Limitations on the recruitment of the rare sand shrubby legume Eremosparton songoricum (Fabaceae) in Gurbantunggut Desert, China

Eremosparton songoricum,a rare and endemic sand dune plant,appears to be experiencing recruitment failure.The structure of five populations from the Gurbantunggut Desert,China,was investigated for recruitment patterns,and two of them were examined for flowering,pollination and seed germination limits on regeneration.The results showed that total 150 seedlings only occurred on line transects in riverside Dure population,but they all died half a month later;no seedlings occurred in other four hinterland desert populations indicating recruitment was a failure at all populations although flowers were plentiful.Reproductive success depends on pollinators.Nectar is 'reward' for pollinators,with 0.06 μL-0.12 μL and 0.15 μL-0.35 μL per flower in Dure and Kabu populations,respectively,in continuously two secreting days.Spontaneous self pollination is rare with nearly zero fruit production.Geitonogamous self pollination is predominant with 14.47% fruit set.Seed mass in the riverside Dure population was significantly greater than that in other hinterland desert populations.Consequently,the Dure population exhibited a significantly higher germination rate(about 90%) than those in other populations(about 30%).Results suggested that recruitment failure of E.songoricum is not due to flower shortage,pollination limitation,or poor seed germination but environmental pressure and/or human disturbance.     

Fine-scale genetic structure of Eremosparton songoricum and implication for conservation

Eremosparton songoricum (Litv.) Vass. is a clonal shrub that reproduces both asexually by under-ground rhizomes and sexually by seeds. It is now a rare species with a narrow distribution in fragmented habitat patches in the Gurbantunggut Desert of Xinjiang, China. The objective of this study was to determine the spatial pattern or structure of genetic variation within population. The within-populations genetic structure of E. songoricum in a plot (10 m×10 m) was analyzed using inter simple sequence repeats (ISSR) markers. Correlograms of Moran's I showed significant positive value was about 7 m, but changed into a negative correlation with the increase of distance, indicating strong genetic structure. The natural character of clonal reproduction, restricted seed and pollen dispersal were the main factors of influencing the spatial pattern. The knowledge of clonal structures within populations was crucial for understanding evolutionary processes and ecological adaptation. This study provided basic data for the conservation and management of E. songoricum, especially for sampling strategies for ex situ conservation.     

Dual ecosystem services of syrphid flies (Diptera: Syrphidae): pollinators and biological control agents

With increasing worldwide pressure on bee pollinator populations and an increase in insecticide resistance amongst pest insects, there is a growing need for diversification of pollinator and pest control systems. Syrphid flies (Diptera: Syrphidae) contribute ecosystem services to agroecosystems through their supporting roles as crop pollinators and predators of pests. Adult syrphids are important pollinators with high floral visitation rates and pollen carrying capacity, while predatory syrphid larvae are natural biological control agents, reducing aphid populations in both field and laboratory conditions. The present challenge is to determine whether syrphid flies have the potential for application as pollinators and in integrated pest management schemes as biological control agents. Currently, there are gaps in research that are hindering the use of syrphids as dual service providers. Such gaps include a lack of knowledge of syrphid floral preferences, the role and viability of adult syrphids as pollinators in natural and agro‐ecological pollinator networks, and the predatory efficiency of larvae in field and glasshouse conditions. By reviewing relevant literature, we demonstrate syrphid flies have the potential to be used as pollinators and biological control agents. © 2020 Society of Chemical Industry     

Fruit set and the diurnal pollinators of the invasive Lantana camara and the endemic Lantana peduncularis in the Galapagos Islands

Fruit set is highly relevant to a plant's reproductive success. Fruit set can vary due to predation on flowers, pollinator services and/or resource availability. Reproductive success, measured as the fruit set of the invasive Lantana camara and the endemic Lantana peduncularis in the cool–dry season and the warm–wet season of the Galapagos Islands, was studied. Also, autonomous self‐pollination ability and seed viability were probed for both species. Furthermore, flower visitors and their activity were registered for both species during the warm–wet season. Lantana peduncularis produced fewer flowers per inflorescence, but had a higher fruit set in the cool–dry season, compared to the warm–wet season. In contrast, the fruit set in L. camara did not change seasonally. The fruit set in L. camara was higher than in L. peduncularis in the warm–wet season. Moreover, ～18% of the bagged flowers of the invasive Lantana produced fruits by autonomous self‐pollination, while for the endemic Lantana, the rate of autonomous self‐pollination was very low. More than 80% of the fruits for both species had at least one viable seed per fruit. The number of pollinators and their frequency, inflorescence‐ and flower‐visiting rates and the duration of the visit per flower were higher in the invasive Lantana than in the endemic one. The endemic Lepidoptera Urbanus galapagensis (the main pollinator of both Lantana species) and the introduced Hymenia perspectalis were observed pollinating both Lantana species. These results indicate that the alien L. camara is more attractive to pollinators and it has reproductive advantages regarding fruit set in comparison with L. peduncularis, factors that contribute to the colonization pattern of this invasive species.     

Response of susceptible and resistant cantaloupes (Cucumis Melo) to cucumber mosaic Virus under field conditions

A green-fleshed cucumber mosaic virus (CMV)-resistant cantaloupe line, ‘Xy 140’, resembling the recurrent parent, was obtained after five cycles of backcrossing followed by selfing from a cross between the cultivars ‘Noy Yizre’el’ (susceptible) and ‘Freeman Cucumber’ (resistant). Compared with the respective non-infected cultivars, CMV infection in an early stage of growth reduced the yield of Noy Yizre’el by 73% and of Xvl40 by 31%. Yield reduction in Noy Yizre’el was due to fewer fruits and lower fruit weight, whereas in Xvl40 fruit weight was not affected although the number of fruits per plant was reduced. CMV content of Xvl40 was much lower than that of Noy Yizre’el, but slightly higher than that of the resistant parent — Freeman Cucumber. These results may indicate that during the breeding process a slight loss in the level of resistance had occurred. For all practical purposes, Xvl40 possesses a high level of resistance which will enable good commercial yields even under conditions of very early CMV infection.     

杨桃园桔小实蝇综合防治初报

近年来，随着种植结构的改革，对外交往频繁，广东地区桔小实蝇发生严重，发生量是过去的数倍至数十倍。部分杨桃、番石榴等果树因为害严重而失收。为此我们开展了桔小实蝇发生规律调查、监测和综合防治措施的研究。结果表明：桔小实蝇在广州地区有二个高峰期6月和8月份。通过诱杀去雄，适时喷药，养鸡除虫，套袋、拾烂果等综合防治措施，二年来使三个试验地的虫口密度大幅下降，在2002年7月桔小实蝇为害高峰期，马来西亚大果杨桃为害率为1．7—5．5％，对照区为94％，本地种的小果杨桃为害率为23—35．2％，对照为74．5％，取得了较好的防治效果，初步扭转了杨桃近年来基本失收的局面。     

Genetic diversity of Ziziphus lotus natural populations from Algeria based on fruit morphological markers

The xerophytic shrub Ziziphus lotus (L) Lam may constitute the best choice as a fruit crop in arid regions and seems to have a great importance in uncultured and marginal soils. As the first report, this study investigates the genetic diversity among and within nine natural populations of Z. lotus encompassing wide range of ecological conditions in Algeria through analyses of fruits characteristics. Results reveal significant differences of fruit traits among and within populations; the morphological variability was significantly correlated with the variation of ecological conditions. In general, fruits color ranges from light to dark brown with mostly oval-shaped endocarps containing one or two seeds. In addition, fruits weight ranged between 0.43 and 0.75?g while length was comprised between 10 and 13?mm and fruit thickness varied between 9.85 and 12.81?mm. Overall, quantitative traits were significantly influenced by the environmental conditions, whereas qualitative traits were not clearly affected. Hence, three phenotypes were distinguished allowing detection of a gradual phenotypic variation following latitudinal gradient related mainly to aridity and sand content in the soil. Such variation offers a good basis for breeding objectives, principally for food and medicine objectives along with wide adaptations for various range of climate and soil. Management and conservation of Z. lotus germplasm in Algeria is highly recommended.     

Phenotypic plasticity in response to soil moisture availability in the clonal plant Eremosparton songoricum (Litv.) Vass.

Eremosparton songoricum(Litv.) Vass is a dwarf clonal shrubby legume developed on the windward slopes of mobile or semi-fixed sand dunes of Central Asia. It is assumed that E. songoricum must possess a high degree of phenotypic plasticity for such a heterogeneous habitat. The variations of E. songoricum plants growing in two typical microhabitats(the upper slope and the lower slope of semi-mobile dune) were investigated. The morphological characteristics and the biomass allocation patterns were measured and compared at the clonal fragment level. Compared with the clonal fragment on the lower slope of dune,the clonal fragment on the upper slope of the dune(a) declined in total biomass and ramet height,(b) increased the length of rhizomes and the number of roots,(c) increased the degree of asym-metry,and(d) heightened allocation to the belowground biomass. Our results confirmed the hypothesis of high phenotypic adjustment capacity of E. songoricum to habitat moisture availability. Phenotypic plasticity of E. songoricum contributed to reduce the damage risk,led to an environmentally induced specialization in function of resources exploitation,resulted in its persistence in heterogeneous environments and was adaptive in sand dune environment.     

瓜实蝇、桔小实蝇、南瓜实蝇在广州地区的种群动态

利用Ｓｔｅｉｎｅｒ诱捕器和灯笼式诱捕器，内放有诱捕剂ｃｕｅ－ｌｕｒｅ或ｍｅｔｈｙｌ ｅｕｇｅｎｏｌ和化学农工马拉硫磷混合物的棉芯，在广州地区６个不同生境，从１９８９－１９９２年，连续诱捕结果表明，３种果实蝇的自然种群密度依交为瓜实蝇、南瓜实蝇和村小实蝇，它们每年有两个密度高峰，瓜实蝇和桔小实蝇的第１个高峰出现的１－３月；第２个高峰出现在７－１１月上旬，第２个高峰比第１个高峰的密度大。南瓜实蝇的第１     

桃果套袋对6种典型农药沉积分布和残留的影响

建立了一种基于QuEChERS方法提取净化,超高效液相色谱/气相色谱-串联质谱检测桃叶、桃果和土壤中吡虫啉、嘧菌酯、腈苯唑、苯醚甲环唑、毒死蜱及β-氯氰菊酯6种农药残留量的分析方法。结果表明:在0.05~20 mg/kg (桃叶)、0.05~2 mg/kg (桃果) 和0.05~5 mg/kg (土壤) 添加水平下,6种农药在桃叶、桃果及土壤中的回收率为72%~111%,相对标准偏差 (RSDs) 为0.90%~18% (n = 5),均满足农药残留检测的要求。不套袋施药时,6种农药在桃叶中的原始沉积量最高,其沉积量占比为桃叶、桃果和土壤中总残留量的57%~69%;其次是土壤中,占比为25%~39%,桃果中占比仅为3%~6%;此外,2次施药后14和21 d时桃果上6种农药的最终残留量分别为 (0.07 ± 0.01)~(0.77 ± 0.13) mg/kg和 <0.05~(0.27 ± 0.05) mg/kg,分别为其对应最大残留限量(MRL)值的15%~60%和9%~34%。套袋可以显著降低桃果中6种农药的原始沉积量和最终残留量。套袋后,桃果上6种农药的原始沉积量占比均小于1%,且2次施药后14和21 d时的最终残留量均低于中国国家标准GB 2763—2019《食品安全国家标准 食品中农药最大残留限量》中对应MRL值的10%。本研究明确了果实套袋对6种农药在桃园中的沉积和残留的影响,为指导果实套袋措施在桃园中的安全使用提供了理论依据。     

Selection of pathometric variables to assess resistance and infectivity in the passion fruit woodiness pathosystem

The objective of this work was to compare the efficiency of four pathometric variables, i.e., grading scale, infection intensity index, global leaf disease index, and global incidence and severity index, in evaluations of the passion fruit/Cowpea aphid-borne mosaic virus (CABMV) pathosystem. In ??yellow?? passion fruit plants, mechanically inoculated with CABMV isolates, the degree of association between leaf symptoms and the total fruit yield was determined, as well as the relative infectivity between viral isolates. Only infection intensity index and the global incidence and severity index presented significant regressions with yield (p?=?0.007 and 0.006, respectively). These two pathometric variables could also distinguish groups of viral isolates inducing different severity levels (0.001 and 0.002, respectively). The results indicate that infection intensity index and global incidence and severity index are equally efficient in early identification of passion fruit populations with a higher resistance/susceptibility level to CABMV, and can be helpful in identifying more severe CABMV isolates, both useful aids in breeding programs.     

沙区濒危植物准噶尔无叶豆引种试验

通过对濒危植物－准噶尔无叶豆的生物学特性、生理特征、繁殖技术等试验研究表明：该植物具有抗旱性的生态特 征，气孔调节灵敏，水势不大，吸水力弱，蒸腾作用小；种子坚硬，播前须经浓硫酸处理。早期在４月初芽前平茬，后期平茬在种子成熟后进行。     

油茶园主要害虫茶袋蛾及其天敌间相互关系

2003年6月至2004年5月在对油茶园害虫茶袋蛾及其天敌种群数量系统调查基础上,运用生态位理论和灰色关联度及模糊贴近度方法,系统研究了茶袋蛾与其天敌间相互关系。结果表明:与茶袋蛾空间生态位重叠值>0.8758的天敌有跳蛛、圆蛛和蟹蛛;时间生态位重叠值>0.4748的天敌有蟹蛛、圆蛛和肖蛸。天敌与茶袋蛾灰色关联度较高的种类依次为圆蛛、姬蜂、小蜂、寄蝇和微蛛;与理想天敌关联度较高的天敌种类为微蛛、肖蛸、跳蛛、姬蜂和小蜂;天敌同茶袋蛾和理想优势种关联度总积分较高的依次为微蛛=姬蜂>圆蛛=肖蛸=小蜂。茶袋蛾与其天敌模糊贴近度最大的是圆蛛,其次为肖蛸。这些结果表明圆蛛对茶袋蛾追随效应显著,为优势种天敌,其次为肖蛸。     

Influence of spatial structure on pathogen colonization and extinction: a test using an experimental metapopulation

The Linum marginale–Melampsora lini plant–pathogen interaction has been studied extensively with regard to its epidemiology and population genetic structure (host resistance and pathogen virulence) in a natural metapopulation. In this study, this system was used in an experimental metapopulation approach to investigate explicitly how the distance (degree of isolation) between local population patches influences disease dynamics within a growing season, as well as the genetic structure of pathogen populations through stochastic colonization and extinction processes. The experimental design centred on four replicate sets of populations, within which patches were spaced at increasingly greater distances apart. Each patch consisted of an identical set of host and pathogen genotypes, with each pathogen genotype having the ability to attack only one of four host-resistance types. Over the 2 years of the experiment, the results showed clear 'boom-and-bust' epidemic patterns, with the strongest determinant of disease dynamics within a growing season being the identity of particular host–pathogen genotypic combinations. However, there were also significant effects of spatial structure, in that more isolated patches tended to exhibit lower levels of disease during epidemic peaks than patches that were close together. Extinction of pathogen genotypes from individual populations was positively related to the severity of disease during preceding epidemic peaks, but negatively related to the level of disease present at the final census prior to overwintering. The probability of recolonization of pathotypes into populations during the second growing season was most strongly related to the distance to the nearest neighbouring source population in which a given pathotype was present. Overall, these results highlight the importance of spatial scale in influencing the numerical and genetical dynamics of pathogen populations.     

准噶尔无叶豆的保护生物学研究

特殊生态系统下稀有物种的重要性及保育越来越受到关注.准噶尔无叶豆(Eremosparton songoricum)是分布在流动-半流动沙丘上的稀有物种,对维护沙丘稳定有重要作用.通过对准噶尔无叶豆群落结构、种群生态、生殖生物学特性和遗传结构及多样性等方面进行的研究,介绍了生存现状和有关的研究方法以及取得的重要成果,并从...     

Management of strawberry anthracnose by choice of irrigation system,mulching material and host resistance

We studied, by means of field experiments, the combined effects of irrigation system, mulching material and genetic resistance on the incidence of strawberry anthracnose caused by Colletotrichum acutatum. All trials involved artificial inoculation with fruits colonized by the pathogen. One experiment examined the effects of drip irrigation, overhead sprinkler irrigation, and localized low-pressure tape irrigation, and the effects of grass (Brachiaria sp.) and plastic (polyethylene) mulches, in a split plot, randomized complete block design with four replicates. Lower disease incidence, indicating lower pathogen dispersal, was verified with low-pressure tape and drip irrigation. Flower blight and fruit rot incidence in drip-irrigated plots was minimal (ca. 2% of the disease levels in the plots otherwise irrigated). Grass mulch reduced flower blight in the sprinkler system (up to 80%), but had no significant effect when disease levels were already low due to use of other irrigation systems. A second experiment compared the effects of grass mulch, pine (Pinus elliotti) mulch, and plastic mulch with overhead sprinkler irrigation on strawberry cultivars partially resistant (‘Dover’) and susceptible (‘Campinas’) to the disease in a factorial completely randomized design (CRD). Both organic mulches reduced flower blight and diseased fruit incidence by up to 76% compared to the plastic mulch treatment, especially in the early stages of the epidemics. ‘Dover’ had 70% lower incidence of flower blight than ‘Campinas’, and the effects of organic mulches were more pronounced in ‘Campinas’. A third experiment, with all three irrigation systems combined with inoculated and non-inoculated plots, estimated yield effects due to disease and irrigation system. All plots were covered with plastic mulch in a CRD with six treatments. This experiment clearly confirmed the higher flower blight and fruit rot incidences when sprinkler irrigation was used. In inoculated treatments, fruit yield was significantly reduced in tape-irrigated plots, and more so in sprinkler-irrigated plots. In drip-irrigated plots yield was reduced by only 1%. Overall, our results confirm the importance of cultural and genetic factors as valuable means of strawberry anthracnose management. Adoption of localized irrigation systems, the use of organic mulches and choice of a partially resistant cultivar significantly reduced disease levels in field plots. The importance of water splash for C. acutatum dispersal and its dependency on the soil mulch characteristics are the likely causes for the results observed.     

果蔗脱毒种苗甘蔗花叶病、黄叶病和宿根矮化病分子检测

为监测2016-2017年种植的果蔗脱毒种苗脱毒效果,分别采集广州市南沙区和增城区、湛江市麻章区及华南农业大学甘蔗育种基地共83份果蔗脱毒种苗样本,进行甘蔗花叶病毒(SCMV)、高粱花叶病毒(SrMV)和甘蔗黄叶病毒(SCYLV)RT-PCR检测。结果表明SCMV的阳性样本数为3个,阳性检出率3.61%;SrMV的阳性样本数为0;SCYLV的阳性样本数为78个,阳性检出率93.98%。采用常规PCR和巢式PCR技术对采集于广州市增城区和华南农业大学甘蔗育种基地的30份果蔗脱毒种苗样本进行宿根矮化病菌(Lxx)检测,常规PCR检测阳性样本数为0,巢式PCR检测疑似阳性样本数为8,疑似阳性检出率26.67%。本研究采用茎尖组织培养脱毒技术培育的果蔗脱毒种苗能有效脱除果蔗种苗内的SCMV、SrMV和Lxx,但SCYLV的脱除效果有待进一步研究。     

Co-evolution of potato cyst nematodes and their hosts: implications for pathotypes and resistance1

The co-evolutionary process is believed to have resulted, through interaction of wild populations of potato cyst nematodes and their hosts in geological time, in the resistant hosts now utilized in plant breeding programmes and in nematode populations with genes for resistance-breaking or virulence. It is argued that all such interactions between highly adapted, truly parasitic plant nematodes and their hosts are likely to be governed by gene-for-gene interrelationships. Practical implications of this hypothesis are that only pathotypes (resistance-breaking races) defined against identified resistance genes are scientifically sound and of practical value; that, in the case of potato cyst nematodes, other pathotypes (Ro2, Ro3, Ro5 and Pa2 and Pa3) should be abandoned; and that oligogenically based resistance to potato cyst nematodes, especially important in providing resistance to Globodera pallida, is non-durable. Working definitions of the terms ‘pathotype’, ‘host-race’ and ‘virulence’ are provided.     

Molecular mapping of the blast resistance genes Pi2-1 and Pi51(t) in the durably resistant rice 'Tianjingyeshengdao'

Tianjingyeshengdao' (TY) is a rice cultivar with durable resistance to populations of Magnaporthe oryzae (the causal agent of blast) in China. To understand the genetic basis of its resistance to blast, we developed a population of recombinant inbred lines from a cross between TY and the highly susceptible 'CO39' for gene mapping analysis. In total, 22 quantitative trait loci (QTLs) controlling rice blast resistance were identified on chromosomes 1, 3, 4, 5, 6, 9, 11, and 12 from the evaluation of four disease parameters in both greenhouse and blast nursery conditions. Among these QTLs, 19 were contributed by TY and three by CO39. Two QTL clusters on chromosome 6 and 12 were named Pi2-1 and Pi51(t), respectively. Pi2-1 was detected under both growth chamber and natural blast nursery conditions, and explained 31.24 to 59.73% of the phenotypic variation. Pi51(t) was only detected in the natural blast nursery and explained 3.67 to 10.37% of the phenotypic variation. Our results demonstrate that the durable resistance in TY is controlled by two major and seven minor genes. Identification of the markers linked to both Pi2-1 and Pi51(t) in this study should be useful for marker-aided selection in rice breeding programs as well as for molecular cloning of the identified resistance genes.     

枸杞炭疽病药剂防治药剂筛选

为有效防控厚皮甜瓜细菌性果斑病的发生,提出一套综合防控技术,通过田间开展各单项防控技术的重要性试验,建立标准化综合防控技术体系.结果表明:各单项技术可提高对细菌性果斑病的防效.与对照相比,72％农用硫酸链霉素可溶粉剂浸种可使防效提高16％,病果率降低3％;标准化喷药能使防效提高17％以上,病果率降低3.1％;整枝打杈前后进行防控能使防效提高39％以上;厚皮甜瓜整个生育期不浇水,能够减少病果的数量;在此基础上组装而成的标准化综合防控技术体系防效达89.2％以上,病果率仅为2％.