THE EFFECT OF INDOLYLBUTYRIC ACID ON THE REGENERATION OF MAIZE HYBRIDS IN VITRO

Еру Optimization of the regeneration potential in vitro for maize (Zea mays L.) hybrids with the participation of perspective inbreds is an actual task for biotechnological maintenance of this important crop breeding process. 
The purpose of the research was the investigation of the effect of the auxin phytohormone — indolylbutyric acid (IBA) on the in vitro regeneration capacity of maize hybrids. The task of the work was to determine the effect of IBA in concentrations of 0.1 and 0.2 mg / L on the total regeneration frequency from type II callus tissue, as well as on the number of regenerated plants per 100 calli. The material of the study was 90-day type II callus tissue of maize hybrids between inbreds DK633, DK3070, DK236 and DK267 of Lancaster germplasm from the Dnipro breeding program and inbreds with high regeneration capacity A188, Chi31 and PLS61. The method of cell, tissue and organ culture in vitro was used. The initiation of plant regeneration from callus tissue was performed on the mineral MS medium, supplemented with 100 mg / L inositol, 100 mg / L casein hydrolysate, 690 mg / L L-proline, 20 g / L sucrose, 6 g / L agar, and 0.1 or 0.2 mg / L IBA. 
It was found that IBA significantly affected the maize hybrids’ regeneration capacity. With 0.1 mg / L IBA in the medium, the total regeneration frequency increased up to 32.1 ± 7.7 %, compared to the control without IBA (15.6 ± 5.3 %) and to 0.2 mg / L IBA (17.0 ± 5.5 %). IBA (0.1 mg / L) contributed also to the increase of the number of regenerated plants up to 19.5 ± 4.3 pcs/100 calli, compared with their number without IBA (9.7 ± 4.3 pcs/100 calli) and with 0.2 mg / L IBA (6.5 ± 3.6 pcs/100 calli). The genotype of callus tissue significantly affected the regeneration ability of the hybrids. The highest number of regenerated plants per 100 calli under 0.1 mg / L IBA was obtained in hybrid DK236xChi31 (68.8 pcs/100 calli), the smallest one — in PLS61xDK236 (4.3 pcs/100 calli). The highest total regeneration frequency was observed for DK236xChi31 (75.0 %), and the lowest —for PLS61xDK236 (4.4 %) as well. 
 In the perspective the obtained outcomes can be used to optimize the biotechnology of maize callusogenesis and plant regeneration in vitro and to increase somaclonal production from long-term cultivated calli for application in breeding process.