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Differential response of wheat cultivars to subsoil salinity/sodicity

Harsharn Singh Grewal1, Peter Cornish1 and Shane Norrish

1University of Western Sydney, Hawkesbury Campus, NSW 2753, Australia www.uws.edu.au, Email: h.grewal@uws.edu.au
p.cornish@uws.edu.au
s.norrish@uws.edu.au

Abstract

Response of 15 wheat cultivars (Sunvale, Sunco, Sunlin, Sunbri, Mulgara, Drysdale, Lang, Kennedy, Baxter, Babbler, H 45, Krichauff, Trident, Kamilaroi and Wollaroi) to varied subsoil salt (high subsoil salt: 5000 mg NaCl/kg soil, low-subsoil salinity: no added salt) was studied in a glasshouse experiment. Plants were grown for 8 weeks in a heavy texture clay soil (Vertosol). Key soil properties of the low subsoil salt treatment (EC1:5: 0.5 dS/m, ESP: 5, Cl: 100 mg/kg) contrasted strongly with the high salt subsoil (EC1:5: 2.5 dS/m, ESP: 20, Cl: 3000 mg/kg). Salt affected plants grown in high subsoil salinity had smaller leaves, necrosis of leaf margins, reduced tiller numbers, and reduced dry matter of roots and shoots. Babbler appeared to be the least tolerant variety, with a 52% reduction in shoot DM in the high salt subsoil. Some of the better performing varieties were Drysdale, H45, Sunco and Kennedy, which exhibited 34-37% reduction in shoot DM in the high salt subsoil. The reduction in shoot dry matter (43%) of durum varieties (Kamillaroi and Wollaroi) in high salt subsoil was similar to some of the bread wheats. Although the results indicate a range in tolerance of between varieties, there is little evidence to show that any varieties are tolerant of highly saline subsoils.

Media summary

Wheat cultivars differ in their ability to tolerate subsoil salts, which could be further explored in field to boost wheat yields on soils with subsoil salinity.

Key words

Subsoil salinity, wheat, cultivars, salinity tolerance index

Introduction

Soils with high salt concentrations in topsoil and subsoils are widespread, and reduce growth and yield of crops in Australia and many regions of the world. Soil salinity/sodicity directly affects plant growth through osmotic stress and nutrient disorders. Subsoil salinity/sodicity generally restricts root growth and reduces water and nutrient extraction from subsoil resulting in poorer plant growth, and lower crop yields. Decreases in rooting depth and water extraction by cereal crops have been commonly attributed to high levels of salts and exchangeable sodium in subsoils. Exploitation of subsoil water and nutrients to attain potential yields is particularly imperative for dryland cropping regions (Rengasamy 2003). Therefore, it is imperative to investigate strategies to manage subsoil salinity/sodicity.

Identifying genotypes that are tolerant to saline and/or sodic subsoils is a practical and relatively simple way of improving crop yield and profitability on these difficult soils. Growing tolerant cultivars on soils with subsoil salinity/sodicity reflects the shift to a strategy of ‘tailoring the plants to fit the soil’ in contrast to the older strategy of tailoring the soil to fit the plant.

The aim of the present study was to investigate variation in wheat cultivars for their tolerance to high subsoil salinity/sodicity.

Methods

Fifteen wheat cultivars were evaluated for their response to varied subsoil salinity in a glasshouse experiment. Cultivars tested include 13 bread wheat cultivars (Sunvale, Sunco, Sunlin, Sunbri, Mulgara, Drysdale, Lang, Kennedy, Baxter, Babbler, H 45, Krichauff and Trident) and two durum cultivars (Kamilaroi and Wollaroi).

Heavy texture clay soil (vertosol) from north-western NSW was air dried and passed through a 2-mm sieve. Sodium chloride was either supplied at 5000 mg/kg soil and mixed thoroughly in the subsoil (high subsoil salinity treatment), or omitted from the subsoil (low subsoil salinity). Each pot received 1200g of subsoil, over which a 200g layer of topsoil was added. Key properties for the soils are presented in Table

Table 1: Key physico-chemical properties of vertosol soils in wheat cultivar tolerance experiment

Soil

EC1:5
(dS/m)

ESP

Cl
(mg/kg)

Topsoil

0.3

1

30

Low subsoil salinity

0.5

5

100

High subsoil salinity

2.5

20

3000

Soil for both zones (subsoil and topsoil) was watered to the drained upper limit (0.32 g/g) with double deionised water (DD water) and equilibrated for four weeks at 25˚C temperature. Polythene-lined cylindrical PVC pots (40 cm long, 6.5 cm diameter) were used for growing plants. Four seeds were sown at a depth of 2 cm and after two weeks, only two plants were retained in the pots. In order to ensure that the plants did not suffer water stress during growth, the pots were returned to a constant mass by adding DD water at two day intervals, thereby maintaining soil water content near the drained upper limit.

Plants were harvested at 8 weeks after planting. Roots, leaves and stems were oven dried at 65˚C for 48 h, and weighed. The experiment was set up in a completely randomized design with 3 replicates of each treatment. All data was subject to analysis of variance.

Results and Discussion

There was no difference in germination and emergence of seedlings in the non-saline topsoil. Plants grown in pots with high subsoil salts started showing symptoms of stress 21 days after sowing and the symptoms became more pronounced with time. Symptoms included smaller leaves, necrosis of leaf margins and reduced tiller numbers. At harvest there was a marked reduction in dry matter (DM) of roots and shoots (Table 2).

Table 2: Shoot and root dry matter (g/plant) and subsoil salinity tolerance index (SSTI) of wheat cultivars grown in a glasshouse experiment for 8 weeks.

Cultivars

Shoot dry weight
(g/plant)

SSTI
(%)

Root dry weight
(g/plant)

-Salt

+Salt

(+Salt/-Salt) x 100

-Salt

+Salt

Babbler

1.98

0.97

48

0.53

0.23

Sunbri

1.64

0.86

52

0.70

0.33

Sunlin

1.66

0.89

54

0.60

0.27

Trident

1.86

1.02

55

0.51

0.25

Mulgara

2.02

1.10

55

0.52

0.30

Kamillaroi

1.56

0.89

57

0.45

0.19

Wollaroi

1.97

1.13

57

0.38

0.17

Sunvale

1.83

1.07

59

0.51

0.31

Krichauff

1.90

1.12

59

0.43

0.24

Lang

1.95

1.15

59

0.68

0.33

Baxter

1.99

1.18

59

0.47

0.31

Kennedy

1.80

1.13

63

0.44

0.26

Sunco

1.83

1.15

63

0.52

0.34

Drysdale

2.03

1.30

64

0.51

0.33

H45

1.87

1.24

66

0.47

0.31

LSD (p<0.05)

         

Cultivar x subsoil salt

0.15

4

0.06

Shoot and root DM was significantly decreased in all the wheat cultivars due to subsoil salinity. The ratio of shoot DM produced in high-subsoil salinity to shoot DM in low-subsoil salinity was used an index of tolerance to subsoil salinity (SSTI). The range in SSTI values (48-66%) indicated varieties differed in their tolerance to subsoil salinity. Despite having similar shoot DM to the highest yielding varieties under low subsoil salt, Babbler appeared to be the least tolerant of saline subsoils with a 52% reduction in DM. In contrast, H45, Drysdale, Sunco and Kennedy produced more shoot DM than many varieties in the high subsoil salt, and achieved relatively high SSTI of 66%, 64%, 63% and 63% respectively. The 43% reduction in DM of durum wheat cultivars Kamillaroi and Wollaroi due to subsoil salinity was similar to many of the bread wheats. This result contrasts with previous work showing durum wheat to be more salt-sensitive than bread wheat (Francois et al., 1986; Rawson et al., 1988). However, there was no differences between durum and bread wheat cultivars when these were exposed over a short periods of time to salinity (Munns et al., 1995).

Root DM the durum wheats, Kamillaroi and Wollaroi and the bread wheats, Babbler and Sunlin declined more than 55% in high subsoil salinity. The roots of Drysdale, Sunco, Baxter and H45 appeared the least susceptible to the high salt subsoil, shown by the relatively lower reductions in root DM (<35%). Subsoil salinity resulted in significantly lower root to shoot ratio in Kamillaroi, Wollaroi, Babbler, Sunlin and Sunbri (data not presented).

Despite the range in apparent tolerance between varieties shown by the SSTI, the relatively large reduction in shoot and root DM of all varieties provide little evidence of tolerance to the saline subsoil.

Acknowledgement

This work is supported by the Grains Research and Development Corporation of Australia. Technical assistance from Mr Mark Emanuel is gratefully acknowledged.

References

Francois LE, Maas EV, Donovan TJ and Youngs VL (1986). Effect of salinity on grain yield and quality, vegetative growth and germination of semi-dwarf and durum wheat. Agronomy Journal 78, 1053-1058.

Munns R, Schachtman DP and Condon AG (1995). The significance of two-phase growth response to salinity in wheat and barley. Australian Journal of Plant Physiology 22, 561-569.

Rawson HM, Richards RA and Munns R (1988). An examination of selective criteria for salt-tolerance in wheat, barley and triticale genotypes. Australian Journal of Agricultural Research 39, 759-772.

Rengasamy P, Chittleborough D and Helyar K (2003). Root-zone constraints and plant-based solutions for dryland salinity. Plant and Soil 257, 249-260.

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