Sorghum is a suitable break crop to minimiseFusarium pseudograminearumin any location regardless of climatic differences, whereasGibberella zeaeis location and climate specific

Abstract

The susceptibility of grain sorghum (Sorghum bicolor) to infection and colonisation by Fusarium pseudograminearum and Gibberella zeae was assessed by isolation studies involving plants grown in field plots and commercial fields in New South Wales. F. pseudograminearum was isolated at a low frequency from plants sampled from an experimental trial site at Livingston Farm, Moree where five different residue management practices had been implemented. In this trial site, 1000 plants were analysed at the pre- and post-senescence stages from four replicate plots in each of five residue management treatments. There was an insignificant level of recovery of F. pseudograminearum from sorghum from the different treatments and inoculum levels. No G. zeae was isolated from this trial site. The effect of agro-climate factors on the occurrence of F. pseudograminearum and G. zeae in mature sorghum stems was assessed from 31 commercial sites representing two climatic regions, Goondiwindi/Moree and the Liverpool Plains. F. pseudograminearum was rarely isolated from the commercial crops that were from two different climatic regions. In contrast, G. zeae was isolated at low to medium levels from the Liverpool Plains region as this region has been identified as suitable for survival of this pathogen. The result also indicated that infection and colonisation of G. zeae was dependent on inoculum levels present in the residues of the preceding crop in the field and in the presence of medium to high rainfall distribution in areas that were detrimental to dispersal and initiation of infection. However, G. zeae was not isolated from sorghum stalks from the Goondiwindi/Moree region. In addition, G. zeae was more frequently isolated from sorghum crops where the wheat residues were known to be infested with G. zeae.