| Soil pollution has gradually developed into a major environmental problem that human beings must pay attention to at all times,especially the serious pollution caused by heavy metals in the soil.Heavy metal pollution not only leads to the decline of soil fertility,the reduction of crop production,and the excessive content of heavy metals in agricultural products,which greatly affects the economic development of agriculture and the health of human and animal life.As the main type of fresh maize,sweet and glutinous maize is highly praised by people because of its excellent taste,rich nutrition and other advantages.With the increase of population and the promotion and popularization of the concept of healthy diet in China,the market demand for sweet and glutinous maize is growing rapidly,and the planting area and scale are expanding constantly.At the same time,sweet and glutinous maize stalks can be used as silage for the consumption of farms.Therefore,the market potential of sweet and waxy maize is huge.Then,fresh maize,like other vegetable crops,is seriously affected by heavy metal Cd pollution in some areas.Therefore,the cultivation and promotion of fresh maize varieties with low Cd accumulation can not only provide safe and reliable fresh maize to meet people’s daily needs,but also further promote the healthy and green development of the fresh rice industry chain.Therefore,the identification and analysis of genes related to Cd accumulation in fresh maize is of great significance for the improvement of Cd accumulation characteristics of existing materials by genetic engineering in the future,In this experiment,some agronomic characters and Cd content of fresh maize population in germination,seedling and maturity were identified by pot culture and different Cd Polluted Environment in field.The main results were as follows:1.In the pot cultivation environment,the analysis of the germination potential,germination rate and germination index of 204 sweet and waxy maize populations under different Cd pollution levels during germination showed that the above indicators all decreased with the increase of Cd treatment concentration,and with the The increase in treatment concentration showed an overall increase in the inhibitory effect,which is consistent with the results of previous studies.Under the treatment of potted medium Cd(18.50 mg / kg),compared with the control group,it was found that the germination potential,germination rate and germination index did not reach a significant level(P >0.05),while the severe Cd(34.90mg/kg)treatment,Germination potential,germination index were 42.77% and 10.93% respectively,compared with the germination potential of the control group 51.35% and germination index 13.21%reached a significant level,and found that the average value of the germination rate under the two Cd treatment levels was 74.22% and 70.53%,compared with 73.93% of the control group,did not reach a significant level(P>0.05),and the germination rate showed a trend of increasing first and then decreasing,indicating that with the increase of Cd treatment concentration,the germination potential and germination of sweet and waxy maize seeds The influence of the index increases and reaches a significant level,but the influence on the germination rate is not obvious.Analysis of Plant height at seedling stage,Plant height at maturity and ear height of sweet and waxy maize in pots and fields,the results showed that the above indicators all decreased with the increase of Cd treatment concentration in different environments,and reached a significant impact compared with the control The level(P<0.01)showed that Cd had a significant(P<0.05)inhibitory effect on the Plant height at seedling stage,Plant height at maturity and ear height of sweet and waxy maize at seedling stage.The flowering cycle and spinning cycle of potted and field maize under different Cd treatment concentrations were studied.The results showed that under different Cd treatment environments,the flowering cycle and spinning cycle of maize were delayed compared with the control,and reached a significant level(P <0.01);The higher the Cd content in the soil,the longer the cycle,and also found that the interval between the flowering cycle and the spinning cycle increased with the increase of Cd content.2.Statistical analysis of the Cd content of sweet and waxy maize mixed population in pot and field environment,and calculation of its enrichment coefficient;The results showed that the Cd content in seedling stage was moderate(18.50 mg/kg),the content of Cd in the above ground part of the mixed population was in the range of 3.07-126.23mg/kg,and the average value of 35.5mg / kg;the Cd content under the treatment of severe Cd(34.90 mg/kg)was 0.43-180.77 mg/kg,the average value is 60.01 mg/kg;the coefficients of variation under the above Cd treatment are 60.58% and 47.5%,and the enrichment coefficients are 1.919 and 1.72,respectively;at medium and severe Cd treatment concentrations,the leaf Cd at the ear of mature stage that the average content was 18.7mg/kg and 28.82 mg/kg respectively;the coefficients of variation were 81.79% and 81.37%,and the enrichment coefficients were 1.011 and 0.826;the Cd content of the leaves in the aerial part and the mature stage of the seedling stage increased with the increase of the treatment concentration,While the coefficient of variation and enrichment coefficient are reduced.At the same time,the study found that the mean value of Cd content in the aerial parts of waxy maize seedlings and ears at the mature stage is greater than that of sweet maize,and the enrichment coefficient is also greater than that of sweet maize,indicating that waxy maize is more likely to accumulate Cd than sweet maize.Field test results showed that the mean Cd content in the aerial parts of the maize seedling stage and the ear position at the mature stage increased with the increase of the treatment concentration,and the enrichment coefficient decreased with the increase of the treatment concentration;the sweet and waxy maize populations were analyzed The results showed that under different Cd pollution environments,the Cd content of the above-ground part of the waxy maize seedling stage and the maturity stage was greater than that of sweet maize,and the enrichment coefficient was also greater than that of sweet maize,which is consistent with the pot experiment results.The analysis of the Cd content in the mixed population of sweet and waxy maize under different Cd pollution in the field revealed that the accumulation of Cd increased with the increase of concentration,while the enrichment coefficient and coefficient of variation decreased;for sweet and waxy maize that the population analysis showed that with the increase of Cd pollution,the Cd content and enrichment coefficient of sweet maize grains were greater than that of waxy maize,but the coefficient of variation was smaller than that of waxy maize,indicating that sweet maize accumulates Cd more easily than waxy maize in high Cd environment.By synthesizing the results under different environments,this experiment screened out the low-enrichment material waxy corn N16A628 and the high-enrichment material waxy corn N16A625 at the seedling stage.Six waxy varieties 17CL66,17CL131＿1,N16A628,N17D293,N17D300,and 17CL76 were selected as low-enriched grain materials.Among them,N16A628 was also selected in the low accumulation of aboveground parts at the seedling stage,indicating that N16A628 showed stable low accumulation characteristics of Cd There are four varieties with high grain enrichment,17CL138,17CL123＿2,17CL13 and 17CL204,of which 17CL138 is sweet maize and17CL123＿2,17CL13 and 17CL204 are waxy maize.3.In this experiment,Maize56 K SNP Array was used to analyze the material genotypes,and finally 25,715 high-quality SNP markers were obtained.By constructing an evolutionary tree,the 183 materials used for correlation analysis were divided into three subgroups,of which 105 waxy maize and 6 sweet maize were a subgroup,and 42 sweet maize and one waxy maize(17CL14)were a subgroup.Group,another 29 parts of sweet maize is a subgroup.The PCA analysis also divided the population into three subgroups.Admixture was used to analyze the structure of the sweet waxy maize population.At the same time,combined with evolutionary tree analysis and PCA analysis,K=3 was selected to divide the population into 3subgroups,which is closest to the real situation.An analysis of the kinship of the group structure found that kinship values less than 0.05 accounted for 74%,0-0.3accounted for 95.9%,0.3-0.5 accounted for 2.25%,and greater than 0.5 accounted for1.84%,indicating that the sweet and waxy group Kinship is far away.4.This experiment used Maize56 K SNP Array to analyze the material genotype,and finally obtained 25715 high-quality SNP markers for subsequent genome-wide association analysis.Through genome-wide association analysis of Cd content in the above-ground part of the sweet and waxy corn mixed seedlings at the seedling stage,and in the ears and leaves at the mature stage,at a significant level-log P≥4.41(p<1/25715,α= 1),we selected 39 SNPs related to the Cd content in the aerial part of the seedling stage,of which 31 were screened in the pot test and 8 in the field test,and they were mainly concentrated on chromosome 2.At the same time,2 SNPs were screened in the pot and field environent on chromosome 2.The significant SNPs are AX-86282590 and AX-86262369,respectively.20 SNPs related to Panicler leaves at maturity stage were screened out,of which 11 SNPs were screened under pot experiments and 9 field environments were selected.A common SNP marker AX-86282590 was screened in pot and field trials.The marker is located at163,041,471 bp on chromosome 2.A genome-wide association analysis was performed on the Cd content in the field grains,and a total of 15 significant SNPs were screened,all of which were located on chromosome 2.Among them,8significant SNPs were screened in the field with mild Cd pollution,and severe Cd pollution Screened to 7 under the environment.The above test results show that the significant SNPs associated with controlling Cd content in the aerial part of the seedlings,ears and grains at the mature stage are mainly concentrated on chromosome2 and are clustered.Therefore,the Cd accumulation content in different tissues of different growth stages of corn It is a quantitative trait controlled by multiple genes on chromosome 2.At the same time,it was found that a common SNPs that was AX-86282590 on chromosome 2 controls the Cd accumulation of the above three traits.5.According to the physical locations corresponding to the above-mentioned significant SNPs,they were compared with the Maize GDB and NCBI gene databases,and 25 protein-coding genes with known functions and 5 genes with unknown functions were screened.The common genes HMA2 and HMA3 are located in the aerial part of the seedling stage,ears and grains at the mature stage under different Cd treatment environments.They encode Zn and Cd transporters and belong to the HMA protein family.Therefore,this gene is in different tissues in different growth stages of maize.It plays an important role in regulating the accumulation of Cd. |
