Boron tolerance hit to increase barley yields
GroundCover™ Issue: 33
A suite of genes that control boron tolerance in barley has been flagged with genetic markers, providing a major boost for fast and accurate breeding of higher-yielding barley varieties.
The breakthrough comes from a scientific team at the University of Adelaide headed by senior research fellow Steve Jefferies, with help from research staff at the Victorian Institute for Dryland Agriculture.
Mr Jefferies told the recent International Barley Genetics Symposium* that in a gene-mapping exercise the team had found:
- one important and one less important gene which control how much boron a barley plant takes up
- another gene which allows a plant to produce good root growth even though there may be toxic levels of boron in the plant
- a third gene which appears to be involved in controlling the movement of boron through the plant.
"I suspected when we started that there was more than one factor involved in boron tolerance, and there is," Mr Jefferies said. "The research means we now have a much better idea of how boron tolerance works and know the genes we have to select in barley varieties. Previously we were selecting only on visual symptoms.
Answers out of Africa
"After identifying the chromosomal location of the genes we were able to find markers, 'gene flags', linked to these genes and so we were able to track these through a whole range of crosses — the Algerian variety Sahara being the source of boron tolerance.
"We took a number of Sloop crosses, with and without boron-tolerant genes, into the field at Minnipa in 1998.
"There were far fewer leaf symptoms in the boron-tolerant lines. They also had larger grain size but overall little difference in yield. A similar thing happened in 1999. In those two very dry years there was no subsoil moisture, so improved root growth from boron tolerance was not an advantage when it came to yields."
Mr Jefferies said the results were particularly impressive given the fact that Sloop was not the best variety to use for boron tolerance crosses for the low-rainfall Minnipa area. Sloop is more suited to medium-rainfall districts.
"Andrew Barr at the University of Adelaide is now trying to develop Keel and Barque types with malting qualities and boron tolerance but won't be discarding Sloop crosses for the medium-rainfall areas," he said.
Contact: Mr Stephen Jefferies 08 8303 4455 email@example.com
* See p6 for a report on Australian breeding advances which could start boron-proof barleys into production within the next year or two and promise boron-tolerant durum wheat lines even earlier.
* On p7 you'll find a roundup of other news from the International Barley Genetics Symposium.
BORON IN SUBSOIL SPELLS TROUBLE
Boron toxicity is a widespread problem in Australian cropping soils, especially in the lower-rainfall areas of WA, SA and western Victoria.
Plant root growth and hence water and nutrient uptake are affected in susceptible plants growing in soils containing high levels of the element.
The most obvious symptoms in barley are chlorosis and necrosis extending from leaf tips and the formation of brown lesions, initially at the leaf margins, then extending over other parts of the leaf.
Soil amelioration to overcome boron toxicity is not a practical alternative (as is the case with, say, acidity and lime) and so scientists are using a genetic approach—the breeding of tolerant cultivars.
Sloop-like'breeding lines, with and without boron-tolerance genes, grown at Minnipa, South Australia.