Hansfordia pulvinata Hyperparasiting Passalora fulva on Organic Tomato Plants

Abstract

Tomato (Solanum lycopersicum L.) is one of the most commonlyused vegetables worldwide. The production of organic tomatoes,grown without using any chemicals, has continuously increased inKorea since consumers started to demand organic foods. In organictomato greenhouses in Iksan and Jeonju, Korea, a change wasobserved in a tomato leaf mold ( Passalora fulva , syn. Fulvia fulva )in spring, 2009. The dark brown lesions of this mold changed intowhite to pale grayish ones, by growth of an overgrowing fungus(Fig. 1A). On some old leaves, the leaf mold lesions were largelydestroyed and covered with the white fungus (Fig. 1 B & C). It wasalso observed that young colonies of leaf mold were suppressed bythe white fungus, and further expansion of the lesions was arrested.The overgrowing white fungus was microscopically examinedfrom representative samples, which are housed at Korea University(KUS-F24001, F24017). Conidiophores were erect, straight, smooth,variable in length, reaching up to 500 µm, 2-4 µm wide, branchedrepeatedly at the upper part, pale olivaceous brown (Fig. 1D).Conidiogenous cells were integrated, terminal, cylindrical, sub-hyaline, denticulate, 7-15×2-3.5 µm (Fig. 1E & F). Conidia weresolitary, globose, smooth, aseptate, subhyaline, 4-6µm, with aninconspicuous hilum (Fig. 1G). Based on these morphologicalcharacteristics, the fungus was identified as Hansfordia pulvinata(Berk. & M. A. Curtis) S. Hughes (Saccardo, 1886).To confirm the identity of the fungus, the ITS rDNA region of anisolate obtained from KUS-F24001 was amplified and sequenced.A resulting sequence of the isolate was deposited in GenBank(HM060587). A BLAST search indicated that the ITS sequenceshared 98% similaritywith a sequence of H. pulvinata (AY908993). Monoconidial isolates of H. pulvinata were successfully cultur-ed, forming velvety grayish colony with abundant conidia on PDA(Fig. 1H). The isolates were deposited in Korean AgriculturalCulture Collection, Suwon, Korea (KACC44498 and 44502). Amycoparasitic test was carried out using detached leaves from 1-month-old tomato plants infected with P. fulva . An inoculum (ca. 10