Biological features of Brassica rapa L. vegetable leafy crops when growing in an intensive light culture

One of the main components of the successful production of plant products is the choice of crops with a high realization of their production potential under the formed conditions, including in the conditions of intensive light culture. The problem of compensating or eliminating the deficit of green crops is currently quite acute in Russia and in the world. The genetic diversity of the most widespread green brassicas plants of the species Brassica rapa L. for use in protected ground facilities has developed in Southeast Asia and includes numerous morphotypes of Chinese cabbage, pakchoi, tatsoi, wutacai, mizuna, and leafy turnip. In Russia, leafy B. rapa vegetables are used to a limited extent, mainly as salad vegetables. The main areas of B. rapa crops breeding for artificial light culture include a high growth rate (the duration of vegetative period is not more than 28-35 days, depending on the biological characteristics of the crop), the yield is not less than 3-8 kg/m2, depending on crops, a certain compact plant habit, high quality of leaves, valuable biochemical composition, resistance to early bolting, resistance to possible low light and high air temperature, suitability for growing in a thin layer of soil or hydroponics. The biological features of the diversity of B. rapa leafy crops as sources for breeding for intensive light culture conditions have not been sufficiently studied, first of all, this concerns little-known crops (tatsoi, wutacai, mizuna) and certain morphotypes within common crops (Chinese cabbage and pakchoi). In this study, for the first time, we studied the wide genetic diversity from the Russian worldwide B. rapa collection of the Russian Federation, stored in the VIR, and morphotypes within them (72 accessions), including genotypes contrasting in morphological characteristics, under different supply light intensity for the development of energy-saving agro-technologies in intensive light culture. For the first time, correction factors were determined for calculating the leaf surface area from easily measured linear dimensions for each studied crop and type of leaves, which will speed up the calculations of photosynthesis characteristics. A different degree of variation in the variability of the size and weight of plants of various crops, depending on the illumination, is shown, the highest in Chinese cabbage and leafy turnip. It was found that the intensity of the light regime is largely determined the increase in the productivity of plants of all studied crops, mostly of Chinese cabbage and pakchoi and leafy turnip. High-yielding accessions of Chinese cabbage, pakchoi and leafy turnip were identified (more than 6.3 kg/m2 for 28 days of growing season). The studied accessions of wutacai and mizuna are low-yielding and have a longer growing season, but are of interest as vegetables for functional nutrition and for decorative purposes. Semi-cabbage types of Chinese cabbage (Shantung, Santo, Xiao), which are of primary interest for light culture, have been identified. We recommend Chinese cabbage accessions vr.k-1375, Bice (vr.k-1376), and pakchoi k-647 for thickened cultivation,, and pakchoi Extra Dwarf Pack Choi (vr.k-1405 ) and tatsoi Xiao Ba Je Ta Cai (k-695) for growing with a small distance between the shelves of 25 cm. Accessions of Chinese cabbage Chokurei (k-177), Tokyo Bekana (k-395), Zao Shi No. 5 (vr.k-1120), and Fun jen F1 (vr.k-1410) showed the highest salad qualities of the leaves. Under the conditions of a biopolygon, we managed to determine accessions with a stable manifestation of the traits, of early maturity and high productivity, practically independent of light intensity. These are accessions of Chinese cabbage Harumaki Shin Santousai (k-270), Tokyo Bekana (k-395), Xiaobaikou (k-74), pakchoi Kangre 605 (vr.k-1131), Gai Lang Jin Pin 25 F1 (vr.k-1124). In addition, it was shown that the Chinese accession of Chinese cabbage Zao Shi No. 5 (vr.k-1120) and the Russian cultivar of the leafy turnip Selecta (vr.k-1371) have increased the activity of the photosynthetic apparatus. The obtained data on the crops in general and the determined accessions of B. rapa are of interest for the practice of vegetable growing, in the development of elements of cultivar technology of B. rapa crops under conditions of light culture and as sources of valuable traits in breeding programs, including the development of city farming.