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One of the most dangerous biotic factors that reduce the sunflower productivity is its infection by an obligate parasite of higher plants - broomrape (Orobanche cumana Wallr.). Over the past few years, a number of inbred lines of various origins that are immune to race G have been developed at V.S. Pustovoit All-Russian Research Institute of Oil Crops (VNIIMK). To combine different genes in the same sunflower genotype, it is necessary to determine their allelism.  The research material was the sunflower lines – donors of resistance to race G of broomrape: RG, RGP1, RGP2, RGB, RGL1, RGL2, RGM. The identification of the race of broomrape seeds by means of lines-differentiators showed that the seeds were collected from the plants of race G. Hybrids F1 and F2 were obtained by the VNIIMK method. The mathematical processing of the segregation results was conducted by means of χ2 criterion of correspondence of the actual segregations to the theoretically expected ones in dihybrid crossings. The research results showed that, overall, the parent lines were affected by broomrape to a small degree. During the test for allelism, seven generations of F1 and F2 were obtained from pair crossing of resistant lines with each other. The tested hybrids F1 were either not affected by the parasite, or were affected to a small degree, which allowed us to classify sunflower plants as resistant. To determine the identity of resistance genes in the lines of RG with RGP1, RG with RGM, RG with RGL1, RG with RGB, RGP2 with RGL2, RGM with RGL1, RGB with RGL1, we analyzed the F2 progeny from these hybrids. The test for allelism of the resistance genes to race G of these lines showed their identity, with the possibility of some distortion of the phenotypic manifestation of the trait in various crossing combinations.

The work was conducted in the laboratory of immunity of the V.S. Pustovoit All-Russian Research Institute of Oil Crops during 2016–2020. Twelve homozygous lines resistant to broomrape races A–G were developed from the sources of different origin. A line RG and other five: RGL1, RGL2, RGР1, RGР2, and RGВ, were described in the previous articles (Antonova et al., 2016, Araslanova et al., 2020) [1; 2]. Further new lines we named as 2RGB, 2RGN, 2RGL, 2RGS, 2RGNV, and 2RGA. We tested these lines for distinguishability, homogeneity and stability according to a technique “Sunflower (Helianthus annuus L.)” stated in a publication RTG/01/3 “Common introduction into testing of distinguishability, homogeneity and stability and compilation of description” of 22.07.2002 No 12-06/52 (Official bulletin of the State Commission No 6, 2002) [3]. The new lines also as the previous ones are differed from each other by their morphological traits, such as duration of a period from emergence to plants flowering, plants height, shape and color of a leaf and ray flower, etc. This description of the lines resistant to broomrape race G can be used in breeding practice at development of sunflower hybrids.