Reduced Germination and Vigour of Green Beans

Germination

Germination has been defined as the ability of a seedlot to produce normal mature plants under favourable conditions. For soybeans, favourable conditions are 95 -100% relative humidity at 25ºC. This is the major seed quality consideration used by seed companies to determine the suitability of seedlots. This information can be found printed on the seed bag tags of certified seed. Remember that stress conditions in the field often reduces field emergence compared to that in the lab.

Green soybeans from 2002 are very similar to yellow soybeans in appearance and have essentially the same protein and fat levels. However, germination and vigour appears to be significantly reduced. Of three varieties tested the average decrease in germination was 19%. Please see Graph #1 below.

Graph #1. Three different seedlots (varieties) were hand segregated into green (100% green) and yellow (100% yellow) samples. These samples were then tested for germination by an Ontario seed laboratory accredited by the Canadian Food Inspection Agency.

Vigour

A better predictor of stand establishment than germination is a vigour rating. Seed vigour is defined as the ability of a seedlot to have rapid uniform emergence of normal seedlings under a wide range of conditions. A vigour test (cold test), or more appropriately referred to as a stress test, usually involves placing seed in a growing medium at cool temperatures (5ºC - 8ºC) for seven days followed by seven days of warm (25ºC) temperatures. Due to possible post planting stress conditions such as cold wet weather a vigour test can more accurately predict a seedlots overall strength in the field.

Green soybeans from 2002 show a drastic reduction in seed vigour compared to yellow soybeans. Of three samples tested vigour dropped by an average of 38%. Please refer to Graph #2.

Graph #2. Three different seedlots (varieties) were hand segregated into green (100% green) and yellow (100% yellow) samples. These samples were then tested for vigour by an Ontario seed laboratory accredited by the Canadian Food Inspection Agency.

Conclusion

Excluding green seed, overall germination and vigour from 2002 is generally good. So if the seedlot in question has only a small percentage of green beans (5 - 10%) a drop in both germination and vigour of that small percentage will have little affect on the overall quality of the whole seedlot. Also, if the seed is certified the Seed Company has run quality tests. But if the seed in question is bin run and has a high percentage of green beans (30 - 60%) it is well worth doing a germination and vigour test for the relatively low lab costs involved. (Approximately $30 per sample.) Remember every good crop starts with good seed.

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