Evaluation of in vitro viability and pollen morphology of asparagus vigna (Vigna unguiculata) accessions during introduction in the south of Western Siberia

Background. Vigna is a new for Russia vegetable crop with high heat requirements, which prevents the expansion of its cultivation in regions with a continental climate. Based on the selection of the optimal concentration of the osmotically active substance (sucrose, PEG 6000), the relationship between pollen germination of vignaaccessions in vitro at optimal (25°) and low (6°) temperatures and its morphometric parameters was assessed. Materials and methods. The morphometric features and response of microgametophytes of 8 Vigna unguiculata accessions to low temperature in vitro were studied. The optimal concentration of the osmotically active substance (sucrose, PEG 6000) was determined at different concentrations in the medium (10, 20, 30 %). A Hitachi TM 4000 plus SEM was used for pollen grain morphometry. Results. According to the criterion of minimal variation of pollen germination in sucrose and PEG 6000 solutions (53 % versus 60–147 %) with a fairly high germination rate for most accessions (6.2–27.4 %), the best result was shown by PEG 6000 at a 20 % concentration with the addition of boric acid (0.006 %). According to the cold resistance of pollen in vitro at a temperature of 6°, pollen of k-36 and Krasnaya pozdnyaya accessions stood out with an indicator of 52.0 and 53.5 %, respectively, whereas pollen of the cv. Yunnanskaya did not germinate under these conditions. Pollen of five vigna cvs. is three-lobed, large, almost round in the projection of the polar axis and round in the equatorial plane. The surface of the exine has numerous grooves, the surface texture is coarsely meshed. The length of the p.z. polar axis 63.0–76.5 μm, the equatorial diameter is 57.2–66.3 μm and varies significantly among different vignaaccessions. The largest pollen was found in the cv. Yunnanskaya (76.5×65.2 μm), while the cv. Grafinya had a comparatively small pollen (63.0×57.2 μm). Conclusions. The optimal medium for pollen germination was a medium with 20 % PEG 6000 + 0.006 % boric acid. In pollen germination experiments at 25° and 6°, cold resistance negatively correlated with the polar axis length (r = –0.603 – –0.683) and the equatorial diameter (r = –0.375 – –0.549).