The reason domesticated lentils are fussy about their lighting is in their genes

If your crop is a fruit or a seed, then controlling when it flowers is important. Temperature and day length are factors, but for lentils, so too is the quality of light. A reduction in the ratio of red to near infra-red (R/FR) light can trigger flowering. Hai Ying Yuan and colleagues in Canada, Spain, and Australia have examined how genes correlated with a lentil’s sense of light quality.

Light quality isn’t a matter of lentils enjoying a stunning sunset, but in what light the plants can use for photosynthesis. Plants can use red light but not light in the near infra-red part of the spectrum. As a plant canopy grows, the red light gets used, and the infrared light gets reflected. The plant senses the light colour through phytochromes, light sensors that respond to either red or far-red light. If you reduce the red light to infrared light ratio in domesticated lentils, you can induce flowering.

Things are not the same for all lentils though, say Yuan and colleagues. “In a recent study, we found that the flowering time of most wild lentil genotypes was not significantly affected by light quality changes, whereas it was consistently accelerated under the low R/FR conditions in cultivated lentil (Yuan et al., 2017). This variation in flowering time sensitivity toward the light quality change indicated that genes or specific alleles associated with this trait could be used to select or modify flowering time in cultivated lentil.”

To examine how genes affected a plant’s response to light quality, the scientists created a cross between Lens culinaris cv. Lupa and L. orientalis thought to be the wild progenitor of L. culinaris. This cross-breeding created a hybrid, or recombinant inbred line (RIL), whose genes they could analyse.

The team found, as expected, plants could have different responses to light quality, depending on which genes they picked up from their parents. However, some of these hybrids were more sensitive to light than L. culinaris. Also, some plants were less sensitive than L. orientalis, indicating that both plants had alleles that contributed to the light response. All in all, Yuan and colleagues identified thirteen points in the genome that correlated with response to light quality.

“Overall, our results from QTL analysis and gene expression point most clearly to FTa1 as a probable basis for the observed differences in flowering sensitivity to light quality between L. orientalis BGE016880 and L. culinaris cv. Lupa. Similar parallel evidence suggests a weaker role for FTb1/2 genes, and identifies an AGL6/13-like MADS-box transcription factors as a potential candidate for a third QTL,” write Yuan and colleagues.

The results could have quite an impact on commercial lentil growth. Bringing in genes from wild relatives could help improve crop performance in variable light environments. Such a change would help intercropping or improve the plant’s response to weed pressure — good news for anyone with a taste for lentils.