- H.J. Hope, R. Maamari, for Southwestern Ontario Agricultural Research Corporation (SWOARC), Harrow, Ont.
Evaluation Summary (Tech. Transfer Report Summaries)
View / Download Final Report [592 KB pdf]
Associated SWEEP/LSP Research
Completed: May, 1992
corn hybrids, no-till, emergence, cold tolerance, germination, early
growth, root growth, coleoptile
It has been shown that when no-till (NT) management is practiced with
grain corn, plant residues on the soil surface can accumulate, shading as
much as seventy percent of the soil from the warming effect of the sun.
Springtime soil temperatures are 4-8° C cooler than under conventional till
(CT) causing reduced seedling emergence and economic losses to farmers.
A rapid, efficient laboratory measurement of corn cold tolerance during
germination and early growth is needed to identify hybrids which germinate
and grow best under cool NT conditions.
Two series of low temperature experiments (I and II) were carried out
to do a detailed study (I) of germination on a small number of hybrids and
a less detailed study (II) on as many hybrids as time permitted using the
germination parameters identified in Series I as being the most efficient
predictors of NT emergence under cool conditions.
In Series I experiments, seven hybrids each from DeKalb and Pioneer plus
an internal standard, Pride 5, were studied. Germination was measured under
optimal conditions at 25° C. Root and shoot germination and also 1 cm shoot
production were studied in detail over a period of up to 45 days at 11°
C. Growth of seedlings at 12° C during 4 weeks in a growth chamber was also
Series II work focused on a survey of 126 hybrids chosen from the Ontario
Hybrid Corn Performance Trials. Germination under near optimal conditions
was verified at 25° C. Readings on days 5 and 6 of germination at 11° C
were done for root germination and on days 20 and 22 for 1 cm coleoptile
In addition to Series I and II, a brief report is included on a field
emergence experiment performed by a farm group in 1988. It was possible
to relate field emergence data on five DeKalb and five Pioneer hybrids to
laboratory data on time to produce a 1 cm coleoptile at 11° C.
Germination at 25° C was uniformly high, in most cases exceeding 90%
in both Series I and II experiments. Of the 126 hybrids studied in Series
II, only 4 were rejected for further study because of germination below
80%. The viability of hybrid seed from commercial sources was found to be
generally very good.
In Series I, growth at 12° C over 4 weeks in a controlled environment
chamber showed considerable contrast between hybrids with no potential to
grow at this temperature and those which grew steadily. Interestingly, the
check (internal standard), Pride 5, had the best genetic potential to grow
under these cool conditions. Leaf number, chlorophyll content, anthocyanin
content, plant vigour and root vigour were also studied but found not to
be as efficient predictors of cold tolerance over the four weeks of study
as root and 1 cm coleoptile production.
A detailed study of germination at 11° C over 45 days completed Series
I work. Data was analyzed using the SAS statistical package and correcting
germination curves for deviations from 100% viability using PROC PROBIT.
Time for 50% production of root, coleoptile and 1 cm coleoptile as calculated
by the probit routine was taken as the most representative measure of each
physiological response. The relationships among time-to-50% responses were
investigated statistically. A highly significant correlation of 1 cm coleoptile
production (r=0.814, p=0.0002) to coleoptile germination was found while
those to other physiological responses were not significant. Published data
(H.J. Hope et al, 1992. Can. J. Plant Sci 72: 83-91) on time to 50% 1 cm
coleoptile for 30 short-season maritime hybrids demonstrated a significant
correlation with field emergence. In addition, a significant correlation
(p=0.05) was found between time-to-50% 1 cm coleoptile production and the
difference between field emergence under NT and CT (1988 field experiment).
Further field work is needed to extend this limited comparison of laboratory
and field data on 10 hybrids to a larger more representative group.
In series II, laboratory germination at 11° C for 122 hybrids was studied.
Data on percent root germination after 5 and 6 days and 1 cm coleoptile
production after 20 and 22 days were compiled. The widest distribution of
data was found for roots on day 5 and for 1 cm coleoptiles on day 22. Using
these 2 growth parameters, several predictors of cold tolerance were investigated.
A weighting of three times as much for 1 cm coleoptile germination as for
root germination is predicted to be most efficient (see conclusion 5) pending
Time to production of a 1 cm coleoptile is the best of the predictors
of cold tolerance under NT management practices considered in this study
probably because it gives a measure of low temperature tolerance to both
germination and early growth. Use of this predictor allows easy identification
of the above average hybrids.
CHU ratings do not correlate with cold tolerance.
Seedling growth at 12° C does not predict good cold tolerance during
Rapid 1 cm coleoptile production correlates with minimal reduction
in emergence of hybrids under NT as compared to hybrids under CT in the
limited one year field trial from 1988.
Use of a cold tolerance rating is proposed as an efficient method of
identifying corn hybrids that will emerge well under cold NT soil conditions.
Field verification of this laboratory-derived rating calculation must
also be done on a subset of the hybrids tested in the laboratory to assure
the general applicability of the rating to hybrids grown in Ontario. Based
on a rating scale from 1 to 100, hybrids would be grouped into three cold
tolerance groups: 1 (very good), 2 (good) or 3 (average). A cold tolerance
rating for a given hybrid, based on laboratory measurements would be calculated
[(Day5 %-germination) + (3 × Day22 %-germination)]/4
(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank,
This study was initiated to determine how cold tolerance of corn hybrids
might best be determined. The objective of these determinations was to make
a predictor of successful field emergence available to growers who could
then select the hybrids best adapted to their individual no-till management
system. This report includes the findings of two sets of low temperature
experiments and also includes a brief report on a field emergence experiment
performed by a farm group in 1988.
In the first experiment 15 hybrids were studied. Germination was measured
at 25° C, root and shoot germination and 1 cm shoot production at 11° C
and seedling growth at 12° C. Germination was uniformly high, most exceeded
90%. The time to production of a 1 cm coleoptile was found to be the best
predictor of cold tolerance under NT management practices because it gives
a measure of low temperature tolerance to both germination and early growth.
The addition of time-to-root-germination as a second constraint serves to
identify the elite members within a population of above average hybrids.
In the second experiment one hundred and twenty-two corn hybrids were
evaluated during the summer of 1991. Results indicated that of the 122 hybrids
tested the majority germinated under average to better than average conditions
of temperature. At 25° C germination of 92% was observed. A broad genetic
range is found in the response of root and coleoptile to cold stress during
germination at 11° C. The study suggests that the cold tolerance predictor
be: [(1 × % Day5 germination) + (3 × % Day22 germination)]/4.
Significant correlation was found between time-to-50% 1 cm coleoptile
production and the difference between field emergence under NT and CT (1988
These studies have developed a cold tolerance predictor for corn hybrids
but field studies are needed to verify the results. It is essential that
recommendations do not come from this report alone but field data be used
as well. Cold tolerance is only 1 factor to consider when selecting a hybrid
- yield, stalk strength, etc., are also important.
Future Research: ( ) indicates reviewers suggestion for
priority, A - high, C - low.
(A) Verify the accuracy of the test with field evaluations of the hybrids
under no-till conditions. Continue to evaluate the hybrids on the Ontario
Corn Committee performance list and provide recommendations for farmers.
Thursday, May 19, 2011 02:17:37 PM