Effect of Forchlorfenuron (CPPU) and Ethychlozate on Fruit Development and Quality of Mango Cultivar 'Tainong 1'

The fruit swelling effect of forchlorfenurun （CPPU） and fruit thinning effect of ethychlozate on Tainong 1 mango （Mangifera indica L. cv. ） were studied. Spraying 32 mg/L CPPU at 7 and 21 d post flowering for just once significantly improved the fruit size of mango, but had no significant impact on fruit quality and flavor. Spraying 200 mg/L ethychlozate at 7 d post flowering for just once significantly increased fruit drop rate and single fruit weight of mango; fruit grade was improved and total soluble solid increased to the maximum value, so ethychlozate had good fruit thinning effect.

Construction of high-density SNP genetic maps and QTL mapping for dwarf-related traits in Litchi chinensis Sonn

Litchi chinensis Sonn is widely cultivated in subtropical regions and has an important economic value.A high-density genetic map is a valuable tool for mapping quantitative trait loci(QTL)and marker-assisted breeding programs.In this study,a single nucleotide polymorphism(SNP)-based high-density linkage map was constructed by a genotyping-by-sequencing(GBS)protocol using an F1 population of 178 progenies between two commercial litchi cultivars,‘Ziniangxi’(dwarf)and‘Feizixiao’(vigorous).The genetic map consisted of 3027 SNP markers with a total length of 1711.97 cM in 15 linkage groups(LGs)and an average marker distance of 0.57 cM.Based on this high-density linkage map and three years of phenotyping,a total of 37 QTLs were detected for eight dwarf-related traits,including length of new branch(LNB),diameter of new branch(DNB),length of common petiole(LCP),diameter of common petiole(DCP),length of internode(LI),length of single leaf(LSL),width of single leaf(WSL),and plant height(PH).These QTLs could explain 8.0 to 14.7%(mean=9.7%)of the phenotypic variation.Among them,several QTL clusters were observed,particularly on LG04 and LG11,which might show enrichment for genes regulating the dwarf-related traits in litchi.There were 126 candidate genes identified within the QTL regions,55 of which are differentially expressed genes by RNA-seq analysis between‘Ziniangxi’and‘Feizixiao’.These DEGs were found to participate in the regulation of cell development,material transportation,signal transduction,and plant morphogenesis,so they might play important roles in regulating plant dwarf-related traits.The high-density genetic map and QTLs identification related to dwarf traits can provide a valuable genetic resource and a basis for marker-assisted selection and genomic studies of litchi.

Biological Characteristics of Fusarium oxysporum f. sp.niveum Isolated from Watermelon Cultivated in Plastic Greenhouse and Indoor Toxicity Determination of Different Fungicides in Hainan Province of China

[ Objective] The paper was to study biological characteristics of Fusarium oxysporum f. sp. niveum in watermelon cultivated in plastic greenhouse in Hainan Province of China and to determine indoor toxicity of fungicides. [ Method] Effects of various factors on mycelial growth and spore germination were stud- ied, and the lethal temperature of spores and indoor toxicity of fungicides were also determined. [Result] The fungal mycelium had a better growth rate on water- melon juice medium than the others. The optimum temperature for mycelial growth and spore germination were 28 ℃ and 30 ℃, and the optimum pH values were 7 - 8 and 7 - 9, respectively. Light-dark alternation was conducive for mycelial growth. The lethal temperature of spore was 60 ℃ for 5 min. The fungal mycelium grew better while taking fructose and glucose as carbon sources and yeast extract and peptone as nitrogen sources. Toxicity determination showed that 50% pro- chloraz-manganese chloride complex WP had the greatest inhibition effect on mycelial growth, with the ECso value of 0.730 9 μg/mL; followed by 32.5% benzoic azoxystrobin SC, 30% benzoylate· propieanazol EC, 10% difenoconazole WG, 25% bromothalonil · carbendazim WP and 25% bromothalonil WP, with the ECso values from 1.884 7μg/mL to 8. 161 0μg/mL. [Conclusion] The study provided basic data for field control against F. oxysporum f. sp. niveum on watermelon cultivated in plastic greenhouse in Hainan Province.

Establishment of a Real-time Fluorescent Quantita- tive RT-PCR Method for Pineapple mealybug wilt as. sociated virus-2

Pineapple mealybug wilt associated virus-2 （PMWaV-2） is an important pathogen causing Mealybug wilt of pineapple （MWP）. We established a realtime quantitative RT-PCR （RT-qPCR） method with TaqMan probe based on specific primers of conserved nucleotide sequence of PMWaV-2 coat protein gene. The results showed that the method was higldy sensitive to positive sample, but had no fluorescence signal to health sample and blank control. The sensitivity of RTqPCR was about 100 times higher than general PCR. Reproducibihty test revealed that the coefficients of variation between intra-and inter-assay were beth within 1.85%, indicating it was a quantitative detection method for PMWaV-2 with simple operation, strong specificity, high sensitivity, and reliable reproducibility.

Study on Biological Characteristics and Toxicity Determination of Colletotrichum orbiculare Causing Anthracnose of Watermelon in Hainan Province

[Objective] This paper was aimed to study the biological characteristics of Colletotrichum orbiculare（Berk.et Mont.） Arx, and accomplish the preliminary screening the test of fungicides. [Method]The pathogen was isolated from the infected leaves of watermelon collected from greenhouse in Hainan Province. The biological characteristics of C. orbiculare and indoor toxicity of fungicides were studied. [Results] The mycelium grew fastest on the medium with leaf extract of watermelon. The optimum temperature for mycelial growth and spore germination was 28 and 30 ℃, and the optimum pH was 7-9 and 6-8, respectively. The continuous darkness condition was most suitable for mycelial growth. The lethal temperature of spore was 55 ℃ water bath for 10 min in water bath. The suitable carbon sources were maltose, L-arabinose and glucose, and the suitable nitrogen sources were yeast extract, beef extract and peptone. In the indoor toxicity determination, 32.5% Benzoic azoxystrobin SC, 50% Dichlorotetrakis WP and 10% Difenoconazole WG showed better inhibition effects against the mycelial growth of C. orbiculare, with the EC50 values of 0.018 0, 0.060 2 and 0.471 5 μg/ml, respectively. [Conclusion]The research provided theoretical basis for the control of watermelon anthracnose in watermelon fields.

Establishment of Real-time Fluorescent Quantitative PCR for Pineapple mealybug wilt associated virus-3

[ Objective ] The paper aimed to establish a real-time fluorescent quantitative PCR （qPCR） detection method for Pineapple mealybug wilt associated vi- rus-3 （ PMWaV3 ）. [ Method] Specific TaqMan probe and primers were designed and synthesized according to the conserved sequence of coat protein（CP） gene of PMWaV-3, and the standard curve was established after optimizing the amplification condition of qPCR. [ Result] The results showed that the method was specific for the detection of PMWaV-3, and the sensitivity of the present method was about 10 times higher compared to general RT-PCR ; the variation coefficients of intra- assay and inter-assay were less than 1.73, respectively. [ Conclusion] The qPCR is an easy, fast and reliable method for quantitative detection of PMWaV-3.