Crop Protection 23 (2004) 1119–1124

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doi:10.1016/j.cro

On-farm seed priming reduces yield losses of mungbean(Vigna radiata) associated with mungbean yellow mosaic virus

in the North West Frontier Province of Pakistan

Abdul Rashida, Dave Harrisb,*, Phil Hollingtonb, Shamsher Alia

aDept of Soil Science, North West Frontier Province Agricultural University, Peshawar, PakistanbCentre for Arid Zone Studies, University of Wales, Deiniol Road, Bangor LL57 2UW, Wales, UK

Received 13 February 2004; received in revised form 16 March 2004; accepted 6 April 2004

Abstract

The effect of priming seed for 8 h with water before sowing on the incidence and severity of infection of mungbean (Vigna radiata

(L.) Wilczek) with mungbean yellow mosaic virus (MYMV) was investigated in a replicated, large-plot trial in 2002. Primed seeds

germinated and emerged faster and more completely, resulting in the establishment of 45% more plants per unit area than non-

primed seeds. However, subsequent mortality during the growth cycle in both treatments reduced this to a small, non-significant

difference between treatments at final harvest. Symptoms of MYMV infection were assessed using a visual scoring index (VSI).

More than 70% of the non-primed plants were judged to have severe or lethal symptoms whereas only 14% of the primed plants

were similarly affected. Only 9% of non-primed plants showed no disease symptoms in contrast to 32% of primed plants. These

marked differences between priming treatments in the incidence and severity of disease were reflected in the components of yield.

Primed crops produced 80% more above-ground biomass (3.3 versus 1.9 t ha�1), 264% more pod yield (1.0 versus 0.28 t ha�1) and

415% more grain (0.36 versus 0.07 t ha�1) than did non-primed crops. Several possible hypotheses to explain these differences in

response to MYMV are discussed.

r 2004 Elsevier Ltd. All rights reserved.

Keywords: On-farm seed priming; Mungbean; Disease resistance; Pakistan

1. Introduction

Mungbean (Vigna radiata (L.) Wilczek) is grown onover 200,000 ha with production of more than 100,000 tunder rainfed and irrigated conditions in Pakistan. Inthe North West Frontier Province (NWFP), there isabout 9500 ha of mungbean grown, half of which isirrigated and half rainfed, and which produces around6000 t of grain (Government of Pakistan, 2002). Yieldsfor the rainfed area are generally low and variable due tosparse, erratic rainfall and marginal soils.Various authors (e.g., Naseem et al., 1997; Rahmian-

na et al., 2000) have cited poor crop emergence andseedling establishment as a major constraint for

ng author. Tel.: +44-1248-382922; fax: +44-1248-

ss: d.harris@bangor.ac.uk (D. Harris).

front matter r 2004 Elsevier Ltd. All rights reserved.

pro.2004.04.002

mungbean production. A simple, low-cost, low-risktechnology called ‘on-farm’ seed priming—soaking seedin water for 8 h before sowing—was shown to improveemergence and seedling vigour in mungbean in NWFPand was also observed to improve yield consistentlyacross a wide range of rainfed and irrigated environ-ments during the 4 years between 1999 and 2002 (Rashidet al., 2004). These authors also reported that a large(206%) priming-related yield advantage in one of theirtrials in 1999 was associated with marked differencesbetween treatments in the apparent level of infection ofthe crop by mungbean yellow mosaic virus (MYMV),which is a serious disease of mungbean and otherlegumes in Pakistan (Ayub and Ilyas, 1988; Bashir et al.,1991), elsewhere in South Asia (Kaiser et al., 1968) andworldwide (Bashir et al., 2000). The disease is primarilytransmitted by the whitefly Bemisia tabaci Gemm.,although Bashir et al. (2000) have reported a low

ARTICLE IN PRESSA. Rashid et al. / Crop Protection 23 (2004) 1119–11241120

incidence (around 3%) of seed-borne transmission. Inthe study reported here, incidence and severity ofinfection with MYMV were recorded, together withcomponents of yield, in primed and non-primedmungbean fields during 2002 in NWFP.

2. Materials and methods

2.1. Experimental site

The NWFP Agricultural University research station isin Peshawar (34�010N, 71�400E). The area has a warm tohot, semi-arid, sub-tropical, continental climate withmean annual rainfall of about 360mm.The soil is ahaplustalf, a silty clay loam, well drained and stronglycalcareous, with a pH of 8.2. The soil is deficient innitrogen and phosphorus but has adequate potassium.Organic matter is less than 1%.

2.2. Experimental design and cultural details

Four fields each approximately 0.4 ha, were cultivatedafter rainfall in the first week of June, 2002. Two fieldswere adjacent to each other, while the two others wereseparated by a field of pigeonpea. All fields were within200m of each other and were surrounded by fieldscontaining cotton, sugarcane, maize and potatoes. Thepreceding crop in all fields was wheat. Diammoniumphosphate was mixed into the soil at the rate of24 kg ha�1N and 26 kg ha�1 P. Each field was dividedinto two plots, each 40m� 50m. On 28th June, seed ofmungbean cv NM 92 was broadcast uniformly at therate of 30 kg ha�1 (60 seeds m�2) and mixed into the soilby shallow cultivation and planking. In vitro germina-tion of seeds was more than 90%. One, chosen atrandom, of each pair of plots was sown with seeds thathad been soaked in fresh water for 8 hours, surface-driedto facilitate handling and then sown immediately; theother plot was sown at the same time using non-primedseeds. Plots were irrigated uniformly 21 days aftersowing (DAS) when crops were top-dressed with urea atthe rate of 23 kg ha�1 N. Two further irrigations wereapplied, at flowering and at the grain-filling stage.Mospilan (acetamiprid) was sprayed immediately beforeflowering at a rate of 250 g per 250 l ha�1 to controlaphids.

2.3. Measurements

2.3.1. Rate of emergence

Six 1m� 1m quadrats were sited at random in eachof the eight plots and the number of plants that hademerged was counted every 12 h, beginning 48 h aftersowing (HAS) and ending 148 HAS.

2.3.2. Disease incidence and severity

The number of plants and the proportion of thoseplants showing MYMV disease symptoms were mea-sured during the final stage of pod formation (68 DAS)within four 4m� 4m randomly sited quadrats in eachof the eight plots. A visual scoring index (VSI), based onexternal symptoms such as stunted growth, chlorosisand flower malformation, was used as described byBashir and Hassan (1998) and Hassan et al. (2003). Theseverity of the symptoms shown by each plant in thequadrat was used to categorise plants into: 0=noinfection; 1=mild; 2=moderate; 3=severe; 4=lethal.No measurements were made of whitefly incidence.

2.3.3. Components of yield

As mungbean is an indeterminate crop, pods wereharvested as they matured. It was necessary to beginpicking pods earlier in the primed plots and one pickingwas made 69 DAS to avoid losses due to shattering,whereas final harvest of all plots was 24th September (88DAS) when more than 80% of all pods had matured. Allplants within four 4m� 4m randomly sited quadrats ineach of the eight plots were counted, harvested and sun-dried in a glasshouse. Total above-ground biomass wasweighed then pods were separated and weighed. Finallypods, including those from the picking 69 DAS, werethreshed by hand and the weight of grains recorded.

2.3.4. Statistical analysis

Each of the four fields was treated as a replicate and atwo-way analysis of variance (4 fields � 2 treatments)was performed using the means of six quadrats per plotfor emergence counts and four quadrats per plot fordisease assessment and yield components. Non-trans-formed data were used for the analysis of plantpopulation density and yield components but theanalysis of disease incidence and severity was done afterarcsin transformation of the percentage data.

3. Results

3.1. Rate of emergence

Primed mungbean seeds emerged earlier, faster andmore completely than non-primed seeds. After emer-gence began around 60 HAS, primed plants emerged atan average of around 0.75 plantsm�2 h�1, in contrast toa mean rate of only about 0.5 plantsm�2 h�1 in the non-primed plots. Consequently, mean stand density mea-sured 148 HAS was 44.9 plantsm�2 in primed plots butonly 30.6 plantsm�2 (SED=2.03) in non-primed plots.This response is common in a wide range of crops andenvironments and is generally associated with greatersubsequent vigour of the seedlings from primed seeds.This vigour, together with more plants per unit area in

ARTICLE IN PRESSA. Rashid et al. / Crop Protection 23 (2004) 1119–1124 1121

the primed crop, is often associated with earlier flower-ing and maturity and higher yields (e.g. Harris et al.(2001) for wheat; Harris et al. (2002a) for maize; Harriset al. (2002b) for upland rice; Musa et al. (2001) forchickpea). All these effects of priming were reported inmungbean in Pakistan by Rashid et al. (2004).Conversely, in cases where priming seed does not resultin faster, better establishment and early vigour none ofthe development- and growth-related benefits mentionedabove are observed, although priming is not generallydetrimental in such circumstances. The pattern ofemergence observed in this experiment is often indica-tive that yield benefits are likely to occur.

3.2. Final population density

The primed crop initially exceeded the target popula-tion density of 30–35 plantsm�2 (based on an expected60% field emergence observed in previous experi-ments—data not shown), whereas the non-primedtreatment resulted in significantly fewer (32%) plantsper unit area. Subsequent mortality throughout the cropcycle reduced the population density to below20 plantsm�2 by the time of final harvest, which issub-optimal for mungbean in these conditions.Although the primed crop was slightly denser, thedifference was not statistically significant (Table 1).

Table 1

Plant population density m�2 at harvest and the percentage of healthy, moder

4) of symptoms of MYMV

Seed treatment

Not primed

A. Plant population density at harvest

Total number of plants (m�2) 14.1

B. Disease incidencea 17.8 (9.4)

No disease

(VSI=0) (%)

Mild or moderate disease 25.4 (18.7)

(VSI=1 or 2) (%)

Severe or lethal disease 58.3 (72.0)

(VSI=3 or 4) (%)

�Statistically significant at po0.05.��Significant at po0.01.ns: Not significant.aAnalysis of disease incidence used arcsin transformed data. Transformed m

values were calculated using transformed data.

Table 2

Final yield and yield components

Variable Seed treatment

Not primed

Total above-ground biomass (kg ha�1) 1859

Pod yield (kg ha�1) 284

Grain yield (kg ha�1) 70

3.3. Disease incidence and severity

The symptoms of MYMV infection were apparent ononly 68% of the primed plants whereas 91% of non-primed plants showed symptoms (Table 1). Of that 68%most (55%) plants showed only mild or moderatesymptoms (VSI=1 or 2) while most (72%) of the non-primed plants had symptoms that were classed as severeor lethal (VSI=3 or 4). There were statisticallysignificant differences between the primed and non-primed treatments for each of the three VSI classes. Themeasurements clearly showed that the primed cropexhibited fewer obvious symptoms of MYMV than didthe non-primed crop.

3.4. Components of yield

The primed crop, although not significantly denserthan the non-primed crop (Table 1), produced 80%more biomass, 264% more pod yield and 415% moregrain than the non-primed crop (Table 2).

4. Discussion

The results of this study confirm the observation ofRashid et al. (2004) that mungbean crops grown from

ately or severely diseased plants based on a visual scoring index (VSI, 0-

SE diff. Significancea

Primed 8 h

17.6 2.0 ns

33.7 (31.6) 4.49�

47.4 (54.5) 2.74��

21.2 (13.7) 4.97��

eans are presented (with non-transformed means in brackets). SE diff.

SE diff. Significance

Primed 8 hours

3345 355.9�

1034 127.9��

361 41.3��

ARTICLE IN PRESSA. Rashid et al. / Crop Protection 23 (2004) 1119–11241122

primed seed were less affected by MYMV infection thanthose from non-primed seed. There was a five-foldincrease in grain yield due to priming in this trial as wellas a marked increase in biomass (Table 2). The grainyield of the non-primed crop in 1999 (336 kg ha�1) andthis trial (70 kg ha�1) were both very low—the averageyield of mungbean in NWFP is around 600 kg ha�1

(Government of Pakistan, 2002) while that for the non-primed crops reported from 11 irrigated on-station trialsat the Peshawar site by Rashid et al. (2004) was1375 kg ha�1—and the reasons for the below-averageyield in the 2002 trial are not known. However, biomasswas quite large (Table 2) and it is possible that therelatively high (for a legume) rates of N applied,together with a residual effect from N applied to thepreceding wheat crop, might have stimulated vegetativegrowth at the expense of pods and grain.There have been other reports that crops from primed

seeds are more resistant to pests and diseases. Musa et al.(2001) showed that primed chickpea crops had 37%fewer plants infected with collar rot (Sclerotium rolfsii)than crops from non-primed seeds, which contributed toa mean yield increase of 33% due to priming. Harriset al. (1999) reported Indian farmers’ comments thatprimed chickpea was less damaged by pod borers. Theauthors were unable to confirm this effect in India;pod borer damage on chickpea in other trials inBangladesh was also much reduced in primed cropsbut the apparent difference was not statistically sig-nificant (Musa et al., 2001).The mechanism(s) by which seed priming is able to

increase resistance to infestation and infection inmungbean and chickpea is unknown but there areseveral possibilities. Resistance might simply be areflection of plants having greater vigour following themore rapid emergence of primed seed. Kumar et al.(1989) linked higher yield in mungbean with successfulestablishment and early vigour. Rashid et al. (2004)analysed the components of yield and demonstrated thatpriming-related increases in biomass and grain yield ofmungbean were due to a combination of more plantsemerging and better performance per plant, the latterlinked to more rapid, vigorous growth and development.We can call this the ‘‘health’’ hypothesis, although itseems likely that plant resistance associated with vigouror health might be the resultant of many mechanisms.Rapid development of root systems following primingmay be particularly important. Singh et al. (1988)reported that varieties with early, deep rooting oftenyield well, particularly in drought conditions. Harris(1996) reported more prolific rooting in seedlingsderived from primed sorghum seeds and similarobservations were made on maize seedlings (L. Clark,pers. comm.). Priming has also been reported toincrease nodulation substantially in chickpea (Musaet al., 2001)

The faster development often associated with primedcrops might reduce the size of infection ‘‘windows’’. Thismight be applicable to chickpea and collar rot which is asoil-borne disease. It is possible that, since primedseedlings emerge more rapidly and thus spend less timewith sensitive tissues exposed to inoculum in the soil, thelevel of initial infection might be reduced. Fasterdevelopment in primed crops could also explain thereduced pod borer damage in chickpea reported byHarris et al. (1999) when pods mature earlier and podwalls thicken and become harder for larvae to penetrate.This ‘‘escape’’ hypothesis may also be valid formungbean and MYMV in this study if the primed cropbecame exposed to infection by whitefly at a later stageof development than the non-primed crop, since it is wellestablished that losses due to MYMV decrease as thetime of infection is delayed (e.g. Vohra and Beniwal,1979; Ahmad, 1991; Gill and Singh, 1999).The ‘‘health’’ and ‘‘escape’’ mechanisms are indirect

in their relation to disease and pest attack. A third, moredirect, mechanism is that of Systemic Acquired Resis-tance (SAR) that is analogous to the immune responsein animals. There are many reports of this in theliterature for many plant species, including mungbean(Poonam Jindal Sohal and Bajaj, 1998) although theexact nature of the elicitors, subsequent signallingpathways and final mode of action vary widely(Kessmann et al., 1994; Mishra and Raja, 1999;Hammerschmidt and Becker, 1997; Sticher et al.,1997). A common theme is often cell disruption causedby chemical, physical or microbiological elicitors fol-lowed by an ‘oxidative burst’—release of highly reactivechemicals such as superoxides or hydrogen peroxidethen rapidly increasing activity of enzymes such assuperoxide dismutase and peroxidase (Kombrink andSchmelzer, 2001). This hypersensitive response can thenresult in the accumulation of molecules such as salicylicacid and jasmonic acid that are thought to be signalsinvolved in the expression of systemic resistance in non-stimulated tissues (M!etraux, 2001). Rapid imbibition ofseeds, which is what happens during on-farm seedpriming, is known to disrupt cell membranes and causelocalised cell death in cotyledons and the embryonic axisof seeds (e.g. Powell and Mathews, 1978) and is knownto produce reactive oxygen species (Blokhina et al.,2003). It may be that on-farm seed priming might resultin a quasi-hypersensitive response, the effects of whichcould persist as a systemic resistance in seedlings.More detailed studies are necessary to resolve which,

if any, of the three hypotheses contributes to theobserved phenomenon of priming-induced resistance.Biochemical studies in primed seeds and seedlings tomeasure activities of molecules associated with thehypersensitive response would be a useful first stepbecause the authors know of no significant literature inthis field. The ‘‘escape’’ hypothesis could be tested by

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comparing primed and non-primed crops sown over arange of dates while monitoring the populationdynamics of pests (whitefly in the case of MYMV) anddiseases. It should be noted that this resistance, if real,might be transient and could breakdown if primed cropswere to be adopted widely and pest and diseasepopulations adjusted themselves accordingly.The current experiment was not designed to discrimi-

nate between the hypotheses described above but it didclearly demonstrate that the growth and yield of primedmungbean was much less adversely affected by MYMVthan that of the non-primed crop. Additional studies areplanned to confirm further the phenomenon of priming-induced resistance and to look at potential mechanismsin more detail.

Acknowledgements

The authors thank Dr. Sher Hassan for his guidanceand for the help of Mr. Muazam Stephen during thedisease survey. This paper is an output from projectR7438 funded by the UK Department for InternationalDevelopment (DFID) Plant Sciences Research Pro-gramme and administered by the Centre for Arid ZoneStudies. The views expressed are not necessarily those ofDFID.

References

Ahmad, Q., 1991. Growth attributes and grain yield of mungbean

plants affected by mungbean yellow mosaic virus in the field.

Indian Phytopathol. 43 (4), 559–560.

Ayub, M.A., Ilyas, M.B., 1988. Biology and control of mungbean yellow

mosaic virus disease—a review. In: Proceedings of the National

Seminar on the Role of Plant Health and Care in Agricultural

Production, 28–29 December 1988. Department of Plant Pathology,

University of Agriculture, Faisalabad, Pakistan, pp. 123–129.

Bashir, M., Hassan, A.S., 1998. Diagnostic Methods for Plant Viruses.

Pakistan Agricultural Research Council, Islamabad, Pakistan,

pp. 32–42.

Bashir, M., Mughal, S.M., Malik, B.A., 1991. Assessment of yield

losses due to urdbean leaf crinkle virus in urdbean, Vigna mungo

(L.) Hepper. Pak. J. Bot. 23 (1), 140–142.

Bashir, M., Ahmad, Z., Murata, N., 2000. Seed-Borne Viruses

Detection, Identification and Control. Pakistan Agricultural

Research Council, Islamabad, Pakistan, pp. 82–83.

Blokhina, O., Virolainen, E., Fagerstedt, K.V., 2003. Antioxidants,

oxidative damage and oxygen deprivation stress: a review. Ann.

Bot. 91, 179–194.

Gill, C.K., Singh, L., 1999. Effect of mungbean yellow mosaic virus on

yield components in a mungbean cultivar. Insect Environ. 5 (3),

112–113.

Government of Pakistan, 2002. Agricultural Statistics of Pakistan

2000–01. Ministry of Food, Agriculture and Livestock, Islamabad,

Pakistan. pp. 46–47.

Hammerschmidt, R., Becker, J.S., 1997. Acquired resistance to disease

in plants. Hort. Rev. 18, 247–289.

Harris, D., 1996. The effects of manure, genotype, seed priming, depth

and date of sowing on the emergence and early growth of Sorghum

bicolor (L.) Moench in semi-arid Botswana. Soil Till. Res. 40,

73–88.

Harris, D., Joshi, A., Khan, P.A., Gothkar, P., Sodhi, P.S., 1999. On-

farm seed priming in semi-arid agriculture: development and

evaluation in maize, rice and chickpea in India using participatory

methods. Exp. Agric. 35, 15–29.

Harris, D., Raghuwanshi, B.S., Gangwar, J.S., Singh, S.C., Joshi,

K.D., Rashid, A., Hollington, P.A., 2001. Participatory evaluation

by farmers of ‘on-farm’ seed priming in wheat in India, Nepal and

Pakistan. Exp. Agric. 37 (3), 403–415.

Harris, D., Rashid, A., Hollington, P.A., Jasi, L., Riches, C., 2002a.

Prospects of improving maize yields with ‘on-farm’ seed priming.

in: Rajbhandari, N.P., Ransom, J.K., Adikhari, K., Palmer, A.F.E.

(Eds.), Sustainable Maize Production Systems for Nepal: Proceed-

ings of a Maize Symposium held, December 3–5, 2001, Kathman-

du, Nepal. Kathmandu: NARC and CIMMYT, pp. 180–185.

Harris, D., Tripathi, R.S., Joshi, A. (2002b). ‘On-farm’ seed priming to

improve crop establishment and yield in dry direct-seeded rice. In:

Pandey, S., Mortimer, M., Wade, L., Tuong, T.P., Lopez, K.,

Hardy, B., (Eds.) Proceedings of the International Workshop

on Direct Seeding in Asian Rice Systems: Strategic Research

Issues and Opportunities, 25–28 January 2000, Bangkok, Thailand.

Los Banos (Philippines): International Rice Research Institute.

383pp.

Hassan, S., Khan, A., Stephen, M., 2003. Integrated Control of Viral

Diseases of Tomato in Malakand and Swat. Final Report 200-

2003. Faculty of Crop Protection Sciences, NWFPAU, Peshawar,

pp. 19–24.

Kaiser, W.J., Danesh, D., Okhovar, M., Mossahebi, H., 1968. Diseases

of pulse crops (edible legumes) in Iran. Plant Dis. Rep. 52, 687–691.

Kessmann, H., Staub, T., Hofmann, C., Maetzke, T., Herzog, J.,

Ward, E., Uknes, S., Ryals, J., 1994. Induction of systemic

acquired disease resistance in plants by chemicals. Ann. Rev.

Phytopathol. 32, 439–459.

Kombrink, E., Schmelzer, E., 2001. The hypersensitive response and

its role in local and systemic disease resistance. Eur. J. Plant Pathol.

107 (1), 69–78.

Kumar, R., Tyagi, C.S., Ram, C., 1989. Association of laboratory seed

parameters with field performance in mungbean. Seeds Farms 15

(4), 33–36.

M!etraux, J.P., 2001. Systemic acquired resistance and salicylic acid:

current state of knowledge. Eur. J. Plant Pathol. 107 (1), 13–18.

Mishra, S.K., Raja, R., 1999. Systemic acquired resistance: a review.

Annals Ag. Res. 20 (3), 249–259.

Musa, A.M., Harris, D., Johansen, C., Kumar, J., 2001. Short

duration chickpea to replace fallow after aman rice: the role of on-

farm seed priming in the High Barind Tract of Bangladesh. Exp.

Agric. 37 (4), 509–521.

Naseem, S.B., Khan, A.H., Islam, M., Mollah, U., Ali, M.A., 1997.

Effect of seeding methods and varying surface soil moisture on the

stand establishment of mungbean (Vigna radiata L.). Bangl. J. Sci.

Ind. Res. 32 (2), 295–301.

Poonam Jindal Sohal, B.S., Bajaj, K.L., 1998. Effect of uniconazole on

the polyphenol metabolism in the leaves of mungbean (Vigna

radiata L. Wilczek) infected with mungbean yellow mosaic virus.

Plant Physiol Biochem. (New Delhi) 25 (1), 62–66.

Powell, A.A., Matthews, S., 1978. The damaging effect of water

on dry pea embryos during imbibition. J. Exp. Bot. 29 (112),

1215–1229.

Rahmianna, A.A., Adisarwanto, T., Kirchhof, G., So, H.B., 2000.

Crop establishment of legumes in rainfed lowland rice-based

cropping systems. Soil Till. Res. 56 (1/2), 67–82.

Rashid, A., Harris, D., Hollington, P.A., Rafiq, M., 2004. Improving

the yield of mungbean (vigna radiata) in the north west frontier

province of Pakistan using on-farm seed priming. Exp. Agr. 40,

233–244.

ARTICLE IN PRESSA. Rashid et al. / Crop Protection 23 (2004) 1119–11241124

Singh, P., Singh, D.P., Kumar, A., Chaudhary, B.D., Thakural, S.K.,

1988. Response of mungbean–blackgram hybrids under water

stress conditions. In: Shanmugasundaram, S., McLean, B.T. (Eds.),

Mungbean. Proceedings of the Second International Symposium’

held in Bangkok, Thailand, 16–20 November 1987. pp. 263–271.

Sticher, L., Mauch-Mani, B., M!etraux, J.P., 1997. Systemic acquired

resistance. Ann. Rev. Phytopathol. 35, 235–270.

Vohra, K., Beniwal, S.P.S., 1979. Effect of mungbean yellow mosaic

virus on yield and seed quality of urdbean (Vigna mungo). Seed

Res. 7 (2), 168–174.