Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2015
Publication Date: 12/15/2015
Citation: Prom, L.K., Cuevas, H.E., Isakeit, T., Droleskey, R.E. 2015. Excised leaf method for high volume evaluation of sorghum germplasm for resistance against Colletotrichum sublineolum. Plant Pathology. 15(1):11-16.
Interpretive Summary: Anthracnose is the most important foliar disease of sorghum and yield losses can reach 100% when susceptible lines are planted in humid and wet areas. Due to the existence of many races of the pathogen, there is a need to identify new sources of resistance by evaluating sorghum lines in the field or greenhouse. However, field or greenhouse evaluations can be costly, take too long, and require a lot of labor. Therefore, an excised leaf test was conducted in the laboratory to determine whether it can be used to screen sorghum for resistance to anthracnose. Our work showed that this excised leaf test produced the same results as those in the greenhouse using the same sorghum lines. Thus, the excised leaf method could offer a number of advantages in screening sorghum for anthracnose resistance over field and greenhouse testing such as reducing the time for conducting the experiment, labor, space, and increasing the number of isolates that can be tested within a short period.
Technical Abstract: Foliar phase of anthracnose, caused by Colletotrichum sublineolum is the most important leaf disease of sorghum. Due to the hyper-variable nature of the fungus, continuous evaluation of sorghum germplasm to identify new sources of resistance is imperative. Field and greenhouse evaluations for anthracnose resistance, especially with large numbers of sorghum lines/accessions can be expensive, time consuming, and require large spaces and labor. In this study, 16 sorghum lines were evaluated by putting a drop of the mixture of C. sublineolum isolates suspension on each side of the mid-rib of adaxial excised leaves plated on half-strength potato dextrose agar medium and concurrently as whole plants inoculated with a mixture of C. sublineolum-isolates-colonized grain and conidial suspension in the greenhouse. Each line exhibited the same reaction when challenged with C. sublineolum either using the excised leaf assay or screened in the greenhouse, indicating that the excised leaf assay is as effective in identifying susceptibility or resistance to the anthracnose pathogen. In both screening methods, SC748 was the only resistant line. The excised leaf assay was completed in 4 d, while the greenhouse evaluation was arrested 44 d post-inoculation. Thus, the excised leaf method could offer several advantages in screening sorghum for anthracnose resistance such as reducing the time for conducting the experiment, labor, space, and increasing the number of isolates that can be tested within a short period.