Detection of Ustilago nuda (Jensen) Rostrup in winter barley seed

Abstract

Barley is one of the most important cereals grown in our agroecological conditions. The causal agent of loose smut on barley Ustilago nuda (Jensen) Rostrup occurs frequently as varieties susceptible to this pathogen are present in the production. Disease symptoms are manifested on barley head (spike). Parasite is transmitted by seed (seedborne) and stays in the embryo tissue of the infected kernel as dormant mycelium. Recommended method for detection of U. nuda is given by ISTA Rules (method 7-013). In tests, nine samples (weighing 120 g each) of naturally infected barley seed (about 1000 seeds, depending on the absolute mass of seed) were examined, observed and described using a Zeiss microscope with sub stage illumination with magnification range x 40 or higher. Mycelium of the fungus approximately 3 μ thick, golden brown in colour was detected and visible without a stain. The percentage of infected embryos in the examined samples of barley seeds ranged from 0.8% to 5.2%.

Ječam spada u najvažnija strna žita koja se gaje u našim agroekološkim uslovima. Prouzrokovač otkrivene gari ječma Ustilago nuda (Jensen) Rostrup javlja se često, jer su u proizvodnji zastupljene sorte osetljive prema ovom patogenu. Simptomi bolesti se manifestuju na klasu. Parazit se prenosi semenom, a održava se u embrionu zaraženog semena u vidu mirujuće micelije. Prema preporuci International Seed Testing Association (ISTA) za detekciju U. nuda korišćen je metod brojanja zaraženih embriona. U ispitivanjima je korišteno 9 uzoraka prirodno zaraženog semena ječma (oko 1000 semena u zavisnosti od apsolutne mase semena). Posmatranje, ocena i fotografisanje zaraženih embriona obavljeno je pomoću Zeiss mikroskopa pri uveličanju od x 40. Konstatovana je micelija gljive debljine oko 3 μ, zlatno-mrke boje koja je vidljiva bez bojenja. Procenat zaraženosti embriona ispitivanih uzoraka semena ječma kretao se od 0,8% do 5,2%.