Effects of Drought and Low Nitrogen Stress on Provitamin A Carotenoid Content of Biofortified Maize Hybrids

Abstract

Maize (Zea mays L.) hybrids with enhanced provitamin A (proVA) content have been deployed in sub‐Saharan Africa, where low soil nitrogen and drought stress are common. The objectives of this study were to assess: (i) the effects of drought and low‐N stress on grain proVA content of hybrids with enhanced proVA content, and (ii) the inheritance of proVA carotenoids under these stress conditions. An 11‐line diallel cross (55 F1 crosses) was evaluated for carotenoid content and grain yield under optimum conditions, drought, and low‐N stress. Compared with the optimum treatment, mean proVA was lower under both stress treatments. The consistency of genetic effects across stress treatments suggested that hybrids with improved proVA content can be developed for a broad range of environments, provided they are sufficiently adapted. General combining ability (GCA) was significant (P < 0.01), and accounted for >85% of the variation among hybrids, whereas specific combining ability (SCA) effects were generally weak (P < 0.05), accounting for 5 to 15% of hybrid sums of squares across the three treatments. These results indicated that the inheritance of proVA was not affected by stress treatments. A negative correlation between grain yield and proVA carotenoids was detected, but the data suggested that it was caused by the genetic background of the germplasm used rather than pleiotropy. Our results provide insights that may help breeders design effective breeding strategies to develop proVA‐enriched cultivars for resource‐limited farming systems.

Assessing Effect of Marker-Based Improvement of Maize Synthetics on Agronomic Performance, Carotenoid Content, Combining Ability and Heterosis

“…However, the result is consistent with the findings of [14]who used S 1 selection method to improve provitamin A and other carotenoids in open-pollinated maize cultivars. The increase in provitamin A content with either improvement or little change in grain yield in the present study, was contrary to the results reported in other studies indicating undesirable association between the two traits [14,47,48]. Consequently, simultaneous improvements in grain yield and provitamin A can be made through combined use of marker-based and phenotypic selections to develop desirable source populations.…”

Molecular Breeding for Nutritionally Enriched Maize: Status and Prospects

“…Nonetheless, the levels of PVA carotenoids in adapted tropical and sub-tropical maize inbred lines were far below the breeding target of 15 µg g −1 of PVA set for maize (Bouis et al, 2011), emphasizing the need for accessing and mining novel sources of favorable alleles to boost PVA concentration to new levels. The less complex nature of control of provitamin A content, high heritability, mode of inheritance regulated primarily by additive genetic effects, and statistically non-significant correlation between PVA and agronomic performance suggested that concurrent improvements of PVA carotenoids and grain yield would be possible (Suwarno et al, 2014;Menkir et al, 2018;Ortiz-Covarrubias et al, 2019). Through systematic breeding efforts, significant improvement has been made in enhancing provitamin A content of tropical maize inbred lines developed at CIMMYT ( Figure 2).…”

“…Foreground MAS selection was done in segregating F 2 or F 3 populations, selecting seeds that had the homozygous favorable alleles at the CrtRB1-3′ TE and LcyE-3′Indel polymorphisms. However, combining foreground and background MAS may be preferable to reduce linkage drag considering that most of the PVA maize donor germplasm is agronomically inferior Ortiz-Covarrubias et al, 2019).…”

Genomics-Integrated Breeding for Carotenoids and Folates in Staple Cereal Grains to Reduce Malnutrition

“…This is due to the weak correlation between provitamin A and agronomic performance. Other factors, like the relatively high heritability of the trait, the mode of inheritance (additive genetic effects), and the genetic control of provitamin A, are also accountable (Suwarno et al, 2014;Menkir et al, 2018;Ortiz-Covarrubias et al, 2019). So far, the enhancement of provitamin A is mostly focused on the selection of β-carotene content.…”