A wheat genotype developed for rapid leaf growth copes well with the physical and biological constraints of unploughed soil
Michelle Watt A B , John A. Kirkegaard A and Gregory J. Rebetzke AA CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
B Corresponding author. Email: michelle.watt@csiro.au
Functional Plant Biology 32(8) 695-706 https://doi.org/10.1071/FP05026
Submitted: 7 February 2005 Accepted: 2 May 2005 Published: 3 August 2005
Abstract
Conventional wheat (Triticum aestivum L.) cultivars grow slowly in unploughed soil because of physical and biological constraints. Here a conventional cultivar (Janz) is compared with a novel experimental line (Vigour 18), bred for high leaf vigour, to explore the hypothesis that a vigorous wheat grows better in unploughed soil. Roots of both genotypes in unploughed soil were three times more distorted with 30% shorter apices and 60% shorter expansion zones than roots in ploughed soil, because of voids between blocky peds and packed sand particles that impeded root apices. More than half the root length contacted dead, remnant roots. Vigour 18 roots grew 39% faster, were thicker and distorted less than Janz roots in unploughed soil, but developed similarly in ploughed soil. Vigour 18 shoots grew 64% faster in unploughed soil, but 15% faster in ploughed soil. Fumigation of unploughed soil improved the growth of Janz only. We suggest that faster root growth, different exudates promoting a more beneficial rhizosphere microflora, or modified shoot responses are possible mechanisms to explain Vigour 18’s superior growth. Vigorous genotypes may present a new opportunity for increased productivity with conservation farming.
Keywords: direct-drill, genetic variation, rhizosphere, root, sustainable agriculture, tillage.
Acknowledgments
We thank Geoff Howe for running the field sites, Cheng Huang for assistance with the cryo-scanning electron microscopy, and Catherine Pohlman, Kerry Vinall and Linda Magee for help with plant and soil measurements. The CSIRO Ginninderra Experiment Station sowed field trials. Microscopy and image analysis was done at the CSIRO Plant Industry Microscopy Centre with assistance from Rosemary White. This study was funded by the Grains Research and Development Corporation of Australia.
Abeysekera RM, McCully ME
(1993) The epidermal surface of the maize root tip. II. Abnormalities in a mutant which grows crookedly through soil. New Phytologist 125, 801–811.
Beemster GTS, Baskin TI
(1998) Analysis of cell division and elongation underlying the developmental acceleration of root growth in Arabidopsis thaliana. Plant Physiology 116, 1515–1526.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Bengough AG,
Croser C, Pritchard J
(1997) A biophysical analysis of root growth under mechanical stress. Plant and Soil 189, 155–164.
| Crossref | GoogleScholarGoogle Scholar |
Brady, NC (1990).
Chan KY,
Mead JA,
Roberts WP, Wong PTW
(1989) The effect of soil compaction and fumigation on poor early growth of wheat under direct drilling. Australian Journal of Agricultural Research 42, 221–228.
Cook RJ
(2001) Management of wheat and barley root diseases in modern farming systems. Australasian Plant Pathology 30, 119–126.
| Crossref | GoogleScholarGoogle Scholar |
Cornish, PS (1987). Crop and pasture plant selection for new cultural systems. In ‘Tillage. New directions in Australian agriculture’. pp. 355–378. (Inkata Press: Sydney)
Farrar J,
Hawes M,
Jones D, Lindow S
(2003) How roots control the flux of carbon to the rhizosphere. Ecology 84, 827–837.
Gerhardson B,
Alström S, Rämert B
(1985) Plant reactions to inoculation of roots with fungi and bacteria. Phytopathology 114, 108–117.
Jones DL,
Hodge A, Kuzyakov Y
(2004) Plant and mycorrhizal regulation of rhizodeposition. New Phytologist 163, 459–480.
| Crossref | GoogleScholarGoogle Scholar |
Kirkegaard JA
(1995) A review of trends in wheat yield responses to conservation cropping in Australia. Australian Journal of Experimental Agriculture 35, 835–848.
| Crossref | GoogleScholarGoogle Scholar |
Kirkegaard JA,
Angus JF,
Gardner PA, Müller W
(1994) Reduced growth and yield of wheat with conservation cropping. I. Field studies in the first year of the cropping phase. Australian Journal of Agricultural Research 45, 511–528.
| Crossref | GoogleScholarGoogle Scholar |
Kirkegaard JA,
Munns R,
James RA,
Gardner PA, Angus JF
(1995) Reduced growth and yield of wheat with conservation cropping. II. Soil biological factors limit growth under direct drilling. Australian Journal of Agricultural Research 46, 75–88.
| Crossref | GoogleScholarGoogle Scholar |
Kirkegaard JA,
Munns R,
James RA, Neate SM
(1999) Does water and phosphorus uptake limit the growth of Rhizoctonia-infected wheat seedlings? Plant and Soil 209, 157–166.
| Crossref | GoogleScholarGoogle Scholar |
Liao M,
Fillery IRP, Palta JA
(2004) Early vigour growth is a major factor influencing nitrogen uptake in wheat. Functional Plant Biology 31, 121–129.
| Crossref | GoogleScholarGoogle Scholar |
López-Casteñeda C,
Richards RA, Farquhar GD
(1995) Variation in early vigour between barley and wheat. Crop Science 35, 472–479.
Masle J, Passioura JB
(1987) The effect of soil strength on the growth of young wheat plants. Australian Journal of Plant Physiology 14, 643–656.
Materechera SA,
Dexter AR, Alston AM
(1991) Penetration of very strong soils by seedling roots of different plant species. Plant and Soil 135, 31–41.
| Crossref | GoogleScholarGoogle Scholar |
McCully ME
(1995) Water efflux from the surface of field-grown grass roots. Observations by cryo-scanning electron microscopy. Physiologia Plantarum 95, 217–224.
| Crossref | GoogleScholarGoogle Scholar |
McKee KL
(2001) Root proliferation in decaying roots and old root channels: a nutrient conservation mechanism in oligotrophic mangrove forests? Journal of Ecology 89, 876–887.
| Crossref | GoogleScholarGoogle Scholar |
Passioura JB
(2002) Soil conditions and plant growth. Plant, Cell and Environment 25, 311–318.
| Crossref | GoogleScholarGoogle Scholar |
Pietola LM
(2005) Root growth dynamics of spring cereals with discontinuation of mouldboard ploughing. Soil and Tillage Research 80, 103–114.
| Crossref |
Rasse DP, Smucker AJM
(1998) Root colonisation of previous root channels in corn and alfalfa rotations. Plant and Soil 204, 203–212.
| Crossref | GoogleScholarGoogle Scholar |
Rebetzke GJ, Richards RA
(1999) Genetic improvement of early vigour in wheat. Australian Journal of Agricultural Research 50, 291–301.
Richards RA
(2002) Current and emerging environmental challenges in Australian agriculture — the role of plant breeding. Australian Journal of Agricultural Research 53, 881–892.
| Crossref | GoogleScholarGoogle Scholar |
Richards RA, Lukacs Z
(2002) Seedling vigour in wheat — sources of variation for genetic and agronomic improvement. Australian Journal of Agricultural Research 53, 41–50.
| Crossref | GoogleScholarGoogle Scholar |
Rovira, AD (1987). Tillage and soil-borne root diseases of winter cereals. In ‘Tillage. New directions in Australian agriculture’. pp. 335–354. (Inkata Press: Sydney)
Simpfendorfer S,
Kirkegaard JA,
Heenan DP, Wong PTW
(2002) Reduced early growth of direct-drilled wheat in southern New South Wales — role of inhibitory pseudomonads. Australian Journal of Agricultural Research 53, 323–331.
| Crossref | GoogleScholarGoogle Scholar |
van Bruggen AHC,
Semenov AM, Zelenev VV
(2000) Wavelike distributions of microbial populations along an artificial root moving through soil. Microbial Ecology 40, 250–259.
| PubMed |
Watt M,
McCully ME, Kirkegaard JA
(2003) Soil strength and rate of root elongation alter the accumulation of Pseudomonas spp. and other bacteria in the rhizosphere of wheat. Functional Plant Biology 30, 483–491.
| Crossref | GoogleScholarGoogle Scholar |
Zobel R
(2003) Fine roots — discarding flawed assumptions. New Phytologist 160, 273–280.
| Crossref |
