Host-Range Dynamics ofCochliobolus lunatus: From a Biocontrol Agent to a Severe Environmental Threat

Abstract

We undertook an investigation to advance understanding of the host-range dynamics and biocontrol implications ofCochliobolus lunatusin the past decade. Potato (Solanum tuberosumL) farms were routinely surveyed for brown-to-black leaf spot disease caused byC. lunatus. A biphasic gene data set was assembled and databases were mined for reported hosts ofC. lunatusin the last decade. The placement of five virulent strains ofC. lunatuscausing foliar necrosis of potato was studied with microscopic and phylogenetic tools. Analysis of morphology showed intraspecific variations in stromatic tissues among the virulent strains causing foliar necrosis of potato. A maximum likelihood inference based onGPDHlocus separatedC. lunatusstrains into subclusters and revealed the emergence of unclustered strains. The evolving nutritional requirement ofC. lunatusin the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots. Our results contribute towards a better understanding of the host-range dynamics ofC. lunatusand provide useful implications on the threat posed to the environment whenC. lunatusis used as a mycoherbicide.