Causes of seed deterioration

 

Seed deterioration

Seed deterioration can be defined as the loss of quality, viability, and vigour either due to aging or the effect of adverse environmental factors. The rate of deterioration rapidly increases with an increase in either seed moisture content or temperature of storage.

Causes of seed deterioration:

        1. Mechanical Mixtures

It may often take place at the time of sowing, if more than one variety is sown with same seed drill. Two varieties growing side by side in the field are often mixed somewhat during harvesting and threshing operations. Often the seed produce of all the varieties is kept on the same threshing floor, resulting in considerable varietal mixtures. Combining or threshing equipment is often contaminated with seeds of other varieties, Further, the gunny bags, seed bins etc. are also quite often contaminated with seeds of other varieties.

        2. Attack of diseases

New varieties often become susceptible to new races of diseases, which are crop out of seed programs. Similarly, in species that are vegetatively propagated (e.g. sugarcane) there may be an accumulation of viral, fungal, and bacterial disease within some of the seed stock of variety. These are transmitted through the sets from one year to the next and results in disease spreading.

        3. Adulteration

Mixing of poor quality seed with good quality seed or mixing of seed of different varieties by some dealers of PSC and other seed merchants.

        4. Storage conditions

The viability of the seed rapidly decreases when the storage conditions are not ideal. The rate of deterioration of seed increases as the seed moisture content increase beyond 8 to 12% due to mold growth on and in the seed and higher respiration losses. Very low moisture contents (below 4%) may also damage seeds due to extreme desiccation.

Seed moisture contents cereals (%)	Storage life (years)
11 to 13	1/2
10 to 12	1
09 to 11	2
08 to 10	4

Stored grain fungi and bacteria are active above 75 and 90% relative humidity respectively. At high-temperature respiration losses are also high. Dry cool conditions are best for seed storage. For good storage %age of R.H. and storage temperature in Fahrenheit should add up to 100.