Bean Golden Mosaic Research Articles

Comparison of Bemisia tabaci Infestation, Virus Infection, and Yield in Conventional and Transgenic Bean Golden Mosaic Virus-Resistant Common Bean Elite Lines

No Brasil, o Cowpea mild mottle virus transmitido pela Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae), é uma ameaça emergente ao feijão comum (Phaseolus vulgaris L.; Fabaceae), incluindo as linhas elites de feijão geneticamente modificadas desenvolvidas para resistência ao Bean golden mosaic virus. Para investigar essa interação, quantificamos a suscetibilidade de dez linhas geneticamente modificadas resistentes ao Bean golden mosaic virus à infecção pelo Cowpea mild mottle virus em duas regiões do Brasil com incidência natural de B. tabaci virulíferas. Em dois ensaios de campo, B. tabaci estabeleceu em todas as variedades, mas mostrou preferência pelas cultivares convencionais ‘Pérola’ e ‘BRS Pontal’ quando comparadas com as linhas elite geneticamente modificadas (média > 400 ninfas por folíolo e > 97% taxa de infecção por virus em um dos estudos). No entanto, embora as linhas elite foram resistentes ao Bean golden mosaic virus, todas foram infectadas pelo Cowpea mild mottle virus. As maiores taxas de infecção (19 a 99% de plantas infectadas) ocorreram nas linhas elite geneticamente modificadas derivadas da BRS Pontal versus Pérola (12 a 16%). Ao comparar a produtividade, a maioria das linhas elite superou seu pai convencional recorrente. Os aumentos relativos de rendimento foi de 199 a 1.045% sendo as variedades CNFCT 16205 e CNFCT 16210 as mais produtivas. Nossos resultados mostraram que o uso de cultivares de feijão resistentes ao mosaico dourado é uma ferramenta importante dentro das estratégias integradas de manejo para moscas-brancas e vírus. No entanto, mais estudos são necessários para elucidar à ameaça do Cowpea mild mottle virus e a natureza das interações da mosca-branca com estes diferentes vírus.

Detection of Bean golden mosaic virus in Fabaceae family plants / Detecção de Bean golde nmosaic vírus em plantas da família Fabaceae

The Bean golden mosaic virus (BGMV) is the causal agent of the golden mosaic of bean, one of the main diseases of common bean ( Phaseolus vulgaris ). This virus is transmitted by the whitefly [ Bemisia tabaci (Gennadius)], an insect of great agricultural importance due to its polyphagous behavior. This study aimed to identify plants of the Fabaceae family, host of BGMV. Sixteen plant species belonging to the Fabaceae family were inoculated with BGMV by whitefly. Fifteen days after inoculation, the plants were evaluated for the manifestation of the mosaic symptom, and leaves were collected for molecular detection of the virus. The experiment was carried out in a greenhouse, with a completely randomized design, five replicates, and one virus-free control for each species. The presence of BGMV was confirmed in Lathyrus sativus , Glycine max , Canavalia ensiformis , Vigna unguiculata and Macroptilium atropurpureum, in addition to beans ( Phaseolus vulgaris ).

IPR CELEIRO: Common bean cultivar moderately resistant to bean golden mosaic virus

Abstract IPR Celeiro is a common bean (Phaseolus vulgaris L.) cultivar with a carioca-type seed and moderate resistance to Bean Golden Mosaic Virus (BGMV). IPR Celeiro has a normal life cycle and an upright architecture. This cultivar was released for the purpose of integrating its use with disease management systems in the cultivation areas affected by this virus.

Estudio de insecticidas para el control de mosca blanca Bemisia tabaci Genn enn el cultivo del frijol Phaseolus vulgaris L.

Several trials were conducted to evaluate the effectiveness of new insecticides in controlling the white fly Bemisia tabaci Genn, which is the vector of the Bean Golden Mosaic Virus (BGMV), at the Zapotitlan Valley and at the San Andres Experimental Station at 460 masl, during the dry season, from December 22, 1989 to May, 1990. A complete randomized block experimental design with 4 and 5 replications was used. Four trials were planted with the Rojo de Seda, Sangre de Toro and CENIA-Cuscatleco bean varieties. In the first and second trials, the chemicals bifentrin 100 EC (60 g.ai./ha) and fenpropatrin 375 EC ( 203 g.ai/ha) were efficient in controlling the whitefly, reducing the incidence of BGMV. If B. tabaci Genn is not controlled efficiently and timely, the BGMV incidence reaches 100% between 36 and 32 days after planting (DAP) on the susceptible varieties Rojo de Seda y Sangre de Toro. Seed and soil treatments combined with foliage spraying were also used in the third and fourth trials. The treatments of carbosulpan + bifentrin (1519.9 kg/ha) and acephate + bifentrin (1428 kg/ha) produced the highest yields with the resistent variety CENIA- Cuscatleco. Acephate + fenpropatrin (756.6 kg/ha), acephate + bifentrin (725.1 kg/ha) and carbofuran + fenpropatrin (636.3 g/ha) produced the highest yields with the susceptible variety Rojo de Seda. Of the tested products, fenpropatrin 375 EC showed the lowest populations of eggs and nymphs of B. tabaci Genn. There was a significant correlation between production and the time when the disease symptoms appeared. The largest Net Benefit was obtained with acephate 95% + bifentrin 100 EC treatment, followed by carbofuran 5% + bifentrin 100 EC.

Golden Mosaic of Common Beans in Brazil: Management with a Transgenic Approach

Common bean and its importance for the brazilian population. Golden mosaic of common beans (Bean golden mosaic virus). The BGMV whitefly vector: Bemisia tabaci. Breeding for BGMV resistant varieties. The development of a BGMV-Resistant common bean transgenic event. Other whitefly-transmitted viruses reported on common beans in Brazil. Whitefly-borne disease and insect management. Future perspectives.

Estudo do Perfil Oxidativo de Feijões Transgênicos por meio da RMN HR-MAS

No Brasil, o feijão é uma das leguminosas alimentares mais importantes, sendo considerada a principal fonte de proteínas das populações de baixa renda. Uma das principais doenças que atingem os feijoeiros é mosaico dourado, transmitido pela mosca branca, pelo vírus BGMV (Bean Golden Mosaic Virus). Deste modo, a EMBRAPA Arroz e Feijão desenvolveu um genótipo resistente ao BGMV, denominado Olathe 5.1. Outras duas linhagens geneticamente modificadas foram produzidas (Tesouro 5.1 e Marfim 5.1). Os espectros de RMN de 1H HR-MAS conduziram às estruturas dos flavonóides quercetina e miricetina, presentes em maior concentração no feijão geneticamente modificado. Deste modo foi realizado um estudo do perfil oxidativo destes cultivares, onde o flavonóide miricetina sofreu uma variação em seu teor devido à exposição destes genótipos às condições físicas não controladas.Palavras chave: Flavonóides; HR-MAS; Quimiometria.

Adelantos en el mejoramiento de frijol andino caribeno.

Bean golden mosaic, rust, web blight, and common bacterial blight frequently limit bean (Phaseolus vulgaris L.) yield in the Caribbean. Results from the PROFRIJOL Caribbean Adaptation Nurseries demonstrate that CIAT and the bean breeding programs in the Caribbean have developed red mottled and light red kidney bean varieties with resistance to one or more of these diseases. The availability of molecular markers should permit the combination of specific genes conferring resistance. However, the effective use of these genes for disease resistance will require learning about the virulence patterns of pathogens. Sources of tolerance to some abiotic factors such as high temperatures have been identified. Nevertheless, bean breeding programs in the Caribbean have not yet developed bean varieties that combine disease resistance and tolerance to abiotic stress. The Dominican Republic, Haiti and Cuba have made collections of native Andean Caribbean bean varieties, which should prove to be the source of many valuable traits.

RNAi‐based Bean golden mosaic virus‐resistant common bean (Embrapa 5.1) shows simple inheritance for both transgene and disease resistance

AbstractBean golden mosaic virus (BGMV) is the causal agent of bean golden mosaic of common beans. A transgenic bean line that has been developed based on RNA interference to silence the BGMV rep gene showed immunity to the virus. Crosses were done between the transgenic line and six bean cultivars followed by four backcrosses to the commercial cultivars ‘Pérola’ and ‘BRS Pontal’. The transgene locus was consistently inherited from the crosses analysed in a Mendelian fashion in the segregating populations. The disease resistance reaction co‐inherited with the transgene. Nevertheless, the expression of disease resistance displayed a dosage effect phenomenon in the F1 generation. The analysis of the homozygous near‐isogenic lines in field conditions, under high BGMV disease incidence, indicated that the transgenic lines were completely resistant. These results show the strength of the disease resistance obtained, the stability of the trait across generations and its usefulness in the management of a disease for which there is no reported Phaseolus germplasm with immunity.

Molecular characterization of the first commercial transgenic common bean immune to the Bean golden mosaic virus

Golden mosaic of common bean is caused by the Bean golden mosaic virus (BGMV). The disease is one of the greatest constraints on bean production in Latin America and causes significant yield losses. The RNAi concept was explored to silence the rep (AC1) viral gene and a transgenic bean line immune to BGMV upon inoculation at high pressure was previously generated. Identification of the transgene insert confirmed the presence of a single locus corresponding to two intact copies of the RNAi cassette in opposite orientation and three intact copies of the AtAhas gene. It is flanked by Phaseolus genomic sequences and interspersed by one nuclear and three chloroplastic genomic sequences. Southern analyses showed that the transgenes were structurally stable for eight self-pollinated generations and after backcrosses with a non transgenic commercial variety. Transgene expression analyses revealed similar levels of siRNA in leaves of transgenic plants cultivated under field conditions in three distinct regions. siRNA were also analyzed during seed development in common bean transgenic plants. siRNA signals were also detected in seeds, albeit at significantly lower levels than those observed in leaves, and could not be detected in seeds cooked during 10min. This information is relevant to demonstrate that GM beans are free of siRNA signals after cooking and therefore suitable for human consumption. Additionally, characterization of the locus where the transgene was integrated in the common bean genome provides a valuable tool to trace this GM bean material in the field and in the market.

Begomoviruses Associated with Bean Golden Mosaic Disease in Nicaragua.

Begomovirus spp. cause substantial losses in bean crops in tropical and subtropical regions of the Americas. The predominant Begomovirus sp. in Central America associated with golden mosaic symptoms in bean is Bean golden yellow mosaic virus (BGYMV). However, Calopogonium golden mosaic virus was previously found to infect bean crops in the northern region of Costa Rica. The objective of this research was to identify Begomovirus spp. that infect bean plants in different geographical regions of Nicaragua. In all, 126 samples of young bean leaves with symptoms of golden mosaic were collected from eight different regions of Nicaragua. Using DNA hybridization with specific probes, 120 samples tested positive for BGYMV, 14 samples tested positive for Squash yellow mild mottle virus, and 7 samples tested positive for Calopogonium golden mosaic virus. Sequence analysis of polymerase chain reaction-amplified products from three samples (MA-9 Managua, BE-8 Rivas, and SO-9 Granada) also indicated that the symptoms of golden mosaic in bean are associated with viral sequences from three different Begomovirus spp. Management of bean golden mosaic disease must take into account that BGYMV is the predominant virus (95% of the samples) and that 12% of the samples exhibited possible mixed infections or recombination events in the south and central geographical regions of Nicaragua.

Comunidade bacteriana como indicadora do efeito de feijoeiro geneticamente modificado sobre organismos não alvo

O objetivo deste trabalho foi avaliar o efeito do feijoeiro geneticamente modificado quanto à resistência ao Bean Golden Mosaic Vírus, BGMV (Olathe M1-4), sobre organismos não alvo. De um experimento implantado no campo, em delineamento inteiramente casualizado, com dois tratamentos (Olathe Pinto e evento elite Olathe M1-4), dois períodos amostrais (estádio V4 e R6) e dez repetições, obtiveram-se células bacterianas cultivadas e não cultivadas da rizosfera e do solo não rizosférico, para as quais se procedeu à extração de DNA total. A região V6-V8 do 16S rDNA foi amplificada para a comunidade bacteriana total, e também realizou-se amplificação com iniciadores específicos para o subgrupo alfa (α) do filo Proteobacteria a partir de células não cultivadas. Foram obtidos dendrogramas comparativos entre a variedade Olathe Pinto (convencional) e o evento elite Olathe M1-4 (geneticamente modificado) utilizando-se o coeficiente de Jaccard e o método UPGMA (Unweighted pair-group method with arithmetic mean). Os agrupamentos obtidos dos perfis de 16S rDNA PCR-DGGE indicam alterações na comunidade bacteriana da rizosfera em função da transformação das plantas são mais notáveis nos perfis obtidos para alfa-proteobacteria. A origem das amostras e o estágio de desenvolvimento das plantas afetam a comunidade bacteriana.

RNAi-Mediated Resistance to Bean golden mosaic virus in Genetically Engineered Common Bean (Phaseolus vulgaris)

Bean golden mosaic virus (BGMV) is transmitted by the whitefly Bemisia tabaci in a persistent, circulative manner, causing the golden mosaic of common bean (Phaseolus vulgaris L.). The characteristic symptoms are yellow-green mosaic of leaves, stunted growth, or distorted pods. The disease is the largest constraint to bean production in Latin America and causes severe yield losses (40 to 100%). Here, we explored the concept of using an RNA interference construct to silence the sequence region of the AC1 viral gene and generate highly resistant transgenic common bean plants. Eighteen transgenic common bean lines were obtained with an intron-hairpin construction to induce post-transcriptional gene silencing against the AC1 gene. One line (named 5.1) presented high resistance (approximately 93% of the plants were free of symptoms) upon inoculation at high pressure (more than 300 viruliferous whiteflies per plant during the whole plant life cycle) and at a very early stage of plant development. Transgene-specific small interfering RNAs were detected in both inoculated and non-inoculated transgenic plants. A semiquantitative polymerase chain reaction analysis revealed the presence of viral DNA in transgenic plants exposed to viruliferous whiteflies for a period of 6 days. However, when insects were removed, no virus DNA could be detected after an additional period of 6 days.

Evaluación de líneas de frijol negro, en Veracruz y Chiapas, México.

Several experiments were conducted out during the 1999-2000 and 2000-2001 growing cycles: The adaptation and grain yield of 15 advanced lines of black and a local variety used as a control, were evaluated. These genotypes belong to the Central American Assay for Adaptation and Yield (ECAR).The bean genotypes were evaluated in eleven localities, five in the state of Chiapas and six in the state of Veracruz; the experiments were established under irrigated, upland and residual moisture conditions. ICTA Ju 97-1, II- 307, DOR-678 and Cut-45, were the most oustanding lines for yield, wide range of adaptation and stability. During the 1999-2000 Fall-Winter growing cycle, the response of the lines against Bean Golden Mosaic Virus (BGMV), angular leaf spot (Phaseoisariopsis griseola), rust (Uromyces appendiculatus), and anthracnose (Colletotrichum lindemuthianum) were evaluated; ICTA Ju 97-1 and Cut-45 were tolerant to those diseases. Both lines must be validated in farmer fields in order to be considered for releasing as new varieties for some bean growing areas of Veracruz and Chiapas, Mexico.

Cuban Isolate of Bean golden yellow mosaic virus is a Member of the Mesoamerican BGYMV Group.

In Cuba, the emergence of bean golden mosaic was associated with high populations of Bemisia tabaci in common bean (Phaseolus vulgaris L.) plantings in the 1970s (1). During the last two decades, the disease has caused significant economic losses, forcing some growers to abandon bean production. In Holguín, one of the main bean producing provinces of the country, about 2,000 ha of beans were abandoned in 1991 due to the high incidence of this whitefly-transmitted virus. At that time, yield losses associated with this disease reached 90 to 100% in farmer's fields. In spite of various control measures, the disease affected 33, 28, and 6.5% of the total area planted in Cuba to common bean in 1990, 1992, and 1996, respectively. For this investigation, common bean leaves showing systemic yellowing symptoms were collected in fields located in the provinces of Havana, Matanzas, and Holguín during 1998-1999. Sap and total DNA leaf extracts were used to inoculate healthy bean plants by manual and biolistic procedures, respectively. Characteristic yellowing symptoms were more efficiently reproduced using a particle gun device than by manual inoculation (18/20 plants and 5/20 plants, respectively, for a Holguín virus isolate). DNA extracts were further analyzed by polymerase chain reaction using two degenerate primer sets: PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722 (2). Fragments of approximately 1.4 and 1.2 kb were amplified and cloned. Restriction fragment length polymorphism analysis of the cloned 1.4-kb fragments was performed with BglII, HincII, SalI, EcoRI, PstI, and XbaI, indicating that selected isolates from the three Cuban provinces shared identical restriction patterns. The nucleotide sequence obtained from two clones of a virus isolate from Holguín, was compared to sequences available for other begomoviruses using BLAST. The Cuban isolate shared up to 94% nt sequence identity with various strains of Bean golden yellow mosaic virus (BGYMV) in the first 250 nt of the rep gene. For the common region (CR), scores were 93% for BGYMV-GA (Guatemala), 92% for BGYMV-MX (southern Mexico) and BGYMV-PR (Puerto Rico), and 91% for BGYMV-DR (Dominican Republic). The iterative sequence ATGGAG was identified in the CR of the Cuban BGYMV isolate, as reported for other BGYMV isolates. Finally, the Cuban begomovirus, hereafter referred to as BGYMV-CU, shared nt and aa sequence identities of 94 and 100%, respectively, with the coat protein gene of BGYMV-MX. We conclude that the begomovirus isolated from mosaic-affected common bean plants in the province of Holguín is a member of the Mesoamerican BGYMV group (3).

Development of a continuous whitefly cell line [Homoptera: Aleryrodidae: Bemisia tabaci (Gennadius)] for the study of begomovirus.

The whitefly Bemisia tabaci (Gennadius) is a widely distributed pest of many important food and fiber crops. This whitefly is also a vector of more than 70 plant-infecting viruses. A cell line was established in vitro using embryonic tissues from the eggs of Bemisia tabaci (Gennadius), B biotype (pseudonym B. argentifolii Bellows & Perring), and referred to as 'Btb(Ba)97, Hunter-Polston'. Cell cultures were successfully inoculated with begomovirus (BGMV and ToMoV)-infected tomato plant sap. Embryonic tissues were seeded into Kimura's modified medium and kept at a temperature of 24 degrees C. Continuous cell cultures were established and have since undergone 92 passages in 25-cm(2) flasks. Cell doubling time is approximately 3 days and the cells have been successfully revived after 1 year after storage at -80 degrees C. The cell population is monolayers of predominately fibroblast with some epithelial cells. Begomoviruses (bean golden mosaic begomovirus, BGMV, and tomato mottle begomovirus, ToMoV) were inoculated to the cell cultures independently and detected by labeling by an indirect immunofluorescence technique. The viruses were detected bound to the cell membranes and within the cell cytoplasm. This is the first report of a continuous cell line established from a species of whitefly and its inoculation with two begomoviruses. The successful inoculation of whitefly cell cultures with begomoviruses shown in our results represents great promise for the development of systems that allow researchers to achieve a better understanding of the complex relationship between begomoviruses and their whitefly vectors.

Selection for Bean Golden Mosaic Resistance in Intra‐ and Interracial Bean Populations

Bean golden mosaic (BGM) resistance within any one bean (Phaseolus vulgaris L.) race is inadequate. Pyramiding genes from different races would increase resistance and reduce pesticide use. Our objectives were to: (i) pyramid and compare BGM resistance of genotypes from intraracial versus interracial populations, (ii) verify pyramided resistance by means of molecular markers, and (iii) combine BGM resistance with resistance to other diseases. One intraracial (GV 10625) and four interracial (DC 10622, GV 10624, GV 10626, and GV 10627) populations were developed at CIAT. Plants within each F1‐derived F2 (F1:2) were advanced in bulk. The F3 was grown in the field under common bacterial blight [CBB, caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and angular leaf spot [ALS, caused by Phaeoisariopsis griseola (Sacc.) Ferraris] pressure. Single plant selections were made in the F3 and F4 Plants within F4:5 were harvested in bulk to screen for ALS, bean common mosaic (BCM), BGM, and CBB. The 39 selected genotypes, 12 parents, and six checks were again evaluated for the four diseases. Seventeen genotypes, parents, and checks also were screened for the RAPD marker OR2530 linked with bgm‐1 gene and the SCAR marker SW12700 linked with a QTL controlling BGM resistance. Selected genotypes differed in their BGM reaction. None of the genotypes from the intraracial population were resistant to BGM. Five genotypes with the highest resistance were obtained from GV 10626 and GV 10627. DC 10622 and GV 10624 produced genotypes with intermediate resistance. Three genotypes from DC 10622 and four from GV 10627 possessed OR2530 marker linked with resistance derived from `Garrapato' and SW12700 marker linked with resistance derived from `Porrillo Sintetico'. All genotypes possessed the I gene for BCM and were intermediate to ALS. Five also were intermediate for CBB. Combined use of interracial populations, disease screening, and molecular markers should be emphasized for resistance breeding.

Identification, geographical distribution and host plants of Bemisia tabaci (Genn.) biotypes (Homoptera: Aleyrodidae) in the State of Paraná, Brazil

This work was carried out in order to identify Bemisia tabaci (Genn.) biotypes present in the state of Paraná and to determine their geographical distribution and host plants. About 50 adults were collected in several host crops, weeds and ornamental plants in North, Northwest, Northeast, West and Central areas of the state, from January to May, 1998 and 1999. The species were identified by means of RAPD-PCR, using the primer Operon H-16. Whitefly populations were detected mainly from February on, in both years, seldom achieving more than one adult per leaf. The insect was found in only 66% of the sampled areas. Bean golden mosaic was almost never observed during the period. Both biotype A and biotype B of B. tabaci were found in the State of Paraná, the last one being more restricted to the north region. Although biotype B was found colonising a wider range of host plants, it has not spread out in all the state and most of the whitefly specimens found are still the biotype A. A banding pattern distinct of those obtained for A and biotype B of B. tabaci was obtained exclusively with the populations collected from cassava, thus indicating the possible presence of a biotype specific for this crop.

Effect of Silver Reflective Mulch and a Summer Squash Trap Crop on Densities of Immature <I>Bemisia argentifolii</I> (Homoptera: Aleyrodidae) on Organic Bean

Polyethylene mulch with a reflective silver stripe and a yellow summer squash, Cucurbita pepo L., trap crop were tested alone and in combination as tactics to reduce densities of Bemisia argentifolii Bellows & Perring eggs and nymphs, and incidence of bean golden mosaic geminivirus on snap bean, Phaseolus vulgaris L. Egg densities were consistently higher on squash than on bean, but egg densities and virus incidence were not lower on bean grown with squash than on bean grown in monoculture. Silver reflective mulch reduced egg densities compared with bean grown on bare ground during the first week after crop emergence for 2 of the 3 yr that the study was conducted. However, egg suppression by silver mulch was not enhanced by the presence of a squash trap crop when both tactics were combined. The obstacles to suppressing B. argentifolii through the use of trap crops are discussed.

First Report of a Bean-Infecting Begomovirus from Macroptilium lathyroides in Puerto Rico That Is Distinct from Bean Golden Mosaic Virus.

Bean golden mosaic begomovirus (BGMV) was long suspected to cause bright yellow mosaic symptoms in Macroptilium lathyroides (L.), a weed common to Puerto Rico. M. lathyroides plants exhibiting bright yellow mosaic symptoms were collected from Puerto Rico during 1994 to 1999, and the biotic and molecular characteristics of the suspect begomovirus were determined. Symptoms in M. lathyroides, indistinguishable from those observed in field-infected plants, were reproducible by whitefly transmission (Bemisia tabaci type B) and biolistic inoculation of leaf extracts (1). In bean, Phaseolus vulgaris (L.) 'Topcrop,' the M. lathyroides virus caused green-yellow mosaic foliar symptoms and stunting, reminiscent of symptoms caused by BGMV from Puerto Rico (BGMV-PR). However, biolistic- or whitefly-mediated inoculation of M. lathyroides with BGMV-PR resulted in no discernible infection. Sequence analysis (2) of the coat protein (CP) gene (AF176092) and common region of the A (CR-A) (AF176093) and B (CR-B) (AF176094) components of the virus from M. lathyroides indicated that these sequences shared only 77.3 to 79.3% and 62.4 to 68.8% identity, respectively, with BGMV from the Dominican Republic, Honduras, Guatemala, Jamaica (JAM), and PR. Alignment of the M. lathyroides virus CP sequence with other well-studied begomoviruses indicate its closest relative is BGMV-PR (82%) and that it shares less than 73% identity with partial CP sequences of Macroptilium golden mosaic virus-JAM (AF089839, AF089840). The directly repeated CR sequences of the M. lathyroides virus, putatively involved in AC1 binding, are TGGTGACTGGTG and are distinct from TGGAGACTGGAG, the analogous direct repeat in BGMV-PR. We provisionally designate the new, previously undescribed begomovirus species from M. lathyroides, Macroptilium mosaic virus (MaMV). Results indicate MaMV-PR and BGMV are distinct, bean-infecting begomoviruses from the Caribbean and that MaMV-PR may pose a new threat to bean production, particularly where the type B vector is established.

Resistance to Bean Golden Mosaic Virus in Bean Genotypes.

Bean lines MD 806, MD 807, MD 820, MD 829, MD 808, and MD 821, all with high levels of resistance to bean golden mosaic virus (BGMV), were selected under field conditions. On a 1 to 9 scale (1 = symptomless plant; 9 = severe symptoms), the mean disease severity of the MD lines ranged from 1.7 to 3.9 for mosaic symptom (foliar yellowing) and from 1.7 to 2.2 for malformation. In contrast, disease severity in the susceptible cultivars Carioca, Carnaval, and Iapar 20 ranged from 4.1 to 8.7 for mosaic and from 4.0 to 7.3 for malformation. Symptoms on the selected lines were expressed later than on susceptible controls. The MD lines yielded 1.2- to 5.9-fold the yield of the cultivars Carioca and Iapar 20. Under greenhouse conditions, reactions of the bean genotypes to BGMV were similar to those observed in the field. MD 806 and MD 807 were obtained from early crosses involving genotypes that reacted to BGMV infection with mild mosaic (Aeté 1/38 and TMD-1) and mild malformation (Porrillo Sintético and Turrialba 1). Parents of the lines MD 820 and MD 829 were Phaseolus coccineus (of unknown reaction to BGMV) and Carioca. Line MD 648 (DOR-selected line) was the ancestral parent of lines MD 808 and MD 821, which had the highest levels of resistance or tolerance to BGMV. Severity of all BGMV symptoms showed gradual reductions from the earliest parents to their later selected progenies. Responses of the parent genotypes and progenies to BGMV infection suggest a combination of resistance characters in the selected MD lines. MD 806, MD 820, and MD 821 were released in the state of Paraná under the names Iapar 57, Iapar 72, and Iapar 65, respectively.