Two Resistance Modes to Clover yellow vein virus in Pea Characterized by a Green Fluorescent Protein-Tagged Virus

ABSTRACT This study characterized resistance in pea lines PI 347295 and PI 378159 to Clover yellow vein virus (ClYVV). Genetic cross experiments showed that a single recessive gene controls resistance in both lines. Conventional mechanical inoculation did not result in infection; however, particle bombardment with infectious plasmid or mechanical inoculation with concentrated viral inocula did cause infection. When ClYVV No. 30 isolate was tagged with a green fluorescent protein (GFP) and used to monitor infection, viral cell-to-cell movement differed in the two pea lines. In PI 347595, ClYVV replicated at a single-cell level, but did not move to neighboring cells, indicating that resistance operated at a cell-to-cell step. In PI 378159, the virus moved to cells around the infection site and reached the leaf veins, but viral movement was slower than that in the susceptible line. The viruses observed around the infection sites and in the veins were then recovered and inoculated again by a conventional mechanical inoculation method onto PI 378159 demonstrating that ClYVV probably had mutated and newly emerged mutant viruses can move to neighboring cells and systemically infect the plants. Tagging the virus with GFP was an efficient tool for characterizing resistance modes. Implications of the two resistance modes are discussed.     

Signal Transduction in Resistance to Plant Viruses

Salicylic acid is part of a signal transduction pathway that induces resistance to viruses, bacteria and fungi. In tobacco and Arabidopsis the defensive signal transduction pathway branches downstream of salicylic acid. One branch induces PR-1 proteins and resistance to bacteria and fungi, while the other triggers induction of resistance to RNA and DNA viruses. This virus-specific branch can be activated using antimycin A and cyanide, or inhibited with salicylhydroxamic acid, suggesting a role for alternative oxidase in resistance to viruses. The virus-specific defensive pathway activates multiple resistance mechanisms. In tobacco, salicylic acid induces resistance to systemic movement of cucumber mosaic virus but has no effect on its replication or cell-to-cell movement. However, in the case of tobacco mosaic virus in tobacco, salicylic acid appears to induce interference with the synthesis of viral RNA.     

Use of detached tomato leaves to test for resistance to tomato mosaic virus

Samenvatting Een methode werd ontwikkeld om de resistentie van in de kas geteelde tomateplanten tegen tomatemozaïek virus (ToMV) te bepalen. Bladeren van een vatbare en een resistente cultivar werden afgesneden en geïnoculeerd met ToMV. Na 6, 10 en 17 dagen werden de geïnoculeerde bladeren getoetst op de aanwezigheid van virus met ELISA en door inoculatie van bladeren vanNicotiana glutinosa. Met beide toetsmethoden kon de virustoename in de vatbare cultivar al vroeg na inoculatie duidelijk worden aangetoond. In de bladeren van de resistente cultivar was een zeer kleine hoeveelheid virus pas laat na de inoculatie aantoonbaar. Met deze methode is het mogelijk om de resistentie tegen ToMV te bepalen, tevens zaad te winnen en landbouwkundige eigenschappen te evalueren, zonder de plant te infecteren.     

Use of Green Fluorescent Protein-Transgenic Strains to Study Pathogenic and Nonpathogenic Lifestyles in Colletotrichum acutatum

ABSTRACT Colletotrichum acutatum, which causes anthracnose disease on strawberry, can also persist on several other plant species without causing disease symptoms. The genetic and molecular bases that determine pathogenic and nonpathogenic lifestyles in C. acutatum are unclear. We developed a transformation system for C. acutatum by electroporation of germinating conidia, and transgenic isolates that express the green fluorescent protein (GFP) were produced. Details of the pathogenic and nonpathogenic lifestyles of C. acutatum were determined by using GFP-transgenic isolates. Major differences between colonization-mediating processes of strawberry and of other plants were observed. On the main host, strawberry, the germinating conidia formed branched, thick hyphae, and large numbers of appressoria were produced that were essential for plant penetration. In strawberry, the fungus developed rapidly, filling the mesophyll with dense mycelium that invaded the cells and caused necrosis of the tissue. In nonpathogenic interactions on pepper, eggplant, and tomato, the conidia germinated, producing thin, straight germ tubes. Appressoria were produced but failed to germinate and penetrate leaf tissue, resulting in epiphytic growth without invasion of the plant. Penetration of the plant occurred only several days after inoculation and was restricted to the intercellular spaces of the first cell layers of infected tissue without causing any visible damage. Much of the new fungal biomass continued to develop on the surface of inoculated organs in the nonpathogenic interaction. The differences in fungal development on strawberry compared with the other plant species suggest that signal molecules, which may be present only in strawberry, trigger appressorial germination and penetration of the primary host.     

烟草品种对烟草花叶病毒病和黄瓜花叶病毒病的抗性鉴定

由烟草普通花叶病毒(TMV)和烟草黄瓜花叶病毒(CMV)引致的烟草病毒病是世界烟草主产区普遍发生且危害严重的侵染性病害,每年给烟叶生产造成了重大的经济损失。本文采用温室苗期接种鉴定的方法,对16份烟草种质进行了TMV和CMV的抗病性鉴定。结果表明:不同的烟草品种对TMV和CMV的抗病性存在较大差异。在供试种质中,对TMV表现免疫的有‘牛耳烟’、‘8301’、‘台烟7号’、‘三生-NN’共4份材料;表现抗病的有‘吉烟5号’、‘双抗70’、‘大护脖香’、‘秦烟95’共4份材料;表现中抗的有‘铁把子’、‘中烟15’、‘秦烟98’、‘中烟98’共4份材料;表现中感的有‘NC89’、‘翠碧1号’、‘云烟97’共3份材料;表现感病的只有‘秦烟97’。对CMV表现中抗的材料有1份,是‘铁把子’;表现中感的有‘秦烟95’、‘三生-NN’、‘8301’、‘牛耳烟’、‘翠碧1号’共5份材料;表现感病的有‘秦烟98’、‘云烟97’、‘中烟98’、‘NC89’、‘大护脖香’、‘双抗70’、‘秦烟97’、‘中烟15’、‘台烟7号’、‘吉烟5号’共10份材料。研究发现,‘铁把子’是兼抗这两种病毒病的材料。本研究明确了我国16个烟草品种资源的抗病性水平,为抗耐病品种的利用与品种合理布局提供科学依据,同时为烟草抗病毒病育种的亲本选择提供抗源信息。     

Use of Green Fluorescent Protein and Image Analysis to Quantify Proliferation of Trichoderma harzianum in Nonsterile Soil

ABSTRACT One drawback of traditional methods for fungal biomass measurement is the inability to distinguish biomass of an introduced fungus from that of the indigenous microbial community in nonsterile soil. We quantified biomass of a specific fungal biological control agent in nonsterile soil using epifluorescence microscopy and image analysis of green fluorescent protein (GFP)-expressing Trichoderma harzianum (ThzID1-M3). Numbers of colony forming units on a semiselective medium were compared with biomass estimates from image analysis, after ThzID1-M3 was incubated in soil that either remained moist (-0.05 MPa) for 14 to 21 days or remained moist for approximately 5 days and then was allowed to dry to <-3.0 MPa. Recovery of significant numbers of ThzID1-M3 propagules lagged approximately 3 days behind initiation of hyphal growth. Reductions in both colony counts and biomass were observed over time when soil was allowed to dry. However, in soil that remained moist, colony counts increased over a 14- to 21-day period even though biomass declined after approximately 3 to 5 days. Our results confirm that use of GFP, along with epifluorescence microscopy, is a useful tool to distinguish active hyphal biomass, the form of the fungus that is functional for biological control, from inactive propagules such as conidia or chlamydospores that are enumerated by plate counts.     

Resistance of Capsicum species to tobacco,tomato and pepper strains of tobacco mosaic virus

A number ofCapsicum accessions including nine species were tested for resistance to TMV based on hypersensitivity. The tobacco strain MA and the tomato strain SPS, which were both isolated from tomato, and two pathogenically distinct pepper strains P 11 and P 8, were used. Of the 73Capsicum accessions tested 58 were resistant to MA and SPS, 31 were resistant to P 11 and five were resistant to P 8.Samenvatting Om verschillen in pathogeniteit tussen twee in Nederland voorkomende paprikastammen van het TMV nader vast te stellen, werd een aantalCapsicum-herkomsten, waaronder negen soorten, op resistentie getoetst. Hierbij werden de representatieve paprika-isolaten P 11 en P 8 vergeleken met de uit tomaat afkomstige isolaten MA en SPS als vertegenwoordigers van respectievelijk de tabaks- en tomatestam van het TMV. Bij het beoordelen van de symptomen duidden lokale, necrotische vlekken en afvallen van geïnoculeerde bladeren op resistentie, systemische necrosen of mozaïeksymptomen op vatbaarheid. In deze symptomen kwamen tussen de gebruikte stammen verschillen in virulentie tot uitdrukking. Er werden echter vooral verschillen in agressiviteit waargenomen met betrekking tot zowel afzonderlijke, voor resistentie uitsplitsende,Capsicum-herkomsten als het totale aantal getoetste herkomsten. Van de ruim 73 herkomsten waren er 58 resistent tegen MA en SPS, 31 daarvan tegen P 11, maar slechts vijf daarvan tegen P 8. Deze resistentie tegen P 8 werd gevonden inC. chinense.     

A Quantitative Method to Screen Common Bean Plants for Resistance to Bean common mosaic necrosis virus

ABSTRACT A quantitative method to screen common bean (Phaseolus vulgaris) plants for resistance to Bean common mosaic necrosis virus (BCMNV) is described. Four parameters were assessed in developing the quantitative method: symptoms associated with systemic virus movement, plant vigor, virus titer, and plant dry weight. Based on these parameters, two rating systems (V and VV rating) were established. Plants from 21 recombinant inbred lines (RILs) from a Sierra (susceptible) x Olathe (partially resistant) cross inoculated with the BCMNV-NL-3 K strain were used to evaluate this quantitative approach. In all, 11 RILs exhibited very susceptible reactions and 10 RILs expressed partially resistant reactions, thus fitting a 1:1 susceptible/partially resistant ratio (chi(2) = 0.048, P = 0.827) and suggesting that the response is mediated by a single gene. Using the classical qualitative approach based only on symptom expression, the RILs were difficult to separate into phenotypic groups because of a continuum of responses. By plotting mean percent reduction in either V (based on visual symptoms) or VV (based on visual symptoms and vigor) rating versus enzyme-linked immunosorbent assay (ELISA) absorbance values, RILs could be separated clearly into different phenotypic groups. The utility of this quantitative approach also was evaluated on plants from 12 cultivars or pure lines inoculated with one of three strains of BCMNV. Using the mean VV rating and ELISA absorbance values, significant differences were established not only in cultivar and pure line comparisons but also in virus strain comparisons. This quantitative system should be particularly useful for the evaluation of the independent action of bc genes, the discovery of new genes associated with partial resistance, and assessing virulence of virus strains.     

Genetic and Phenotypic Analysis of Soybean mosaic virus Resistance in PI 88788 Soybean

ABSTRACT Resistance to Soybean mosaic virus (SMV) was identified in PI 88788 soybean, a germ plasm accession from China that is used widely as a source of resistance to soybean cyst nematode. Strains SMV-G1 through -G7 infected the inoculated leaves of PI 88788 but were not detected in upper, noninoculated trifoliolate leaves. Inheritance of resistance was determined by inoculating progenies of crosses of PI 88788 with susceptible cvs. Essex and Lee 68 with SMV strains G1 and G7. Allelomorphic relationships with known genes for resistance to SMV were tested in crosses with the resistant genotypes PI 96983, L29, and V94-5152, possessing Rsv1, Rsv3, and Rsv4 genes, respectively. Data analyses showed that resistance in PI 88788 to SMV-G1 is controlled by a single, partially dominant gene; however, to SMV-G7, the same gene was completely dominant. The PI 88788 gene was independent of the Rsv1 and Rsv3 loci, but allelic to Rsv4 in V94-5152. Expression of the Rsv4 gene in PI 88788 resulted in a reduced number of infection sites and restricted short- and long-distance movement of virus, rather than hypersensitivity. A unique late susceptible phenotype was strongly associated with heterozygosity. This gene has potential value for use in gene pyramiding to achieve resistance to several SMV strains, as well as for rate-reducing resistance.     

Economic impact of Turnip mosaic virus, Cauliflower mosaic virus and Beet mosaic virus in three Kenyan vegetables

Screenhouse experiments conducted in Kenya showed that inoculation of cabbage seedlings with Turnip mosaic virus (TuMV), either alone, or in combination with Cauliflower mosaic virus (CaMV), reduced the number and weight of marketable harvested heads. When viruses were inoculated simultaneously, 25% of cabbage heads were non-marketable, representing 20-fold loss compared with control. By contrast, inoculation with CaMV alone had insignificant effects on cabbage yield. This suggests that TuMV is the more detrimental of these pathogens, and its management should be a priority. Early exposure to TuMV produced cabbages that were 50% lighter than non-infected plants, but later infection was less damaging suggesting that controlling virus infection at the seedling stage is more important. TuMV was far less damaging to kale than it was to cabbage; although high proportions of TuMV-inoculated kale plants showed symptoms (>90%), the marketability and quality of leaves were not significantly reduced, and no clear relationship existed between timing of infection and subsequent crop losses. Early inoculation of Swiss chard with Beet mosaic virus (BtMV) significantly impaired leaf quality (∼50% reduction in marketable leaf production), but the impact of disease was greatest in plants that had been inoculated at maturity, where average leaf losses were two and a half times those recorded in virus-free plants. Disease-management of BtMV in Swiss chard is important, therefore, not only at the seedling stage, but particularly when plants are transplanted from nursery to field.     

The reaction of two lettuce cultivars to mixed infection by beet western yellows virus, lettuce mosaic virus and cucumber mosaic virus

The interaction of beet western yellows virus (BWYV), lettuce mosaic virus (LMV) and cucumber mosaic virus (CMV) has been studied in lettuce cultivars Little Gem and Saladin. LMV infection alone or in combination with BWYV and or CMV caused the most severe symptoms and yield losses in both cultivars. BWYV caused more severe reactions in Little Gem than in Saladin; the reactions caused by CMV were mild in both cultivars. The interaction between BWYV and CMV infection resulted in a significantly greater yield loss in both cultivars than that caused by BWYV or CMV infection alone.     

The 5' Third of Cauliflower mosaic virus Gene VI Conditions Resistance Breakage in Arabidopsis Ecotype Tsu-0

ABSTRACT Arabidopsis thaliana ecotypes vary in their responses to viruses. In this study, we analyzed the variation in response of A. thaliana ecotype Tsu-0 to Cauliflower mosaic virus (CaMV). This ecotype was previously reported to be resistant to two CaMV isolates (CM1841 and CM4-184), but susceptible to W260. In this study, we show that Tsu-0 is resistant to four additional CaMV isolates. CaMV propagated within the rosette leaves of Tsu-0 plants, but did not appear to spread systemically into the inflorescence. However, virus viability in rosette leaves of Tsu-0 plants apparently was not compromised because infectious CaMV could be recovered from these organs. W260 overcomes Tsu-0 resistance by a passive mechanism (i.e., this virus avoids activating plant defenses). The portion of the viral genome responsible for W260 resistance breakage was mapped to the 5' third of gene VI, which we have termed RBR-1. This region is also responsible for controlling the ability of CaMV to infect different types of solanaceous plants. Hence, the pathways by which plants of different families interact with CaMV may be conserved through evolution.     

两种人工接种方法鉴定RNA干涉介导的转基因玉米对矮花叶病的抗性

本研究采用两种人工接种方法,以玉米成株期病情指数为指标,鉴定了63个转基因玉米株系的田间抗病性。结果表明,T4代转化株系‘47’和‘13h2-3’的抗病性达R抗级,超过抗病对照‘H9-21’。有82.5%(52/63)的转基因株系抗病性比未转化对照显著提高,表明用反向重复的RNA干涉表达载体转化玉米,可获得转基因抗病毒材料,且干涉片段适度延长可增加获得抗病材料的几率。另外,本文通过两种病毒接种方法的比较,发现采用玻璃纤维刷苗床穿刺接种比常规石英砂摩擦接种具有更小的误差。     

Transmission by Olpidium brassicae of Mirafiori lettuce virus and Lettuce big-vein virus, and Their Roles in Lettuce Big-Vein Etiology

ABSTRACT Big-vein disease occurs on lettuce worldwide in temperate conditions; the causal agent has been presumed to be Lettuce big-vein virus (LBVV), genus Varicosavirus, vectored by the soilborne fungus Olpidium brassicae. Recently, the role of LBVV in the etiology of big-vein disease has been questioned because a second soilborne virus, Mirafiori lettuce virus (MiLV), genus Ophiovirus, has been found frequently in big-vein-affected lettuce. LBVV and MiLV, detectable and distinguishable by enzyme-linked immunosorbent assay using specific antisera, were tested for their ability to be transmitted from lettuce to lettuce by mechanical inoculation of sap extracts, or by zoospores of O. brassicae, and to cause big-vein disease. Both viruses were mechanically transmissible from lettuce to herbaceous hosts and to lettuce, but very erratically. LBVV was transmitted by O. brassicae but lettuce infected with only this virus never showed symptoms. MiLV was transmitted in the same manner, and lettuce infected with this virus alone consistently developed big-vein symptoms regardless of the presence or absence of LBVV. With repeated mechanical transmission, isolates of both viruses appeared to lose the ability to be vectored, and MiLV appeared to lose the ability to cause big-vein symptoms. The recovery of MiLV (Mendocino isolate, from Cali-fornia) from stored O. brassicae resting spores puts the earliest directly demonstrable existence of MiLV at 1990.     

The identification of bean mosaic,pea yellow mosaic and pea necrosis strains of bean yellow mosaic virus

Twelve virus isolates from pea, broad bean, red clover and yellow lupin have been compared with the B25 strain of bean yellow mosaic virus (BYMV-B25), the E198 strain of pea mosaic virus (PMV-E198) and the pea necrosis virus (E178), which were described earlier (Bos, 1970).On the basis of host ranges, symptoms and bean and pea varietal reactions most isolates could be classified into three groups, representatives of which did not differ appreciably serologically. These groups were considered to be typicalbean yellow mosaic virus isolates (E212, L1, B25),pea yellow mosaic strain isolates of BYMV (E198, E204, Kow28) andpea necrosis strain isolates of BYMV (E197, E199, E221). From these results and from a survey of literature it is concluded that PMV is only a strain of BYMV.The pea necrosis virus (E178), described earlier as a distinct entity, is still considered a different virus. A severe pea necrosis isolate (Kow14) resembled E178 in many respects and was also more distantly related serologically to the BYMV isolates tested. Four other virus isolates from pea and broad bean (E196, Vf15, Vf18 and Vf30) could not yet be identified. Lettuce mosaic virus (LMV) was found to be serologically rather closely related to BYMV.Results of cross-protection tests were erratic, and particle length measurements were no help in differentiating the strains and viruses studied.Samenvatting Twaalf virusisolaten uit erwt, tuinboon, rode klaver en gele lupine werden vergeleken met de eerder beschreven (Bos, 1970) B25-stam van het bonescherpmozaïekvirus (BYMV), de E198-stam van het erwtemozaïekvirus (PMV) en het erwtenecrosevirus (E178) (Tabel 1).Op grond van waardplantreeksen, symptomen en de reacties van bone- en erwterassen (Tabel 2) konden de meeste isolaten worden ingedeeld in drie groepen, waarvan vertegenwoordigers serologisch niet duidelijk verschilden (Tabel 5). Een groen erwteisolaat (E212) en een met zaad overgaand isolaat uit gele lupine (L1) bleken typische bone-isolaten van hetbonescherpmozaïekvirus, dat duidelijke symptomen veroorzaakt in de meeste bonerassen en groen mozaïek in erwt (Fig. 1A) en tuinboon. InChenopodium amaranticolor geven deze isolaten in tegenstelling tot alle andere getoetste isolaten gewoonlijk systemische symptomen, die met het lupineïsolaat zeer hevig zijn (Fig. 4A).Twee erwtegeelmozaïekisolaten (E198 en E204) en een isolaat uit rode klaver (Kow28), die geelmozaïek in erwt en tuinboon doen ontstaan en slechts milde symptomen in een deel der op het bonescherpmozaïekvirus reagerende bonerassen, werden opgevat als behorend tot deerwtegeelmozaïekstam van het bonescherpmozaïekvirus.Drie erwtenecrose-isolaten (E197, E199, E221), die necrose veroorzaken in erwt (Fig. 3) en tuinboon (Fig. 2) terwijl de bonerassen gewoonlijk overgevoelig bleken, werden beschreven alserwteecrosestammen van het bonescherpmozaïekvirus.De drie voor erwtemozaïek onvatbare erwterassen bleken immuun voor alle isolaten van het bonescherpmozaïekvirus behalve E197, dat een latente systemische infectie gaf in Relonce.Het eerder als een aparte eenheid beschreven erwtenecrosevirus (E178) gedroeg zich ook nu duidelijk verschillend van de bonescherpmozaïekvirusisolaten. Het isolaat Kow14, dat in erwt eveneens ernstige necrose veroorzaakte, leek op E178 in de necrose die werd teweeggebracht in erwt en tuinboon, in de lokale vlekken in komkommerzaadlobben en in het ontbreken van systemische necrose inLupinus angustifolius, maar de meeste bonerassen waren onvatbaar voor Kow14. Het was ook serologisch minder nauw verwant aan de onderzochte bonescherpmozaïekvirusisolaten.Vier andere virusisolaten uit erwt en tuinboon konden nog niet worden geïdentificeerd. Eén ervan (Vf18) vertoonde een unieke latente systemische infectie in alle drie mozaïekonvatbare erwterassen (Tabel 2).Resultaten van de premunitieproeven (Tabel 3) waren wisselvallig en nergens werd een volledige bescherming verkregen. Deeltjeslengtemetingen (Tabel 4) bleken niet van nut bij de onderscheiding van de onderhavige stammen en virussen.Uit de verkregen resultaten en uit een overzicht van de literatuur wordt tenslotte geconcludeerddat het erwtemozaïekvirus opgevat moet worden als een stam van het bonescherpmozaïekvirus. Het laatstgenoemde virus is tamelijk nauw verwant aan het slamozaïekvirus, zoals met een antiserum tegen dit virus werd aangetoond.De variabiliteit van het bonescherpmozaïekvirus en zijn relaties met een groep van nauw verwante virussen wordt verder besproken. Biologische eigenschappen van de onderhavige virussen hoeven niet samen te vallen met de lichamelijke eigenschappen van hun deeltjes, inclusief de serologische. De virussen en hun stammen kunnen gemakkelijk worden onderscheiden met behulp van een beperkte reeks van differentiërende waardplantsoorten (Tabel 6). Een indeling van de betrokken virussen op grond van pathogeniteit is zowel van betekenis om praktische redenen, als voor het verkrijgen van inzicht in hun ontstaan.Guest worker from May through November 1973 as a fellow of the International Agricultural Centre, Wageningen. Research worker of the Institute of Plant Genetics, Polish Academy of Sciences, Pozna, Poland.     

Properties of viruses of the potyvirus group. 1. A simple method to purify bean yellow mosaic virus,pea mosaic virus,lettuce mosaic virus and potato virus YN

Bean yellow mosaic virus, pea mosaic virus, lettuce mosaic virus, and potato virus Y^N were purified by homogenizing and clarifying infected leaves in a mixture of 0.1 M tris-thioglycollic acid buffer pH 9, carbon tetrachloride and chloroform, followed by differential centrifuging applying moderate centrifugal forces.Samenvatting Het bonescherpmozaïekvirus B25, het erwtemozaïekvirus E198, het slamozaïekvirus en het aardappelvirus Y^N konden worden gezuiverd door geïnfecteerde bladeren te vermalen in een mengsel van 0,1 M tris-thioglycolzuur pH 9, tetrachloorkoolstof en chloroform, en de geklaarde suspensie vervolgens differentiëel te centrifugeren bij matige centrifugaalkrachten.     

Resistance to Turnip mosaic virus in Brassica rapa and B. napus and the analysis of genetic inheritance in selected lines

Forty-two Brassica rapa and Brassica napus lines were tested for resistance to Turnip mosaic virus (TuMV) isolates representing the three major pathotypes in Europe. Of these lines, 11 were susceptible to all pathotypes; nine were resistant to one pathotype; eight were resistant to two pathotypes; and 14 were resistant to all three pathotypes. Of the lines tested, 23 were either able to, or had the potential to, discriminate between two different pathotype-3 isolates. Genetic models for inheritance of resistance were proposed for four B. rapa lines: Jong Bai No. 2 had dominant resistance to pathotype 1 conferred by a single allele; PI418957C and Jin G 55 had recessive resistance to pathotype 4 where a single allele was required; PI418957C also had recessive resistance to pathotype 3 where a model with one of two epistatic, unlinked loci was proposed. Jong Bai No. 1 also had recessive resistance to pathotype 3, apparently conferred by alleles at three loci, where any two of the three loci were epistatic and required for resistance.