

Harvesting

Panicle bagging

• 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 (5 cm x 2 m) 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.

Rice being grown inside an IRRI screen house. Notice the bagged panicles (photo: IRRI)

Panicle harvesting

• 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 two weeks, before carefully hand-threshing and cleaning the seeds.

Post harvest management

Disposal of contaminated material

Storage management

Documentation of information during regeneration

System for tracking material/inventory system during regeneration

• Use databases of stock and location (databases are needed to keep track of information).
• Use pegs, tags or barcodes for labelling:
  • Use impermeable ink and write clearly.
  • Plots must be well labelled to avoid errors.
  • Barcodes help avoid errors in recording.

Recording information during regeneration

The following information should be recorded for each step:

• Site name and map/GPS reference.
• Name of collaborator.
• Regeneration site name (a code to identify the site location).
• Plot reference (the plot number at the field site).
• Accession number; population identification.
• Name of staff (name of staff recording the data).
• Method of planting, date and spacing.
• Screen house layout used.
• Screen house management details (watering, fertilizer, weeding, pest and disease control, stresses recorded, others).
• Environmental conditions (altitude, precipitation, temperature, soil type and others).
• Number of plants established.
• Days from planting to flowering (note: this will only be important if seed collection is anticipated).
• Harvest date and method.
• Number of plants harvested.
• Comparisons with reference materials (record any identification numbers or references of any samples taken from the plots).
• Any evaluation undertaken during the growing period or at harvest.
• Post harvest (describe any relevant procedures).
• Others.

References and further reading