EFFECT OF SOLARIZATION TO KILL BRADYSIA CELLARUM ON CHINESE CHIVE GROWTH AND SOIL MICROBIAL DIVERSITY.pdf

EFFECT OF SOLARIZATION TO KILL BRADYSIA CELLARUM ON CHINESE CHIVE GROWTH AND SOIL MICROBIAL DIVERSITY Caihua SHI 1 2 Linlin SHI 3 Qingjun WU 1 Shaoli WANG 1 Baoyun XU 1 Youjun ZHANG 1 1 Department of Plant Protection Institute of Vegetables and Flowers Chinese Academy of Agricultural Sciences Beijing 100081 China 2 College of Agriculture Yangtze University Jingzhou 434025 China 3 Key Laboratory of Entomology and Pest Control Engineering College of Plant Protection Southwest University Chongqing 400716 China Front Agr Sci Eng 2022 9 1 52 62 https doi org 10 15302 J FASE 2021402 RESEARCH ARTICLE KEYWORDS Bradysia cellarum Chinese chive control soil microbes soil solarization HIGHLIGHTS C15 Soil solarization achieved 100 control of Bradysia cellarum C15 The initial growth of Chinese chive was lower in solarized than control plots but day 20 after treatment plants in the solarized had recovered and leaf height and yield were equivalent among the treatments C15 Soil microbial community diversity in the treat ment group rst decreased and then recovered gradually and abundance of bene cial micro organisms increased signi cantly Received February 7 2021 Accepted April 28 2021 Correspondence zhangyoujun GRAPHICAL ABSTRACT These authors contribute equally to the work 1 INTRODUCTION Chinese chive Allium tuberosum Rottler ex Sprengel is a perennial herbaceous vegetable with medicinal qualities It is generally grown in Malaysia the Philippines Vietnam and other countries including China 1 2 Unfortunately Chinese chive crops particularly those grown in northern or north west China such as in Hebei Henan Shanxi and Shandong Provinces are severely damaged by the soil insect Bradysia cellarum Frey 3 B cellarum Diptera Sciaridae has a broad host range within seven families and 30 plant species including garlic Welsh onion radish and melon 4 5 Populations of B cellarum are mainly found in humid and mild temperate soils and in particular the surface soil to a depth of 5 cm 6 This pest can reduce the yield of Chinese chive by about 50 in the absence of effective control 7 There are many methods used to control B cellarum such as modifying crop cultivation patterns to stagger the peaks of pest populations 8 deploying sticky black colored traps to catch adults 9 using sweet and sour liquids to lure adults 10 and releasing entomopathogenic nematodes to attack larvae 11 Unfortunately each method has limitations including low ef cacy high cost and environmental risks and this is why B cellarum can still cause serious damage to Chinese chive in China At present application of pesticides to control B cellarum remains the most common method used in Chinese chive production 12 However B cellarum populations can become resistant to pesticides after long term use of the same type of pesticide Moreover with a lack of better alternatives to control B cellarum farmers will increase pesticide application rates or apply a more toxic pesticide that is banned for use on vegetable crops thus contaminating crops and hampering the sustainable development of the Chinese chive industry 13 Resolving this serious problem requires more research to nd effective and safe methods to control B cellarum Soil solarization has been used to control microbial weed and insect pests and Shi et al 14 speci cally demonstrated the effective control of B cellarum by solarization To thoroughly kill B cellarum populations the method must be applied where there is suf cient intensity of sunlight e g between late April and mid September in Beijing China Also Shi et al 14 determined that light blue anti dropping lm LBADF of 0 10 or0 12 mm thickness was more effective than other types of lm However it is not known whether soil solarization affects soil microbial diversity If soil solarization can kill B cellarum and also avoid affecting Chinese chive growth and the soil microbial ecological balance it will be an environmentally friendly control technology Here B cellarum was controlled by soil solarization and the in uence of soil solarization on Chinese chive growth and soil microbial diversity in the chive crop soil investigated This study provides further understanding of the effects of soil solarization on soil microbial ecology and scienti c data to support management strategies of crop pest control 2 MATERIALS AND METHODS 2 1 Experimental site The experiment was conducted on Yang Town farm in Shunyi 40 1 N 116 6 E Beijing China Chinese chive cv Pingjiu No 1 was grown in 0 2 m rows at a density of about 5 million plants The Author s 2021 Published by Higher Education Press This is an open access article under the CC BY license http creativecommons org licenses by 4 0 ABSTRACT Bradysia cellarum Frey Diptera Sciaridae is an important subterranean pest and is especially damaging to Chinese chive An effective and more environmentally safe method than pesticides is needed for its control The ef cacy of B cellarum control growth of Chinese chive and soil microbial diversity were investigated after uae of soil solarization to exterminate this insect pest The results show that on the rst day after soil solarization 100 control of B cellarum was achieved Growth of Chinese chive was lower in solarized plots than in control plots over the rst 10 days after treatment Chive growth in solarized plots increased subsequently to match that in the control plots Moreover the soil microbial community diversity in the treatment group decreased initially before gradually recovering In addition the abundance of bene cial microorganisms in the genus Bacillus and the phyla Proteobacteria Chloro exi and Firmicutes increased signi cantly Soil solarization is therefore practical and worthy of promotion in Chinese chive growing regions Caihua SHI et al The safety assessment of solarization after the control of pests 53 ha 1 The soil type was silt loam with a ratio of 40 40 18 2 sand silt clay and organic matter The estimated densities of B cellarum larvae inhabiting the soil ranged from 400 to 2000 individuals m 2 No insecticides were used in the experimental eld in the previous year 2 2 Treatment application The experiment was conducted from May to July 2018 Three treatments were applied soil solarization and untreated control Soil solarization was applied on a day with full sunlight Plant leaves were cut prior to application of LBADF 0 1 mm thick to cover the soil surface for 10 h from 8 00 to 18 00 Each plot was 6 5 mC220 m The mean numbers of B cellarum larvae from ve arbitrarily selected soil samples 20 cm C2 20 cm C2 10 cm per plot were recorded just before applying the treatments day 0 and on days 1 5 10 15 and 20 after treatment In addition automatic temperature meter probes ZigWSN C A Beijing China were inserted 5 cm into the soil in each plot but were covered with the lm only in test one Soil temperatures were recorded every 15 min during the treatment period There were three replicate plots of each treatment 2 3 Growth measurements Leaf height of 60 arbitrarily selected chive plants were measured and used to calculate mean leaf height per plant per plot Leaf height sampling was conducted on days 5 10 15 and 20 after treatment The mean yield of Chinese chives was determined by taking the average plant yield from ve arbitrarily selected subplots 0 6 m C2 0 2 m within each plot on day 20 after treatment 2 4 Sampling and determination of soil microbial diversity 2 4 1 Soil sampling and preparation Soil cores 5 cm C2 5 cm were collected from each of the nine plots with a 5 cm diameter spiral sampler on the same days that larvae were sampled Six soil cores were initially sampled from each of the plots Instead of homogenizing all six samples for each plot we separately took one arbitrarily selected soil core from the three replicate plots of each treatment and homo genized the samples as a new replicate in order to reduce the variation in the microbial community among replicate plots of the same treatment We systematically repeated this process to give six replicate samples of each treatment These soil samples were sieved to obtain only soil particles 2 mm cleared of any root material and stored at 20 C 2 4 2 DNA extraction ampli cation and sequencing DNA extraction ampli cation and sequencing were conducted by Allwegene Beijing China We took a 1 g subsample from each soil sample to extract total DNA using a Fast DNA Spin Kit for Soil MP Biomedicals Solon USA To measure the concentration of total DNA we used a NanoDrop spectro photometer 2000 Thermo Scienti c Waltham USA Bacterial 16S rRNA genes were PCR ampli ed GeneAmp 9700 Applied Biosystems Foster City USA in a 25 L reaction composed of 12 5 L KAPA HiFi HotStart ReadyMix KAPA Biosystems Wilmington USA 2 5 L DNA template 5 ng L 1 1 Lof each primer F338 5 ACTCCTACGGGAGG CAGCAG 3 and R806 5 GGACTACHVGGG TWTCTAAT 3 15 and 8 L RNase free water The PCR ampli cation procedure consisted of initial denaturation at 95 C for 3 min 27 cycles of 95 C for 30 s 55 C for 30 s and 72 C for 30 s and nal elongation at 72 C for 5 min A PCR reaction without DNA template was conducted as a negative control The ampli cation products were run on 1 0 agarose gels and puri ed The puri ed products were diluted to 20 nmol L 1 mixed in equimolar proportions and paired end sequenced on the Illumina MiSeq platform Illumina San Diego USA 2 5 Data and bioinformatics analysis Pest control ef ciency CE was calculated based on the formula described by Shi et al 14 CE 1 NbcC2Nat NacC2Nbt C19 C2100 C18 where Nbc is the number of larvae before treatment in the control area Nat is the number of larvae after treatment in the treated area Nac is the number of larvae after treatment in the control area and Nbt is the number of larvae before treatment in the treated area SPSS version 17 0 for Windows IBM Armonk NY was used for statistical analysis We used Tukey s test to analyze the data described in Section 2 3 A signi cance level of P 0 05 was used Values are expressed as meanC6SD Primers adapters low quality reads and redundant tags were trimmed or deleted from microbial DNA sequences to obtain unique tags The unique tags were aligned against the 16S rRNA V3 V4 database using the BLASTN algorithm Operational taxonomic units OTUs with a 97 cutoff in similarity were clustered using UPARSE ver 7 1 16 and chimeric sequences were identi ed and removed using UCHIME ver 3 0 617 17 Rarefaction analysis Mothur v 1 30 1 was conducted to investigate microbial diversity using species richness Chao 54 Front Agr Sci Eng 2022 9 1 52 62 evenness ACE and diversity Shannon indices 18 19 Differ entially abundant OTUs were found between solarization and the controls identi ed using linear discriminant analysis effect size LDA LEFSE analysis The LDA LEFSE analysis was coupled with the microbiota community structure to search for statisticallydifferent biomarkers betweenthesolarizationand control groups using the Kruskal Wallis test P 4 0 20 The larger the LDA score the greater the differences in taxonomic abundances of the groups compared 3 RESULTS 3 1 Pest control ef ciency by soil solarization The control ef ciency ofB cellarum bysolarization was 100 on the rst day after treatment DAT The maximum soil temperature was 48 7 C on the test day The time for which the soil temperature was 40 C was 8 5 h on the test day 3 2 Effect of soil solarization on the growth of Chinese chive The growth of Chinese chive was lower in solarized plots than in control plots for the rst 10 DAT but subsequently was faster in the solarized plots Table1 At day 5 after treatment the mean leaf heights in the controls were 9 8 cm signi cantly higher than with solarization 5 3 cm By day 10 after treatment the leaf heights in the controls were 16 6 cm signi cantly higher than with solarization 10 6 cm However by days 15 and 20 after treatment there were no signi cant differences in leaf heights between the two treatments P 0 05 Table1 3 3 Effect of soil solarization on soil microbial diversity 3 3 1 Microbial alpha diversity A total of 4 759 435 reads with a mean length of 440 bp were obtained in the solarization and control treatments through the MiSeq sequencing analysis The alpha diversity with solarization based on Chao ACE and Shannon indices initially decreased and then gradually increased compared with the controls The lowest diversity was observed in the soil one day after solarization Table2 3 3 2 Microbial beta diversity Principal component analysis shows that the rst and second components PC1 and PC2 accounted for 48 2 and 15 7 of Table 1 Effect of soil solarization on height and yield of Chinese chive on days 5 10 15 and 20 after treatment Treatment Height of Chinese chive after treatment cm Yield at day 20 g Day 5 Day 10 Day 15 Day 20 Solarization 5 3C60 8 b 10 6C61 7 b 27 4C62 2 a 35 3C62 8 a 375 8C639 4 a Control 9 8C61 3 a 16 6C61 6 a 29 2C61 4 a 33 2C63 7 a 347 1C636 5 a Note Values are meansC6SD of three replicate plots Mean leaf height was determined by measuring the leaves of 60 arbitrarily selected Chinese chive plants for each plot Mean yield was determined by averaging yield measured from ve arbitrarily selected subplots 0 6 m C2 0 2 m within each plot Means followed by the same letter within a column are not signi cantly different according to Tukey s test P 0 05 Table 2 Analysis of microbial alpha diversity indices Sample Shannon Ace Chao CF C F C F SQ 7 31 7 31 8190 43 8180 50 8204 23 8226 22 S1 7 27 6 90 8113 53 7874 91 8197 81 7985 25 S2 7 33 7 15 8060 24 7841 15 8105 82 7886 50 S3 7 24 7 22 7785 04 7559 13 7808 12 7604 25 S4 7 34 7 33 8184 54 8125 65 8214 36 8158 71 S5 7 27 7 22 8120 60 8088 59 8212 83 8144 34 Note CandFindicatecontrolandsolarizationtreatments andSQ S1toS5indicatesamplingdays SQsamplingonday0 justbeforetreatmentapplication andS1toS5samplingondays1 5 10 15 and 20 after treatment Caihua SHI et al The safety assessment of solarization after the control of pests 55 the total variance in the bacterial communities of the 72 soil samples Fig 1 All bacterial communities overlapped each other except for two distinct bacterial communities obtained from the soil samples one and ve days after solarization Fig 1 3 4 Effect of solarization on soil bacterial species 3 4 1 Differences in bacterial species within groups The distribution of phyla of the OTUs shows that the clean sequence reads were classi ed in Proteobacteria Acidobacteria Actinobacteria Chloro exi Bacteroidetes Firmicutes Gemma timonadetes Nitrospirae Planctomycetes Saccharibacteria Latescibacteria and Cyanobacteria Members unassigned to a phylum others were likely not true bacteria Fig 2 The abundance of Firmicutes 23 8 one day after solarization was signi cantly higher than the abundance of Firmicutes in other soil samples The distribution of classes of the OTUs shows that the clean sequence reads were classi ed in Acidobacteria Actinobacteria Alphaproteobacteria Betaproteobacteria Deltaproteobacteria Gammaproteobacteria Gemmatimonadet