Dynamic QTL analysis for developmental behavior of cell wall components and forage digestibility in maize (Zea mays L.)

Background Cell wall architecture plays a key role in stalk strength and forage digestibility. Lignin, cellulose and hemicellulose are the three main components of the plant cell wall and can impact stalk quality by affecting cell wall structure and strength. To explore cell wall development during secondary cell wall lignification in maize stalks, conventional and conditional genetic mappings was used to identify the dynamic quantitative trait locus (QTL) for cell wall components and digestibility traits in five growth stages after silking. Results Acid detergent lignin (ADL), cellulose (CEL), Acid detergent fiber (ADF), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD) of stalk were evaluated in a maize recombinant inbred line (RIL) population. The cell wall components gradually increased in the 10–40 days after silking (DAS), reached a maximum at 30–40 DAS, and then steadily decreased. IVDMD decreased over the initial 40 DAS and then increased slightly. Seventy-two QTL were identified for five traits and each accounted for 3.48–24.04% of the phenotypic resistance variation. Twenty-six conditional QTL were detected using conditional QTL mapping. 22 out of 24 conditional QTL were found for stages III|II and V|IV. Six QTL hotspots were found localized in bins 1.08, 2.04, 2.07, 7.03, 8.05, and 9.03 in the maize genome. Conclusion The unconditional pleiotropic QTL in bins 1.08 and 8.05 were also associated with stalk strength. Furthermore, several pleiotropic QTL for cell wall and digestibility were found not associated with stalk strength. A simultaneous improvement in forage digestibility and lodging resistance can be achieved by pyramiding multiple effective QTL identified in the present study.

Genetic dissection of flour whiteness by unconditional and conditional quantitative trait locus mapping in wheat

SUMMARYFlour whiteness (FW) is an important factor in assessing flour quality and determining the end product quality. It is an integrated sensory indicator reflecting flour colour and is negatively correlated with protein content. In order to dissect the genetic relationship between FW and its five related traits at the quantitative trait locus (QTL)/gene level, a recombinant inbred line population was evaluated under three environments. Quantitative trait loci for FW were analysed by unconditional and conditional QTL mapping. Four unconditional additive QTLs and 16 conditional additive QTLs were detected across the three environments. Of these QTLs, only one major additive QTL (Qfw1D1-1) was consistently identified using both unconditional and conditional QTL analysis. This QTL was independent of flour colour a* (a function of red-green with a positive a* for redness and negative for greenness) and b* (a green-blue value with positive value for yellowness and negative for blueness) and was only slightly affected by flour protein content. A minor additive QTL (Qfw4A-4) was also detected using these two QTL mapping methods, being independent of flour colour a* and b*. Five unconditional and ten conditional epistatic minor QTLs were detected, from which only one pair (Qfw3A-10/Qfw6B-6) was identified by both unconditional and conditional QTL mapping, also independent of flour colour a* and b*. The major QTL (Qfw1D1-1) identified in the current study for the first time can be used for improving wheat FW in marker-assisted breeding.