Identification of alleles at two loci controlling resistance to Phomopsis stem blight in narrow-leafed lupin (Lupinus angustifolius L.)

The genetics of resistance to Phomopsis stem blight caused by Diaporthe toxica Will., Highet, Gams & Sivasith. in narrow-leafed lupin (Lupinus angustifolius L.) was studied in crosses between resistant cv. Merrit, very resistant breeding line 75A:258 and susceptible cv. Unicrop. A non-destructive glasshouse infection test was developed to assess resistance in the F₁, F₂, selected F₂-derived F₃ (F_2:3) families, and in selfed parent plants. The F₁ of Unicrop × 75A:258 (and reciprocal cross) was very resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible), which suggested the presence of a single dominant allele for resistance in 75A:258. In Merrit × Unicrop (and reciprocal), the F₁ was moderately resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible). Thus Merrit appeared to carry an incompletely dominant resistance allele for resistance. The F₁ of Merrit × 75A:258 (and reciprocal) was very resistant and the F₂ segregated in a ratio of 15:1 (resistant: susceptible), which supported the existence of independently segregating resistance alleles for resistance in 75A:258 and Merrit. Alleles at loci for early flowering (Ku) and speckled seeds (for which we propose the symbol Spk) segregated normally and independently of the resistance alleles. Resistant F₂ plants gave rise to uniformly resistant or segregating F_2:3 families, whereas susceptible F₂ plants gave rise only to susceptible F_2:3 families. However, the variation in resistance in the F₂ and some F_2:3 families of crosses involving 75A:258, from moderately to extremely resistant, was greater than that expected by chance or environmental variation. We propose the symbols Phr1 to describe the dominant resistance allele in 75A:258, and Phr2 for the incompletely dominant resistance allele in Merrit. Phr1 appears to be epistatic to Phr2, and expression of Phr1 may be altered by independently segregating modifier allele(s). This revised version was published online in July 2006 with corrections to the Cover Date.     

Accumulating polygenes for partial resistance in barley to barley leaf rust,Puccinia hordei. I. Selection for increased latent periods

Summary The barley cultivar Cebaba Capa was crossed to the cultivar L94, which is assumed to carry no genes for increased latent periods, and Vada, which is assumed to carry five to six minor genes for a longer latent period (LP). In the F2 selection was carried out for short and long LP's in the young flag leaves to Puccinia hordei in both crosses. In the F3, F4 and F5 the selection for short as well as for long LP continued by selecting the extreme plants in the extreme lines, a typical pedigree selection approach.The LP's are given relative to those of L94, set at 100 and of Vada, set at 185. From the cross with L94 homogeneous lines were obtained with relative LP's of 100 and of 220. From the cross with Vada the extreme lines had LP's of 135 and around or even beyond 300.Cebaba Capa is thought to carry four to six minor genes with an average gene effect slightly larger than those of the five to six minor genes in Vada. From the four to six minor genes one or two may be identical to or closely linked with minor genes of Vada, the others appeared to be different. In the lines with LP's of close to 300 or even more the number of minor genes accumulated is thought to be in the order of eight or nine. These gene number estimates are based on independent assortment. If linkage occurs the number of genes involved may be larger.Because of the high correlation between LP in the young flag leaf and the partial resistance in the field the selected lines are assumed to have a partial resistance to barley leaf rust far beyond that of Vada, which represents almost the highest level of partial resistance in European cultivars.     

基于改进PT-hybrid算法的地表潜热通量变化分析

潜热通量(LE)影响陆地生态系统的水量平衡和能量收支.[目的]提高不同植被类型对应的地表潜热通量的反演精度对于探究生态水文过程具有重要的现实意义.[方法]本研究采用动态植被模型——LPJ-GUESS模型,引入表征植被占比的参数fv对PT-hybrid潜热通量算法加以改进,从而提高陆面蒸散发的反演能力.[结果]根据全球4...     

Symptomless Spread of Blight-inducing Strains of Xanthomonas campestris pv. campestris on Cabbage Seedlings in Misted Seedbeds

Xanthomonas campestris pv. campestris induces two types of symptoms, namely, black rot and blight. Black rot symptoms are V-shaped lesions and black veins on the leaf, and blight symptoms are sudden collapse of interveinal tissues following the lack of veinal necrosis at early stages of infection. These two symptoms can occur simultaneously. However, the tendency to induce either symptom type is strain-dependent. Six strains were evaluated for their rate and pattern of spread in misted seedbeds by using strain-specific monoclonal antibodies and miniplate enrichment/ELISA. Data on pathogen incidence was defined as the presence of the pathogen in or on plants rather than visual symptoms. The results indicated that blight-inducing strains spread to more seedlings than black rot-inducing strains. The high incidences of blight-inducing strains in experimental plots were associated with non-randomness of spatial pattern of pathogen spread, indicating that high incidence is primarily due to the spread from adjacent plants by leaf contact and water splash. Most ELISA-positive seedlings were symptomless, indicating that the sensitivity of the system used in this study was adequate for detection of latent or epiphytic spread.     

Internal colonization pathways of potato plants by Erwinia carotovora ssp. atroseptica

Transmission of pectinolytic Erwinia species from infected mother tubers to daughter tubers has been studied mainly through detection tests, carried out at harvest, on limited samples of tubers produced by plants grown from artificially inoculated mother tubers. However, detection has not been performed on samples collected at different stages of crop development, in order to follow the contamination progress in different organs through the plants to the progeny tubers. In this study the bacterial contamination of progeny tubers was investigated by detecting Erwinia carotovora ssp. atroseptica in different symptomless plant organs (stolons, stems, progeny tubers) and in the parts with or without symptoms of diseased stems, collected at various stages of crop development. Infection levels in below- and above-ground organs of plants of two cultivars differing in their resistance to Erwinia, infected by either vacuum infiltration or sand wounding, were monitored throughout the growing season and at harvest using DAS-ELISA and PCR. Detection tests showed that healthy organs from symptomless plants were less frequently contaminated than symptomless organs from diseased plants, and that stolons were precociously and more frequently contaminated than stems and daughter tubers, irrespective of the health of the plant. Stem infections were shown to progress latently in the stem, bacteria usually being recovered 10–15 cm past visible lesions. In many cases, typical aerial stem-rot symptoms could be related to this upward movement of bacteria from the infected mother tuber. Daughter tubers without symptoms were shown to be frequently contaminated, usually at heel ends, suggesting internal contamination from mother tuber to progeny.     

Species composition and abundance of aphids in Australian hop gardens and their impact on spatiotemporal patterns of Carlavirus epidemics

The species composition and abundance of aphids in commercial cv. Agate and cv. Super Pride hop gardens in Tasmania, Australia, were characterized over three seasons (1999–2001). Gunns Plains recorded 14 aphid species and Bushy Park 11 species, with nine of these common to both sites. The majority of aphids were trapped in the first 2 months (October and November) of active hop growth in all three seasons. Cultivar and geographical location had significant effects on the abundance of total aphids (species pooled) trapped and several individual aphid species in the three seasons. In general, significantly more aphids (total and individual species) were trapped in cv. Agate than cv. Super Pride gardens, and higher numbers were trapped at Bushy Park than at Gunns Plains. This coincided with a higher incidence of plants infected by carlaviruses in cv. Agate gardens at both locations. Differences in the spatiotemporal dynamics of Carlavirus epidemics were described by fitting a stochastic model to the data, with parameters for local spread within the garden (contagion) and background infection (disease increase unrelated to infected plants within the gardens). Local spread of Hop latent virus (HpLV) and Hop mosaic virus (HpMV) was indicated within all gardens. For HpMV in cv. Agate at Gunns Plains, however, infections caused by immigrant viruliferous aphids were also apparent. Using join-count statistics, spatial aggregation of both virus diseases was found for all years, except for the initial year (1999) when incidence was low. Clusters of diseased plants extended to greater distances for HpLV than for HpMV. Based on spatial and spatiotemporal analyses, local spread (mechanical transmission and/or aphid movement within the garden) appears to be the dominant factor in the epidemics of HpLV. Aphid immigration from outside the crop over time may play a more significant role for HpMV epidemics, at least for one location.     

Inheritance of resistance in carnation against Fusarium oxysporum f.sp. dianthi races 1 and 2, in relation to resistance components

Four carnation cultivars, Novada (resistant to races 1 and 2 ofFusarium oxysporum f.sp.dianthi), Elsy (susceptible to race 1), Lena (susceptible to race 2) and Sam's Pride (susceptible to both races), were selfed and crossed. When three months old, the seedlings were inoculated via the roots or via the stems, after which wilting was recorded weekly according to a 5-point ordinal scale.Analyses were carried out on the proportions of diseased plants. For race 1 variation between the progenies could be described by means of general combining abilities only; GCA values were not affected by the inoculation method used. Also for race 2 GCAs were most important but the GCA values appeared different for the two inoculation methods. It is concluded that resistance to both races is inherited in an additive way.Indications for independently inherited root-specific resistance components (extravascular resistance) were only found with race 2. With both races, the ability to confine the pathogen at the infection site appeared the most important resistance component. Resistant progenies were also characterized by longer latent periods and lower wilting rates.Both race 1 and race 2 induced the accumulation of the phytoalexins dianthalexin and methoxydianthramide S, but race 2 induced higher amounts than race 1. The accumulation of phytoalexins was positively correlated to the resistance level of the progenies against the respective races. The progenies of the double-resistant cultivar Novada appeared to produce particularly high levels of phytoalexins.     

An epidemic of celery mosaic potyvirus in celeriac (Apium graveolens var. rapaceum) in the Netherlands

An annually recurring virus epidemic has caused severe damage and sometimes total yield loss in crops of celeriac in the south-west of the Netherlands for several years since 1969. Celery leatent virus, cucumber mosaic cucumovirus and tobacco rattle tobravirus were isolated from diseased plants, but a potyvirus was the most prevalent virus present. It did not cause local lesions inChenopodium amaranticolor orC. quinoa and did not infect other non-Umbelliferae. The virus was identified as celery mosaic potyvirus and confirmed to be the causal agent.Field surveys from 1971 to 1977 showed a rapid increase of disease incidence in consecutive years, soon leading to near-abandonment of the crop in the original centre of cultivation and its northward translocation, gradually followed by the disease. Incidence in fields often increased from zero by the end of July, when symptoms first appeared, to 100% early during September. In 1976 final incidence was 75 to 100% in 41% of the fields inspected. Temporary protection with aphid-proof cages showed that first infection occurred about three weeks before symptoms appear and not before the beginning of July, and that the virus may still spread after late September.When testing samples from other umbelliferous crops and wild species near infested crops, several viruses were detected but not celery mosaic virus. The virus may be introduced from yet unknown distant sources, as also suggested by the pattern of spread in crops of celeriac.Celeriac cultivars differe considerably in resistance to the virus, but resistant cultivars generally are of poorer quality for consumption and processing than the original highly sensitive cultivar. In recent years cultivation has recovered considerably with the advent of new cultivars.Samenvatting Sinds 1969 trad gedurende een aantal opeenvolgende jaren in de provincie Zeeland in knolselderij een ernstige virusziekte epidemisch op. Vaak mislukten gewassen geheel. Uit viruszieke planten konden het latente selderijvirus, komkommermozaïekvirus, tabaksratelvirus en een potyvirus worden geïsoleerd. Het laatste kwam echter het meest voor en was in zijn optreden gecorreleerd met de voor de epidemie karakteristieke symptomen. Het kon op grond van waardplanten en symptomen, deeltjesvorm en grootte (ca 780 nm) en serologie worden geïdentificeerd als het selderijmozaïekvirus. In de kas konden in selderij de voor de ziekte kenmerkende symptomen ermee worden gereproduceerd.Reeds in 1970 waren in de omgeving van Kruiningen en Waarde in 12 van de 25 geïnspecteerde velden meer dan 60% van de planten ziek. Een systematische inventarisatie gedurende 1971 tot en met 1977 toonde aan dat de ziekte in die periode snel verder om zich heen greep en de teelt in het oorspornkelijke teeltgebied niet meer lonend maakte. De ziekte volgde echter geleidelijk de noordwaarts uitwijkende teelt. In 1976 was 41% van de 117 geïnspecteerde velden voor meer dan 75% aangetast. In zulke velden kon het percentage zieke planten vanaf eind juli tot begin september toenemen van 0 tot nagenoeg 100.De eerste symptomen treden jaarlijks rond eind juli of begin augustus op. Proeven, waarbij veldjes met planten gedurende bepaalde perioden werden afgedekt met bladluisdichte gaaskooien, toonden aan dat de eerste infectie optreedt ca 3 weken (2–4) voor het verschijnen van de eerste symptomen en op zijn vroegst begin juli, en dat verdere verspreiding nog tot na 20 september plaatsvindt. De besmettingsbronnen zijn nog steeds niet gevonden. De wijze van optreden van de ziekte in het veld doet vermoeden dat het virus niet afkomstig is van dichtbij voorkomende wilde planten.Er blijken grote rasverschillen in resistentie te bestaan. De voor consumptie en conservenverwerking gewilde rassen, waaronder vooral Roem van Zwijndrecht, zijn alle zeer kwetsbaar. Met het geleidelijk naar voren komen van meer resistante, en voor de export vooral gevraagde anthocyanine-vrije rassen, zoals Monarch en Iram, heeft de knolselderijteelt zich in Zeeland grotendeels hersteld.     

Parsley latent virus,a new and prevalent seed-transmitted,but possibly harmless virus of Petroselinum crispum

Parsley latent virus, a hitherto undescribed virus, was isolated from 38 out of 54 samples of seed of parsley (Petroselinum crispum) of 17 out of 24 cultivars and from all five European countries tested, but not from some samples from the USA. It could easily be detected in seedlings and also in seeds germinated on moist filter paper, but not in dry seeds or in seeds soaked in water. Strawberry latent ringspot virus was detected in five samples. The parsley virus is symptomless in parsley and caused latent systemic infection inGomphrena globosa, three cultivars ofSpinacia oleracea and weak and often transient systemic symptoms inChenopodium amaranticolor, C. giganteum, C. glaucum andC. quinoa, but did not infect any other species out of all 32 species of seven plant families tested in total.The virus could easily be transmitted mechanically but not by seven aphid species in the non-persistent manner. Dilution end-point was between 100 and 1000, thermal inactivation between 55 and 60°C and ageing in vitro between 7 and 10 days.Purification yielded a single infectious component. The particles were spherical, ca. 27 nm in diameter, with a sedimentation coefficient of 127.5 S, a buoyant density of 1.449 g/ml, an RNA content of 36% and one type of protein with a relative molecular mass of 22×10³. Purificition without Triton and urea resulted in preparations with aggregates each consisting of 12 particles in icosahedral array.The virus differs from all viruses described so far and did not show clear serological affinity with antisera to any of 34 widely differing viruses tested. It does not seem of direct practical importance and may be easily overlooked.Samenvatting In zaailingen van peterselie (Petroselinum crispum) werd een nog niet eerder beschreven virus aangetroffen. Het virus kon niet worden aangetoond door toetsing van droge of in water geweekte zaden opChenopodium quinoa maar wel in op filtreerpapier gekiemde zaden en vooral in zaailingen. Het werd aangetroffen in 38 van de 54 getoetste herkomsten, in 17 van de 24 getoetste rassen en in zaad vermeerderd in alle zes hierop onderzochte Europese landen maar niet in enkele zaadmonsters uit de USA. In sommige monsters bevatten nagenoeg alle zaden het virus. In vijf herkomsten werd eveneens het nog niet eerder in peterselie gerapporteerde latente aardbeikringvlekkenvirus geconstateerd. Dit virus kan bij toetsing gemakkelijk worden herkend door systemische symptomen inC. amaranticolor en komkommer.In geïnfecteerde peterselieplanten zijn geen afwijkingen waargenomen. Het virus kon niet op non-persistente wijze worden overgebracht met zeven bladluissoorten maar wel gemakkelijk met sap. Van 32 getoetste plantesoorten van zeven families, waaronder vier schermbloemigen, kon het virus slechts worden overgebracht op vierChenopodium-soorten,Gomphrena globosa en alle drie getoetste spinazierassen. AllenC. quinoa (Fig. 1),C. giganteum, C. glaucum en soms ookC. amaranticolor (Fig. 2) reageerden met vaak voorbijgaande systemische symptomen. Een lokalelesietoetsplant werd niet gevonden. Zaadovergang bijC. quinoa kon niet worden aangetoond.Voor de houdbaarheid van het infectievermogen werden de volgende waarden gevonden: verdunningseindpunt 100–1000, thermaal inactiveringspunt 55–60°C en houdbaarheid in vitro 7–10 dagen.Zuivering door homogenisatie in fosfaatcitroenzuurbuffer, behandeling met Triton X-100 en ureum en differentiële en daarna dichtheidsgradiëntultracentrifugering leverde preparaten op met uniforme deeltjes van ca. 27 nm diameter (Fig. 3B), een sedimentatiecoëfficiënt van 127,5 S, een zweefdichtheid van 1,449 g/ml, een RNA-gehalte van 36% en een relatieve moleculaire massa van de eiwitondereenheid van 22×10³. Bij zuivering zonder toepassing van Triton en ureum werd een extra zone verkregen met aggregaten van 12 deeltjes in icosaëdrische rangschikking (Fig. 4). In ruw plantesap waren slechts met grote moeite enkele deeltjes met behulp van de elektronenmicroscoop te vinden.Het virus reageerde niet met antisera tegen 33 bolvormige virussen en luzernemozaïekvirus (Tabel 1). Of de zwakke reactie verkregen met één antiserum tegen het tomate-aspermievirus een verre serologische verwantschap inhoudt, dan wel het gevolg is van een verontreiniging, werd niet vastgesteld.Het virus wordt beschouwd als een geheel nieuw virus waarvoor de naamlatent peterselievirus wordt voorgesteld. Het lijkt door zijn beperkte waardplantenreeks en symptoomloosheid in de vatbaar bevonden soorten, behalve in enkele als toetsplant te gebruikenChenopodium-soorten, nauwelijks van praktische betekenis.     

Incidence of Viruses Infecting Allium Spp. in Greece

A survey identified viruses infecting garlic, leek and onion crops and wild Allium species in Greece. Virus identification was based on ELISA, immunoelectron microscopy, and occasionally on RT-PCR. Samples of cultivated Allium species were collected from five districts, whereas samples of twenty-seven wild Allium species were also collected from all over Greece. Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV) were identified in 98.5% and 83.7% of all samples, respectively, and were found in all regions. Allexiviruses were also detected in all regions and their incidence ranged from 62.5% to 70.5% (depending on region and type of allexivirus). Garlic common latent virus (GCLV) was detected in samples from Arcadia (97.6%) and Evia (18.0%) and in one field in Larissa (23.0%). Shallot latent virus (SLV) was found only in two areas (Evros and Theva) and in fields planted with imported propagative material, from Iran and China. The incidence of virus-like symptoms in leek crops ranged from 10.0% to 90.0% in different regions and fields and all symptomatic plants were found to be infected by LYSV. Onion yellow dwarf virus was only found in seven symptomatic onion samples from southern Greece. Allium ampeloprasum spp. ampeloprasum and Allium flavum, were the only wild Allium species found to be infected with LYSV. Finally Turnip mosaic virus (TuMV) was found in A. sphaerocephalon, A. guttatum, A. subhirsutum, and A. neapolitanum.