Color and color stability are key characteristics for wheat grain quality. The yellow color of the endosperm is a consequence of the accumulation of carotenoids, which are bioactive compounds of major importance for human nutrition and health. Thus, grain carotenoid content has historically been an important trait considered in wheat breeding following different strategies. Bread wheat has generally been selected for whitish endosperm, whereas durum wheat breeding has focused on increasing grain yellowness.

Inter-specific variability is a valuable resource for broadening the genetic base of wheat because hybrid crosses, although difficult in some cases, are feasible. Here, we present two strategies based on inter-specific breeding for wheat biofortification which are currently being implemented in our research group to increase grain carotenoid content in common wheat (via increasing biosynthesis) and in durum wheat (via increasing biosynthesis, accumulation and stability).

Due to the selection for white endosperm, common wheat harbors alleles for carotenogenic genes associated with low carotenoid content. Psy1 is known to be the main rate-limiting gene in carotenoid biosynthesis. The Psy1-A1 and Psy1-B1 genes from durum wheat were then transferred to common wheat to evaluate their combined effect on grain carotenoid content, considering that there is an emerging market for yellow-pigmented breads due to the renewed interest in the nutritional aspects of cereal-derived food. To date, pre-breeding materials have been obtained with increases in grain carotenoid content ranging from 16 to 23 %.

A second inter-specific breeding program is aimed to incorporate into durum wheat the Hordeum chilense genes Psy1-Hch (for increasing carotenoid biosynthesis) and XAT-7Hch responsible for carotenoid esterification. Carotenoid esterification has emerged as a new target for cereal biofortification, as this process increases both carotenoid accumulation and stability.

Prior to the identification of both the phenotypic variability and the gene responsible for carotenoid esterification (XAT-7A) in durum wheat, we considered this approach to increase grain carotenoid content in this species. Based on a marker-assisted selection strategy, durum wheat pre-breeding materials harboring both Psy1-Hch and XAT-7Hch have been obtained, which can be used for pyramiding with XAT-7A to putatively increase the carotenoid biosynthesis and esterification capacity in this species.

Acknowledgements

This research was financed by projects AGL2017-85368-P and PID2021-122152NB-I00 funded

by MCIN/AEI/10.13039/501100011033/ and by ERDF “ERDF A way of making Europe”.