Nitraria komarovii Iljin & Lava ex Bobrov is newly reported for the flora of Kazakhstan. The two new records extend the range of this species eastward from its previously known range in Azerbaijan and Turkmenistan. A full description of N. komarovii is given for the first time, along with illustrations, notes on its taxonomy, and a distribution map. Nitraria komarovii is most similar to N. schoberi L., but differs in its habit, narrower and longer, linear-spatulate, greenish-yellow leaves, which gradually narrow to the base, more subtle inflorescences, size of the stone, petal, stamen, and pistil, and color of the fruit.

Intragenomic polymorphism of ITS2 of nuclear ribosomal DNA sequences was analysed in 30 samples belonging to Nitraria schoberi, N. sibirica. The nucleotide variability of the ITS2 region was detected in the studied Nitraria species as single-nucleotide substitutions (mainly transitions) and single-nucleotide deletion. Five ribotypes of Nitraria were identified in Russia, Kazakhstan and Tajikistan. These ribotypes formed two haplogroups that belong to the species N. schoberi and N. sibirica, respectively. The high importance of the discriminatory role of the ITS2 spacer in identifying species of the genus Nitraria is confirmed.

The paper shows composition and content of phenolic compounds in leaves of 4 Nitraria L. species from 58 populations of Russia, Kazakhstan, and Tajikistan studied with high-performance liquid chromatography(HPLC). The investigation has revealed 27 compounds of phenolic nature: the maximum number (18 components) is detected in leaves of N. sibirica Pall. from Kazakhstan (the Karatal river valley), 16-17 components – in plants from three populations of Siberia, the minimum (6 components) – in leaves of N. komaroviiilljin & Lava ex Bobrov. The analysis has identified hyperoside (quercetin O-glycoside), narcissin (isoramnetin O-glycoside), quercetin (flavonol) and luteolin (flavon). The studied plants accumulate a generous quantity of phenolic compounds. Their content reaches 4.64% in leaves of N. sibirica, 3.11% – in N. schoberi L., up to 3.96% – in N. komarovii. The research results allow speaking about the species-specific composition and content of phenolic compounds of N. sibirica, N. schoberi and N. komarovii. The component composition is weaker in extracts of N. komarovii leaves, but there is a higher content of total phenolic compounds compared to N. schoberi plants. N. pamirica L. Vassil sample is close to N. schoberi on multidimensional analysis of the phenolic compound composition and content.

The variability of metric traits has been studied in 20 Kazakhstan populations of three Nitraria species (N. schoberi L., N. sibirica Pall., and N. komarovii Iljin & Lava ex Bobrov). According to the results, N. sibirica differs from N. schoberi and N. komarovii in small leaves, fruits, and seeds, as well as in the structural features of inflorescences and flowers. N. sibirica is characterized by a greater number of flowers per inflorescence (25–66 on average) than N. schoberi and N. komarovii (14–28 on average). Additionally, N. sibirica differs from N. schoberi by narrower (1.3×) petals and smaller anthers (1.46× in length and 1.2× in width) and pistils (1.25× in length and 1.44× in width). N. komarovii differs from N. schoberi by narrower leaves (1.7×). N. komarovii is characterized by relatively large (especially in width) size of anthers that, together with smaller petals, makes it possible to distinguish this species during flowering. Flowers of N. komarovii are bright yellow, while those in N. schoberi and N. sibirica are white and light purple, respectively. N. komarovii fruits are orange, pale red, or bright red. Fruits of N. schoberi and N. sibirica are dark burgundy and black, respectively. At the intraspecific level, most of the studied metric traits (except for the habitus of N. sibirica plants) are stable and do not depend on the 16 climatic parameters of plant habitats. At the same time, a number of morphological features have been revealed in N. sibirica plants from the Ili Depression. In these populations, N. sibirica plants form shrubs up to 1.8 m in height with a large (up to 90) number of flowers per inflorescence, large petals (3.5 mm in length and 2.2 mm in width on average), small (~0.6 mm) anthers, small (5–5.5 mm in length) fruits, and small (~4 mm in length) narrow ovate stones. These features indicate the ecological–geographical differentiation of N. sibirica under the extra-arid conditions of the stony desert of the depression and evidence a separate taxonomic rank of these populations.