Selection of the source material for the creation of black currant varieties with complex resistance to diseases and pests

The requirements of new intensive technologies for newly created varieties of berry crops are increasing every year. Therefore, there is a need to involve new donors and sources of economically valuable traits in the breeding process. The successful implementation of the breeding program is largely determined by the correct selection of parental forms, and for the successful solution of this task, constant screening of both newly created material and existing material is necessary. Over the years of research, work has been done to obtain, study and isolate the most promising genotypes of black currant for use in breeding for resistance to biotic factors. The article presents the results of the evaluation of potential black currant donors of the VNIISPK selection. As a result of the study, donors were identified not only with complex resistance to biotic factors, but also donors with high productivity.


Introduction
Changes in soil and climatic conditions, deterioration of environmental ecology, improvement of production technologies contribute to changing and increasing the evaluation criteria for the created agricultural crop varieties.
The main role in plant breeding is assigned to the selection of original genotypes, which must have certain qualities and meet modern requirements. Based on the task that the breeder faces, certain parent forms are selected.
The leading role is given to donors and sources, and both wild species and currently created forms of black currant can be used as them. It should be remembered that the use of wild ancestors does not always have a positive effect, since seedlings are often given unnecessary traits.
In this way, for example, the seedlings obtained from Ribes glutinosum derivatives at the initial stage had small berries and were not adapted to the conditions of the Orel region [4]. Consistent implementation of saturating crosses with various donors of valuable traits and strict selection at all stages of the breeding process allowed to identify a number of genotypes adapted to the region conditions and then varieties on their basis (Arapka, Blagoslovenie, Gamma, Kipiana, Nadya, Narianna) that had a complex resistance to biotic factors [4; 5; 6].
The search for new donors of resistance to the most dangerous diseases and pests is of great importance for black currant breeding.

Materials and methods
As experimental material, selected forms of black currant obtained in VNIISPK from targeted crosses were studied. During the growing season, at different stages of plant development, they determined the berry weight, yield, and degree of damage by main pests and diseases. To determine all the indicators, we were guided by the method of selection and variety study of fruit, berry and nut crops [7,8].
In the field, the degree of disease damage was assessed on a five-point scale. American powdery mildew: 0 -no damage; 1 -very weak: single leaves are affected, up to 1% of berries; 2 -weak: up to ¼ of shoot length are affected, up to 25% of leaves, 1-3% of berries; 3 -medium: from ¼ to ⅓ of shoot length are affected, 26-50% of leaves, 4-10% of berries; 4 -severe: from ⅓ to ½ of shoot length are affected, 51-70% of leaves, 11-20% of berries; 5 -very strong: more than ½ of shoot length are affected, more than 70% of leaves, more than 20% of berries.
Anthracnose and Septoria spot: These diseases develop simultaneously and have similar symptoms. 0 -no damage; 1 -very weak damage of single leaves; 2 -weak: up to 10% of leaves are affected; 3 -medium: up to 30% of leaves are affected; 4 -severe: up to 50% of leaves are affected; 5very strong: more than 50% of leaves are affected. The degree of studied forms resistance to columnar rust was taken into account visually according to the same scale as for anthracnose.
The assessment of resistance to the currant gall mite was carried out in the spring before budding. The damage degree was determined visually by plots in scores: 0 -no signs of damage; 1 -very weak damage to single buds; 2 -weak damage: up to 10% of buds are infected with mite; 3moderate: up to 30% of buds are affected; 4 -severe: from 30 to 50% of buds are affected; 5 -very strong: more than 50% of buds are affected.
To study the inheritance of resistance to powdery mildew, initially in a hybrid nursery, artificial infection of seedlings with powdery mildew conidiospores was carried out by shaking-off the spores on the wet surface of the leaves during the active growth of seedlings at the age of 6 -8 true leaves. After artificial infection, a 2-fold screening was carried out. All affected seedlings were subject to rejection, regardless of the degree of disease development. Resistant seedlings were once again evaluated for resistance in the field at the breeding plot in the first and second year of the growing season. The identified seedlings susceptible to powdery mildew were also subject to rejection. The correspondence of the expected and actual cleavage was evaluated according to the Pearson criterion.

Results and discussions
An important direction in the breeding work on black currant in the VNIISPK is the creation and identification of the necessary donors and sources. The following issues and tasks are solved: -analysis and involvement of currently known donors in breeding process; -identification of necessary donors among wild species and their derivatives; -creating donors with necessary traits; -creation of donors with resistance to 2 or more pathogens; In recent years, more than 500 forms of black currant of the VNIISPK breeding have been studied as potential donors and sources.
Based on the fact that in the conditions of the Orel region the most harmful disease is Sphaerotheca mors-uvae, Cronartium ribicola, Pseudopeziza ribis Kleb, Septoria ribis, and the most dangerous pest -Cecidophyopsis ribis ( Fig. 1,2,3), the main goal in the selection of potential donors and sources are genotypes that combine resistance to these pathogens. Therefore, at the initial stages of the breeding process, in addition to the strict selection of donors of resistance to certain diseases and currant gall mite, a number of crossbreeding combinations were also performed and genotypes combining these traits were selected.  A significant contribution to black currant breeding for the creation of disease-and pesttolerant genotypes was made by the involvement of descendants of nutmeg currant as parental forms in the breeding process, which exhibit group resistance to American mildew (Sph3 gene), columnar rust (Pe gene) and currant gall mite (Ce gene) [9]. Since the derivatives of glutinous currant taken in the breeding process were small-fruited and low-yielding, highyielding, large-fruited samples were used as reciprocal parent forms, which after 2-3 generations allowed to select genotypes resistant to diseases and pests with a high level of economic traits.
Another effective donor of resistance to Sphaerotheca mors-uvae is Ribes scandinavicum derivatives. Among the studied samples, Sunderbyn Ⅱ variety (R gene) showed the highest resistant to the disease and the ability to transmit this trait to offspring. But at the same time, the Sunderbyn Ⅱ variety and in many cases its derivatives had a restrained growth, and were also affected by columnar rust and currant gall mite. This circumstance made it necessary to select the parent forms, when crossing with which samples with the required characteristics were cleaved.
Since the derivatives of nutmeg currant had a high level of tolerance to Cronartium ribicola and Cecidophyopsis ribis, they were quite intensively involved in the breeding process with the Sunderbun Ⅱ variety. In addition to the fact that plants with the necessary properties were selected in such crossing combinations, it is very important that some seedlings combined the Sph3 and R genes in one genotype. This, we assume, will allow the created varieties to remain immune to powdery mildew for a longer time. Since there were no phenotypic traits that allow visually to select plants that combine the Sph3 and R genes, a number of analytical crosses were performed with varieties susceptible to powdery mildew. Genotypes combining the Sph3 and R genes were selected based on hybrid offspring cleavage.
To date, more than two thousand crossbreeding combinations have been carried out in breeding studies to create varieties with group resistance to diseases and pests using derivatives of Sunderbun Ⅱ nutmeg currant. Table 2 shows the most promising donors and sources, selected according to a set of traits that were multiplied and studied in detail at the primary variety study plot. As it can be seen, the selected forms combine not only resistance to American mildew at a high level, but also to columnar rust and currant gall mite.
It should also be noted that the potential donors listed in the table are more or less affected by leaf spots (anthracnose, Septoria blight). This is primarily due to the fact that no effective donors of oligogenic resistance to these diseases have been found, and the donors of polygenic resistance used do not give the expected effect.   A number of analyzing crosses were performed with some forms, and as the analysis of hybrid offspring shows, they transmit the necessary traits quite well by inheritance, which will allow many of them to be recommended as donors in the future.

Conclusion
1. According to the complex of economically important traits, resistance to biotic factors, more than 500 forms of black currant were evaluated as potential donors of high group resistance.
2. Complex donors of resistance to American mildew, columnar rust and currant gall mite with a potential yield of more than 50 c/ha were identified in the hybrid offspring obtained from derivatives of nutmeg currant (Sph3 gene) and Sunderbyn Ⅱ variety derivatives (R gene).