Effect Of The Q^s2 Allele On Yield,Quality And Fusarium Head Blight Resistance In Wheat

Wheat（Triticum aestivum L.）is one of the three major food crops and plays a pivotal role in food production.With the improvement of living standards,higher requirements have been put forward for wheat yield and quality.Fusarium head blight（FHB）is one of the main diseases of wheat,since it seriously affects the yield and quality of wheat.Therefore,breeding of wheat cultivars with high yield,good quality and high FHB resistance is strongly required.To achieve this goal,it is important to identify new genes/alleles and germplasm.Q is an important domestication gene in wheat,affecting wheat yield,quality and resistance.It maybe possible to obtain favorable Q alleles that can synergistically improve the yield,quality and FHB resistance of wheat.In this study,the Q gene mutant SS2 was created by chemical mutagenesis,which contains the new allele Q^s2.The effect of Q^s2 on yield,quality and FHB resistance was elevated.The main results are as follows:1.A missense mutation was occurred in the first AP2 domain of the Q^s2 allele in SS2,which led to the replacement of the 119^thamino acid residue from serine（Ser）to leucine（Leu）.This amino acid change did not significantly affect the predicted tertiary protein structure.2.The results of RT-q PCR showed that the expression of Q gene in the mutant SS2 was higher than that in the wild type（WT）at the floral differentiation stage and the gynostamen differentiation stage.In the two-leaf one-heart period,the expression of Q gene was the highest in stem,but there was no significant difference between SS2 and WT.Subcellular localization experiment showed that both Q and Q^s2 proteins were localized in the nucleus.These data suggests that the point mutation in the AP2 domain can affect the expression of the Q gene,but Q^s2 still functions as a nuclear transcription factor.3.The results of agronomic trait analysis showed that in the three growing seasons,i.e.2018-2019,2020-2021 and 2021-2022,compared with WT,the plant height,spike length and grain per main number of SS2 were significantly increased,the volume weight was significant increased,the spike density,thousand kernel weight and grain width were significantly reduced.There was no significant change in grain length,spikelet per main spike,effective tiller number（significantly decreased in 2021-2022）and yield.4.Measurement of processing quality indicated that in the three growing seasons,the grain protein content of SS2 were significantly reduced,and there were no significant differences in sedimentation value,gluten index,water absorption,development time and degree of softening when compared to WT.In the 2018-2019 growing season,stability time and farinograph quality number of SS2 was shorter than that of WT.In the 2021-2022growing season,the wet gluten content and dry gluten content of SS2 were less than those of WT.In the three growing seasons of 2018-2019,2020-2021 and 2021-2022,there were no significant differences in the diameter and extension factor of cookies between SS2 and WT.Notably,the maximum thickness and minimum thickness of SS2 were significantly decreased in 2018-2019,when compared to those of WT.In the 2020-2021 and 2021-2022 growing seasons,there were no significant differences in bread volume,slice width,aspect ratio,total depression,stomata number and stomatal elongation evaluation,when comparing the bread of SS2 and WT.5.SS2 showed much better FHB resistance than WT.At the flowering stage,the contents of salicylic acid（SA）and ethylene biosynthetic precursor（ACC）were significantly reduced.The expression results of hormone-related target genes showed that salicylic acid-related target genes were up-regulated and ethylene-related target genes were down-regulated.The results of bacterial mass determination showed that there was no significant change in bacterial count in the mutant material compared with wild type.6.The results of analysis of varianceshowed that the effect of environment（growing season）,genotype(Q and Q^s2)and environment and genotype interaction on wheat agronomic traits and processing quality was as follows:environment>genotype>environment and genotype interaction.