Abstract
Stalk rot caused by Colletotrichum graminicola is a disease of worldwide importance. Stalk rot is difficult to detect at the early stages of infection because the fungus colonizes the tissues inside the maize stem. Current diagnostic methods are time-consuming, laborious, and destructive to the stem tissue. We utilized Raman spectroscopy to follow the development of stalk rot in three different maize genotypes grown either in the field or the greenhouse. We then used the acquired spectra to calibrate statistical models to differentiate amongst the different disease timepoints and the genotypes themselves. This non-invasive spectroscopic method enabled high-accuracy identification of stalk rot based on both stalk and leaf spectra. We additionally found that leaf spectra were favorable for identifying maize by genotype. Finally, we identified Raman bands that showed correlation with the sizes of stalk rot-associated lesions in the stems. We demonstrated that Raman spectroscopy is a viable tool for detection of stalk rot disease, as well as potent for the differentiation of maize genotypes.
Highlights
Colletotrichum graminicola is one of the most economically disruptive fungi of corn and the causative agent of a disease associated with 5–20% corn yield loss in the United States alone (Sukno et al, 2008, 2014; Jackson-Ziems et al, 2014)
To investigate the ability of Raman spectroscopy (RS) to differentiate between maize varieties that contrast in their resistance or susceptibility levels to anthracnose stalk rot (ASR), we inoculated stalks of the susceptible lox4-7 mutant, its near-isogenic wild type recurrent parent, (NIL-WT) B73 inbred, which displays intermediate susceptibility and MP305 inbred with C. graminicola
Our findings show that RS can be used for highly accurate identification of stalk rot of maize at both early and late stages of disease progression
Summary
Colletotrichum graminicola is one of the most economically disruptive fungi of corn and the causative agent of a disease associated with 5–20% corn yield loss in the United States alone (Sukno et al, 2008, 2014; Jackson-Ziems et al, 2014). This pathogen can infect and cause disease primarily the leaves and stem of maize, where it leads to anthracnose leaf blight (ALB) and stalk rot diseases, respectively. SA is produced from compounds such as phenylalanine and cinnamic acid These are examples of phenylpropanoids, a family of organic compounds comprising many essential components for defense against herbivores and pathogens. As key defense molecules such as phenylpropanoids can be assigned
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