Effects of plant growth regulators on seed productivity of maize lines
Authors: Kyrychenko V. V. , Chernobay L. M. , Buriak S. Yu. 
Published: August 2023

Рurpose and objectives. To study the influence of growth regulators on seed productivity and seeding quality of the development of maternal forms, and the pollen-forming ability of parental forms of corn hybrids, as well as to develop ways of using growth regulators in the primary stages of seed production.
Material and methods. The experiments were conducted in the crop rotation fields of the Plant Production Institute named after V.Ya. Yuriev of NAAS in 2018-2019. The experiments were conducted in the crop rotation fields of the Plant Production Institute named after V.Ya. Yuriev of NAAS in 2018-2019. Seeds of maize lines were sown with manual planters in six-row plots of 29.4 m2 (arrangement 4♀:2♂), in four replications. Phenological observations and biometric measurements were performed on 10 plants in each replication. Eight maize lines – hybrids’ parents were taken as the test material: 4 lines – steryl counterparts (Kharkivska 126 M, Kharkivska 215 M, Kharkivska 164 M, and Kharkivska 155 M) and 4 lines – sterility maintainers (Kharkivska 126 ZM, Kharkivska 215 ZM, Kharkivska 164 ZM, and Kharkiv 155 ZM). There were 4 treatments: 1) no treatment (control); 2) Appetizer - spraying in the phase of 4-5 leaves; 3) Nertus Planta Peg – pre-sowing seed treatment; 4) Nertus Planta Peg - pre-sowing seed treatment + spraying in the phase of 4-5 leaves. The stigma viability was determined by sequential removal of plastic bags. To evaluate the accession performance, the following parameters were recorded: - The plant number per plot; - The infertile plant number; - The number of plants with undeveloped cobs; - The number of plants with complete cobs. One average quantitative sample of cobs (10 cobs) was taken and weighed for drying and analyzing the cob structure.
Results and discussion. In the lines - steryl counterparts, a significant influence of the growth regulators on the plant weight and condition was observed before the tassel emergence onset. The best response of plants to the PGRs was observed in lines Kharkivska 155 M and Kharkivska 155 ZM. After treatment 2 (Appetizer), we noted the greatest surplus in the biometric parameters in comparison with the corresponding control plots. In the PGR-treated plots, the tassel flowering occurred later and stigmas appeared earlier, which reduced the gap in between the anthesis in the male and female lines. Line Kharkivska 126 showed the best synchrony of anthesis in experiment 2 (Appetizer) - the anthesis time in the male and female forms almost coincided (♂ 27/07 - ♀ 28/07). In the treatment 3 (Nertus treatment of seeds) and 4 (Nertus  treatment of seeds + spraying) plots, the anthesis peaks in the both forms coincided (♂ 27/07-♀ 27/07), however, the male forms stopped flowering much earlier than the female ones: there was an anthesis gap (as of 03/08 2% of ♂ forms and 43% of ♀ forms flowered). We recorded a significant increase in the kernel weight of the sample, 1000-kernel weight, the total yield and other indices in the PGR-treated plots in comparison with the corresponding control ones. Nevertheless, in the experiment the 3 treatments (Appetizer, Nertus, Nertus +) influenced the pollen productivity of the maize lines - sterility maintainers. The plant growth regulators had no significant effect the pollen viability in the lines - sterility maintainers. Of the sterile analogues, the PGR effect on the stigma viability was noted for lines Kharkivska 126 M and Kharkivska 215 M. It was less noticeable in the other lines.
Conclusions. The results on the growth regulator effectiveness allow us to recommend Appetizer and Nertus Planta Peg as improvers of the seed productivity of the 1st generation maize hybrids’ parents.