Journal de pathologie végétale et de microbiologie

Abstrait

Responses of Johnsongrass Against Sorghum Anthracnose Isolates

Ezekiel Ahn, Louis Prom, Gary Odvody, and Clint Magill

Johnsongrass is a creeping perennial weed that interferes with crop productivity. Due to genetic similarity to sorghum, Johnsongrass is considered to have potential as an alternate source of pathogen resistance genes for sorghum. In order to test this hypothesis, sorghum isolates of anthracnose (Colletotrichum sublineolum) were inoculated onto twenty-six Johnsongrass cultivars collected from across the southern US by using an excised leaf method. Upon inoculation with a C. sublineolum sorghum isolate, different Johnsongrass cultivars showed different degrees of infection. Moreover, three different C. sublineolum isolates caused different responses on the same Johnsongrass cultivar. Expression of early defense response related genes, including β-1,3-glucanase, chalcone synthase 8 (CHS8), pathogen induced chitinase, flavonoid-3’-hydroxylase, pathogenesis related protein-10 (PR10), and thaumatin-like protein, were measured 24 hrs and 48 hrs post inoculation in selected Johnsongrass cultivars by Real-Time qRT-PCR. The results revealed that levels of defense responses varied among cultivars but were not sufficient to establish a basis for resistance. When the same Johnsongrass cultivars were inoculated in a greenhouse study with conidia of Colletotrichum sublineolum isolate FSP53 from sorghum, some showed evidence of a hypersensitive response. However, successful reproduction of the pathogen as detected by formation of acervuli and setae was seen only on SH1116 and on only one leaf of this cultivar.