Appearance of fungus Sclerotinia sclerotiorum (Lib.) de Bary on soybean seed in the period from 2005 to 2007

Abstract

Sclerotinia sclerotiorum causes white rot disease in plants and has a very wide range of hosts. The highest levels of susceptibility to this pathogen are found in plants from the families Asteraceae (sunflower) and Fabaceae (soybean, bean, string bean). The fungus overwinters in nature in the form of sclerotia and mycelia in soybean seed. Seed health testing is done under laboratory conditions as one of the most important parameters of seed quality. According to the Rulebook on Health Testing of Seed, Seedlings and Planting Material (Official Gazette of RS, Issue No. 119/07), soybean seed is allowed to be 10% infected by S. sclerotiorum. Some 30 individual soybean samples were included in our investigation and the average level of seed infection at different localities in Vojvodina (Vrbas, Bačka Palanka, Srbobran, Rimski Šančevi) during 2005, 2006 and 2007 was determined. Isolation, identification and determination of Sclerotinia sclerotiorum were done on the PDA nutrient medium according to the NSHS Sf 3.1. method. Seed incubation was done for 10 days at 25ºC, and infection was estimated after 3, 5, 7 and 10 days. The fungus develops characteristic and easily recognized colonies. The fungus mycelia are white or cream in colour, and the sclerotia develop regularly, mostly at the edges of the colony. Our results showed relatively low levels of infection by the fungus, with the average levels over the years being 0.25-3.25% in 2005, 0.25-1.75 % in 2006, and 1.50-2.5% in 2007.

Sclerotinia sclerotiorum je prouzrokovač bele truleži biljaka i ima vrlo širok krug domaćina, a posebno su osetljive biljke iz fam. Asteraceae (suncokret) i Fabaceae (soja, pasulj, boranija). Gljiva se u prirodi održava u obliku sklerocija i micelijom u semenu soje. Ispitivanje zdravstvenog stanja semena vrši se u laboratorijskim uslovima, kao jedan od važnih parametara kvaliteta semena. Pravilnikom o zdravstvenom pregledu semena, rasada i sadnog materijala ('Službeni glasnik RS' 119/07), dozvoljeno je do 10% zaraze gljivom S. sclerotiorum na semenu soje u prometu. Naša istraživanja obuhvataju ispitivanje 30 pojedinačnih uzoraka soje i utvrđivanje prosečne infekcije semena, proizvedenih u različitim lokalitetima Vojvodine (Vrbas, Bačka Palanka, Srbobran, Rimski Šančevi) tokom 2005, 2006. i 2007. godine. Izvršena je izolacija, identifikacija i determinacija gljive Sclerotinia sclerotiorum na hranljivoj PDA podlozi (NSHS Sf 3.1.). Inkubacija semena traje 10 dana na 25ºC, a ocena zaraze vrši se nakon 3,5, 7. i 10. dana. Gljiva stvara karakteristične i lako prepoznatljive kolonije. Micelija gljive je bele ili smeđe boje, a sklerocije u kulturi se stvaraju redovno, uglavnom na rubovima kolonije. Naši rezultati ukazuju na relativno nisku zarazu semena ovom gljivom i u proseku procenat infekcije zaraženog semena po godinama se kreće: 2005. (0,25-3,25%); 2006. (0,25-1,75 %); 2007. (1,50-2,5%).