Culture collections, the new herbaria for fungal pathogens

Abstract

This paper discusses the importance of culture collections in plant pathology and reviews the methods currently available to store cultures. The preservation and maintenance of plant pathogenic fungi in a viable yet stable state for long periods has always been important, because isolates of these fungi can serve as standards for identification of quarantine taxa. Such isolates are also important for testing disease resistance and for plant breeding programs. The increasing use of molecular sequences analysis in the systematics of plant pathogenic fungi has meant that maintaining fungi in culture collections has become essential. Herein we discuss trends in the identification of plant and post-harvest pathogens, using Aspergillus, Colletotrichum, Phyllosticta and Mycosphaerella and its anamorphs as examples. Herbarium specimens, although still a requirement of the Botanical Code when describing new species are, perhaps, less important in providing useful information when defining a pathogenic species. Many pathogen groups consist of complexes of species and morphology alone can no longer distinguish among species. However, ex-type living cultures are essential for identification and future species comparisons that incorporate the use of molecular techniques. As such, ex-type cultures of any new species of pathogen, or when new diseases are reported or studies involving pathogenic strains are published, cultures of the taxa studied should be deposited in widely available culture collections, preferably in at least three members of World Federation for Culture Collections. Methods for the storage of fungal cultures such as water preservation, freezing, mineral oil overlay, freeze drying and lyophilization are reviewed in this paper. The main objective of culture preservation is to maintain the vigor and genetic characteristics of a pure culture. Therefore, safe long-term preservation methods are required to ensure fungal survival and retention of any valuable characteristics. To minimize the risk of any morphological, physiological, or genetic changes, several different preservation conditions should be used whenever possible. The present review also describes a complete preservation methodology that can be used for plant pathogenic fungi.

The genus Phomopsis: biology, applications, species concepts and names of common phytopathogens

“…Isolates that represent type species are needed. Publication of new species should be amalgamated with type derived sequences and type derived cultures should deposit in recognized culture collections (Shenoy et al 2010;Abd-Elsalam et al 2010;Hyde et al 2010a, b). Species and infraspecific research should be expanded and incorporate a polyphasic approach.…”

“…Prof. Zide Jiang). It is paramount that efforts are made to preserve these important cultures (Abd-Elsalam et al 2010). If cultures are maintained in the regional collections with limited resources, they should also be deposited in international collections such as CBS and ATCC.…”

“…If cultures are maintained in the regional collections with limited resources, they should also be deposited in international collections such as CBS and ATCC. It is necessary to distribute holotypes, isotypes and extype specimens and cultures in several herbaria and culture collections, and deposit the type derived sequences in public databases (Ozerskaya et al 2010;Abd-Elsalam et al 2010).…”

The need to carry out re-inventory of plant pathogenic fungi

“…Given the importance of living cultures for understanding the biology and systematics of plant pathogenic fungi (Abd-Elsalam et al, 2010), there is an urgent need to epitypify many fungal species and reidentify pathogens, especially those previously placed in the species complex. This may necessitate returning to the original collecting localities and original hosts to collect morphologically identical specimens and to deposit them as epitypes, supplemented with ex-epitype strains (Hyde & Zhang, 2008).…”

Evaluation of the gelatin technique for the preservation of phytopathogenic fungi

“…The existence of a method that is able to preserve viability, sporulation and pathogenicity of as many genera and species as possible, will be more reliable, and more preferably, but isolated no technique has been successfully applied to all fungi (ABD-ELSALAM et al, 2010;CAMILO, 2013). Several protocols have been developed and applied, however, most have not proven fully effective, because of the peculiarities of the cultures and even the characteristics of techniques; therefore it comes to explaining the combination of two or more methods in order to ensure the best recovery (GREEN, 2008).…”