Association Analysis Between Mugineic Acid Release Character And SSR Markers In Seedling Stage Of Maize Inbred Lines

Graminaceous plants secrete phytosiderophores (PS) from their root to acquire insolubleiron (Fe) from calcareous soils, so the PS secretion of corn can be used to evaluate theiron-efficiency. Identification of iron-deficiency-tolerant germplasms in seedling stage is anefficient way to exploit useful genes. To make advances in maize breeding, it is important tostudy germplasm diversity of main maize inbred lines, and identify SSR markers associatedwith important agronomic traits, including PS secretion rates under+Fe and–Fe condition. Inthis study,123historical maize inbred lines and153pairs of SSR markers evenly distributedon the chromosomes of maize were used in association analysis. The results were summarizedas follows:1. Tested the PS secretion of123maize inbred lines under+Fe and-Fe condition. Theaverage of secretion was (7.281±0.45) mg/(g*8h) under+Fe condition, and rang from1.786to19.69mg/(g*8h). The average of secretion was (9.583±0.57) mg/(g*8h) under-Fecondition, and rang from2.414to24.53mg/(g*8h).2. Clustering analysis shows that all the materials could be divided into low, medium andhigh PS secretion form. Under Fe-sufficient condition, the average PS secretion of threegroups are4.306,7.001and11.79mg/(g*8h) respectively. The number of three groupsaccount for43.1%、26.8%and30.1%of total number of materials respectively. UnderFe-deficient condition, the average PS secretion of three kinds iron-deficiency tolerantmaterials are7.891,10.01and12.54mg/(g*8h) respectively. The number of three groupsaccount for46.3%、31.7%and22.0%of total number of materials respectively. Varianceanalysis showed that there were significant differences in the PS secretion of three kindsmaterials. Results indicate that the PS secretion of different materials has great difference inthe same period and the inbred lines have profuse phenotypic diversity.3. The study that use12maize inbred lines to analyses the diurnal variation of PSsecretion has found that PS secretion patterns of different inbred lines were not uniform. Thesecretion peaks appeared at different time under Fe-sufficient condition. The twelve inbredlines can be divided into two groups based on the numbers of secretion peak. One has onlyone main secretion peak at7:00-10:00and the other one has two secretion peaks at 7:00-10:00and16:00-19:00. Under Fe-deficient condition, all inbred lines can be also dividedinto two groups according to the numbers of DMA secretion peak. One has only one mainpeak at7:00-10:00, and the other has two secretion peaks, the main peak occurred at7:00-10:00, while the second peak occurred at19:00-22:00or13:00-16:00. Plants underFe-deficiency secreted more PS than plants under Fe-sufficiency and PS secretion rates weredifferent at different times of the day. PS secretion by all inbred lines under Fe-deficientcondition increased significantly compared to the control. Paired t-test results showed thatFe-deficiency had significant effects on PS secretion patterns and rates.4. The study that use six maize inbred lines, which showed different secretion patternsunder Fe-deficiency, to analyze the diurnal variation of PS secretion under shading treatments.The results showed that collecting root exudates in dark did not affect secretion pattern ofmaize, indicating that PS secretion was triggered not by dark/light, but followed the biologicalclock in short darkness. The PS secreted per day increased after treated24h in dark, whichhad no influence on diurnal secretion rules. The results of two shading treatments indicatelight or dark induces the relevant gene expression and then makes PS secretion increased.5. Association analysis of PS secretion traits in maize inbred lines. A total of30(P<0.05)markers were associated with PS secretion related traits. Four SSR loci were significantly(P<0.01) associated with PS secretion under+Fe condition, and their explained portion ofphenotypic variation were rang from4.07%to21.19%. Three SSR loci were significantly(P<0.01) associated with PS secretion under-Fe condition, and their explained portion wererang from11.15%to25.90%. Three SSR loci were significantly (P<0.01) associated with theincrement of PS release rate induced by-Fe, and their explained portion were rang from9.48%to18.19%. There were three same loci which were constitutive loci associated with+Fe and-Fe traits related to PS secretion, and seven different loci which might be induced byFe-deficiency under+Fe and-Fe conditions. In present study, a set of elite alleles, loci andtheir carrier materials were screened out. The alleles, phi308707-A128and phi062-A170, hadbiggist positive effect on PS secretion under-Fe condition and PS secretion incrementinduced by-Fe respectively, while bnlg1305-A195had biggist negative effect on PS secretionunder+Fe condition.