A higher far-red intensity promotes the transition to flowering in triticale grown under speed breeding conditions

It typically takes 12 to 15 years to develop a new promising variety. One of the ways to reduce this time is through speed breeding. This method allows for up to six consecutive generations of spring cereals in a single year. Although far-red light is often overlooked in speed breeding protocols, it serves as a potent inducer of accelerated flowering in various plant species. In this study, we explored the advantages of far-red light as a means to optimize the speed breeding of spring triticale. Experimental plants were cultivated under three conditions with different red to far-red ratios at 660 nm (R - red) and 730 nm (FR - far red): 1) 3.75 (R > FR); 2) 0.8 (R = FR) and 3) 0.3 (R < FR). We found that the onset of triticale flowering occurred significantly earlier at the lowest red to far-red light ratio (R/FR 0.3). On average, plants bloomed 2.6 and 4.1 days earlier in a mineral wool and a soil mixture at R/FR 0.3, respectively, than those grown at R/FR 3.75. A negative effect of higher-intensity far-red light on the reproductive system of triticale was observed. Additionally, seeds obtained from plants grown under higher-intensity far-red light showed significantly lower germination energy and capacity. No differences were found in the regenerative capacity of isolated embryos in vitro obtained from plants grown under the different spectral compositions. Our results demonstrate that the accelerated triticale development requires not only the involvement of far-red light, but also a specific red to far-red light ratio close to 0.3. A modified speed breeding protocol relying on this ratio enabled flowering to commence as early as 33.9 ± 1.2 days after sowing. The same triticale variety grown under field conditions in the Krasnodar region and in traditional laboratory growing conditions with a photoperiod of 18/6 h day/night flowered 25 to 29 days later than those cultivated under the speed breeding conditions.