Red smudge infection modifies sprouting response in four wheat lines

Fox, S. L., Fernandez, M. R. and DePauw, R. M. 2003. Red smudge infection modifies sprouting response in four wheat lines. Can. J. Plant Sci. 83: 163-169. Infection of wheat (Triticum aestivum L.) spikes by Pyrenophora tritici-repentis (Died.) Drechs. (Ptr) causes kernel discolouration, reducing the commercial value of the grain. Preharvest sprouting in wheat causes loss of grain yield, grain functionality and value as seed. The objective of this research was to determine the effects of Ptr infection on the expression of preharvest sprouting response. Four genotypes representing a range of preharvest sprouting response were studied: RL4137 has very good sprouting resistance; SC8021V2, good; AC Karma, fair; and Genesis, poor. These genotypes were grown in a growth cabinet and their spikes were artificially inoculated with a conidial suspension of Ptr or water. Spikes were collected at physiologic maturity, threshed by hand and germinated on wetted filter paper at 10 or 20degreesC to obtain a percentage germination and a mean germination time. Healthy seeds were also germinated in a solution containing a crude extract of the fungus. At 20degreesC, sprouting-resistant genotypes showed a significant delay in germination compared to susceptible genotypes; however, differences were not significant at the lower temperature. Genesis germinated quickly at both temperatures. All genotypes except Genesis had reductions in sprouting resistance when infected by Ptr, but these effects were significant only at 20degreesC. When inoculated with,Ptr and germinated at 20degreesC, AC Karma germinated as quickly as the water controls and gave a preharvest sprouting response similar to Genesis. However, SC8021V2 and RL4137 inoculated with Ptr retained 40 and 78%, respectively, of their mean germination time compared to the water controls. Germination of healthy seeds in a solution containing a crude extract of Ptr increased the percentage germination and shortened the mean germination time of all genotypes, but did not result in significant changes for any individual line.