Analysis of Population Genetic Change to Single Oospore Strains of Phytophthora infestans

The occurrence of sexual reproduction accelerates the population genetic variation of Phytophthora infestans and makes it more difficult to control.The systematic analysis of the differentiation of phenotype(mating type and metalaxyl sensitivity)and genotype(mtDNA haplotype and SSR genotype)of 65 single oospore strains of P.infestans was carried out in this article.Five test strains were isolated from Heilongjiang Province and Mongolia Autonomous Region.The experiment results showed that the isolation ratio of metalaxyl resistance(MR:HR)of single oospore strains produced through the cross of medium resistance and high resistant parents was 18:13;the isolation ratio of the metalaxyl resistance(S:MR:HR)of single oospore strains produced through the cross of sensitive and high resistant parents was 4:12:7.The progenies of single oospore strains produced through self-fertility parents with medium resistance were all of the medium resistance.The mating types A1:A2 was greater than 1:1 in single oospore strains of the progenies,which did not conform to the Mendel's law of inheritance.All single oospore strains of the progenies inherited mitochondrial DNA fragments from only one parent.Sexual recombination of single oospore strains was verified by using two pairs of SSR primers(Pi4B and Pi4G).At the locus of Pi4B and Pi4G in the cross of KS-37 and KS-25,the separation frequencies of allele were 19:12 and 14:17,respectively.They produced two new genotype strains.This study could provide a basis for formulating disease control strategies.

On the Bifurcations and Multiple Endemic States of a Single Strain HIV Model Dedicated to Professor Toshikazu Sunada on the Occasion of his 60th Birthday

The dynamics of a single strain HIV model is studied. The basic reproduction number R0 used as a bifurcation parameter shows that the system undergoes transcritical and saddle-node bifurcations. The usual threshold unit value of R0 does not completely determine the eradication of the disease in an HIV infected person. In particular, a sub-threshold value Rc is established which determines the system＇s number of endemic states： multiple if Rc 〈 Ro 〈 1, only one if Rc=Ro = 1, and none if R0 〈 Rc 〈 1.

Influence on the aroma substances and functional ingredients of apple juice by lactic acid bacteria fermentation

This study aimed to analyze the influence of lactic acid bacteria fermentation on the aroma composition and functional composition of apple juice,selected Lactobacillus reuteri to ferment apple juice,used HS-SPME-GC-MS and HPLC to analyze the changes of volatile aroma composition,organic acids and phenols after fermentation.The results showed the best fermentation time was about 18 h;The type and content of volatile substances(mainly alcohols and esters)in fermented juice changed and affected the overall aroma;The content of organic acids such as succinic acid,tartaric acid,malic acid and pyruvic acid affected the taste and flavor;The content of polyphenols such as gallic acid and protocatechuic acid increased,which enhanced the antioxidant capacity and functionality of fermented juice.This result showed the positive effect of fermentation on juice and provided a reference for the subsequent research on the aroma and functional composition of apple juice.