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Journal of Food, Agriculture & Environment Vol.7 (3&4) : 739-743. 2009
www.world-food.net
Screening various ryegrass cultivars for salt stress tolerance
Mohammad Pessarakli * and David M. Kopec
School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
*e-mail: pessarak@email.arizona.edu, pessarak@ag.arizona.edu
Received 17 May 2009, accepted 25 September 2009.
Abstract
Various ryegrass (Lolium perenne L.) cultivars [Covet, OSC129 (Covet II), Galileo, OSC127 (Galileo II), Michelangelo, Newton, Whitney and
OSC126 (Whitney II)] were studied in a greenhouse to evaluate their growth responses in terms of shoot and root lengths, shoot (clippings) fresh and
dry matter (DM) weights and grass general quality under salinity stress conditions. Grasses were grown hydroponically using Hoagland solution
No.1. Treatments included control and sodium chloride (NaCl) at various EC levels (2, 4, 6, 8, 10, 12, 14 and 16 dSm-1). The 8 ryegrass cultivars were
grown with 4 replications of each salinity treatment in a Randomized Complete Block (RCB) design trial. Shoot and root lengths and shoot (clippings)
fresh and DM weights were determined weekly. After the fresh weight determination, shoots were oven-dried at 60ºC and DM weights recorded. At
the last harvest, roots were also harvested and fresh weights were determined, then oven-dried at 60ºC and DM weights were recorded. Grass general
quality was daily evaluated at each stress level (one week growth period at each stress level). The results show shoot and root lengths and shoot
(clippings) fresh and DM weights of all the cultivars decreased linearly with increased salinity levels. However, at each salinity level, there were only
some numerical differences found in the shoot (clippings) lengths or fresh and DM weights of the various cultivars. In contrast, for all the cultivars,
under any level of salinity, the root length was more severely affected than the shoot length. There were significant differences in root lengths or fresh
and DM weights of various cultivars at each level of salinity. Grass general quality followed the same pattern (decreased) as the shoot (clippings)
lengths, fresh and DM weights. The canopy color of all the cultivars turned to lighter green at the higher levels (EC >6 dS/m) of salinity. Based on the
results of this study, all the cultivars exhibited a high level of salinity tolerance.
Key words: Ryegrass, cultivars, salinity, stress, tolerance, shoot, root, grass quality.
Introduction
Salinity stress is one of the major issues in agriculture and turfgrass
management, and almost nowhere the plants/turfgrasses are
immune to the adverse effects of salinity. Therefore, to find the
most tolerant turfgrass species/cultivars to salinity stress and
their uses under such conditions would probably be one of the
most logical and effective solutions of the salinity stress problems.
Researchers are continuously working on finding the most tolerant
plants/crops 1, 2, 4, 5, 7, 13-18, 21, 25, 34 and turfgrasses species/cultivars 3,
8-12, 19, 20, 22-24, 26-33, 35
to environment stresses (i.e. salinity and drought).
Using proper types of turf species/cultivars for cultural practices
under such conditions will prevent unexpected surprises and
unwanted results. This is a critical issue in agricultural/turfgrass
management/cultural practices, particularly considering the
turfgrass managers growing concerns on the adverse effects of
any stress on plants/grasses growth and development.
There are numerous new turfgrass cultivars continuously
developed by the breeders and used in wide range of
environmental conditions with very limited or no tests prior to
their release for broad cultural practices and use. Proper scientific
tests on these cultivars before their release for general use results
in at least the following advantages: 1) better and successful plant/
turfgrass growth/development/establishment by using proper
cultivars and more tolerant ones for areas under stress (i.e. salinity)
conditions; 2) savings in investments and expenses for reclamation
of saline soils for reducing the salinity levels of soils and waters
to the level suitable or practical for specific turfgrass species/
cultivar growth and development; 3) prevent the heavy costs of
total or partial renovations of the turf covered areas in cases of
improper and failure in establishment and performance of the turf
due to soil salinity problems or irrigating turfgrasses with saline/
effluent/low quality waters.
The agricultural investigators, particularly those involved with
plant/turfgrass stress tolerances usually consider the above issues
in the initiation and conducting of their research work.
The objectives of this study were to find the most salinity
tolerant cultivar(s) of ryegrass for optimum growth/development
and performance under various salinity stress levels, and
recommendation of the tolerant cultivar(s) to turfgrass managers
for broad cultural practices.
Materials and Methods
Eight cultivars of perennial ryegrass (Lolium perenne L.), including
Covet, OSC129 (Covet II), Galileo, OSC127 (Galileo II),
Michelangelo, Newton, Whitney and OSC126 (Whitney II) were
studied hydroponically in a greenhouse to evaluate their growth
responses in terms of shoot and root lengths, shoot (clippings)
fresh and dry matter (DM) weights and grass general quality under
various levels of sodium chloride (NaCl) salinity stress.
The grasses were grown from seeds in cups, 9 cm diameter and
7 cm height. Silica sand was used as the plant anchor medium.
Journal of Food, Agriculture & Environment, Vol.7 (3&4), July-October 2009
739
Each cup was fitted into one of the 9 cm diameter holes cut in a
rectangular plywood sheet 46 cm (length) x 37 cm (width) x 2 cm
(thickness). The plywood sheets served as lids for the hydroponics
tubs and supported the cups above the solution to allow for root
growth. The lids were placed on 42 cm (length) x 34 cm (width) x
12cm (depth) Carb-X polyethylene tubs, containing half strength
Hoagland solution No.1 6.
Prior to the salinity treatments, the grasses were grown in this
nutrient solution for 90 days. During this period, the grass shoots
(clippings) were harvested weekly in order to allow the grass to
reach full maturity and develop uniform and equal size plants. The
harvested plant materials (clippings) were discarded. The culture
solutions were changed bi-weekly to ensure adequate amount of
plant essential nutrient elements for normal growth and
development. After 90 days growing in this nutrient solution, the
salinity treatments were started by adding NaCl to the culture
solution equivalent to EC of 1 dS/m per day to reach desired
levels of salinity stress. Treatments included control (no salt) and
NaCl at various salinity levels (EC = 2, 4, 6, 8, 10, 12, 14 and 16
dS/m). The 8 ryegrass cultivars were grown in a Randomized
Complete Block (RCB) design with 4 replications of each treatment
for one full week at each salinity level. The culture solution levels
in the tubs were marked at the 10 litre volume level and maintained
at this level by adding distilled water and adjusted the salinity
levels of the culture solutions as needed. During this period, also,
culture solutions were changed bi-weekly to maintain the desired
plant nutrient levels.
The grass shoots (clippings) were harvested weekly for the
evaluation of the dry matter (DM) production. At each weekly
harvest, shoot and root lengths were measured and recorded.
The grass canopy general quality was also daily evaluated at
each stress level (one week growth period at each stress level)
and recorded. The harvested plant materials were oven-dried at
60oC and DM weights measured and recorded. The recorded data
were considered the weekly plant DM production. At the
termination of the experiment, the last harvest, plant roots were
also harvested, oven dried at 60oC, and DM weights determined
and recorded.
The data were subjected to Analysis of Variance (ANOVA),
using SAS statistical package 36. The means were separated, using
Duncan Multiple Range test.
Results and Discussion
The results presented in Tables 1-7 show that (except, for the
shoot to root ratio) shoot and root lengths and shoot (clippings)
fresh and DM weights, shoot succulence and the grass general
quality of all the cultivars decreased linearly with increased salinity
levels. However, at each salinity level, there were only some
numerical differences found in the shoot (clippings) lengths or
fresh and DM weights of the various cultivars (Tables, 1, 3 and 4).
In contrast, for all the cultivars, under any level of salinity, the
root length was more severely affected than the shoot length
(Table 2). There were significant differences in shoot or root lengths
or shoot fresh and DM weights of various cultivars at each level
of salinity (Tables 1-5). Shoot to root ratio was higher under salinity
Table 1. Average shoot length (cm) of eight ryegrass cultivars under various salinity
stress conditions.
Salinity
EC
(dS/m)
2
4
6
8
10
12
14
16
1
2
Covet
14.1a
12.3b
12.8b
10.7c
9.9c
8.9c
7.7d
6.8d
OSC129
Covet II
15.2a
11.5b
11.1b
10.4c
9.6c
8cd
7.4d
6.9d
Galileo
14.7a
12.2b
11.4b
10.4c
9.3c
8.4cd
7.7d
7.1d
Cultivar
OSC127
GalileoII
14.5a
12.5b
11.7b
10.7c
8.5cd
7.7d
7.2d
6.8d
Michelangelo
15.4a
12.9b
11.9b
10.5c
10.3c
8.1cd
7.5d
7.2d
Newton
13.9a
11.6b
11.2b
10.5c
9.4c
8.5cd
7.4d
7.1d
Whitney
14.5a
12.7b
11.1b
10.4c
9.2c
8.1cd
7.2d
7.1d
OSC126
Whitn.II
13.9a
12.2b
10.9b
9.4c
9.1c
8.2cd
7.1d
6.7d
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each column and across the rows are not significantly different at the 0.05 probability level.
Table 2. Average root length (cm) of eight ryegrass cultivars under various salinity stress conditions.
Salinity
EC
(dS/m)
2
4
6
8
10
12
14
16
1
2
Covet
5.9ab
3.6c
3.0c
2.7c
2.4cd
2.2cd
1.3de
1.1de
OSC129
Covet II
5.5b
3.3c
3.0c
2.8c
2.2cd
2.0cd
1.8d
0.9e
Galileo
6.6ab
2.8c
2.7c
2.4cd
2.1cd
2.1cd
1.8d
1.4de
Cultivar
OSC127
GalileoII
7.2a
4bc
3.5c
3.3c
2.5cd
2.4cd
2.2cd
2.0d
Michelangelo
6.2ab
4.8bc
4.6bc
4.4bc
4.3bc
4.1bc
3.3c
2.2cd
Newton
7.2a
2.8c
2.7c
2.1cd
1.9d
1.8d
1.6d
1.3de
Whitney
7.1a
3.8c
3.6c
3.5c
3.2c
3.0c
2.6cd
2.2cd
OSC126
Whitn.II
8.5a
4.6bc
3.7c
3.4c
2.8cd
2.6cd
2.4cd
1.6d
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each column and across the rows are not significantly different at the 0.05 probability level.
740
Journal of Food, Agriculture & Environment, Vol.7 (3&4), July-October 2009
stress compared to the control plants, and shoot succulence
significantly decreased under NaCl stress condition (Table 6).
Higher shoot to root ratio under salinity stress is another indication
that the root growth was affected more severely than the shoot
growth under stress. This is common in non-halophytic plants.
However, the reverse was observed and reported in halophytes
by several investigators 9, 11-13, 15, 16, 18-20, 22, 23, 26-28, 31, 33, 35. Tables 5
and 6 present average of the data for the various cultivars of
ryegrass shoot and root lengths and clippings fresh and dry matter
(DM) weights and the shoot to root ratio and the shoot succulence
(Shoot fresh wt./Shoot dry wt.) for the control and EC 12 dS/m
salinity stress level. The data in Tables 5 and 6 also confirm the
presented data in Tables 1-4. Grass general quality followed the
same pattern (decreased) as the shoot (clippings) lengths, fresh
and DM weights (Table 7). The canopy color of all the cultivars
turned to lighter green at the higher levels (EC >6 dS/m) of salinity.
Based on the results of this study, all the cultivars exhibited a
high level of salinity tolerance.
Table 3. Average shoot fresh weight (g) of eight ryegrass cultivars under various salinity stress conditions.
Salinity
EC (dS/m)
2
4
6
8
10
12
14
16
1
2
Covet
2.43a
2.07ab
1.42bc
1.15c
1.01dc
0.67d
0.30e
0.15f
OSC129
Covet II
2.71a
1.98b
1.34c
1.27c
0.98d
0.71d
0.30e
0.19f
Galileo
2.80a
2.34a
1.43bc
1.27c
1.20dc
0.84d
0.45e
0.26ef
Cultivar
OSC127
GalileoII
2.17ab
1.87b
1.34c
1.18c
0.85d
0.69d
0.28e
0.24ef
Michelangelo
2.74a
2.12ab
1.62bc
1.41bc
1.06dc
0.67d
0.38e
0.25ef
Newton
2.45a
1.99ab
1.36c
1.31c
0.83d
0.69d
0.47e
0.12f
Whitney
2.06ab
1.75bc
1.24c
0.95d
0.81d
0.62d
0.22ef
0.11f
OSC126
Whitn.II
1.95b
1.24c
1.19c
1.12c
1.04dc
0.55de
0.17f
0.12f
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each column and across the rows are not significantly different at the 0.05 probability level.
Table 4. Average shoot dry matter (DM) wt. (g) of eight ryegrass cultivars under various salinity stress
conditions.
Salinity
EC (dS/m)
2
4
6
8
10
12
14
16
1
2
Covet
2.43a
2.07ab
1.42bc
1.15c
1.01c
0.67d
0.30e
0.15ef
OSC129
Covet II
2.71a
1.98b
1.34bc
1.27c
0.98dc
0.71d
0.30e
0.19ef
Galileo
2.80a
2.34a
1.43bc
1.27c
1.20c
0.84d
0.45de
0.26e
Cultivar
OSC127
GalileoII
2.17ab
1.87b
1.34bc
1.18c
0.85d
0.69d
0.31e
0.24e
Michelangelo
2.74a
2.12ab
1.32bc
1.41bc
1.06c
0.67d
0.38e
0.25e
Newton
2.45a
1.99b
1.36bc
1.31bc
0.83d
0.69d
0.47de
0.12f
Whitney
2.06ab
1.75b
1.24c
0.95dc
0.81d
0.62d
0.22e
0.11f
OSC126
Whitn.II
1.95b
1.24c
1.19c
1.12c
1.04c
0.55de
0.17ef
0.12f
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each column and across the rows are not significantly different at the 0.05 probability level.
Table 5. Ryegrass shoot and root lengths, clippings fresh and dry matter (DM)
weights (average of 4 replications) for control (EC = 0) and salt-stressed
(EC = 12 dSm-1).
Grass
ID
Covet
Covet II
Galileo
Galileo II
Michel-Ang.
Newton
Whitney
Whitney II
.Sht. leng.
Rt. leng.
0
12
0
12
...........…....... (cm)…......………..
14.8a
7.7b
5.9ab
1.9de
12.7a
7.4b
5.3b
1.8de
14.7a
7.7b
5.7ab
1.8de
14.5a
7.2b
7.2a
2.3d
15.4a
7.5b
6.5a
3.3c
14.0a
7.4b
7.2a
1.5e
15.0a
7.2b
7.1a
2.6cd
13.9a
7.1b
6.9a
2.2d
Sht. FW
Sht. DW at EC
0
12
0
12
…......………..(g)………..........…..
2.4ab
0.5d
0.5ab
0.2c
2.7a
0.3e
0.6a
0.1d
2.9a
0.4de
0.6a
0.2c
2.5ab
0.4de
0.5ab
0.1d
2.7a
0.4de
0.6a
0.1d
2.3b
0.5d
0.5ab
0.2c
2.1bc
0.4de
0.4b
0.1d
2.0bc
0.4de
0.4b
0.1d
1
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each two adjacent columns (two salinity levels, 0 and 12 dS/m) for each parameter (Sht.
leng., Root leng., Sht FW, Sht DW) are not significantly different at the 0.05 probability level.
2
Journal of Food, Agriculture & Environment, Vol.7 (3&4), July-October 2009
741
Table 6. Ryegrass shoot length to root length ratio and shoot succulence
(shoot FW/shoot DW) (average of 4 replications) for control
(EC = 0) and salt-stressed (EC = 12 dSm-1).
____________________________________________________________________
Grass
ID
Covet
Covet II
Galileo
Galileo II
Michel-Ang.
Newton
Whitney
Whitney II
Sht. leng./Rt. leng.
Sht. succulence
EC (dS/m)
_____________________________________________________
0
2.51bc
2.40bc
2.58bc
2.01c
2.37bc
1.94c
2.11c
2.01c
12
4.05a
4.11a
4.28a
3.13b
2.27c
4.93a
2.77bc
3.23bc
0
4.8ab
4.5b
4.8ab
5.0a
4.5b
4.6ab
5.25a
5.0a
12
2.5dc
3.0c
2.0d
4.0b
4.0b
2.5dc
4.0b
4.0b
1
The values are the means of 4 replications of each cultivar at each salinity level.
The values followed by the same letter in each two columns (two salinity levels, 0 and 12 dS/m) for each parameter
(Shoot length/Root length and Shoot succulence) are not significantly different at the 0.05 probability level.
2
Table 7. Ryegrass general quality (average of 4 replications at each weekly evaluations) at
various salinity levels.
Grass
ID
Grass general quality at EC
______________________________________________________________________
0
2
4
6
8
10
12
14
16
_____________________________________________________________________________________
Covet
10a
10a
9.0a
8.5ab
7.5bc
6.5cd
5.5de
4.5ef
3.5fg
Covet II
10a
10a
9.5a
8.5ab
7.5bc
6.5cd
5.5de
4.5ef
3.0g
Galileo
10a
10a
9.5a
9.0a
8.0b
7.0c
6.0d
5.0e
3.5fg
Galileo II
10a
10a
9.5a
9.0a
8.0b
7.0c
6.0d
5.0e
3.5fg
Michel-Ang.
10a
10a
9.5a
9.0a
8.0b
7.0c
6.0d
5.0e
3.5fg
Newton
10a
10a
9.5a
8.5ab
7.5bc
6.5cd
5.5de
4.5ef
3.0g
Whitney
10a
10a
8.5ab
8.0b
7.0c
6.0d
5.0e
4.0f
3.0g
Whitney II
10a
10a
8.0b
7.5bc
6.5cd
5.5de
4.5ef
3.5fg
3.0g
1
The values are the means of 7 daily evaluations of the grass quality and 4 replications of each cultivar at each salinity level (one week stress period).
The values followed by the same letter in each column and across the rows are not significantly different at the 0.05 probability level.
2
Conclusions
Ryegrass shoot and root lengths and shoot (clippings) fresh and
dry matter (DM) weights decreased linearly with increased salinity
levels for all the cultivars. However, at each salinity level, there
were only some numerical differences found in the shoot
(clippings) lengths and fresh and DM weights of the various
ryegrass cultivars. For all the cultivars, under any level of salinity
stress, the root length was more severely affected than the shoot
length. General quality of various ryegrass cultivars followed the
same pattern as the shoot (clippings) lengths and fresh and DM
weights. It decreased linearly with increased salinity levels. The
canopy color of all the cultivars turned to lighter green at the
higher levels (EC >6 dS/m) of salinity. Overall, based on the results
of this study, all the cultivars exhibited a high level of salinity
tolerance.
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