The presented study sought to phenotype the rice cultivars procured from the Unique Scientific Installation (USI) – Collection of Federal Scientific Rice Centre, Krasnodar, Russian Federation, as sources of valuable grain quality traits, as well as BC₂ populations with the selection of the best genotypes for quality traits in developing the red grain rice cultivars with high nutritional properties. The studied rice plant material, grown in the artificial climate chambers of FSBSI – Federal Scientific Rice Centre, had the following conditions: temperature – 28–30 °C during the day (12 h) and 24 °C at night (12 h); illumination – 30,000 lux, and humidity = 70%. Rice determination and phenotyping for grain quality traits commenced on high-tech certified equipment per GOSTs. The experiment results had the parental genotypes used in the backcrossing program assigned to the group of medium-grain cultivars, except for the long-grain cultivars, i.e., Svetlana and Gagat. The 1000-grain weight ranged from 23.0 to 27.4 g, filminess (17.8% to 19.9%), and total milling yield (65.0% to 70.4%). Low fracturing appeared in rice cultivars, viz., Rubin, Alliance, Kurazh, Gagat, and VNIIR10163, while a high vitreosity emerged in rice cultivars Veles, Svetlana, VNIIR10163, and Khaw-sri-nin. BC₂ plant populations’ evaluation depended on the technological quality traits. The effective heterosis was evident for most grain quality traits. Rice genotypes selected based on lower fracturing and higher grain size will undergo further breeding work to develop the high-yielding rice genotypes with desirable grain quality traits.

Keywords: Rice, cultivars, backcrosses, rice breeding, technological grain quality traits, grain vitreosity, grain fracturing

Key findings: In the accelerated breeding program of rice cultivars, using the BC₂ populations helped identify the promising rice genotypes with lower fractures and a larger grain size than the parental genotypes. The best-isolated rice samples with lower grain fracturing distinctly included BC₂ Gagat/Svetlana//Svetlana, Dig.2327/Veles//Veles, and Dig.2327/Alliance//Alliance. Noting also the heterotic effects based on the grain size occurred in BC₂ populations Mavr/Svetlana//Svetlana and Mavr/Kurazh//Kurazh. These hybrid combinations and their parental genotypes are deployable in an accelerated breeding of rice cultivars.