Submitted to: Open Agriculture Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2009
Publication Date: 4/13/2009
Citation: Prom, L.K., Perumal, R., Erpelding, J.E., Isakeit, T., Montes-Garcia, N., Magill, C.W. 2009. A pictorial technique for mass screening of sorghum germplasm for anthracnose (Colletotrichum sublineolum) resistance. Open Agriculture Journal. 3:20-25. Interpretive Summary: Anthracnose is one of the most important leaf diseases of sorghum. One of the major problems in identifying resistant sorghum lines is having an effective method of inoculating plants in the field and greenhouse. In this work, we demonstrated in picture presentation an effective method of screening sorghum lines for resistance by using grains that were colonized by the disease causing agent. The colonized grains are placed in the plant whorls either 30-days after planting or at the 8 to 10 leaf-stage. Disease evaluations are conducted 30-days after inoculating the plants and weekly thereafter until the plants flower. For large scale screening, we found that this method is more effective and reliable than using spore suspensions. Using this method, we were able to identify resistant sources from 320 sorghum lines that were obtained from India. This method helps the global scientific community to identify anthracnose resistance lines from the available and exotic germplasm sources and from segregating lines at large scale field and green house screening.
Technical 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 whor,l 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.