A Preliminary Study on Biological Activity of Wikstroemia chamaedaphne Meissn

[ Objective ] The insecticidal and antibacterial bioactivity of Wikstroemia chamaedaphne Meissn were screened and bioactive substances in it were separated and purified. [ Method] The Wikstroemia chamaedaphne Meissn was conducted ultrasonic extraction in petroleum ether, ethyl acetate and methanol. The insecticidal activity of Wikstroemia chamaedaphne Meissn to Mythimna separata walker and aphid were determined. The antibacterial activity of Wikstroemia chamaedaphne Meissn to Fusarium graminearu, Glomerella cingulata, F. oxysporium f. sp niveum, Alternaria solani and Fusarium oxysporium were also determined. The bioactivity-guided methods such as opencolumn chromatography and Pre-HPLC method were used to separate active components in petroleum ether extract from Wikstroemia chamaedaphne Meissn. [ Result] When the concentration was 500 mg/L, 3 kinds of extracts from Wikstroemia chamaedaphne Meissn didn＇ t show obvious antibacterial bioactivity to 5 kinds of test samples. When the concentration was 5%, petroleum ether extract show certain topical toxicity to aphids. The ethyl acetate extract showed certain antifeedant activity to 3^rd instar Larvae of Mythimna separata Walker. The fraction F4 of petroleum ether extract possessed highest topical toxicity to aphids and the lethality was 60.00%. [ Conclusion] Wikstroemia chamaedaphne Meissn contained many insecticidal constituents whose active parts and mechanism were needed further researches.

Molecular Marker Assisted Selection for Fusarium Wilt Resistance Breeding in Watermelon(Citrullus lanatus)

Molecular identification on diploid and tetraploid watermelon breeding lines which were resistant to Fusarium wilt was carried out with the published dCAPS marker ＂4451_fon＂ which was closely linked with resistance gene of Fusarium wilt race 1. The results showed that all the diploid and tetraploid lines expressed as re- sistant genotype, which were defined as Fusarium wilt-resistant materials. The re- sults were consistent with that of artificial inoculation identification. Molecular identifi- cation results also indicated that the resistant lines were homozygote, and the Fusarium wilt-resistant gene would not separate or lose during the future self- crossed purification. Therefore, resistance selection would not be necessary in their progeny populations. The study results thought that dCAPS marker ＂4451_fon＂ could be applied on molecular marker assisted selection for Fusarium wilt resistance breeding in watermelon to increase breeding selection efficiency and accelerate breeding progress.

Purification of Antifungal Protein from Biocontrol Strain XG-1 against Fusarium Wilt of Watermelon

[Objective] This study aimed to isolate and purify the antifungal protein against Fusarium oxysporum f. sp niveum （FON） from Bacillus subtilis XG-I. [Method] The crude protein was obtained by using fractional precipitation with am- monium sulfate, then chromatography using both DEAE-Sepharose FF anion ex- change and Sephacryl S-100 gel filtration columns was adopted for further purifica- tion of the protein, followed by MALDI-TOF-MS analysis of the structure of the at- tained protein which was antagonistic to FON. [Result] The result from MALDI-TOF- MS analysis suggested that the antifungal protein extracted from strain XG-1 was highly homologous to the flagellin （gi114278900） deriving from B. subtilis, with a pro- tein score of 248 and a coverage rate of 63%. It was thus speculated that this an- tagonistic protein was a kind of flagellin with a molecular mass of 30.6 kD. [Conclusion] The results from this study provide theoretical basis for clarifying the mechanisms of the action of strain XG-1 as well as important references for the preven- tion and control of watermelon Fusarium wilt.

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.

Introduction of Bottle Gourd DNA into Watermelon by Soaking Embryo for Resistance to Wilt Disease

In order to utilize wilt disease resistance of bottle gourd,total DNA of bottle gourd was introduced into watermelon through the method of aoeking embryo.The DNA-introduced variant were cultured in contaminated soil to elect the wilt disease resistance for more than 3 genera- tions.2 high-resistant and 2 middle-resistant watermelon materials were obtained.

Utilization and Inheritance of Watermelon Resistance to Fusarium oxysporum f.sp.niveum Introduced from Bottle Gourd

Sugar Baby susceptible to Fusarium oxysporum f.sp.niveum was crossed with high resistant male parents D3-1 and D3-2,respectively.F1 hybrids showed high resistance.The segregation ratios of resistance to susceptibility of F2 and of BC1 hybrid population from Sugar Baby tallied with 3:1 and 1:1,respectively.The results indicated that the resistance to Fusarium wilt was a kind of dominant inheritance controlled by mono-gene or mono-segment DNA.Furthermore,5 hybrid combinations with fine character were bred.Among them,3 were high resistant to Fusarium wilt,and 2 were medium resistant.