Sunflower will be the next broadacre crop to benefit from pioneering research into transpiration efficiency that allows plant breeders to select for higher yields during droughts.

Scientists define transpiration efficiency (TE) as dry matter production per unit of water transpired and the unlocking of its secrets has opened the way for plant breeders to develop crop varieties that are more tolerant of the frequent moisture deficits faced by Australian farmers.

Years of Grains Research and Development Corporation (GRDC) supported research by CSIRO and the Australian National University paid off with the release of the drought tolerant wheat varieties Drysdale and Rees.

Now the first germplasm from similar TE research in sunflowers has gone to private sector seed companies which will incorporate the drought tolerance characteristic into commercial varieties for release to farmers.

The responsible scientist, Chris Lambrides, University of Queensland research fellow in molecular plant breeding, says the parent breeding material passed to seed companies also incorporated excellent and new rust resistance which would be a valuable addition to that currently used in commercial hybrids.

The transfer also included molecular markers that will allow seed company breeders to select for the TE genes in their development of new hybrid varieties for the commercial market.

"We worked with data from computer simulations and research into improved TE in other crops to begin our selection work in sunflower," Dr Lambrides said.

"Using surrograte trait carbon isotope discrimination, we identified significant genetic variation for TE in sunflower lines and made segregating populations to construct a genetic linkage map and to identify molecular markers for the TE trait

"We tested the yield advantage of hybrids selected for improved TE by top-crossing lines selected for high and low TE to a common female breeding line,

"Then we tested these experimental hybrids at three locations and found the group with high TE out-yielded the low TE group by 35% in the droughted environments.

"Of course we don¹t expect this yield advantage in commercial hybrids, but our computer simulations suggest that a 10% to 15% yield advantage in hybrids containing the high TE trait may be possible in droughted environments.

"On one occasion, at Capella in 2001, experimental hybrids selected for high TE outyielded the commercial check varieties by 15%."

Dr Lambrides said the experimental hybrids were also tested under irrigated conditions to ensure there was no yield disadvantage from the TE characteristics under favourable conditions.

Under conditions producing yields as high as two tonnes to the hectare ­ almost twice the average commercial yield ­ they found there was less advantage for lines with the high TE characteristic but no yield penalty.

"A significant point is that the experimental hybrids in this trial had only one high TE parent. Obviously there¹s potential for even greater benefits from hybrids made with two high TE parents," Dr Lambrides said.