Resistance of modern maize hybrids to smut diseases in the conditions of the Northern Steppe of Ukraine

The research results of the resistance determination of the maize hybrids (Zea mays L.) of different maturity groups to the affection by boil (Ustilago zeae (Beckm.) Unger) and kernel (Sphacelotheca reiliana (Ruhn) Clint) smuts in the Northern Steppe of Ukraine were provided. During 2016–2018, the experiments were conducted in the fields of the State Enterprise “Experimental Farm “Dnipro” of the State Enterprise Institute of Grain Crops of NAAS. The assessment scale of maize hybrids resistance to smut was given. Over the years of research, 52 samples were analyzed. It was found that the common boil smut was widely distributed in 2016, when the hybrids disease average was 2.7 %; only on plants of DN Burshtyn medium-ripe hybrid the infection was not detected. 2017 was unfavorable for the spread of the disease: only 23 % of maize hybrids of medium-ripe and medium-late ripening groups had smut tumor, the average disease degree was 0.4 %. In 2018, half of the studied samples showed no boil smut symptoms, the average degree of disease was 0.9 %, and DN Galateia middle-early hybrid had a maximum degree of disease – 6.7 %. The analysis of the received data testifies that for years of researches there were most resistant to affection by boil smut such hybrids as: DB Lada, DN Rubin, Dniprovskyi 181 SV, DN Adzhamka, DN Burshtyn, DN Veles, DN Astra, DN Sarmat, DN Bulat, DN Palanok and DN Dnipro, and they belonged to different maturity groups. According to the hybrids resistance scale to boil smut, all studied samples were highly resistant and resistant. The tumor was the most often found on the ears, less often on the stems and other parts of the plant. Regarding kernel smut, the survey results indicated a tendency to increase of the disease spread level in the Northern Steppe. In 2016 a 40 % of hybrid samples was affected by kernel smut with an average affection of 0.9 %; in 2017 these indicators were 71.0 and 3.7 %, and in 2018 – 86.0 and 5.9 %, respectively. Over the years of research, it was determined that the DN Astra middle-early hybrid is the most resistant to kernel smut compared to plants of DN Palanok, DN Vesta, DN Demetra, DN Bulat and Pochaivskyi 190 MV hybrids, which were affected annually. According to the hybrids resistance scale to kernel smut, it was found that in 2016 all samples were in the highly resistant group, and the disease degree did not exceed 10 %. In 2017, more than 10 % of plants of DN Adzhamka, DN Vesta, DN Hetera and DN Nazar hybrids were affected, so they were classified as resistant forms, other samples – as highly resistant. In 2018, only the DN Palanok hybrid was estimated as medium-resistant, 6 hybrids (DB Lada, Pochaiivskyi 190 MV, Nur, Korund, DN Galateia, DN Dnipro) belonged to the resistant group, the rest – to the highly resistant group. Regarding the affected hybrid plants, kernel smut was mainly detected on the ears and partly on the panicles (sometimes simultaneously). It was found that 2016 was favorable for the maize hybrids affection by boil smut, and 2018 – by kernel smut. It was found that the degree of plants affection by smut diseases did not depend on the maturity group of the hybrids. All tested samples are highly resistant and resistant to both types of smut. Key words: hybrids, maize, affection, kernel smut, boil smut.