BEAN COMMON MOSAIC VIRUS (BCMV)

BCMV is a seedborne virus transmitted by aphids and mechanically by plant sap. Systemically infected plants, especially those from infected seeds, have leaves with green mosaic patterns and distortions (curling, strapping, or puckering of tissues along leaf veins). Plants may be stunted and have only a few pods, which mature later than uninfected pods. Vascular tissue can become necrotic, producing dark streaks on petioles and stems. Nonsystemic infections can appear as ring-like lesions on foliage. Appearance and severity of symptoms depends on strain of the virus, variety, time of infection, and environmental conditions. 
At high temperatures (above 78 F), cultivars with the hypersensitive resistance gene (I gene) respond to necrosis-inducing strains of BCMV with a systemic necrosis called black root. Plants with black root die. 
More than 15 strains of BCMV are known, and breeders have incorporated resistance to the more important strains in many commercial varieties. Certified seed programs are restrictive for BCMV contamination. Many types of beans, alfalfa, and common clover are hosts. Controlling large populations of aphids can reduce spread. The primary control is selection of high quality, virus-tested seed of genetically resistant varieties. 

ISOLATE DESCRIPTION
Host of Isolate and Habitat Details 
Source of isolate: Phaseolus vulgaris. 
Natural host and symptoms 
Phaseolus vulgaris, Phaseolus coccineus — tolerant cultivars develop mosaic and malformation, sensitive ones show rugosity of lower leaves, mosaic, malformation of leaves and pods, those with the dominant necrosis gene develop vein necrosis, 'black root' and death (especially above 26°C). 

CLASSIFICATION
This is a description of a plant virus at the species level with data on all virus properties from morphology to genome, replication, antigenicity and biological properties. 
Name, Synonyms and Lineage:
Synonym(s):  
Bean common mosaic virus — serotype B, Azuki bean mosaic virus; bean mosaic virus, bean western mosaic virus , blackeye cowpea mosaic virus, mungbean mosaic virus, peanut stripe virus; peanut mild mottle virus; peanut chlorotic ring mottle virus; sesame yellow mosaic virus. ICTV approved 
Acronym: 
BCMV. Virus is an ICTV approved species of the genus Potyvirus in the family Potyviridae. 





VIRION PROPERTIES
Morphology
Virions consist of a capsid. Virus capsid is not enveloped. Capsid/nucleocapsid is elongated with helical symmetry. The capsid is filamentous, flexuous with a length of 847-886 nm and a width of 12-15 nm. Axial canal is indistinct. Basic helix is obscure. 
Physicochemical and Physical Properties
Virions have a buoyant density in CsCl of 1.31-1.32 g cm-3. There are 1 sedimenting component(s) found in purified preparations. The sedimentation coefficient is 154-158 S20w. The thermal inactivation point (TIP) is at 60°C. The longevity in vitro (LIV) is 1-4 days. Although the titer is dependent on the host, the decimal exponent (DEX) of the dilution end point is usually around 3-4. 
Nucleic Acid
 The Mr of the genome constitutes 5% of the virion by weight. The genome is monopartite, only one particle size is recovered of linear, positive-sense, single-stranded RNA. The complete genome is about 10000 nucleotides long. Sequence is fully and partially sequenced. Complete sequence is 10000 nucleotides long. Sequence has the accession number

Proteins
Proteins constitute about 95% of the particle weight. The viral genome encodes structural proteins and non-structural proteins. Virions consist of 1 structural protein(s). 
Lipids
Lipids are not reported. 


ANTIGENICITY
The virus is serologically related to 17 potyviruses, including potato Y, watermelon mosaic 2, bean yellow mosaic, blackeye cowpea mosaic and soybean mosaic viruses. 
Isolates originally called azuki bean mosaic virus (Matsumoto, 1922) were first reported in Japan inducing mosaic and green vein banding in Vigna angularis. They are found throughout the East Asian region. They probably differ from type isolates in infecting Nicotiana tabacum, but neither Chenopodium amaranticolor nor Vicia faba. 
Isolates originally called blackeye cowpea mosaic virus (Anderson, 1995), cowpea (aphid-borne) mosaic virus, cowpea (blackeye) mosaic virus and cowpea vein-banding mosaic virus were first reported in the U.S.A. inducing mosaics, mottles, streaks and leaf malformation in Crotalaria spectabilis and Vigna unguiculata. They are found worldwide, and also do not infect Vicia faba. Some gene sequences have been determined. 
Isolates originally called peanut stripe virus (Demski et al., 1984), peanut chlorotic ring virus (Demski et al., 1988; Fukumoto et al., 1986; Wongkaew and Dollet, 1990), peanut mild mottle virus (Zeyong et al., 1983; Demski et al., 1988), peanut mosaic virus and sesame yellow mosaic virus were first found in Georgia, U.S.A. in Arachis hypogaea, which is not infected by type isolates. They cause severe mosaic, striping and stunting in several other legumes including Lupinus albus, Glycine max and Sesamum ssp., and are transmitted not only by Aphis craccivora, but also A. glycines and Rhopalosiphum maidis. Some gene sequences have been determined. 

BIOLOGICAL PROPERTIES
Symptoms and Host Range 
Host of virus belongs to the Domain Eucarya. Host of virus belongs to the Kingdom Plantae. 
Natural Host Range and Symptoms
Symptoms persist. Phaseolus vulgaris, Phaseolus coccineus - tolerant cultivars develop mosaic and malformation, sensitive ones show rugosity of lower leaves, mosaic, malformation of leaves and pods, those with the dominant necrosis gene develop vein necrosis, `black root' and death (especially above 26°C). 
Experimental Host Range and Symptoms
Several (3-9) families susceptible (strain specific response). Experimentally infected plants mostly show symptoms of mosaics, local lesions, necrosis - very variable. 
Diagnostic, Propagational and Assay Host Range
Diagnostic host: susceptible host species and symptoms 
Chenopodium quinoa - faint chlorotic local lesions developing into green rings; not systemic. 
Macroptilium lathyroides - necrotic local lesions; systemic necrosis. 
Phaseolus vulgaris cvs Dubbele Witte, Stingless Green Refugee - green vein-banding, malformed leaves. 
Pisum sativum, Vicia faba - symptomless. 
Diagnostic host: insusceptible host species Cucumis sativus, Medicago sativa, Nicotiana tabacum, N. glutinosa, Pisum sativum. 
Maintenance and propagation host species: Phaseolus vulgaris cvs Dubbele Witte and Stringless Green Refugee susceptible to all known strains. 
Assay hosts (Local lesions or Whole plants) Chenopodium amaranticolor, C. quinoa, Phaseolus vulgaris; Pisum sativum, Vicia faba latent or no infection. 
Susceptible Hosts
Experimentally infected species susceptible to virus: Cajanus cajan, or Cassia tora, or Chenopodium amaranticolor, or Chenopodium quinoa, or Cicer arietinum, or Crotalaria spectabilis, or Cyamopsis tetragonoloba, or Glycine max, or Gomphrena globosa, or Lens culinaris, or Lupinus albus, or Lupinus angustifolius, or Macroptilium lathyroides, or Melilotus albus, or Nicotiana benthamiana, or Nicotiana clevelandii, or Phaseolus coccineus, or Phaseolus lunatus, or Phaseolus vulgaris, or Pisum sativum, or Sesbania exaltata, or Tetragonia tetragonioides, or Trifolium incarnatum, or Trifolium subterraneum, or Vicia faba, or Vicia sativa, or Vicia villosa, or Vigna angularis, or Vigna radiata, or Vigna unguiculata. 
Insusceptible Hosts
Species inoculated with virus, but tested not to be susceptible: Arachis hypogaea, or Bauhinia purpurea, or Capsicum annuum, or Cucumis sativus, or Datura stramonium, or Lablab purpureus, or Lactuca sativa, or Lathyrus odoratus, or Lycopersicon esculentum, or Medicago sativa, or Nicotiana glutinosa, or Nicotiana tabacum, or Pisum sativum, or Trifolium hybridum, or Trifolium pratense, or Trifolium repens, or Vigna unguiculata ssp. sesquipedalis , or Zinnia elegans. 
Families containing susceptible hosts: Amaranthaceae, or Chenopodiaceae, or Leguminosae-Caesalpinioideae, or Leguminosae-Papilionoideae, or Solanaceae, or Tetragoniaceae. 
Families containing insusceptible hosts: Compositae, or Cucurbitaceae, or Leguminosae-Caesalpinioideae, or Leguminosae-Papilionoideae, or Solanaceae. 
Transmission 
Transmitted by a vector. Virus transmitted by mechanical inoculation; transmitted by seed (up to 83% in Phaseolus vulgaris and from 7-22% in tepary bean); transmitted by pollen to the seed. Transmitted by an insect; Acyrthosiphon pisum, Aphis craccivora, A fabae, Myzus persicae and other ssp.; Aphididae. Transmitted in a non-persistent manner. 
Geographic Distribution 
Probably distributed world-wide (in Phaseolus beans wherever they are grown). Spreads in China and the USA. 
Ecology and Control 
Studies reported by Drijfhout (1978) on breeding for resistance. 
Diagnostic and Methods 
Leaf sap contains few virions. Method: Morales (1979). 
Histopathology: 
Virus can be best detected in leaves and stems including the apical meristems. Virions are found in the cytoplasm. 

Cytopathology: 
Inclusions are present in infected cells. Inclusion bodies in the host cell are found in the cytoplasm. Inclusions are cylindrical i.e. pinwheels with associated scrolls. 
Geographical Distribution
The virus is probably distributed worldwide (in Phaseolus beans wherever they are grown). The virus occurs in China and the United States of America. 
Ecology, Epidemiology and Control
Studies reported by Drijfhout (1978) on breeding for resistance. 

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ROLES OF NGOS IN AGROFORESTRY IN BANGLADESH

1. An evolution if involvement of NGOs in the agroforestry reveals that they have achieved success in the following areas (ADAB, 1998):
2. In creating awareness among the people regarding the need to plant trees in farm land and the economic and commercial values of trees.
3. In emphasizing the role of agroforestry as a sustainable means of creating employment opportunities, augmenting income, improving the state of use of marginal land and also as an effective tool of poverty alleviation in the rural sector.
4. In organizing the rural poor, landless farmers, unemployed youth and other socioeconomically marginalized people into coherent, functional and self sustained groups undertaking different income generating activities including agroforestry (Farrington et. al., 1989).
5. In helping the enrichment and replenishment of the depleting homesteads.
6. In expanding the horizon of thought and practice of planting trees with wide spacing and proper trimming agricultural lands also without hampering the output of main crops.
7. In creating increasing interest among the rural land owners to use their personal marginal lands for establishing woodlots.
8. In infusing an idea of balanced planning of homesteads by selecting different varieties and species of timber, fruit, fuel, fodder, bamboo saplings for plantation so that need for all types of forest products can be met from local sources (Huda, 1987).
9. In helping establishment of nurseries by groups, individuals, model nurseries by NGOs are working as practical guide for setting up such nurseries by private individuals. It is worth mentioning that the number of private nurseries in Bangladesh has increased about 4000 from a few hundreds during the last three to four years. This has resulted due to the large demand created for saplings for plantation and the training and support being organized by a large number of NGOs.
10. The NGOs are also playing a very important role in organizing training of their target groups in forestry techniques, improved silvicultural practices and also different updated methods of nursery raising and tree improvement. This is helping in improving the variety and quantity of the rural woodlots and homesteads.
11. It has been marked that compared to govt. social forestry programmes, the number of women participants is much higher in NGO social forestry programmes.
12. A number of NGOs like Proshika MUK, Bangladesh POUSH, BRAC, and SDC etc. have development different successful and innovative approaches and models social and agroforestry, which have gained better acceptability among the people. Replication of these pragmatic and need based models is progressing rapidly and the process is showing remarkable spontaneous response from the people (Hossain, 1992).
13. In areas where govt. programmes are facing difficulty due to bureauticratic constraints, credibility gap, lack of proper commitment, field level involvement and proper orientation, the NGOs are playing a supplementary role to fill up the gaps and collaborating with govt. agencies to remove the constraints.

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