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.
