A Pictorial Technique for Mass Screening of Sorghum Germplasm for Anthracnose (Colletotrichum sublineolum) Resistance

Abstract

Globally, the foliar phase of anthracnose is one of the most destructive diseases of sorghum. In most cases, anthracnose resistance screening relies on the use of a spore suspension. This method is usually conducted after sundown and when there is the possibility of dew formation the following morning. Using a spore suspension for sorghum anthracnose field evaluation in College Station, Texas over five years (1996, 1997, 1999-2001) yielded inconsistent linkage results and failed to identify any closely linked molecular markers. For large scale screening of sorghum germplasm for anthracnose (Colletotrichum sublineolum) resistance, plants are inoculated in the field or in the green house at either 30 d after planting or at the 8-10 leaf-stage. In field inoculation, the use of C. sublineolum-colonized sorghum grains was shown to be the most efficient and effective in identifying resistant sources. For effective, efficient, fast and accurate infection, approximately 10-20 seeds are placed in each plant leaf whorl and it takes about 16.7 kg of colonized grains to cover a 0.4 ha area. In the greenhouse, though colonized grains are equally effective, spray inoculation is preferred for easy and uniform coverage. Using this method of inoculum preparation, spore suspension was extracted and sprayed (10⁶ conidia·ml^-1), followed by 10 hr/d misting for 30 sec at 30-45 min interval continuously for a period of one month resulted in effective infection.