TO achieve the goal for its crop production improvement program, Northern Marianas College-Cooperative Research Extension and Education Service has been using test tubes in propagating various vegetable crops.
In the last couple of years, crop production improvement team leader Dr. Dilip Nandwani, agriculturist Isidoro Cabrera and research assistant Anthony Tudela have been producing a number of vegetables plants through tissue culture.
These include different varieties of sweet potato, taro and banana.
By adopting modern biotechnological tools to improve the CNMI’s agricultural production, NMC-CREES, which has been conducting research and extension activities in agriculture since its establishment in 1987, hopes to provide local farmers with more varieties of planting materials.
Plant tissue culture is the science of growing plant cells, tissues or organs extracted from the mother plant and grown on artificial media in sterile conditions. It includes techniques and methods for research into botanical and agriculture disciplines.
The grant for this, along with other projects, came from the U.S. Department of Agriculture.
New germplasm and varieties of banana, sweet potato and taro produced through tissue culture have been introduced from regional germplasm institutions, such as the Secretariat of the Pacific Community and USDA for field trials at the As Perdido Agriculture Experiment Station.
For sweet potato there were 17 varieties propagated through test tubes.
To obtain the best results, Nandwani, Cabrera and Tudela used tissue culture plants from 17 varieties obtained from the Secretariat of the Pacific Community. These varieties proved to be disease-free and tolerant to insect pests, and to have superior agronomic characteristics.
Tissue culture involves the following steps:
One-half-inch-long sweet shoot tips collected from field-grown plants and washed with running tap water in the lab are dipped into Clorox solution for about 10 minutes. Then the shoot tips are transferred to a growth medium in a clean, microbe-free environment in sterilized containers and kept in a controlled environment. Over a few weeks, the shoot tips will produce tiny buds which will develop into plants.
After a while, these sweet potato shoots will be hardened in a green house to be finally transplanted in the field.
For trials, NMC-CREES multiplied tissue cultured plants in its laboratory, and sent them to Tinian and Rota for preliminary trials.
Growing sweet potato
The production of sweet potato requires a great deal of effort and good cultural practices, according to Nandwani.
Good seed stocks, suitable soil and careful harvesting will help produce a yield that is approximately 2 to 3 pounds per plant on average.
Sweet potato, Nandwani said, grows best in well-drained, sandy loam or silt loam soil with surface and internal drainage aeration. Plants grown in poor soil produce large, misshapen, cracked and rough-skinned tubers. To reduce soil-born diseases, the crops should be rotated every three years.
Sweet potato does not need too much water. Rainfall during the rainy season in the CNMI is adequate. Only during dry season should they be irrigated.
Local varieties are well-adapted to the CNMI’s soil and climate conditions.
NMC-CREES has been testing introduced varieties throughout Saipan, Tinian and Rota to find the most suitable variety in regards to market reference.
The producer still has to choose the best planting materials from disease-free soil to obtain maximum yields and profits. Only through maintenance of seed stock can one achieve a sustainable harvest year after year.
Prior to planting, new bedding materials should be sterilized with an approved fumigant. Beds should be fertilized with a complete fertilizer which should be mixed into the soil. Slips should be set deep, with at least three nodes below ground level. Spacing between plants should be approximately one foot with three feet between rows. Too wide or too close spacing results in structure deformities in tubers such as excessive size, rough tubers with cracked skin or undersized roots.
Depending on variety and marketable size, sweet potato can be harvested after three to five months. Sweet potato can be stored for storage and curing in the same containers that were used for harvest. Harvested roots can be stored without washing them for later marketing or seed stock in a proper ventilated and humid place at about 60 degrees Fahrenheit or 15.5 Celsius.
