Current Situation and Control Measures of Agricultural Non-point Source Pollution in Typical Basin of South China

In view of the serious non-point source pollution of agriculture in the areas where crop production is concentrated in southern China,the present situation of agricultural non-point source pollution in southern watershed and the main technical measures adopted in the practice of comprehensive prevention and control in recent years are analyzed from the perspectives of different pollution sources such as planting,livestock and poultry breeding,aquaculture and village area runoff.From the perspective of functional restoration and optimization of farmland ecosystem,the countermeasures are put forward,such as strengthening the control of high qualityoriented pollution reduction,layout optimization,constructing circulation system and improving management system,constructing comprehensive prevention and control strategies for ecosystem elements and material exchange,energy flow and logistics linkage,information flow exchange,and maintaining and improving the ability of agricultural ecosystem itself to absorb non-point source pollution.

Purification of Starch from Cadmium-Contaminated Rice and Development of Functional Recombinant Rice

In order to provide a new utilization method for cadmium-contaminated rice,a preliminary study of the removal of rice starch cadmium by water,calcium hydroxide,sodium hydroxide and citric acid was conducted,the damage degree of starch was compared by SEM,and then the recombinant rice was obtained by a twin-screw extruder using the starch which met the safety standard.The physical and chemical properties of recombinant rice were analyzed by acid hydrolysis and texture analyzer.The results showed that citric acid was a good rice cadmium removal agent.The quality of recombinant rice prepared from cadmium-removed rice starch was improved;the acid resistance was increased.Heavy metal contaminated rice can be a staple food with better quality and higher value through processing.

Analysis of Rhizosphere Microbial Community Structure in Different Pathogenesis Stages of Watermelon Fusarium Wilt

High-throughput sequencing technique was applied to analyze the microbial community structure of rhizosphere soil at different stages of watermelon fusarium wilt to find out the difference of dominant microbial community in rhizosphere during the occurrence of watermelon fusarium wilt.Illumina-Hiseq high-throughput sequencing platform was used to sequence 16S and ITS rDNA in rhizosphere soil.The soil was named CK1 before planting,CK2 at peak stage and CK3 at stable stage.The results showed that the soil bacterial diversity was in the order of CK1>CK3>CK2,indicating no significant difference between CK1 and CK3 and a significant difference between CK2 and CK1,CK3.At the genus level,the dominant bacteria were Mizugakiibacter(21.9299%),Rhodanobacter(5.0933%),and Lactobacillus(3.1921%).The diversity of soil fungi was in the order of CK1>CK3>CK2,all showing significant differences.At the genus level,the dominant fungus was Lysurus(54.4601%),Papulaspora(12.4252%),Acrophialophora(3.1729%).The results showed that the diversity and abundance of bacteria and fungi in rhizosphere soil decreased during the peak period of watermelon fusarium wilt.With the gradual stabilization of the disease,the diversity and abundance of bacteria and fungi in rhizosphere soil recovered to a certain extent.

Effects of Winter Planting Milk Vetch on Yield and PartialProductivity of Nitrogen Fertilizer of Machine-transplantedDouble-cropping Rice under Straw Returning to the Field

From 2017 to 2018,the effects of winter planting of milk vetch on yield and partial productivity of nitrogen fertilizer of machine-transplanted double-cropping rice under straw returning were studied in Ningxiang city,Hunan Province.The results showed that the dry matter accumulation,effective panicle,yield and partial productivity of nitrogen fertilizer in the stem,leaf,panicle and aboveground parts of early and late rice treated with winter planting milk vetch and straw returning were signi ficantly higher than those treated with straw returning only.Among them,the effective panicles of early and late rice increased by 2.58%,3.18%(2017)and 5.22%,6.32%(2018),respectively.Yield increased by 11.85%,10.07%(2017)and 12.42%,10.92%(2018),annual partial productivity of nitrogen fertilizer increased by 10.90%(2017)and 11.66%(2018),respectively.In conclusion,winter planting milk vetch under straw returning is beneficial to increase dry matter accumulation,rice yield and partial productivity of nitrogen fertilizer in mechanized double cropping rice.

Effects of Wet Superfine Grinding on Polyphenols and Antioxidant Activities of Whole Fruit Pulp of Navel Orange

The navel orange were cleaned and pulverized by a wet superfine grinding and a broken wall cooking machine,then the navel orange whole fruit pulp were obtained by wet superfine grinding once,wet superfine grinding twice,and broken wall cooking machine processing.The particle size distribution,free polyphenols,bound polyphenols and antioxidant activity of whole fruit pulp prepared by the three kinds of pulverization methods were discussed.The results showed that the particle size distribution of the whole fruit pulp by wet superfine grinding was more concentrated compared with the broken-wall cooking machine processing,and the total phenols dissolution rate of the navel orange whole pulp was increased by 6.9%,and the total flavonoid dissolution rate was increased by 13.5%.The results also suggested that wet superfine grinding twice could improve 1,1-diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging activity of polyphenols in the whole fruit pulp,wet superfine grinding once and wet superfine grinding twice also could obviously enhance the reducing power and iron reduction ability of polyphenols in the whole fruit pulp.In conclusion,wet superfine grinding could increase both the polyphenol content and antioxidant activity of navel orange whole fruit pulp,it can be used as a pretreatment processing method for preparing navel orange whole fruit pulp.

Adsorption and Desorption Characteristics of Nitrogen and Phosphorus in Paddy Soils from Different Parent Materials

Reddish clayey soil(HH),alluvial sandy soil(HS),granitic sandy soil(MS)and purple clayey soil(ZS)were used as the test materials to reveal the adsorption-desorption characteristics of nitrogen and phosphorus nutrients in paddy soils from different parent materials.The results showed that the nitrogen desorption amount of each soil was greater than the nitrogen adsorption amount in the low nitrogen concentration range of 0~10 mg/L;in the high nitrogen concentration range of 20~50 mg/L,the soil nitrogen desorption rate gradually decreased with the increase of nitrogen concentration of the equilibrium liquid;when the soil nitrogen adsorption amount was-57.267~352.400 mg/kg,the nitrogen adsorption capacity of the paddy soils from different parent materials was HS>ZS>HH>MS;when the nitrogen desorption amount was 8.367~37.833 mg/kg,the nitrogen desorption capacity of the paddy soils from different parent materials was HH>HS>MS>ZS;the nitrogen adsorption isothermal curves of HH,MS,HS and ZS fitted the Linear model,the correlation coefficients were 0.928~0.978.At the same time,in the range of low phosphorus concentration(0~10 mg/L),the phosphorus adsorption amounts of 4 paddy soils were greater than their phosphorus desorption amounts.When the phosphorus concentration of the equilibrium solution exceeded 10 mg/L,phosphorus fixation capacities of 4 paddy soils weakened,meanwhile their phosphorus desorption increased,but their adsorption amounts were still greater than their desorption amounts.When phosphorus adsorption and desorption amounts of 4 paddy soils were-110.312~534.961 and 0.188~14.320 mg/kg respectively,the phosphorus adsorption and desorption capacities of 4 paddy soils were HS>HH>ZS>MS and ZS>MS>HS>HH,respectively.The phosphorus adsorption isothermal curves of 4 paddy soils fitted the Langmuir and Freundlich models,the correlation coefficient were 0.945~0.995.In general,paddy soils developed from different parent materials in Hunan Province have different adsorption and desorption characteristics for nitrogen and phosphorus.Purple clayey soil has the strongest nitrogen fixation capacity due to its stronger viscosity,which can reduce the risk of nitrogen loss by effectively holding nitrogen in the soil solution.On the contrary,being of strong sandy property,granitic sandy soil has the worst nitrogen fixation capacity and higher risk of nitrogen loss.The four paddy soils have strong adsorption capacity and low desorption rate of phosphorus,which indicates that the main paddy soils in Hunan Province have strong adsorption capacity for phosphorus and relatively small loss risk.

Identification and Expression Analysis of ARF Gene Family in Pepper

In order to understand the functions of ARF（Auxin Response Factor） gene family during the growth and development and under stress in pepper, 20 ARF genes were identified from the capsicum genome by bioinformatics and these genes were not well-distributed on 12 chromosomes of pepper. The results of the phylogeny relationship showed that ARF genes of pepper could be divided into Class I and II and could be further divided into seven sub-groups： Ia, Ib, Ic, Id, Ie, IIa and IIb. The results of gene structure showed that ARF gene family members were composed of 1-15 exons, and for each gene expression level of different tissues at different developmental stages revealed that the gene family had certain expression specificity. The qRT-PCR uncovered that high salt stress could significantly activate and inhibit the expression ofARF gene family.

Storage Characteristics of Five Kiwifruit Varieties in Hunan Province

Five kiwifruit varieties(Hongyang, Donghong, Jinyan, Cuiyu, Miliang1)in Hunan were picked and stored at room temperature. Sensory indicators(softening rate, decay rate, and firmness), nutritional quality(soluble solid content, titratable acid, and VC), tissue cell aging indexes(malondialdehyde, membrane permeability),and activity of polyphenol oxidase(PPO) and peroxidase(POD) during storage were analyzed. Results showed that firmness of Hongyang, Miliang1, and Cuiyu decreased rapidly, particularly Hongyang. The firmness of Donghong and Jinyan decreased slowly, but the decrease of Jinyan was slower than that of Donghong. Softening rate and decay rate were significantly different among the varieties. To be specific, the softening rate and decay rate of Jinyan were lower than those of Hongyang. Soluble solid content rose at early stage and then declined. Soluble solid content was high in Hongyang after storage for 12 d and high in Donghong and Jinyan after storage for 15 d. Content of titratable acid dropped slowly. Maximum VC content of Donghong,Jinyan, and Cuiyu was higher than that of Hongyang and Miliang 1. The inflection point of relative conductivity increase increase of Jinyan appeared later than that of Hangyang. The MAD content of Jinyan and Donghong kept at a low level. Storage characteristics of different kiwifruit varieties were significant. Storage time was in the order of Hongyang < Miliang 1 < Cuiyu < Donghong < Jinyan. In summary,Hongyang, Cuiyu, and Miliang1 should not be stored for a long time, while longterm storage is favorable for Jinyan and Donghong.