Callus formation of sugar sorghum (Sorghum saccharatum) as affected by type and size of explantand level of ploidy

Abstract

Purpose. Investigate the frequency of callus formation of different starting material of sugar sorghum depending on the type and size of explant and the level of ploidy.Methods. Biotechnological, laboratory, field, analytical, statistical.Results. In diploid forms of sugar sorghum in vitro, callus formation from boot was found at 11.7 %, a lower percentage of 9.8 and 9.6 % were respectively found in adapted in soil mixtures and field sorghum plants. The same pattern was observed in triploid forms: 13.6 % with respect to 12.5 and 12.3 %. Tetraploid forms of sugar sorghum had the highest percentage of callus formation compared to diploid and triploid, 16.6 % and 15.8 and 15.5 %, respectively. That is, the above mentioned pattern is observed in all sorghum plants regardless of the growing conditions. Regardless of the ploidy of sugar sorghum starting material and the given explant size (3–5.0 mm; 5.0–8.0; more than 8.0) of leaf blade and boot, a low level of callus genesis was observed, from 1.9 to 5.3 %. Within these sizes, diploid forms of callus formation amounted to only 4.0 % in cultivated plants, 3.3 % in adapted soil mixtures, and 3.1% in field-grown plants. In triploid forms of the above mentioned starting material, callus genesis rates were 3.0 and 3.3 and 3.9 %, respectively. A slight increase in callus formation in tetraploid starting material was from 5.3 to 4.2 %. The type of boot explant provided, regardless of the ploidy of the formation material, 4.5 pcs and leaf blades 17.9 pcs of regenerative explants. However, given the material ploidy, it was found that in diploid forms the number of regenerative explants from laminas in cultivated plants reached 11 pcs, adapted in soil mixtures 8 pcs, grown under field conditions 7 pcs, in triploid forms 21 pcs and 17 and 15 pcs., respectively. Tetraploid forms of sugar sorghum allowed to obtain 31 pcs and 27 and 24 pcs of regenerative explants depending on the type of starting material. The frequency of callus genesis, depending on the level of starting material ploidy, indicates that the highest percentage is established in tetraploid forms of sugar sorghum. Plants in vitro of diploid form had a frequency of callus genesis from leaf blades at the level of 34.1 ± 7.1 %, triploid 54.1 ± 7.2 %, tetraploid – 62.4 ± 5.7 %. Sugar sorghum material grown in vitro conditions and adapted in soil mixtures had a frequency of 28.1 ± 4.6%, triploid forms 35.8 ± 4.2 %, tetraploid – 51.3 ± 6.1 %. In plants grown under field conditions, the lowest frequency of callus formation was established, which in diploid forms was 24.3 ± 2.1 %, triploid 33.1 ± 2.4 %, tetraploid 48.7 ± 3.4 %. The frequency of callus formation in boots of sugar sorghum had the same pattern as that of laminas.Conclusions. The induction and frequency of callus genesis of sugar sorghum were influenced by the type and size of explants and the level of ploidy of the starting material. Genotypic features have been found to influence the formation of callus structures. In diploid forms, the lowest percentage of callus induction was observed and in tetraploid form, the highest. This pattern is observed in all sorghum plants, regardless of the growing conditions. The level of ploidy and starting material influence the regenerative capacity of sugar sorghum. The effect of different sizes of sugar sorghum explants on sorghum callus suggests that it is most appropriate to use 5.0–8.0 mm laminas for both sheath and leaf. Callus formation in sugar sorghum, depending on size, was most intense in polyploid forms compared to diploid ones. Studies indicate that the use of sorghum explants with a sugar size greater than 8.0 mm is not appropriate. The frequency of callus genesis, depending on the level of starting material ploidy, indicates that the highest percentage is established in tetraploid forms of sugar sorghum.