Genetic diversity and mixed infections of begomoviruses infecting tomato, pepper and cucurbit crops in Nicaragua

Begomoviruses were detected in Nicaraguan fields of tomato ( Lycopersicon esculentum ) and adjacently growing plants of pepper ( Capsicum annuum ), chilli pepper ( C . baccatum ), cushaw ( Cucurbita argyrosperma ) and Mexican fireplant ( Euphorbia heterophylla ) using polymerase chain reaction (PCR) and universal begomovirus primers. All tomato and Mexican fireplant plants showing symptoms were infected with begomoviruses, while only 30–46% of the pepper, chilli pepper and cushaw plants showing symptoms tested virus-positive. No begomoviruses were found in potato. The virus species were provisionally identified by sequencing 533 bp of the viral coat protein gene ( AV1 ). Tomato severe leaf curl virus (ToSLCV), Tomato leaf curl Sinaloa virus (ToLCSinV) and Pepper golden mosaic virus (PepGMV) were found to infect both tomato and pepper. A new provisional species designated Tomato leaf curl Las Playitas virus (ToLCLPV) was detected in a tomato plant. Squash yellow mottle virus (SYMoV) and PepGMV were found in cucurbits, the latter for the first time in this host. Euphorbia mosaic virus (EuMV) was detected in Mexican fireplant. Sequencing of a larger number of PCR-amplified clones from selected plants revealed intraspecific viral sequence variability, and also multiple begomovirus infections which could represent up to three species in a single tomato or cushaw plant. Phylogenetic grouping of virus sequences did not correlate with the host of origin.     

晋南地区黄瓜、黑籽南瓜死秧的病原菌鉴定及品种抗性研究

经分离、培养对不同菌种培养性状的观察,确定了侵染黄瓜、黑籽南瓜造成死秧的镰刀菌主要为尖镰孢菌黄瓜专化型、尖镰孢菌西瓜专化型、串珠镰刀菌和腐皮镰孢菌4种。经致病性测定,4种镰刀菌均能侵染黄瓜,引起发病造成死秧,可分为强致病类型和中强致病类型。经抗病性鉴定,黑籽南瓜种子只有南瓜4号为耐病品种;黄瓜种子也只有津优31号为耐病品种。     

低温弱光对西葫芦幼苗渗透调节物质的影响

以西葫芦品种早青一代为试材,研究了不同低温弱光组合及低温弱光持续时间对西葫芦幼苗渗透调节物质的影响。结果表明:可溶性蛋白质含量随低温弱光逆境程度加剧和持续时间延长持续减少;在15℃/5℃以上,弱光处理渗透调节物质游离脯氨酸、可溶性糖含量增加,但增加幅度随着弱光逆境加剧和持续时间延长而减弱;但在15℃/5℃下,弱光逆境导致游离脯氨酸、可溶性糖含量先增加后降低。     

不同种植密度对砍瓜产量的影响

进行了露地砍瓜栽培不同种植密度对砍瓜产量的影响试验。试验结果表明，采用1．5m×2m及1m×2m两种种植密度进行对比，1．5m×2m处理的产量、抗病性、产品外观和经济效益均比1m×2m处理有明显优势，其产量差异达显著水平，每1hm。增产18390kg，增产率达18．4％。综合衡量1．5m×2m种植密度为最佳的种植方式。     

西葫芦双单倍体自交一代离体再生研究

以西葫芦DH12-11409双单倍体植株自交后代种子为试材,研究不同激素组合、外植体类型和苗龄对诱导西葫芦不定芽再生以及不定芽生根的影响。结果表明,取5d龄西葫芦双单倍体黄绿色子叶的子叶节为外植体,在MS+30g/L Suc+8g/L Agar+2.0mg/L 6-BA+0.1mg/L NAA培养基上诱导不定芽效果最好,诱导率高达90.0%,分化系数为8.5;生根培养基则以MS培养基中添加0.05或0.1mg/L NAA为宜;5~6片真叶再生植株经驯化移栽成活率高达90.0%,为再生植株驯化移栽的最佳时期。     

黑籽南瓜种子基质引发适宜条件研究

以黑籽南瓜种子为材料,研究了不同温度、处理时间和基质含水量对黑籽南瓜种子引发效果的影响。结果表明,基质引发处理能明显提高黑籽南瓜种子发芽势、发芽指数和活力指数,明显减少种子平均发芽天数;基质引发温度明显提高幼苗干鲜质量和根体积等,而基质湿度对幼苗生长性状影响不显著。黑籽南瓜种子基质引发处理以5℃、基质湿度65%时激发种子活力的效果最好,在不同基质引发温度和湿度条件下,改变引发持续时间所产生的效果是不一样的。     

Shading of plants facilitates selection for powdery mildew resistance in Squash

Summary Powdery mildew development was assessed on squash (Cucurbita pepo) plants of a susceptible cultivar, a resistant accession, their F₁, and their F₂ in an early summer planting in the field, covered or not covered with a shading net. Three reaction types were observed: susceptible, powdery mildew on stems and on both, the upper and lower leaf surfaces, as in the susceptible parent; resistant, no powdery mildew on leaves or stems, as in the resistant parent; and partially resistant, powdery mildew on upper leaf surfaces only, as in the F₁. Disease presence on the stem was associated with susceptibility. Shading hastened the appearance of powdery mildew and increased the severity of infection on partially resistant and susceptible plants, facilitating identification of resistant individuals in the F₂ population.Contribution No. 1613-E from the Agricultural Research Organization, Bet Dagan, Israel     

印度南瓜与中国南瓜有性杂交亲和性研究

为提供用中国南瓜改良印度南瓜的理论依据，选用印度南瓜的3个栽培品种与中国南瓜的4个栽培品种进行人工杂交，观察其杂交亲和性表现。结果表明：印度南瓜P6，P7等品种与中国南瓜P2，P3，P4，P5等品种间存在杂交不亲和性，印度南瓜P1与中国南瓜P4，P5间存在杂交不亲和性，而与P2，P3间不存在杂交不亲和性。     

观赏南瓜子叶离体培养的初步研究

用‘京乐101’观赏南瓜子叶作外植体进行离体培养,初步建立了其离体组织培养的再生体系。结果表明,以MS为基本培养基诱导不定芽分化时,6-BA的附加是必须的,NAA的附加对诱导不定芽的分化有促进作用,GA3的附加虽未能提高不定芽的诱导率,但却能提高不定芽的诱导分化数,诱导不定芽分化的最佳培养基为MS 6-BA5．0mg/L NAA0．2mg/L CA30．5mg/L。同时在试验中发现,MS 6-BA2.0mg/L NAA0.2mg/L的培养基能从子叶块表面直接诱导出不定芽。不定芽在1／2MS NAA0．05mg/L 20g／L蔗糖的培养基上生根。     

世界南瓜生产现状及其种群多样性特征

本文介绍了世界南瓜生产的现状及其种群多样性特征，并对南瓜多样性功效的开发利用进行了分析。