A plant variety produced using selective breeding is called a cultivar. For most crop plants, breeding new, advanced cultivars requires several years to produce genetically stable lines. After selected parent lines are crossed, typically 4–6 generations of inbreeding are needed to grow genetically stable lines for evaluation of yield and agronomic traits. This cross breeding is extraordinarily time-consuming for field-grown crops that often grow in only 1–2 generations per year.
A group of researchers from Australia and the UK devised a method using a completely controlled environment with specialized LED lighting for “speed breeding” that uses longer photoperiods to accelerate plant development rates as well as the harvesting and germination of immature seed. According to the researchers, their flexible protocols for speed breeding thereby reduce generation time.
The researchers published their results in the journal Nature Plants.
They looked at cereal species, standard genotypes of spring bread wheat (T. aestivum), durum wheat (T. durum), barley (H. vulgare) and the model grass Brachypodium distachyon. They also tested the growth of Canola and chickpeas. In the controlled environment, they extended the photoperiod to 22 hours of light. This photoperiod was then followed by 2 hours of darkness.
The alternating of the light and dark periods was done to support the expression of functional circadian clock genes. Over a one year, the researchers compared these plants under the 22-hour photoperiod with 2 hours of darkness to those grown with 12-hour photoperiod with 12 hours of darkness.
Under normal conditions with a 10-16 hour photoperiod, wheat and barley could only produce 2 to 3 generations per year. However, with the newly devised protocols in the completely controlled environment, they were able to essentially double the number of plant generations to 4 to six per year. In addition to the longer photoperiod, the protocols prescribe the harvesting of immature seed, thereby eliminating the need for labor-intensive embryo rescue.
They found that the viability of harvested seeds appeared to be unaffected by speed breeding, and they observed similar seed germination rates for all species.
Watson, A., and Ghosh, S. et al. Speed breeding is a powerful tool to accelerate crop research and breeding. Nature Plants (2018). doi:10.1038/s41477-017-0083-8.