ABSTRACT
Microdochium nivale is one of the most harmful fungal diseases, causing colossal yield losses and deteriorating grain quality. Wheat genotypes from the world collection of the N.I. Vavilov Institute (VIR) were evaluated for fifty years to investigate their resistance to biotic stress factors (M. nivale). Between 350 to 1085 of winter wheat genotypes were investigated annually. Ten out of fifty years were identified as rot epiphytotics (1978, 1986, 1989, 1990, 1993, 1998, 2001, 2003, 2005 and 2021). The wheat collection was investigated by following the VIR methodological requirements and CMEA unified classification of Triticum aestivum L. The field investigations were carried out in the early spring during fixed-route observations and data collection was included on the spread and development degree of the disease, followed by microbiological and microscopic pathogen identifications. The observations revealed that the primary reason for pink snow mold to infect the wheat crops was abiotic stress factors, such as thawed soil covered in snow that increased the soil temperature by 1.0-4.6 °C above normal. Under these conditions, the plants kept growing, quickly exhausting their carbohydrate and protein resources, thus weakening their immune systems, which made them an easy target for different infections, mainly cryophilic fungi, predominantly Microdochium nivale in the Moscow region. In some years, the joint effect of abiotic and biotic stresses caused crop failure, warranting the replanting of the spring wheat. The investigated wheat genotypes exhibited variable resistance to pink snow mold. The genotypes Mironovskaya 808 (k-43920) from Ukraine;l Nemchinovskaya 846 (k-56861), from Russia; Novobanatka (k-51761) from Yugoslavia; Liwilla (k-57580) from Poland; Zdar (UH 7050) from the Czech Republic; Maris Plowman (k-57944) from the United Kingdom; Pokal (k-56827) from Austria; Hvede Sarah (k-56289) from Denmark; Moldova 83 (k-59750) from Romania; Compal (k-57585) from Germany; Linna (k-45889) from Finland and Kehra (k-34228) from Estonia determined the sources, stability and tolerance to be used in advanced breeding programs.
ABSTRACT
In the light of Vavilov's Law, grain traumatization in the standing crop of wheat and other crops due to the enzyme stage of enzyme-mycotic seed depletion (EMSD) was confirmed, the parameters of open and hidden harmfulness were detected, and a scale of plant resistance to such traumatization was developed. The current study demonstrates that pathogen contamination in grains occurs before harvesting and its degree is determined by favorable humidity and temperature conditions and by the open and hidden grain traumatization due to the enzyme stage of EMSD, i.e., the grain's hydrolytic enzymes providing a growth substrate for a fungal spread that is later substituted by pathogen enzymes leading to grain spoiling and self-warming. The most common technique to preserve grain quality is to support a moisture level that prevents further spreading of the fungi. The grains that are contaminated with very low temperature and humidity levels facilitate the germinability and high quality of the grain. The new ways to withstand EMSD should, first of all, include a selection of activities. Using biological, biochemical and physical (X-ray) methods, genetic sources of resistance towards EMSD were found in the VIR world collection that is recommended for further selection. These sources have become a basis for the varieties, such as Moskovskaya 39, Ilot (winter wheat), Gremme and Gremme 2U (hulless spelt), Alcoran (winter spelt) and Kanysh (spring wheat).
