engleski

Soybean seed decay in Croatia

Soybean seed decay, caused primarily by the fungus Phomopsis longicolla Hobbs, is one of the most serious seed diseases of soybean (Glycine max (L.) Merrill). P. longicolla is different among the other fungus in Diaporthe/Phomopsis complex for his cultural characteristic, morphology and place of infection (primary causing seed decay), and it is one of the most dangerous seed pathogens in the world main areas of soybean production. Considering that the fungus was discovered in our neighbor's countries and there was suspicion of its presence in Croatia, there is danger of becoming a significant pathogen of this important industrial plant in our country as well. The aim of the investigation was to establish the presence of P. longicolla by seed examination out of several locations from large-scale production and during three years (2000 - 2002) to characterize the pathogen by morphological characteristic in culture, and by establish the differences in strain virulence by artificial seed infections in the laboratory. Fungus isolation was accomplished from soybean seed with symptoms of Phomopsis longicolla Hobbs, and separated from samples that were collected during three years (2000- 2002) from large-scale production out of 15 locations. Morphological characteristics of the ten selected strains were studied in aim to determine the isolated fungi and compared with characteristic of strains used in paper by Hobbs et al., (1985). Investigation of obtained strains virulence was carried out by soybean seed inoculation in laboratory through trials in wet chamber and pots. After establishing the most aggressive among selected isolates in previous conducted trials, trials with artificially infected seed were repeated (both, in wet chamber and pots), but this time using the most aggressive isolate and several promising lines created in frame of soybean breeding program at The Agricultural Institute Osijek. Morphological characteristic was investigated through examination of strains on PDA, forming fruiting bodies as well as the measurement of length, width and length-to- width ratio of alpha conidia. Evaluation of strain virulence was done by counting germinated and non-germinated (rotten and healthy) seeds and by determining the germ length and germ necrosis of tested genotypes. Statistical data processing was carried out by computer software Statistical Analysis System Version 8.2 (SAS Institute) with analysis of variance (ANOVA) and LSD (Least Significant Difference) test. According to morphological characteristics and measurement of alpha conidia of investigated strains they respond to characteristic of P. longicolla Hobbs that confirm presence of this pathogen in soybean large-scale production in Croatia. Also, the differences in virulence among tested fungal strains were obtained in this investigation.

soybean ; Phomopsis longicolla Hobbs ; strains ; virulence

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