Phomopsis longicolla - new pathogen on Abutilon theophrasti in Croatia

K. Vrandecic^1*, J. Cosic¹, L. Riccioni², T. Duvnjak³ and D. Jurkovic¹

¹ Faculty of Agriculture in Osijek, PO Box 719, 31000 Osijek, Croatia
² Istituto Sperimentale per la Patologia Vegetale, Via C.G. Bertero 22, I-00156 Roma, Italia
³ Agricultural Institute in Osijek, PO Box 149, 31000 Osijek, Croatia

*kvrandecic@suncokret.pfos.hr

Accepted for publication 03/12/03

As part of a research project ('Mycopopulations on weeds in row crops'), several fungi were recovered from velvetleaf plants (Abutilon theophrasti) in eastern Croatia. During early autumn 2002 velvetleaf plants with canker symptoms were collected from sugarbeet and soybean fields (Fig 1). Using standard phytopathological methods (culturing in a moist chamber and isolation on acidified PDA at 25ºC, with a 12/12 h light/dark regime) a Phomopsis spp. was isolated from diseased stem tissue. The cultural characteristics, pattern of stromata (Fig. 2), the formation of only alfa conidia (Fig. 3), biometrical comparisons of pycnidia and conidia and prominent pycnidial beaks, identified these two isolates from velvetleaf as Phomopsis longicolla (Hobbs et al.,1985).

To confirm the morphological identification of isolates, DNA was extracted from monoconidial cultures and the ITS regions of the rDNA were amplified with universal primers ITS5 and ITS4, and digested with AluI, RseI and MseI restriction enzymes (Riccioni et al., 1998; Riccioni et al., 2003). All isolates showed the characteristic electrophoretic profiles of P. longicolla. The amplified ITS products were also sequenced (M-MEDICAL, Genenco, Rome, Italy) and subsequent searches of the GenBank sequence database revealed that the Croatian isolates from velvetleaf were identical to the sequences of P. longicolla isolates from soybean.

Figure 3: Conidia of P. longicolla from velvetleaf

Pathogenicity testing was done according to Li et al. (2001). Mean stem lesion lengths caused by the velvetleaf and soybean isolates were 16 and 20.6 mm respectively, on soybean stems and 12 and 22 mm respectively, on velvetleaf stems. P. longicolla was reisolated from the stem lesions of the inoculated plants.

P. longicolla is a very harmful seed pathogen and for this reason it is of great importance to recognise possible host plants which could be a source of inoculum. A previous paper (Li et al., 2001) already reported velveleaf as host of P. longicolla in the USA. This however the first report from Europe.

Hobbs TW, Schmitthenner AF, Kuter GA, 1985. A new Phomopsis species from soybean. Mycologia 77, 535-544.

Li S, Bradley CA, Hartman GL, Pedersen WL, 2001. First report of Phomopsis longicolla from velvetleaf causing stem lesions on inoculated soybean and velevetleaf plants. Plant Disease 85, 1031.

Riccioni L, Zhang A, Hartman G, 1998. Messa a punto di un metodo biomolecolare per la identificazione di Diaporthe/Phomopsis spp. Notiziario sulla protezione delle piante, 9, 97-104.

Riccioni L, Conca G, Pucci N, 2003. Identification by PCR-RFLP of Phomopsis/Diaporthe Species on Italian Soybean. Proceedings of the 8th International Congress of Plant Pathology, 2003. Christchurch, New Zealand: ISPP, 322.

The British Society for Plant Pathology