The Journal of Horticultural Science & Biotechnology
Vol. 45 No: 1
Effect of Heat-Treatment for Virus Attenuation on Tomato Seed Viability
High-temperature storage of tomato seed reduced viability to 50% after 112 days at 70° C., or 25 days at 80° C., or about 1 day at 90° C. Viability was above 90% after 70 days at 70° C. or 18 days at 80° C. These responses were independent of seed age, and varietal differences were negligible.
Seed moisture content is critical during heat-treatment. Seeds sealed in glass tubes at 6% moisture content (air-dry) were nearly all killed in less than a day at 70° C., and wet seeds (52% moisture content) kept at 70° C. were only 56% viable after 24 hours. Care must therefore be taken not to place moist seeds in the oven, nor to restrict the rapid loss of seed moisture (down to 1 .3%) which occurs when seed is transferred to the oven.
From previous published work, it is estimated that heat-treatment for 70 days at 70° C. attenuates tobacco mosaic virus (TMV) ten-thousandfold. Considerably better control of seed-borne TMV can therefore be achieved by heat treatment for longer periods than now recommended, without adverse effects on germination or on plant growth and development. TMV-infected seed withstands heat treatment like healthy seed.
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