Andrew Fletcher1, Greg Rebetzke2, Gary Ogden3
1 CSIRO Agriculture and Food, Centre for Environment and Life Sciences, PMB 5, Wembley, WA, 6913, Andrew.L.Fletcher@csiro.au,
2 CSIRO Agriculture and Food, Black Mountain, GPO Box 1700, Canberra, ACT, 2601,
3 CSIRO Agriculture and Food, Centre for Environment and Life Sciences, PMB 5, Wembley, WA, 6913
Reduced tillering wheat genotypes containing the tiller inhibition (tin) gene have been proposed as a way to reduce year-to-year variation in grain yield in Australia in dryland cropping regions. In extremely poor seasons, reduced tillering can lead to improved yield by limiting the crops investment in tillers that do not contribute to yield. However, in average or above average seasons reduced tillering can lead to a lower yield due to a reduction in fertile heads. This research tested whether increased seeding rate could offset this yield decrease. Seven genotypes including two commercial check varieties and near isogenic lines either with or without the tin gene were sown in two consecutive seasons in the low rainfall zone of WA. Crops were sown at 25, 50, 100, 200 and 300 plants/m². In both seasons yield potential, measured by the two commercial check varieties was ~2t/ha. Although emergence was poor in one season (~50%), the number of observed heads varied with density treatment and tillering capacities. Thus, the comparison between yields at similar head densities was valid. In the second season plant population was higher (85%). In both seasons, sowing density and genotype had a significant effect (p<0.001) on wheat yield but there was no interaction between them. Averaged across all genotypes and both seasons, genotypes with the tin gene yielded 62% less (p<0.001) than their free-tillering isogenic pairs. The lack of interaction with sowing density meant that increased sowing rates were unable to offset the yield reduction associated with the tin gene. This research challenged the ability of tin genotypes to stabilise yields by limiting yield loss at low yield levels. Furthermore, if fewer tillers in poor seasons is the objective then reducing plant population would appear a more cost effective option than using a genotype with the tin gene.