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Welcome

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YMV TOLERANCE IN GREENGRAM

SPEAKER: NIDHI SINGHCHAIRMAN: Dr. N. MANDAL

SEMINAR LEADER: Dr. N. MANDAL

DEPARTMENT OF Biotechnology, Instrumentation and Environmental Science, FACULTY OF AGRICULTURE

2/13/2014

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INTRODUCTION

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MUNGBEAN [VIGNA RADIATA (L.) ]

1. One of the thirteen food legumes grown in India and third most important pulse crop of India after chickpea and pigeonpea.

2. Native to India-Burma region of South-East Asia. It is cultivated extensively in the India-Burma-Thailand region of Asia.

3. India covers up to 65% of the total world acreage and 54% of total production

Chatterjee and Randhawa, 1952

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•Grown principally for its high protein seeds that are used as human food•Contains about 24 per cent protein•Being a short duration pulse crop, it fits well in mixtures and crop rotation

•Used as green manure crop •Helps to enrich the soil by symbiotic relationship with specific soil rhizobia of the genus Bradyrhizobium

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1. Cercospora leaf spot (C. canescens, C. cruenta),

2. Powdery mildew (Erysiphe polygoni),

3. Root disease complex (Pythium spp.,

4. Rhizoctonia solani, Fusarium spp.)

5. Reniform (Rotylenchulus reniformis)

6. Root knot (Meloidogyne spp.) nematodes.

o Prone to several diseases

o Harbours different viruses namely alfalfa mosaic virus, bean common mosaic virus, cucumber mosaic virus, leaf crinkle virus, leaf curl virus, mosaic mottle virus and mungbean yellow mosaic virus.

Among all the viruses, mungbean yellow mosaic virus (MYMV) is the most destructive one

First ever reported from fields of IARI, New Delhi in 1960 and is transmitted principally by whitefly, Bemisia tabaci (Genn.) and grafting but not by sap, seed or soil (Nariani, 1960)

Major biotic stresses accounting for the low harvest index and causes significant yield loss

MYMV

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Geminiviruses have been grouped into four genera: Mastrevirus, Curtovirus, Topocuvirus and Begomovirus, depending on their vector, host range and genomic characteristics .

MYMV belongs to the genera begomovirus of the family Geminiviridae (Bos, 1999).

The virus has geminate particle morphology (20 x 30 nm) and the coat protein encapsulates spherical, single stranded DNA genome of approximately 2.8 Kb (Hull, 2004).

MYMV Genome organization

Stanley et al., 2005

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GENETICS OF MUNGBEAN YELLOW MOSAIC VIRUS (MYMV) IN MUNGBEAN

single recessive gene is responsible for MYMV resistance in

mung bean

The expression of the major gene responsible for MYMV

resistance/susceptibility was affected by modifying genes

These modifying genes caused variation in the degree of MYMV

resistance/susceptibility in the progenies derived from a single

cross

Evolution of a highly resistant mung bean line for MYMV

disease would depend on the accumulation of favourable

modifying genes.

Khattak et al., 2000

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SYMPTOMATOLOGY

First symptoms appear on the young leaves in the form of

mild scattered yellow specks or spotsNext trifoliate leaf emerging from the growing apex shows irregular yellow and green patches alternating with each otherThe leaf size is generally not much affected but sometimes the green areas are slightly raised and the leaves show slight puckering and reduction in size. The size of yellow areas goes on increasing in the new growth and ultimately some of the apical leaves turn completely yellow.The diseased plants usually mature late and bear very few flowers and pods. The size of the pod is reduced and more frequently immature small sized seeds are obtained from the pods of diseased plants.

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SURVEY

To obtain information’s on the natural incidence of Yellow

Mosaic disease (YMD) of mungbean (Vigna radiata) in the

agro-ecological condition of lateritic zone of West Bengal a

survey was conducted during the pre kharif season of 2009

in different locations of Birbhum , Bankura and Purulia

District

The natural incidence of the disease in farmers fields

incidence of YMD was varied from 5.33% to 14.00%

according to the location and variety

PAUL, 2013

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Mechanical transmissi

on

Graft transmissi

on

Insect transmissi

on

Transmission

Nariani et al., 1960

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Epidemiology

Murugesan and Chelliah (1977) reported a yellow mosaic on greengram sown during March to May months. A positive correlation of whitefly population on 20 and 30 day crop and disease incidence at 45 days old crop with maximum temperatures was obtained.

In most of the research regarding this aspect it has been found that all the genotypes of mungbean showed a higher disease incidence during summer compared to spring and rainy season crops.

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Growth attributes and losses

Reduction of 9.6 to 38.2 per cent in height, 7 to 28.5 per cent in fresh weight of shoot and 4.3 to 22.1 per cent in dry weight, 25.7 per cent in 1000 seed weight of susceptible cultivar was observed by Premchand and Varma (1983)

However, the germinability of seeds was apparently unaffected due to yellow mosaic.

yield loss of 83.9 per cent and a maximum growth reduction of 62.94 per cent in Vigna radiata cv. Pusa baisakhi was reported by Quaiser Ahmed (1991)

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Mode of inheritance of resistance to mungbean yellow mosaic virus (mymv) in

mungbean

The MYMV resistance was inherited through a major recessive geneNo maternal effect was found for the inheritance of MYMV resistance in mungbean.The monogenic recessive inheritance for MYMV has been reported by Singh and Patel (1977), Malik et al. (1986 & 1988).

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Screening

For the purpose of identifying resistance/tolerance in mungbean germplasm, screening of mungbean genotypes for resistance and tolerance to MYMV has to be done. This can be achieved by developing disease screening nursery Screening has to be done in natural environmental condition. It can also be achieved by using agroinoculation.

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CONSTRAINTS

Lack of enough genetic diversity in the parental material used narrow genetic base results in inherently low yield potential.

The susceptibility to biotic stresses and abiotic stresses has become the major constraints in achieving higher yield in this crops

Lack of suitable varieties and genotypes with adaptation to local conditions,

absence of suitable ideotypes for different cropping systems and poor harvest index have

The disease incidence is seasonal and cannot be created as and when desired by artificial means.

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DEVELOPMENT OF YMV-TOLERANT VARIETY

Identification of resistant lines through conventional breeding is time consuming and requires evaluation at ‘hot spot’ area (Selvi et al. 2006).

Indirect selection using molecular markers linked to MYMIV resistant genes would facilitate precision plant breeding and high-throughput marker assisted selection (MAS) of resistant genotypes.

An attempt should made to develop molecular marker(s) linked with the YMV-tolerance in Vigna mungo

The results of molecular analysis can be relied upon only when there is an accurate phenotypic data. This helps to draw conclusions more precisely by correlating the results obtained through molecular analysis with the phenotypic analysis.

Hence, while exploring the genotypes for the resistant motifs it is necessary to screen them for diseases under natural or artificial conditions.

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STRATEGIES

Mapping of MYMV tolerance genes in greengram.

Development of Yellow Mosaic Virus (YMV) resistance linked DNA marker in Vigna mungo from populations segregating for YMV-reaction

crosses with MYMV-tolerant mungbean germplasm, interspecific crosses with highly MYMV-resistant blackgram, and the use of gamma ray mungbean mutants

Development of MYMV specific DNA Probes

Agro-inoculation technique may lead to the development of a MYMV resistance variety.

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Achievements

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YMV tolerant line identified in the field with in large population of the susceptible cultivar T-9 and crossed with the T-9 and F1, F2, & F3 progenies were raised.

Different generations were phenotype for YMV tolerance reactions by forced inoculation using viruliferous white flies monogenic recessive control of YMV- tolerance was revealed from the F2 - segregation ratio of 3:1 susceptible : tolerant

Of 24 pairs of resistance gene analog (RGA) primers screened, only one pair, RGA 1F-CG/RGA 1R, was found to be polymorphic among the parents.

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Selected F2individuals and F3 families were genotyped with the polymorphic RGA primer pair and the polymorphism was found to be linked with YMV-reaction

This primer pair amplified a 445bp DNA fragment only from homozygous tolerant and the heterozygous lines.

The 445bp marker band was sequenced and named ‘VMYR1’.

The predicted amino acid sequence showed highly significant homology with the NB-ARC domain present in several gene products involved in plant disease resistance, nematode cell death and human apoptotic signaling

This YMV-resistance linked marker is of potential commercial importance in resistance breeding of plants.

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Identification of RAPD marker associated with MYMV resistance in mungbean by employing BSA in RILs.Out of 20 random decamers, only ten primers viz; OPA-03, A-06, A-03, OPA-09, A-09, OPB 7, UBC-391, OPC-08, UBC 499 and A-04 showed polymorphism between parents Chinamung and BL 849. PCR amplified 700 bp marker band was detected in individuals of F5 RILs constituting the MYMV resistant bulk indicating that primer UBC 499 was linked to MYMV resistance

This marker can be used in screening mungbean genotypes for resistance to MYMV disease.

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The present investigation was carried out to study the inheritance and identify molecular markers linked with MYMV resistance gene by using F1, F2 and 167 F2 : 8 recombinant inbred lines (RILs) developed from the cross ‘TM-99-37’ (resistant) × Mulmarada (susceptible). 

The F1 was susceptible, F2 segregated in 3S:1R phenotypic ratio and RILs segregated in 1S:1R ratio in the field screening indicating that the MYMV resistance gene is governed by a single recessive gene.

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Of the 140 RAPD primers, 45 primers showing polymorphism in parents were screened using bulked segregant analysis. Three primers amplified specific polymorphic fragments viz. OPB-07600, OPC-061750 and OPB-12820.  The marker OPB-07600 was more closely linked (6.8 cM) with a MYMV resistance gene as compared to OPC-061750 (22.8 cM) and OPB-12820 (25.2 cM). The resistance-specific fragment OPB-07600was cloned, sequenced and converted into a sequence-characterized amplified region (SCAR) marker and validated in twenty genotypes with different genetic backgrounds.

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The present study was undertaken to identify RAPD marker associated with Mungbean Yellow Mosaic Virus (MYMV) resistance in mungbean ( Vigna radiata (L.) Wilczek) cross ML 267 x CO 4. Bulked segregant analysis was employed to identify RAPD markers linked to MYMV resistant gene of ML 267.  A total of 149 random decamers were surveyed for identification of polymorphic markers between the DNA bulks of resistant and susceptible F2 individuals and their parents

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 Forty one primers produced specific band for resistant parent which were absent in susceptible parent.Out of 41 random primers, three primers viz., OPT 16, OPS 7 and OPAK 19 produced specific fragments viz., OPT 16564, OPS 7900 and OPAK 19400, respectively in resistant parent and resistant bulk, which were absent in the susceptible parent and bulk Amplification of individual DNA samples out of the bulk with putative markers, OPS 7900 only revealed polymorphism in all 8 resistant and 6 susceptible plant, indicating that the marker OPS 7900 was associated with MYMV resistance in ML 267. 

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CONCLUSION Urgent need to develop high-yielding varieties with resistance to diseases with greater yield stability.

Development of tightly linked markers endowed with the features of resistance gene candidates

Generating superior genotypes with durable YMV-resistance.

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