Quantitative trait loci identification reveals zinc finger protein CONSTANS-LIKE 4 as the key candidate gene of stigma color in watermelon(Citrullus lanatus)

Stigma color is a critical agronomic trait in watermelon that plays an important role in pollination.However,there are few reports on the regulation of stigma color in watermelon.In this study,a genetic analysis of the F2 population derived from ZXG1553(P1,with orange stigma)and W1-17(P2,with yellow stigma)indicated that stigma color is a quantitative trait and the orange stigma is recessive compared with the yellow stigma.Bulk segregant analysis sequencing(BSA-seq)revealed a 3.75 Mb segment on chromosome 6 that is related to stigma color.Also,a major stable effective QTL Clqsc6.1(QTL stigma color)was detected in two years between cleaved amplified polymorphic sequencing(CAPS)markers Chr06_8338913 and Chr06_9344593 spanning a~1.01 Mb interval that harbors 51 annotated genes.Cla97C06G117020(annotated as zinc finger protein CONSTANS-LIKE 4)was identified as the best candidate gene for the stigma color trait through RNA-seq,quantitative real-time PCR(qRT-PCR),and gene structure alignment analysis among the natural watermelon panel.The expression level of Cla97C06G117020 in the orange stigma accession was lower than in the yellow stigma accessions with a significant difference.A nonsynonymous SNP site of the Cla97C06G117020 coding region that causes amino acid variation was related to the stigma color variation among nine watermelon accessions according to their re-sequencing data.Stigma color formation is often related to carotenoids,and we also found that the expression trend of ClCHYB(annotated asβ-carotene hydroxylase)in the carotenoid metabolic pathway was consistent with Cla97C06G117020,and it was expressed in low amounts in the orange stigma accession.These data indicated that Cla97C06G117020 and ClCHYB may interact to form the stigma color.This study provides a theoretical basis for gene fine mapping and mechanisms for the regulation of stigma color in watermelon.

HD-Zip Transcription Factor is Responsible for No-Lobed Leaf in Watermelon(Citrullus lanatus L.)

Leaf is a vital organ of plants that plays an essential role in photosynthesis and respiration.As an important agronomic trait in leaf development,leaf shape is classified into lobed,entire(no-lobed),and serrated in most crops.In this study,two-lobed leaf watermelon inbred lines WT2 and WCZ,and a no-lobed leaf watermelon inbred line WT20 were used to create two F_(2)populations.Segregation analysis suggested that lobed leaves were dominant over the no-lobed leaves,and it was controlled by a signal gene.A locus on watermelon chromosome 4 controlling watermelon lobed/no-lobed leaves was identified through BSA-seq strategy combined with linkage analysis.The candidate gene was fine-mapped to a 61.5 kb region between 21,224,481 and 21,285,957 bp on watermelon chromosome 4 using two F_(2)populations.Four functional genes were annotated in the candidate region,while sequences blast showed that there was a single-base deletion(A/-)only in the exon of Cla018360,which resulted in premature termination of translation in the no-lobed leaf lines.Function prediction showed that Cla018360 encodes an HD-Zip protein that has been reported to regulate the development of leaf shape.The single-base deletion also occurred in the HD-Zip domain.We inferred that the Cla018360 gene is the candidate gene for regulating the development of lobed/no-lobed leaves in watermelon.Gene expression analysis showed that Cla018360 was highly expressed in young leaves.Phylogenetic analysis showed that Cla018360 had a close genetic relationship with AtHB51,which had been reported to regulate the formation of leaf shape in Arabidopsis.Furthermore,transcriptome analysis showed that a total of 333 differentially expressed genes were identified between WT2 and WT20,of which 115 and 218 genes were upregulated and downregulated in no-lobed leaved watermelon WT20.This study not only provides a good entry point for studying leaf development but also provides foundational insights into breeding for special plant architecture in watermelon.

Effects of Flooding Stress on Growth and Root Physiology and Biochemistry of Grafted Red-seed Watermelon Seedlings

[Objectives]This study was conducted to explore how to improve the waterlogging tolerance of red-seed watermelon through grafting,to provide a theoretical basis for its cultivation in rainy season.[Methods]The effects of flooding stress on the growth and root physiological and biochemical characteristics of grafted and own-rooted red-seed watermelon seedlings were studied using Luffa as rootstocks and"Zhongxin 1"red-seed watermelon as scions.[Results]After flooding stress,the biomass and root activity of grafted seedlings of red-seed watermelon were significantly higher than those of own-rooted seedlings.With the prolongation of flooding stress time,the soluble sugar and proline content showed a trend of first increasing and then decreasing,and the grafted seedlings had a larger increase and a smaller decrease,and were always significantly higher than own-rooted seedlings in the same period.The content of malondialdehyde in the root system of grafted seedlings increased first and then decreased,while it continued to increase in own-rooted seedlings,and the increase in own-rooted seedlings was significantly greater than that in grafted seedlings during the same period.[Conclusions]Grafting on Luffa rootstocks could improve waterlogging tolerance of red-seed watermelon.

Genome-wide analysis of nuclear factor Y genes and functional investigation of watermelon ClNF-YB9 during seed development

The nuclear factor Y(NF-Y) gene family is a class of transcription factors that are widely distributed in eukaryotes and are involved in various biological processes. However, the NF-Y gene family members in watermelon, a valued and nutritious fruit, remain largely unknown and their functions have not been characterized. In the present study, 22 ClNF-Y genes in watermelon, 29 CsNF-Y genes in cucumber, and 24CmNF-Y genes in melon were identified based on the whole-genome investigation and their protein properties, gene location, gene structure, motif composition, conserved domain, and evolutionary relationship were investigated. ClNF-YB9 from watermelon and its homologs in cucumber and melon were expressed specifically in seeds. Its expression remained low in the early stages of watermelon seed development,increased at 20 days after pollination(DAP), and peaked at 45–50 DAP. Moreover, the knockout mutant Clnf-yb9 exhibited abnormal leafy cotyledon phenotype, implying its critical role during seed formation.Finally, protein interaction assays showed that ClNF-YB9 interacts with all ClNF-YCs and the ClNF-YB9-YC4 heterodimer was able to recruit a ClNF-YA7 subunit to assemble a complete NF-Y complex, which may function in seed development. This study revealed the structure and evolutionary relationships of the NF-Y gene family in Cucurbitaceae and the novel function of ClNF-YB9 in regulating seed development in watermelon.

Summary of Short-vine Watermelon Breeding Practice

This paper expounded the current situation and genetic mechanisms of short-vine watermelon breeding from the aspects of material sources,breeding process and genetic characteristics of F_1,hoping to provide a theoretical basis for short-vine watermelon breeding,and breeding materials for watermelon planting innovation,as well as new opportunities for high-quality and high-yield watermelon.

Heritability of Main Yield Traits in Red-seed Watermelon and Their Correlation Analysis

[Objectives]This study was conducted to provide a reliable theoretical basis for the correct formulation of breeding programs for red-seed watermelon and the effective breeding of hybrid offspring.[Methods]With local varieties and inbred lines of red-seed watermelon as test materials,the generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were estimated by variance analysis;and the heritability,genetic variation coefficients,and correlation of the nine yield traits in 43 red-seed watermelon varieties were studied.[Results]The generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were 12.86%,80.14%,75.96%,74.39%,48.01%,17.12%,24.97%,18.60%,and 37.07%,respectively.The heritability of single-fruit weight,single-fruit seed number and single-fruit seed weight was higher,and early-generation individual selection could achieve a better effect on them;and 1000-seed weight and kernel-producing ratio had a higher coefficient of genetic variation,indicating a high selection potential.[Conclusions]Indirect selection could be achieved for traits such as the single-fruit seed number,single-fruit seed weight,seed kernel weight,and seed volume by selecting the single-fruit weight.In the process of red-seed watermelon breeding,traits with high heritability can be selected in early generations of hybrids,thus playing the role of early-generation orientation.

Effects of Different Concentrations of Paclobutrazol on Seedling Quality of Small Seedless Watermelon in Autumn

[Objectives]The paper was to explore the effects of different concentrations of paclobutrazol on seedling quality of small seedless watermelon in autumn.[Methods]The leaves of watermelon seedlings were sprayed with 30,50,80 and 120 mg/L paclobutrazol at cotyledon expansion stage,and those sprayed with tap water were used as control.[Results]All the treatments of paclobutrazol effectively inhibited the excessive growth of watermelon at seedling stage,significantly enhanced the leaf quality of watermelon seedlings and promoted root growth.The seedlings treated by 50 mg/L paclobutrazol had the best performance compared with the control:a decrease of hypocotyl by 37.9%,an increase of plant dry weight by 46.55%,significantly increased seedling strength index,deep green leaf color,thick leaves,an increase of specific leaf weight by 28.13%,and significantly heavier root weight and longer length.[Conclusions]The results will provide a reference for strong seedling cultivation of small seedless watermelon.

Comparative Test on Spring Medium-sized Watermelon Varieties in Beijing

[Objectives]This study was conducted to select suitable medium-sized watermelon varieties for early spring cultivation in Beijing.[Methods]Seven watermelon varieties were collected,including Beinong Tianjiao 2,Beinong Tianjiao,Hongfuji,Yongfeng 1,Beinong Futian,Beinong Shijia,and Beinong Jinxiu,and Jingxin 2 was used as the control check(CK).The growth period,morphological traits,yield traits and fruit quality of the tested varieties were investigated.[Results]Beinong Tianjiao 2 had an earlier maturation stage,a fruit development period of 38 d and a total growth period of 118 d.It showed stable growth,with a single fruit weight of 7.56 kg,a fruit setting rate of 0.99 per plant,and a yield of 83076.9 kg/hm~2,which ranked,respectively,second,first,and second among all tested varieties,and were significantly superior to the CK.Furthermore,this variety had thin and tough peel,a bright red flesh color,high central sugar content,loose and crisp flesh,and a good taste.[Conclusions]It is preliminarily believed that it is suitable for early spring watermelon production in Beijing area.

Screening Test of Small Seedless Watermelon Varieties in Beijing Area

[Objectives]This study was conducted to select small seedless watermelon varieties with excellent quality and high yield suitable for planting in Beijing.[Methods]Under the conditions of facility cultivation in Beijing,a screening test was conducted on seven small seedless watermelon varieties for growth process,field traits,yield traits,fruit quality,and disease resistance.[Results]Varieties Mitong,Motong and Tianbao Xiaowuzi had a short growth period and relatively stable growth,and bore fruit easily,and their female flowers were closely spaced.Their yields exceeded 60000 kg/hm~2,ranking in the top three among all varieties.The fruit had a thin skin,a bright red flesh color,and a high mass fraction of soluble solids in the center.The flesh was tight or crispy,and tasted good.They also showed good disease resistance.Overall,they showed excellent comprehensive agronomic traits,and are thus suitable for facility cultivation in Beijing and its surrounding areas.[Conclusions]This study provides a theoretical basis for the upgrading of varieties and the increase in production and farmers'income in the suburbs of Beijing.

The Influence of Climate Variability on the Watermelon Production in Zanzibar

Climate change and variability, has embarked societies in Zanzibar to rely on horticulture (i.e. watermelon production) as an adaptive measure due to an unpromising situation of commonly used agricultural yields. Currently, there is either no or scant information that describes the influence of climate changes and variability to watermelon production in Zanzibar. Thus, this study aimed to determine the influence of climate variability on the quantity of watermelon production in Zanzibar. The study used both primary and secondary datasets, which include the anecdotal information collected from interviewers’ responses from four districts of Unguja and Pemba, and climate parameters (rainfall, maximum and minimum temperature (Tmax and Tmin) acquired from Tanzania Meteorological Authority (TMA) at Zanzibar offices. Pearson correlation was used for analyzing the association between watermelon production and climate parameters, while paired t-test was applied to show the significance of the mean differences of watermelon and climate parameters for two periods of 2014-2017 and 2018-2021, respectively. Percentage changes were used to feature the extent to which the two investigated parameters affect each other. The anecdotal responses were sorted, calculated in monthly and seasonal averages, plotted and then analyzed. Results have shown a strong correlation (r = 0.8 at p ≤ 0.02, and r = 0.7) between watermelon production, Tmax and rainfall during OND, especially in Unguja, as well as Tmin during JJA (i.e. r = - 0.8 at p ≤ 0.02) in Pemba. Besides, results have shown the existence of significant differences between the means of watermelon production and climate parameter for the two stated periods, indicating that the climate parameters highly affects the watermelon production by either enhancing or declining the yields by 69% - 162% and 17% - 77%, respectively. Moreover, results have shown that respondents were aware that excess temperature intensity during dry periods can lead to high production costs due number of soil and other environmental factors. Besides the results have shown that OND seasonal rainfall and MAM Tmax had good association with watermelon production in Unguja while JJA Tmin declined the production in Pemba. Thus, the study concludes that seasonal variability of climate parameter has a significant influence on the watermelon production. The study calls for more studies on factors affecting watermelon production (e.g. soil characteristics, pest sides and manure), and recommends for climate based decision making on rain fed agricultural yields and routine monitoring of weather information.

我国西瓜田草害发生及综合防控技术

杂草是西瓜田重要的有害生物之一,近年来西瓜田杂草危害呈加重趋势。初步调查发现我国西瓜田杂草137种,隶属34个科,在样方中出现频率5%以上的杂草87种,隶属26个科。西瓜移栽后20~30 d为杂草防治关键期。西瓜田登记的除草剂有效成分有7个,其中,土壤处理剂精异丙甲草胺、异丙甲草胺、敌草胺、仲丁灵等对禾本科杂草防治效果较好,对大部分阔叶杂草防效差;茎叶处理剂精喹禾灵、高效氟吡甲禾灵、噁草酸等对禾本科杂草有效。西瓜田杂草防控应遵循良好种植规范下的综合治理策略(IPM),利用植物检疫、农作方法、生态调控等除草措施辅助除草剂科学使用,同时注重选育耐除草剂西瓜材料,保证西瓜高产、优质和安全生产。

西瓜新品种农科大14号的选育

农科大14号是以自交系Y2M为母本,以1526为父本配制而成的早熟中果型西瓜一代杂种。全生育期约90 d(天),果实发育期约30 d(天);果实圆形,果皮绿色覆墨绿色齿条纹,果肉大红色,中心可溶性固形物含量12.4%;中抗枯萎病,果皮厚1.1 cm,较耐贮运,平均单瓜质量6.5 kg,每667 m2产量4 200 kg左右,适宜陕西省设施栽培。

西瓜叶斑病病原菌的鉴定及室内药剂筛选

2022年在上海市浦东新区西瓜上发生一种深褐色、不规则至近圆形斑的叶部病害。采用组织分离法对病害样本进行分离,分离物SHCCC01经柯赫氏法则验证具有较强致病性。根据分离物的菌落特征、分生孢子形态、生物学特征以及基于核糖体内部转录间隔区(internal transcribed spacer,ITS)、组蛋白基因(histone,His)、真核翻译延伸因子1α(translation elongation factor 1α,TEF 1-α)和肌动蛋白(actin,Act)基因联合系统发育分析等,将病原菌鉴定为瓜类尾孢Cercospora citrullina。10种杀菌剂对该病原菌的毒力测定试验结果表明:氟啶胺、己唑醇、氟环唑、戊唑醇等4种药剂对病原菌的抑菌活性较高,其EC_(50)分别为0.3752、0.5754、1.4723、1.8902μg/mL。这些结果为西瓜尾孢叶斑病的防控和杀菌剂登记提供了重要依据。

西瓜雄性不育类型的遗传学鉴定与胚胎学观察

为了明确西瓜雄性不育材料的不育类型和花药败育时期,以西瓜雄性不育系GMS4为材料,对花蕾不育性状进行田间观察统计,利用石蜡切片法观察西瓜花药发育过程。结果表明,该材料不育性状由1对隐性基因控制,为细胞核雄性不育类型。可育株雄蕊发育正常,不育株雄蕊较小,花药干瘪无花粉,可育株和不育株雌蕊发育无明显差异,均可正常结瓜。从花药发育的整个过程来看,在花药发育早期,可育株和不育株花药结构形态差别不大,在小孢子母细胞减数分裂期,不育株异常绒毡层细胞过度增殖,体积小,排列不整齐,挤压药室,无二分体和四分体形成,在花药发育后期,无花粉粒形成,最终导致西瓜雄性不育发生。据此认为,花药败育发生时期在小孢子母细胞减数分裂期。

西瓜新品种农科大15号的选育

农科大15号是以自交系M08为母本、自交系1207为父本选育而成的杂交1代西瓜新品种。该品种在陕西关中地区早春塑料大棚种植全生育期100 d,果实发育期36 d;易坐果,果实椭圆形,果形指数1.44;果皮浅绿色上覆深绿色中细齿条,果皮厚度1.2 cm,果皮硬韧、耐贮运;瓜瓤红色,瓤质脆,口感佳,中心可溶性固形物含量(w,后同)11.7%;抗病、抗逆性强;单瓜质量8.7 kg,平均667 m^(2)产量4584.7 kg。适宜在西北生态区陕西省关中和陕北地区春季保护地和露地种植。2021年通过农业农村部非主要农作物品种登记。

BSA联合转录组分析发掘西瓜叶片黄化候选基因

叶片是植物重要的功能器官之一,不仅是植株进行光合作用的主要场所,也可作为重要的形态标记,应用于育种中。叶片颜色作为形态标记,不仅可用于苗期杂种的清除,亦可用于种子纯度的测定。以西瓜全生育期叶片黄化突变体纯合自交系ly104为母本(P_(1))、绿叶自交系w3为父本(P_(2)),通过杂交创制F_(1)代、F_(2)代、BC_(1)代群体。遗传分析结果表明,该突变体的叶片黄化由单隐性基因控制。采用混合分组分析(BSA)进行初定位,通过简化基因组测序(RAD)开发全基因组单核苷酸多态性(SNP)标记构建西瓜高密度遗传图谱,将西瓜叶片黄化基因定位于2号染色体13950306~15517591 bp(大小约为1.57 Mb)。以西瓜97103v2为参考基因组,该区间包含24个注释基因。对P_(1)(P1Y)、P_(2)(P2G)和F 2代群体中黄叶(F2Y)、绿叶(F2G)株系进行转录组水平分析,结果表明,目标区间内基因Cla97C02G035950、Cla97C02G036010、Cla97C02G036020、Cla97C02G036060在黄化叶片与正常绿叶材料中的表达量差异显著,可能是西瓜叶片的黄化候选基因。研究结果可为进一步解析西瓜叶片黄化基因功能和生物学特性奠定重要基础。

“一带一路”背景下老挝西瓜产业现状及发展对策

老挝西瓜产业依托中国生产技术和中国市场而发展,是“一带一路”背景下,中国与东盟农业合作的代表。老挝气候利于早春西瓜栽培,能较好填补中国早春西瓜供应缺口;老挝西瓜生产总成本较中国类似气候地区如海南低1200~2600元·(667 m^(2))^(-1),中老铁路的通车也为老挝西瓜运输降低了成本,缩短运输时间;老挝西瓜生产同时也存在栽培技术落后、西甜瓜产业园区较少等问题,随着中国包括人才、良种良法、资金等资源的涌入,以及“一带一路”通道建设不断向中下寮平原区发展,将建立起完善的西瓜产业链,推动老挝西瓜产业。

44份西瓜种质资源苗期耐盐性综合评价

以44份西瓜种质为试验材料,设置0(CK)和150 mmol·L^(-1)NaCl 2个处理水平,测定不同西瓜种质幼苗的15项指标。以15项指标的耐盐系数作为耐盐性评价依据,运用相关性分析、主成分分析、隶属函数值法、聚类分析等多元分析方法进行综合评价。通过主成分分析将15个单项指标转换为4个相互独立的综合指标,累计贡献率为71.10%;以耐盐系数为基础进行聚类分析,筛选出10个高度耐盐、21个中度耐盐、13个弱耐盐西瓜种质资源。采用隶属函数法进行综合评价,排名前5的种质分别是HY-91、DQ-308、W19-15、HY-73、W19-10,归为聚类分析中的第一类,属于强耐盐性品种。

设施西瓜连作土壤生化性质及微生物群落变化

为探索设施连作西瓜土壤微生态环境变化,通过高通量测序对连作组(连作10年设施西瓜土壤)和对照组(连作10年设施西瓜棚外相同土质的露天西瓜土壤)样品进行测序分析,比较2组土壤细菌和真菌的群落结构差异,测定土壤理化性质及酶活性。结果表明,连作组土壤pH、铵态氮、速效钾、微生物量碳、土壤酶活性极显著低于对照,而硝态氮和有效磷极显著高于对照组。连作组土壤中细菌ACE指数和Chaol指数均极显著高于对照组,土壤中真菌ACE指数、Chaol指数、Simpson指数和Shannon指数均低于对照组。土壤微生物优势物种组成改变,连作组土壤细菌变形菌门、芽单胞菌门、绿弯菌门及硝化螺旋菌门相对丰度较对照组分别增加了9.80%、20.83%、21.76%和27.12%(P<0.05),而酸杆菌门和疣微菌门较对照组分别减少了21.7%和26.27%(P<0.05);连作组土壤真菌子囊菌门相对丰度较对照组增加了10.96%(P<0.05),担子菌门和罗兹菌门的相对丰度分别较对照组减少了13.42%和93.77%(P<0.05)。相关性分析显示,优势菌门除Latescibacteria和己科河菌门丰度与所有土壤环境因子相关性均不显著外,其他优势菌群都与所测土壤环境因子(有机质除外)存在密切相关关系,土壤pH、铵态氮、有效磷、速效钾是影响土壤中微生物群落的主要因素,担子菌门和绿弯菌门能够指示土壤微生物量,微生物群落结构的变化对土壤酶活性有较大的影响。综上,设施西瓜连作10年土壤理化性质、酶活性及微生物群落结构皆显著变化,西瓜连作障碍是多种因素综合作用的结果。

浙江省西瓜中农药残留风险评估

分析流通于浙江市场及全省各地生产的西瓜农药残留情况,明确其中农药残留种类及其水平,并对其农药残留风险进行评估。结果显示,288份西瓜样品共检出29种农药残留,其中检出率较高的3种农药分别为吡唑醚菌酯、啶虫脒、腐霉利;除草甘膦和噻虫嗪各有1例超标外,其他检出农药均符合我国农药最大残留限量标准要求。单项污染指数和急慢性膳食摄入风险值表明,浙江省西瓜膳食摄入风险均为可接受状态,暂无健康风险。此外,要重点关注他国(地区)严格于我国的农药残留限量,立足本国需要,制定符合我国西瓜生产实际和保护我国消费者健康的农药残留限量标准,积极开展国内外标准转化,主动接轨国际提高我国西瓜产业的竞争力。