Effects of Different Rootstocks on Plant Growth and Fruit Quality of Watermelon

[Objectives] This study was conducted to explore the effects of different rootstocks on plant growth and fruit quality of watermelon. [Methods] The scions of two different watermelon varieties Qianmei No. 1,which has yellow flesh,and Qianli No. 1,which has red flesh,were grafted onto six different rootstocks of Lagenaria and Citrullus. Then,the seedling survival rate,growth potential and fruit quality in different rootstock-scion combinations were investigated.[Results]Rootstock type showed an extremely significant correlation with the survival rate of grafted watermelon plants. The watermelons grafted onto Lagenaria rootstocks had higher survival rate and better fruit quality than those onto Cucurbita rootstocks. Among them,Jingxinzhenguan was more suitable for red-fleshed watermelon variety,and bottle gourd rootstock was more suitable for yellow-fleshed watermelon variety. There were significant correlations between rootstock type and the number of leaves,the number of branches and the length of main vine of grafted plants. The number of leaves per seedling of all grafted plants was higher than that of non-grafted plants. There were no significant differences in sugar content at the center part of flesh and total soluble sugar content of fruit between the grafted and non-grafted watermelons. In addition,the interaction between rootstock type and watermelon variety had no significant effect on vegetative growth and fruit quality of grafted watermelon. [Conclusions] This study provides a theoretical basis for the grafting of watermelon.

可摘局部义齿卡环固位力测量系统的研制及其初步效果评价

目的探讨可摘局部义齿卡环固位力测量系统的研制方法,并对其性能进行初步评价。方法设计研制可摘局部义齿卡环固位力测量系统,系统由卡环固位力测量仪、钳式测力计及测试系统软件3部分组成,主要设计指标为力学量程0~50 N、可连续测量固位力变化(每秒采集1000个有效数据)。利用砝码对测量系统的测量精度进行验证。通过增材制造方式制作纯钛、钴铬合金卡环试件各12个,将每种材料卡环随机数字表法分为2组,每组6个。其中,使用电子万能材料试验机测量纯钛卡环和钴铬卡环分别为对照组1和2,每组6个,可摘局部义齿固位力测量系统测量纯钛卡环和钴铬卡环分别为实验组1和2,每组6个。比较2种测量方式测得的卡环初始固位力大小。使用单因素方差分析法比较系统精密度,对不同测量方式测得的义齿卡环试件初始固位力进行独立样本t检验。结果可摘局部义齿固位力测量系统精度符合设计要求。电子万能材料试验机测得对照组1(13.96±1.51)N,对照组2(18.93±1.42)N;可摘局部义齿固位力测量系统测得实验组1(10.35±0.75)N,实验组2(15.34±0.68)N。由相同材料及制作方式制成的卡环,经不同测量方式测得的初始固位力之间差异有统计学意义(t纯钛=-11.740,P纯钛<0.001;t钴铬=-12.492,P钴铬<0.001)。结论本实验研制的测量系统能更真实地体现卡环脱位过程中的固位力变化,更接近临床情况。

Improvement of pristinamycin I(PI)production in Streptomyces pristinaespiralis by metabolic engineering approaches

Pristinamycin,produced by Streptomyces pristinaespiralis,which is a streptogramin-like antibiotic consisting of two chemically unrelated components:pristinamycin I(PI)and pristinamycin II(PII),shows potent activity against many antibiotic-resistant pathogens.However,so far pristinamycin production titers are still quite low,particularly those of PI.In this study,we constructed a PI single component producing strain by deleting the PII biosynthetic genes(snaE1 and snaE2).Then,two metabolic engineering approaches,including deletion of the repressor gene papR3 and chromosomal integration of an extra copy of the PI biosynthetic gene cluster(BGC),were employed to improve PI production.The final engineered strain DPIIDpapR3/PI produced a maximum PI level of 132 mg/L,with an approximately 2.4-fold higher than that of the parental strain S.pristinaespiralis HCCB10218.Considering that the PI biosynthetic genes are clustered in two main regions in the 210 kb“supercluster”containing the PI and PII biosynthetic genes as well as a cryptic polyketide BGC,these two regions were cloned separately and then were successfully assembled into the PI BGC by the transformation-associated recombination(TAR)system.Collectively,the metabolic engineering approaches employed is very efficient for strain improvement in order to enhance PI titer.