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Specificity, interaction and additivity in host‐pathogen systems
Author(s) -
VANDERPLANK J. E.
Publication year - 1988
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.1988.tb02063.x
Subject(s) - flor , biology , column (typography) , confusion , genetics , psychology , mathematics , botany , geometry , connection (principal bundle) , psychoanalysis
In the literature of plant pathology, unspecific interaction, as statisticians use the word, is commonly called ‘specificity’ or ‘race specificity’. Specificity, in the sense used by Flor, is confused with interaction, defined statistically. Admittedly, specificity in Flor's sense implies statistical interaction. But the converse is not true. Statistical interaction does not necessarily imply Flor's specificity. This confusion prompted me to inquire into the concepts of what seem to me to be the three major systems of host‐pathogen relations: additivity, interaction, and specificity. I suggest definitions, the definitions of additivity and interaction following standard statistical usage and the definition of specificity following Flor's sense. Further, I examine briefly tests to distinguish (unspecific) interaction from specificity, and additivity from interaction. Interaction, as the word is used by statisticians, arises from the variation in row differences from column to column or in column differences from row to row (Adams, 1955). Put differently, interaction is measured by the failure of effects to be additive (Snedecor, 1956). Additivity is the antithesis of interaction. There is no significant variation in row differences from column to column or in column differences from row to row. Specificity in a gene‐for‐gene system refers to complementary one‐for‐oneness. Flor's hypothesis reads: “for each gene conditioning resistance in the host there is a specific complementary gene conditioning pathogenicity in the parasite”. Flor's use of the word specific goes back to 1942 when his hypothesis was still embryonic; “The data in the present paper indicate that the range of pathogenicity of a physiologic race of Melampsora lini is determined by pathogenic factors specific for each resistance factor possessed by the host” (Flor, 1942). Specificity is a form of interaction. There is specific interaction, i.e. interaction with complementary one‐for‐oneness, and unspecific interaction, i.e. interaction without one‐for‐oneness.