by Caleb Sooknanan ’20

Dr. Xiao-Lin Li and researchers at Zhejiang University in China recently discovered a new fungal species, now identified as Scopulariopsis gossypii. The species was found in the vascular bundles of cotton plants infected by Verticillium dahlia, a pathogen of economic importance throughout the city of Hangzhou. Scientists have already associated the genus Scopulariopsis with fungi that are isolated from air and soil; some of these fungi have been known to act as colonizers or pathogens of larger animals like humans. With this in mind, the researchers conducted a study to understand the pathogenic and endophytic characteristics of the gossypii species.

The researchers first collected cotton plant samples from one of Zhejiang University’s experimental fields and isolated the fungi present. This was done to isolate the Scopulariopsis species when symptoms of Verticillium wilt were identified during the flowering period. The researchers cut into the middle portion of the stem of 50 infected plants and 50 healthy plants.  Each stem piece was then further cut apart and separated into vascular and avascular tissue. Samples from the discolored parts of vascular tissue in diseased plants were examined via scanning electron microscopy (SEM), and three particular isolates underwent PCR amplification and sequencing. Using these techniques, the researchers were able to identify positive clones and extract their plasmids. Morphological studies and pathogenicity tests were also conducted to obtain further information about the fungal species.

The researchers were able to obtain several details concerning the fungi species’ traits. SEM analyses showed that the fungus was present in parenchymal cells that encased vessels in dark brown vascular stem tissue, and produces asexual spores or conidia within the tissue. The researchers’ phylogenetic, morphological, and molecular analyses proved that S. gossypii was a previously undescribed species of Scopulariopsis. By inoculating wounded roots, the researchers were able to verify that S. gossypii was an opportunistic pathogen that caused leaf interveinal chlorosis and vascular browning of cotton plants, but the species did not infect hosts with undamaged roots, thereby limiting the disease severity under such conditions.

One of the study’s limitations involves S. gossypii’s inability to directly infect cotton plants through healthy roots under the research conditions. Thus, more research is needed to understand how this particular species enters and infects healthy cottons plants. Nevertheless, the study showed that S. gossypii could elicit visible symptoms on cotton plants and significantly increase disease severity when inoculated in conjunction with V. dahliae. Further information on this topic may help scientists control the spread of fungal infections in plants.

References:

1. X. Li, et al. A new species of Scopulariopsis and its synergistic effect on pathogenicity of Verticillium dahliae on cotton plants. Microbiological Research. 201, 12-20 (2017), doi: 10.1016/j.micres.2017.04.006
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