Fraser firs are farmed to supply us with Christmas trees; they can hold their needles well, they have a great color, and their aromatic smell is a pleasant one. However, they are quite vulnerable to root rot diseases, which are caused by Phytophthora water molds that can devastate the trees. Researchers have now found a new species of Phytophthora mold that can affect Fraser firs. The findings have been reported in the journal of the American Phytopathological Society, Plant Disease.
Researchers were assessing various ways to grow healthier Fraser firs, and during their experiments, they came across the previously unknown mold species. They gathered the diseased trees, isolated the offending pathogen, and grew the mold in culture. They proved that it was pathogenic by exposing healthy plants to the new Phytophthora species, and then isolated it again.
The researchers extracted DNA from the pathogenic mold and sequenced various regions of it, which they then compared to known species.
"Once the organism was isolated, the presence of unusually thick spore walls alerted us that this may not be a commonly encountered species, and so comparison of several genes' sequences with known Phytophthora species was used to discover how our unknown was related to other, previously described species," noted Rich Cowles, a scientist at the Connecticut Agricultural Experiment Station involved with this study. It seemed that they had revealed an entirely new species.
The easy identification of this new species has suggested that many more kinds of molds that can affect trees might be awaiting discovery.
"Knowing how many and which species are present is important, not only for Christmas tree growers, but also for protecting our natural environment," added Cowles.
It's important to recognize that this genus might be highly diverse. If infected tree stocks are transported and come into contact with other plants, they might cause contamination. If they meet a different Phytophthora species, it may lead to the generation of new hybrids that have different characteristics than the parent species.
A technique from 1931 was used in this work, showing that old methods are still useful in modern research. "Combining this robust old technique worked well with modern molecular biology methods to isolate, and then identify our unknown plant disease," said Cowles.
Learn more about diseases that can affect Christmas trees from the video above by the University of New Hampshire Cooperative Extension. The video below, also by UNH, illustrates different species of Christmas trees.