Determining the relative roles of different aphid species as vectors of cucumber mosaic and bean yellow mosaic viruses in lupins

Glasshouse and field studies were done to determine the relative roles of different colonising and non-colonising aphid species as vectors of two non-persistently transmitted viruses, cucumber mosaic cucumovirus (CMV) and bean yellow mosaic potyvirus (BYMV) in narrow-leafed lupin (Lupinus angustifolius) crops in Australia. The abilities of nine different aphid species in transmitting CMV from infected to healthy lupins and BYMV from infected subterranean clover to healthy lupins were compared in the glasshouse using 5–10 min acquisition access feeds. The percentage transmission efficiencies found with lupin-colonising aphid species were (CMV/BYMV): Acyrthosiphon kondoi (6/15), Aphis craccivora (10/14) and Myzus persicae (11/77). With non-colonising species the respective efficiencies were: Brachycaudus rumexicolens (0.9/0), Lipaphis erysimi (4/8), Rhopalosiphum maidis (9/6), R. padi (5/5), Sitobion miscanthi (2/11) and Therioaphis trifolii (4/5). When flying aphids were trapped in the field in four successive years (1993–1996) on vertical nets downwind of virus-infected lupins, 13 different species were caught at a “wheatbelt” site and 18 at an urban irrigated site. Of 2833 aphids caught at the “wheatbelt” site, 64 transmitted CMV to lupin test plants. At the irrigated site, numbers of aphids transmitting CMV/numbers caught were 12/186 while the corresponding numbers for BYMV were 11/727. M. persicae, A. kondoi and R. padi transmitted both viruses, while additional vectors of CMV found were A. craccivora, Acyrthosiphon pisum, B. rumexicolens, L erysimi, R. insertum, T. trifolii and Toxoptera citricidus. Averaged over four years, A. kondoi accounted for 50% of CMV transmissions at the “wheatbelt” site, M. persicae for 16% and R. padi for 22%, and these three species were caught in the greatest numbers, comprising 28%, 13% and 37% respectively of the total catch. At the irrigated site R. padi accounted for half the CMV transmissions, while R. padi and A. kondoi together accounted for most of the BYMV transmissions. R. padi, A. kondoi, M. persicae and T. citridus were the most common aphid species at this site. These findings suggest that M. persicae, A. kondoi and R. padi are the aphid species likely to be most important as vectors of CMV and BYMV in narrow-leafed lupins grown in mediterranean-type climatic zones of southern Australia.     

Interaction of Cucumber mosaic virus and Bean yellow mosaic virus in co-infected plants of bean and broad bean

After evaluation of the responses of bean and broad bean common cultivars against an isolate of Cucumber mosaic virus (CMV-K) and Bean yellow mosaic virus (BYMV-K), interaction of isolates was statistically studied on co-infected plants of bean cv. Bountiful and broad bean cv. Lahijan at two trials. Based on viral relative concentration determined by quantitative enzyme-linked immunosorbent assay, BYMV interacts synergistically with CMV in bean at 14 days post inoculation, while in co-infection with BYMV, CMV interacts antagonistically in both host plants at least in one of the two trials. This suggests that CMV/BYMV interaction is dependent on host species and developmental stage of plant. Co-infection like single infection with CMV in bean plants led to significantly decrease in plants’ height and fresh weight than BYMV singly infected and healthy plants, while viral infection of broad bean plants did not significantly affect growth parameters. Decline effect of viral infection (especially co-infection) on chlorophyll and carotenoids value of bean plants was greater than those of broad bean. Viral infection (singly or doubly) caused irregular changes in nutrient elements values of both hosts compared with healthy ones.     

Effects of cereal borders, admixture with cereals and plant density on the spread of bean yellow mosaic potyvirus into narrow-leafed lupins (Lupinus angustifolius)

In studies of virus control measures, field experiments in 1987–1991 investigated the effects of cereal and fallow borders, admixture with cereals and plant density on spread of bean yellow mosaic potyvirus (BYMV) from pastures dominated by subterranean clover (Trifolium subterraneum) into plots of narrow-leafed lupins (Lupinus angustifolius). Virus spread was mainly monocyclic because BYMV killed infected lupin plants and between systemic movement and death there was only a brief period for BYMV acquisition and transmission to other plants by vector aphids. In plots with cereal borders, the rate and extent of BYMV spread into the lupins was decreased; at final assessment the numbers of infected plants were 43–60% less than in plots with fallow borders. Admixture with cereals also decreased the rate and extent of BYMV spread into lupin plots, numbers of infected plants being decreased by 76–96% at the time of final assessment. When lupins were sown at different seeding rates to generate a range of plant densities and weeds were removed, high densities decreased BYMV infection. The higher incidences of BYMV infection in sparse stands were attributed partly to smaller plant numbers and partly to incoming viruliferous vector aphids being more attracted to plants with bare earth around them, than to a plant canopy. BYMV infection decreased grain yield of samples from infected lupin plants by 94–100%. In plots with 34% infection and sparse stands, grain yield was decreased by about one third. Plotted progress curves for the accumulated numbers of alate aphids of the BYMV vector species Acyrthosiphon kondoi and Myzus persicae resembled those for numbers of BYMV infected plants in 1990, but in 1991 only the curve plotted for M. persicae did so. There was a 2 week delay between the curves for aphid numbers and virus counts which reflected the time taken for obvious systemic necrotic symptoms to develop in lupins.     

Effect of mulching with cereal straw and row spacing on spread of bean yellow mosaic potyvirus into narrow-leafed lupins (Lupinus angustifolius)

Two field experiments examined the effect of straw spread on the soil surface on the incidence of bean yellow mosaic potyvirus (BYMV) in plots of narrow-leafed lupin (Lupinus angustifolius) sown at narrow (17.5 cm) vs wide (35 cm) row spacing and low (25–30 kg/ha) vs medium (50–60 kg/ha) seeding rates. Virus ingress was by vector aphids flying from adjacent pastures dominated by subterranean clover. In Expt 1, in which BYMV infection was extensive, straw greatly decreased the rate and amount of virus spread regardless of row spacing or plant density, decreasing infection more than 70% by the final assessment date. This effect of straw was attributed to decreased landing rates of incoming vector alates. In the plots without added straw, narrow row spacing decreased BYMV % infection by 38% by the last assessment date. Sowing at the medium seeding rate also decreased infection. The effect of wide row spacing seemed due to delayed canopy closure between rows which is likely to have increased the landing of aphids while the effect of medium seeding rate was attributed partly to the dilution effect of greater plant numbers and partly to the effects of partial canopy development in decreasing landing rates. In Expt 2, in which the incidence of BYMV infection was low, added straw again decreased BYMV spread, but by only 25–27% at final assessment; there were no effects of row spacing or seeding rate. In both experiments, an additional “reference” treatment was included which had a high (90–100 kg/ha) seeding rate, narrow rows and no straw. The dense canopy it developed also decreased BYMV incidence but less than in the plots with added straw in Expt 1. In Expt 1, adding straw and the resulting decrease in plants killed by BYMV, were associated with an overall increase in lupin grain yield of 20%. The greater plant densities resulting from the medium seeding rate also increased grain yield but row spacing did not affect it significantly. These results indicate that retaining stubble on the soil surface at seeding will assist in management of BYMV infection in lupin crops but that wide row spacing in the absence of retained stubble is undesirable.     

Further studies on cucumber mosaic virus infection of narrow-leafed lupin (Lupinus angustifolius): seed-borne infection, aphid transmission, spread and effects on grain yield

Four field trials were done with narrow-leafed lupins (Lupinus angustifolius) in 1988 - 1989, to examine the effect of sowing seed with 5% and 0.5% cucumber mosaic virus (CMV) infection on subsequent virus spread, grain yield and percentage of infection in harvested seed. A proportion of the CM V-infected seed failed to produce established plants and thus, plots sown with 5% and 0.5% infected seed contained 1.5-2.9% and 0.2-0.3% of seed-infected plants respectively. The rate of virus spread by aphids was faster and resulted in more extensive infection at maturity in plots sown with 5% infected seed than with 0.5% infected seed. In three trials, sowing 5% infected seed resulted in yield losses of 34 - 53% and CMV infection in the seed harvested of 6 - 13%. The spread of CMV infection resulting from sowing 0.5% infected seed did not significantly decrease yield. However, late CMV spread in these plots caused > 1% seed infection. In the fourth trial, which was badly affected by drought, CMV spread only slowly, there was no significant effect of CMV on grain yield and the percentage of infected seed harvested was 3–5 times less than that in the seed sown. When CMV-infected seed was sown at different depths, target depths of 8 and 11 cm decreased the incidence of seed-infected plants by c. 15% and c. 50% respectively compared with sowing at 5 cm. However, in glasshouse tests, treatment with the pre-emergence herbicide simazine failed to selectively cull out seed-infected plants. The field trials were colonised by green peach (Myzus persicae), blue-green (Acyrthosiphon kondoi) and cowpea (Aphis craccivora) aphids. When the abilities of these aphid species and of the turnip aphid (Lipaphis erysimi) in transmitting CMV from lupins to lupins were examined in glasshouse tests, short acquisition access times favoured transmission. With 5–10 min acquisition access times, overall transmission efficiencies were 10.8%, 9.4%, 6.1% and 3.9% for the green peach, cowpea, blue-green and turnip aphids respectively.     

Comparison of flowering time and embryogenesis in Spanish and Portuguese populations of Lupinus albus L. (Leguminosae)

AWOPETU, J. A., 1988. Comparison of flowering time and embryogenesis in Spanish and Portuguese populations of Lupinus albus L. (Leguminosae). Investigations were carried out on flowering-time, leaf or node number on the primary stem and embryo morphogenesis in 16 land races of Lupinus albus collected from the Iberian peninsula, using 'Kali' and 'Kievskij Mutant' as early-flowering reference cultivars. Observations showed that none of the Spanish or Portuguese introductions equalled 'Kali' and 'Kievskij Mutant' with respect to earliness in flowering and low leaf or node number, as well as shorter rate of embryo development and eventual pod maturation. However, genetic variability was established within the land races to indicate intermediate and late-flowering types that could respond to selection for eventual adaptation to central and northern Europe.     

Anther and microspore culture ofLupinus albus in liquid culture medium

Embryo-like structures (ELS) with clearly defined cotyledons and radicles have been regenerated fromLupinus albus L. microspores. ELS induction from microspores in liquid medium was successful, with a maximum of over 3,500 ELS per anther being produced from microspores predominantly at the early binucleate stage of development. Cytological analysis revealed that first pollen grain mitosis occurred in closed buds with maximum ELS production being obtained from buds at the point of first petal emergence. Generally there was a lack of synchronisation of microspores within anthers from the less mature bud germination from ELS has not been observed; recurrent somatic embryogenesis occurred following internal cleavage within the ELS or on the surface of the ELS. Methods of increasing the level of mature ELS capable of germination are under investigation.Abbreviations BA 6-benzyladenine - 24-d 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - 2iP N-isopentyl-adenine - GA₃ gibberellic acid - S&H Schenk & Hildebrandt medium (1972) - M&S Murashige & Skoog medium (1962) - N&N Nitsch & Nitsch medium (1969) - B5 Gamborg's B5 medium (1968) - NNB5 N&N salts plus B5 vitamins - ELS Embryo Like Structures - DAPI 4, 6-Diamidino-2-Phenylindole     

Detection of bean yellow mosaic virus in gladioli corms by the polymerase chain reaction

The polymerase chain reaction (PCR) method readily detected bean yellow mosaic virus (BYMV) in gladioli leaves, but in initial tests PCR did not detect virus in corm tissue. Extracts of RN A from corm tissue were shown to inhibit the amplification of viral sequences when added to a PCR reaction. An additional purification step for the RNA extracts using a Sephadex G-50 column eliminated the inhibitory effect and enabled PCR to amplify and detect viral RNA in corm tissue preparations.     

Nitrate and ammonium as nitrogen sources for lupins prior to nodulation

Two cultivars of Lupinus angustifolius L. were grown in a glasshouse in solutions containing NO₃ ^-, NH₄ ⁺ or NH₄NO₃ with a total nitrogen concentration of 2.8 M m^-3 in each treatment. One cultivar chosen (75A-258) was relatively tolerant to alkaline soils whereas the other (Yandee) was intolerant to alkalinity. Controlled experiments were used to assess the impact of cationic vs. anionic forms of nitrogen on the relative performance of these cultivars. Relative growth rates (dry weight basis) were not significantly different between the two cultivars when grown in the presence of NO₃ ^-, NH₄ ⁺ or NH₄NO₃. However, when NO₃ ^- was supplied, there was a modest decline in relative growth rates in both cultivars over time. When plants grown on the three sources of nitrogen for 9 days were subsequently supplied with ¹⁵NH₄NO₃ or NH₄ ¹⁵NO₃ for 30 h, NH₄ ⁺ uptake was generally twice as fast as NO₃ ^- uptake, even for plants grown in the presence of NO₃ ^-. Low rates of NO₃ ^- uptake accounted for the decrease in growth rates over time when plants were grown in the presence of NO₃ ^-. It is concluded that the more rapid growth of 75A-258 than Yandee in alkaline conditions was not due to preferential uptake of NH₄ ⁺ and acidification of the external medium. In support of this view, acidification of the root medium was not significantly different between cultivars when NH₄ ⁺ was the sole nitrogen source.     

Alfalfa mosaic and cucumber mosaic virus infection in chickpea and lentil: incidence and seed transmission

Samples collected in 1994 and 1995 from commercial crops of chickpeas and lentils growing in the agricultural region of south-west Western Australia were tested for infection with alfalfa mosaic (AMV) and cucumber mosaic (CMV) viruses, and for members of the family Potyviridae using enzyme-linked immunosorbent assay (ELISA). In 1994 no virus was detected in the 21 chickpea crops tested but in 1995, out of 42 crops, AMV was found in two and CMV in seven. With lentils, AMV and/or CMV was found in three out of 14 crops in 1994 and 4 out of 13 in 1995, both viruses being detected in two crops in each year. Similar tests on samples from chickpea and lentil crops and plots growing at experimental sites, revealed more frequent infection with both viruses. No potyvirus infection was found in chickpeas or lentils in agricultural areas either in commercial crops or at experimental sites. However, bean yellow mosaic virus (BYMV) was detected along with AMV and CMV in irrigated plots of chickpeas and lentils at a site in Perth. When samples of seed from infected crops or plots of chickpeas and lentils were germinated and leaves or roots of seedlings tested for virus infection by ELISA, AMV and CMV were found to be seed-borne in both while BYMV was seed-borne in lentils. The rates of transmission found through seed of chickpea to seedlings were 0.1–1% with AMV and 0.1–2% with CMV. Seed transmission rates with lentil were 0.1–5% for AMV, 0.1–1% for CMV and 0.8% for BYMV. Individual seed samples of lentil and chickpea sometimes contained both AMV and CMV. With both species, infection with AMV and CMV was sometimes found in commercial seed stocks or seed stocks from multiplication crops of advanced selections nearing release as new cultivars. Seed-borne virus infection has important practical implications, as virus sources can be re-introduced every year to chickpea and lentil crops or plots through sowing infected seed stocks leading to spread of infection by aphid vectors, losses in grain yield and further contamination of seed stocks.     

黄瓜花叶病毒基因组不同部分及卫星RNA介导的对植株的保护及其作用机理

根据病原物介导的对自身抗性的理论,大量开展了将CMV基因组的单个或多个片断转入植物体内的研究,从而使该植株能够抵抗或延迟受CMV的侵染,CP,RP,MP基因是CMV基因组的重要组成部分,用来转化植株取得了不同程度的抗性效果,另外有些CMV株中存在着起致弱作用的卫星RNA,直接对植株接种含卫星RNA的CMV弱毒或用卫星RNA的cDNA转化植株都会减轻CMV强毒对该植株的侵害,CMV基因组不同组分进入植物体内后,它们对植株产生保护作用的机理不同,文中分别加以阐述。     

核酸酶保护试验在黄瓜花叶病毒株系鉴定中的初步应用

采用黄瓜花叶病毒（ＣＭＶ）亚组Ⅰ株系Ｆｎｙ－ＣＭＶＲＮＡ＿２的１２０９～１６２６核苷酸片段和亚组Ⅱ株系Ｌｓ－ＣＭＶＲＮＡ＿２的２００２～２４３３核苷酸片段的ｃＤＮＡ克隆,体外转录,同时掺入￣（３２）Ｐ获得负链ＲＮＡ探针,与纯化的番茄和甜椒上的ＣＭＶ中国分离物的ＲＮＡ杂交,结果表明：ＣＭＶ番茄和甜椒中国分离物与Ｆｎｙ－ＣＭＶ的核苷酸有高度同源性,隶属于Ｆｎｙ－ＣＭＶ为代表的亚组Ⅰ株系。并利用Ｋ－ＣＭＶ株系（亚组Ⅰ,源于中国）的ＲＮＡ＿２全长ｃＤＮＡ克隆的两个ＥｃｏＲＩ位点间的核苷酸序列（１６５７～２１２５ｎｔ）作探针,与上述两种ＣＭＶ中国分离物的ＲＮＡ杂交,进一步比较分析了这两个分离物和Ｋ－ＣＭＶ株系的关系。讨论了核酸酶保护法在ＣＭＶ株系鉴定中的作用。     

Is there an optimal root architecture for nitrate capture in leaching environments?

Little is known about root architectural attributes that aid the capture of nitrate from coarse-textured soil profiles of high leaching potential. In this study, a range of root architectures from the herringbone to the dichotomous structure were simulated, and their capacity to take up nitrate leaching through a sandy profile was recorded. All root systems had equal total volume at each point in time, and so were considered cost equivalent. These simulations showed that the root architecture likely to maximize nitrate capture from sandy soils (under the Mediterranean rainfall pattern experienced in Western Australia) is one that quickly produces a high density of roots in the top-soil early in the season, thereby reducing total nitrate leached with opening season rains, but also has vigorous taproot growth, enabling access to deep-stored water and leached nitrate later in the season. This is the first published, spatially explicit attempt to assess the ability of different root architectures equivalent in cost, to capture nitrate from a spatially and temporally heterogeneous soil environment.     

Effects of the herbicides Lindex and Simazine on chloroplast and nodule development,nodule activity,and grain yield inLupinus albus L.

Field and laboratory investigations were carried out to determine the influence of two commercial herbicides Lindex and Simazine on symbiotic N₂ fixation, the photosynthetic apparatus, percentage of proteins, and grain yield of lupins (Lupinus albus L. cv. Multolupa). The herbicides were added (3 kg commercial product in 9001 per ha) two weeks after sowing. The nodulated roots were tested for nitrogenase activity by the acetylene reduction assay (ARA) at the first and second flowering. The ARA values decreased with herbicide application. The decrease was smaller in the Simazine treatments with inoculated seeds. The ARA for plants treated with Lindex did not increase with inoculation. Nitrogenase activity was greater in the non-inoculated plants growing together with weeds. The effect of Simazine on the photosynthetic apparatus proved to be more toxic than that of Lindex, not only considerably reducing the size of the chloroplasts but also affecting the grana structure. The latter appeared as an electron-dense compact mass. There were no visible alterations in the photosynthetic apparatus of plants treated with Lindex. However starch, which was not present in the control leaves, accumulated. No ultrastructural changes were observed in the nodule cells treated with Lindex. Simazine altered nodule cells by causing vesicle formation, degeneration of bacteria, and by decreasing the number of N₂-fixing bacteroids. The grain yield decreased with both herbicide treatments, the decrease being lower in the inoculated plants, especially in the Simazine treatment. Our results suggest that each herbicide had a different effect on N₂ fixation, the photosynthetic apparatus and grain yield. Laboratory studies indicated that cyanazine and simazine did not adversely affect the growth of Bradyrhizobium.     

侵染西番莲属(Passiflora)植物的五个黄瓜花叶病毒分离物的特性比较

从紫果西番莲（Ｐａｓｉｆｌｏｒａｅｄｕｌｉｓ）、杂交种西番莲（Ｐ．ｅｄｕｌｉｓＸＰ．ｅｄｕｌｉｓｖａｒ．ｆｌａｖｉｃａｒｐａ）、黄果西番莲（Ｐ．ｅｄｕｌｉｓｖａｒ．ｆｌａｖｉｃａｒｐａ）、转心莲（Ｐ．ｃａｅｒｕｌｅａ）及龙珠果（Ｐ．ｆｏｅｔｉｄａ）分离到的５个黄瓜花叶病毒（ＣＭＶ）分离物（ＰＥ、ＰＥ２、ＰＥｆ、ＰＣ、ＰＦ）所作的生物学性质、理化特性和血清学关系的比较研究结果表明,５个分离物在寄主反应及血清学性质上存在不同,而在病毒粒体形态、体外抗性、蚜虫传毒和病毒外壳蛋白分子量方面无明显差异。根据５个分离物的寄主反应和血清学关系,可将其区分为ＣＭＶ的两个亚组,其中ＰＥ、ＰＥ２、ＰＣ和ＰＦ属ＣＭＶ亚组Ｉ,ＰＥｆ属ＣＭＶ亚组Ｉ。