Influence of year conditions on inheritance parameters of resistance to phomopsis stem canker and botrytis head rot pathogens by F1 sunflower

Abstract

The aim and tasks of the study. To determine the value of sunflower lines by ability to produce hybrids that would be resistant to the most common and harmful diseases (Phomopsis stem canker  and Botrytis head rot) and the type of dominance of mild disease in F₁ depending on year conditions.

Material and methods. To obtain experimental hybrids in 2007-2013, crosses were annually conducted by incomplete top-cross scheme, and 56-90 experimental hybrid combinations were generated. Combinations were chosen by contrasting scores of Phomopsis-  and Botrytis-induced damage in parents. On provocative background, we determined the intensity of Phomopsis-induced damage in each parent and hybrid plant by conventional phytopathological methods. Provocative background was formed by short four-year crop rotation (fallow - winter wheat - millet - sunflower) in the phytopathological sunflower nursery of the scientific crop rotation at the Plant Production Institute nd. a VYa Yuryev NAAS, which was laid out in the early 70-ies of the last century. To characterize the inheritance of resistance to the pathogens, we assessed the type of dominance.

Results and discussion. Assessment of the type of dominance (hp) of resistance to Phomopsis by F₁ sunflower showed significant fluctuations in percentage of hybrid combinations in all types of inheritance. However, the greatest range of variation was recorded both for positive superdominance (4.5% to 83.7%) of resistant parent and for negative superdominance (3.3% to 67.4%) of susceptible parent. In inheritance of resistance to Botrytis by F₁ sunflower, a similar ratio of hybrid combinations with the same types of inheritance was found, but a larger range of variation was observed for negative superdominance of susceptible parent (16.07% to 72.22%) than for positive superdominance of resistant parent (8.89% to 62.50%).

Conclusions. Thus, we revealed the greatest amplitude in the degree of dominance (hp) of resistance to Phomopsis in F₁ sunflower both for positive superdominance of mild disease in parents and for negative superdominance of strongly affected parent. In terms of F₁ sunflower hybrids resistance to Botrytis, we recorded a similar segregation of hybrid combinations with the same types of inheritance. In general, generalization of the data on the types of inheritance of resistance to the both pathogens demonstrated that in 2007-2013 one third of hybrids had hp values indicating positive superdominance of resistant parent and negative superdominance of susceptible parent. The remaining hybrids had hp values typical for intermediate inheritance with slight deviations towards negative or positive dominance of parents with the corresponding level of affection. The established patterns of inheritance of pathogen-induced damage made it possible to select valuable parent that are resistant both to Phomopsis and to Botrytis for efficient breeding of sunflower hybrids. Basing on the percentage of hybrids with positive superdominance, dominance or intermediate inheritance of resistance to the both diseases, we distinguished the following sterile female lines: Skh1 A, Skh2 A, Skh3 A, Skh8 A, Skh15 A; and sunflower pollen fertility restorers - male lines of hybrids Kh 2 V, Kh 5 V, Kh 9 V, Kh 10 V. Analysis of the data suggests advantages of these lines for a number of economically valuable features, including disease resistance, to use them as parents of promising commercial hybrids as well as of hybrids that are in the Register of Plant Varieties suitable for dissemination in Ukraine.