Survey for Pyrenophora teres and Ramularia collo-cygni in barley grain from Italy

A 2 year study (2019/2020 and 2020/2021 growing seasons) investigated the occurrence and distribution of the barley pathogens Pyrenophora teres and Ramularia collo-cygni (Rcc) in grain in Italy. Pyrenophora teres occurs as two forms causing different host symptoms, P. teres f. teres (Ptt), causing net form net blotch and P. teres f. maculata (Ptm) causing spot form net blotch. Ramularia collo-cygni causes Ramularia leaf spot. Pyrenophora teres and R. collo-cygni cause significant economic damage to barley crops, and their seed-borne stages make their control challenging. Distribution of these two pathogens across different geographic regions was examined in 99 barley grain samples collected from northern, central or southern Italy, characterized by different climatic conditions. Fungal isolates from barley grains onto potato dextrose agar were identified using morphology and polymerase chain reaction (PCR) assays with species-specific primers, and amounts of fungal DNA in grain were quantified using quantitative real-time PCR (qPCR). Traditional isolation methods showed presence of Ptt, but did not provide information to assess Rcc distribution and infection levels, as no Rcc isolates were observed. The qPCR assays also revealed presence of Rcc over the two growing seasons, and amounts of Ptt DNA were greater than for Rcc, particularly in malting barley varieties in2019/2020. Presence of Ptm DNA within grain was detected in only two of the 99 grain samples.