Objectives of guar breeding in the Russian Federation in connection with the prospects of domestic guar gum production (review)

Guar ( Cyamopsis tetragonoloba (L.) Taub is a source of guar gum extracted from the endosperm of this annual legume plant (D. Mugdil et al., 2014; R. Pathak et al., 2015). Guar gum has a wide range of applications as gel-forming agent in gas/oil industry and as emulsifier and thickener of substances in food, cosmetic, textile and paper industries (R.J. Chudzikowski et al., 1971; N.Thombare et al., 2016; A.M.A. Hasan et al., 2018). Guar has moderate drought-resistance, it is tolerant to salinized soils and has low demands to soil fertility (D.J. Undersander et al., 1991; R.K. Bhatt et al., 2017). Domestication of guar took place in India and Pakistan where the plant was used as a forage crop (N. Thombare et al., 2016). These countries are the main manufacturers and exporters of Guar gum in the world market today. Guar was introduced into Russian Federation in terms of import submission. Production batches of conditioned seeds were obtained in some regions of South Federal Part and Lower Volga adjacent area last years. Experimental batches of gum extracted from native seeds have demonstrated that guar gum fits the quality standards (I.V. Kruchina-Bogdanov et al., 2019) and in the nearest future guar gum would be produced in Russia. There is a high demand in industrialized-type guar cultivars, well adopted to diverse local conditions in the Russian Federation. Guar was introduced into culture in the Russian Federation, 4 cultivars among 10 registered in the State Register of Breeding achievements were originated by VIR (Vavilov Institute of Plant Genetic Resources). Gum production depends upon guar yield productivity so the problem of high yield is urgent (A.K. Jukanti et al., 2019). However, in the Russian Federation, the most limiting factor for guar production is high temperature demand of the crop (D.V. Lebed et al., 2017), so precocity becomes a priority feature, which, in turn, is associated with the sensitivity of the plant to the photoperiod. Therefore, it is necessary to search in the gene pool for forms with reduced sensitivity to photoperiod, capable for forming full-fledged seeds in a relatively short summer (S.B. Teplyakova et al., 2019). Being introduced to northern altitudes, guar plants may form blackened seeds in pods in conditions of prolonged vegetative period combined with low night temperatures and extra moisture (T. Hymovitz et al., 1963; D.V. Lebed et al., 2018). Due to this fact it is important to use most early guar varieties in Russia. The question arises about the optimal plant architectonics for the conditions of the Russian Federation, contributing to the formation of high productive agrocenosis (M.I. Voloshin et al., 2019). One-stem and few-branched guar plants are recommended as most early and better adopted to mechanized harvesting, such type of plants fit the model of industrial variety (F. Gresta F. et al., 2018; C.M.G. Reis et al., 2021). Plants with determinated type of growth are also early maturing (E.A. Dzyubenko et al., 2017). Guar, like most annual crops, is self-pollinated (R.E. Stafford et al., 1975), its hybridization is a complicated procedure, and the rate оf successful crosses is very low (R.E. Stafford et al., 1980). Main breeding method in guar is selection of outstanding genotypes (A.K. Jukanti et al., 2019). The most effective selection index for breeding for high yield in guar is the number of pods per plant (F. Gresta et al., 2013). The diversity of plant genetic resources and the evolving genomic resources allow the use of traditional, biotechnological and molecular approaches in guar breeding (S. Kumar et al., 2017). Some types of molecular markers are identified but not too much compared to other legume cultures (W. Ravelombola et al., 2021). It is also necessary to be ready to resist to the effects of biotic stressors - diseases and pests, it is urgent to create resistant varieties with a broad genetic basis (E.E. Radchenko et al., 2018). The whole range of these issues is