Expression of cotyledon necrosis in deteriorating soybean [Glycine max (L.) Merrill] seed
1997
Puteh, A.B. (Kentucky Univ. (USA). Department of Agronomy) | Tekrony, D.M. | Egli, D.B.
The occurrence of necrotic tissue on soybean seedlings has been associated with a decline in seed quality. This experiment was conducted to relate seed deterioration during storage to the expression of cotyledon necrosis and the performance of seedlings with cotyledon necrosis during germination and emergence. Seed lots of soybean cultivars Winchester, BE29, and Essex, untreated and treated with fungicide before storage or after storage were stored in a warehouse for 540 days. Cotyledon necrosis on seedlings following storage was evaluated in the laboratory (standard and accelerated aging (AA) germination) and during emergence in the greenhouse or field. As seed vigour (AA) declined during storage, the levels of cotyledon necrosis increased with the rate of deterioration inherently determined for each seed lot. Fungicide seed treatment before or after storage had little effect on the expression of cotyledon necrosis on seedlings during germination and emergence. Seedlings with cotyledon necrosis emerged more slowly in the greenhouse and field and had lower seedling dry weight during field emergence. Seed lots of the cultivar Stafford sealed in aluminium packets containing air or nitrogen were stored at 30 deg C for 119 days. Seed vigour declined with a concomitant increase in cotyledon necrosis during storage in both the air and nitrogen environments. When seeds of the cultivar Flyer were inoculated with bacteria cells isolated from necrotic cotyledons and stored in aluminium packets at 40 deg C for 15 days, the presence of bacteria on seeds did not influence the expression of cotyledon necrosis. The levels of necrosis occurring during storage were not affected by fungicide treatment, bacterial infection or a low oxygen storage environment. Thus, the expression of cotyledon necrosis on seedlings appears to be one of the earliest visual symptoms of declining seed vigour during seed deterioration and does not appear to be associated with seedborne pathogens
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