Effect of seed disinfection on the quality indicators of germination and the incidence of Loose smut disease of barley

Loose smut caused by Ustilago nuda is one of the barley’s critical seed-borne diseases, causing crop yield to decrease. Using a healthy seed disinfected with chemical fungicides is the simplest and most cost-effective way to prevent the damage caused by loose smut disease of barley. The purpose of this study was to investigate the health status of barley fields concerning Loose smut disease and assess the effect of seed infection. It also sought to examine the effectiveness of seed disinfection with Iprodione-carbendazim (Rovral-TS®) and Carboxin thiram (Vitavax-thiram®) fungicides on traits related to germination, disease incidence, and antioxidant defense system responses.

The fields of Isfahan, Markazi, Zanjan, Tehran, Alborz, West Azerbaijan, Hamedan, Razavi Khorasan, Qazvin, Qom, Semnan, Fars, South Khorasan, North Khorasan, Sistan and Baluchestan, Kohgiluyeh and Boyer-Ahmad, Khuzestan, and Ilam provinces of Iran were sampled according to the International Rules for Seed Testing to investigate the health status of barley seeds. Detecting the seed infected with the agent of the Loose smut disease was carried out using the embryo test. Then, the activity level of antioxidant enzymes (superoxide dismutase, catalase, and polyphenol oxidase enzymes), the oxidative damage index malondialdehyde, and the content level of phenolic compounds and total protein were investigated.

In the range of 1.1% to 0.05%, approximately 13% of the barley seed samples collected from various fields were infected with loose smut disease. Infected barley seeds can significantly reduce vigor indices without affecting germination percentage. The results showed that seed disinfection with chemical fungicides improved the dry and fresh weight, average root length, seedling weight vigor index, coefficient of germination velocity, and mean times germination. Chemical fungicides’ effectiveness in reducing disease incidence varied depending on the type of fungicide and the infection level of the seed. Compared to Carboxin thiram fungicide, seed disinfection with Iprodione-carbendazim fungicide significantly improved some quality characteristics in seed germination and reduced disease incidence. The findings of the biochemical mechanisms investigating revealed that the activity level of antioxidant enzymes (superoxide dismutase, catalase, and polyphenol oxidase enzymes) and the content of phenolic compounds in spikes obtained from infected and non-infected seeds were higher than the control. In addition, seed disinfection with chemical fungicides increased total protein content while decreasing the membrane peroxidation index compared to the control.

The current study found that chemical fungicides seed disinfection increased the levels of defensive enzymes and the content of phenolic and protein compounds, which may help to limit infection and improve the level of defense-related antioxidant enzymes in barley. These findings shed new light on the effect of seed infection levels and seed disinfestations on the stimulation of the antioxidant defense system in barley basal resistance, which can be used to manage loose smut disease effectively.