Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2005
Publication Date: 3/1/2006
Citation: Funnell, D., Pedersen, J.F. 2006. Reaction of sorghum lines genetically modified for reduced lignin content to infection by Fusarium and Alternaria species. Plant Disease. 90:331-338. Interpretive Summary: Sorghum lines had been bred for increased digestibility by reducing lignin content, accomplished by incorporating genes that cause modifications in the lignin metabolic pathway. To be certain disease resistance had not been compromised in these lines, seed and leaf tissue from field grown plants from near isogenic lines in 6 genetic backgrounds were screened for colonization by two potentially pathogenic groups of fungi, Alternaria and Fusarium. The reduced lignin lines were at least as resistant as wild-type lines to members of Alternaria and Fusarium. Some reduced lignin lines were more resistant to Fusarium species than wild-type lines. Reduced lignin lines and wild-type lines were tested in controlled greenhouse assays, by inoculating with Fusarium moniliforme, a pathogen that causes grain mold and stalk rot of sorghum. After inoculation with F. moniliforme, reduced lignin lines had significantly smaller lesions than wild-type lines. The results from this work suggest that reduced lignin lines can exhibit increased resistant to Fusarium species, including F. moniliforme.
Technical Abstract: Two genes conferring the brown midrib (bmr) trait had been backcrossed into six elite sorghum lines, resulting in reduced lignin in the bmr lines when compared with the wild-type parent. Seed and leaf tissue from field-grown plants, planted at two locations, were screened for Alternaria spp. and Fusarium spp. on semi-selective media. The results suggest that bmr lines do not have increased susceptibility to colonization by Alternaria species. However, when fungal outgrowths from seed from two genetic backgrounds were selected on Fusarium selective medium, significantly fewer Fusarium spp., including Fusarium moniliforme, were recovered from reduced lignin lines. That the bmr trait, at least in some genetic backgrounds, might enable increased resistance to colonization by F. moniliforme was further supported by greenhouse bioassays in which peduncles of developing heads were inoculated with F. moniliforme. Mean lesion measurements were significantly lower than those resulting from inoculations on wild-type lines. When analyzing near-isogenic lines, mean lesion lengths on bmr lines were significantly less than those produced on their wild-type counterparts in 4 of the 6 genetic backgrounds. These results suggest that reduced lignin lines can exhibit, in some cases, increased resistance to Fusarium spp., including F. moniliforme.