Response of soybean genotypes to infection with Phomopsis longicolla Hobbs

Constant increase of acreage under production of soybean raises the issue of disease control (Glycine max (L.) Merril. There are diseases, which almost regularly appear in our agroecological conditions, such as downy mildew (Peronospora manshurica (Naum.) Syd. ex Gaum.), and diseases caused by fungus from Diaporthe/Phomopsis Complex. The aim of this investigation was to check the reaction of five domestic soybean genotypes (OS-8, OS-49, OS-101, OS-109 and OS-139) to infection with fungus Phomopsis longicolla Hobbs, which causes soybean seed decay. Experiments were carried out through artificial seed infection in wet chamber and in pots with sterile soil. Tested genotypes, maturity group 0-I are created at the Agricultural Institute of Osijek within the program of soybean breeding. Fungus was isolated from soybean seeds that exhibited symptoms of Phomopsis longicolla Hobbs. Soybean seeds were separated from samples that were collected on 10 locations under large-scale production during a period of three years (2000-2002). Evaluation of pathogenicity was done by counting germinated and non-germinated (rotten and healthy) seeds and by determining the germ length and germ necrosis of tested genotypes. According to results obtained during a wet chamber trial, numbers of germinated and non-germinated seeds among tested genotypes were significantly different (P-0.05). Relation between artificially infected seeds and control in trial showed significant differences for each genotype (P-0.05). All genotypes in control had satisfactory germination and there were no significant differences in number of rotten seeds, germinated seeds and non-germinated seeds. The OS-49 and OS-109 genotypes were proved to be more resistant to infection with P.longicolla. Results from pot trial showed that number of germinated seeds of artificially infected genotypes was significantly different (P-0.05) during whole trial, while all genotypes in control germinated satisfactory, showing no significant differences among themselves. Taking into consideration these results, it can be concluded that the OS-8 genotype is more susceptible to infection with P. longicolla. Both trials of artificial infection were successfully completed, resulting in conclusion that there are differences in resistance to infection with this fungus among tested soybean genotypes.