Comments

The authors present important new insights into the biology of the neotropical coffee leaf pathogen Mycena citricolor. It demonstrates for the first time experimentally that different strains from different host plants (including other hosts than coffee) can infect coffee. It is also shown for the first time that different strains also show strain specific morphology, reproductivity and infectivity. The experiments are carefully conducted and evaluated with a broad spectrum of measurements and tests. The study is quite unique by its significant contribution of new knowledge without any molecular study. The rich and esthetically pleasant illustrations will surely further catch citations for the journal!
In spite of the uniqueness of the paper, some shortcomings suggest major revision.
1. The title is a little bit too “pale” compared to the significance, particularly the word “occurrence” could be replaced. “Experimental characterization of reproduction biology of Mycena citricolor from different hosts” would perhaps be better, but too broad. Please, think about highlighting your message more strongly in the title.
2. The English is very “Hispanic” by direct translation of Spanish eloquence, while scientific English should be as simple as possible. Spanish words such as in Table 3, of course, have to be translated. I find that the content is worth of major adjustment of the English. I tried to give some suggestions in the annotated manuscript, but hope that other reviewers, the editor, and particularly the authors themselves will further improve the text!
3. Deposit of strains or specimens in a professional permanent culture collection or/and herbarium is missing but is an absolute requirement for scientific reproducibility. If the institution of one of the authors runs a permanent culture collection, citing this for deposit of the authors’ mineral-oil preserved strains would be ok. Though there is presently no doubt that the species identification of M. citricolor is correct, the authors themselves suggest that future genetic studies may reveal some intraspecific diversity.
4. In the infection experiments, I could not find any control. The authors may add a simple control experiment by using agar plugs and/or killed gemmae as inoculum in order to prove that lesions are not induced by such stimuli alone.
5. Measuring the density of mycelia in culture in the form of pixels is a creative good idea, but the term “optical density” is applied in measuring the speed of light transmitting through a medium, which is quite different from the method applied here. Perhaps “pixel density” or “mycelium density” would be better in order to avoid the misleading “optical density”. To my knowledge, this method has not been widely applied in measuring mycelium density in solid media, but has some good potential. It would, therefore, be good if the authors could explain their method more in detail.
6. The authors correctly address the lack of knowledge about the pathogenesis mechanisms in M. citricolor, but this should be done more general than in the obscure example about a Penicillium species (there are many more really plant pathogenic fungi!), oxalic acid, and the confuse discussion with the misapplied term “hemibiotrophic”. First, the latter term itself is prettily obscure and rather represents the lack of knowledge than a clear-cut distinction between necrotrophic and biotrophic. Usually only fungi which live parasitically in green plant tissues and cannot be cultivated are considered biotrophic. Mycena citricolor can be cultivated, which proves that it can grow saprobically. It induces conspicuous death of plant tissues in which the fungus develops with sufficiently indicates its nectrophism. The production of gemmifers in the Petri dish has nothing to do with necro-, bio-, or “hemibio”-trophic interaction in the plant. Please, delete the paragraph discussing this irrelevant question.
7. The use of the terms related to gemmifer and gemma is inconsistent and should be uniform. In part 2.3 the term gemmifer is erroneously applied for the gemmae. Gemmae are used for inoculation tests, not the gemmifers themselves. For the gemma (plural gemmae), only these terms should be used throughout the text, not “gems” or “gemmas”. The terms gemma/gemmae exactly refer to the asexual propagules as in Buller (1958) and many subsequent authors.
8. In some illustrations, the place and time is given, but in the photos, where this information would be more important, it is missing. The first author wishes to contrast this contribution from the coauthors, but it is not necessary to add “provided” in the legends. In the legend to Fig. 4, I do not understand what A, B, C means. This should be explained in more detail.
9. The authors of scientific names need to be given only once in the text. Particularly when mentioning M. citricolor in the legends, the authors have to be omitted. In the host plants which were only identified to genus, the authors are superfluous, but the plant name should always given as e.g. Commelina sp., not as Commelina or Commelina L.