Australian Cool-Season Pulse Seed-Borne Virus Research: 2. Bean Yellow Mosaic Virus

Abstract

Here, research on seed-borne virus diseases of cool-season pulses caused by bean yellow mosaic virus (BYMV) in Australia's grain cropping regions since the 1940s is reviewed. A historical approach is taken towards all past studies involving the main cool-season pulse crops grown, lupin, faba bean, field pea, lentil and chickpea, and the minor ones, narbon bean, vetches and Lathyrus species. The main emphasis adopted is on describing what these studies revealed concerning BYMV biology, epidemiology and management. The field and glasshouse experimentation that enabled the development of effective phytosanitary, cultural and host resistance control strategies, supported by many image illustrations from past investigations, is emphasized. This review commences by providing brief background information and describing past studies on BYMV symptom and sequence variants, and alternative BYMV hosts. Next, as the lupin/BYMV pathosystem has been investigated in much greater depth than any other cool season pulse/BYMV pathosystem combination in Australia, what past studies using it have found is covered considerable detail under a series of nine different sub-headings. Finally, what is known about the less thoroughly investigated cool-season pulse/BYMV pathosystems, especially those involving faba bean, field pea and lentil, is reviewed under seven different sub-headings. Recommendations are provided concerning future research priorities.

Keywords: Australia; bean yellow mosaic virus; cool-season pulses; epidemiology; future research priorities; history; losses; main research achievements; management; seed-borne viruses; virus diseases.

Figure 1

Map showing both major and minor grain producing regions where pulses are grown in Australia. The acronyms of Australian states and territories used here are WA (Western Australia), SA (South Australia), VIC (Victoria), TAS (Tasmania), NSW (New South Wales), QLD (Queensland) and NT (Northern Territory). Australian Bureau of Meteorology (BOM) climate groupings are used to distinguish the main regions where grain crops (including pulses) grow, but letters distinguish the smaller irrigated grain production regions in WA—BR (Broome) and OR—Ord River Irrigation Area, the NT—DD—Douglas/Daly and K—Katherine, QLD—BU (Burdekin), BN—Bundaberg, G—Gilbert, F—Flinders and M—Mareeba (including Atherton and Ravenshoe) and NSW—NR—Northern Rivers. Black lines delineate boundaries of distinct agro-ecological zones. Image credit@Department of Primary Industries and Regional Development/P. Goulding.

Figure 2

Images of disease symptoms caused by infection with bean yellow mosaic virus (BYMV) in plants of the most widely grown cool-season pulse species for Australia. (A) Young narrow-leafed lupin (Lupinus angustifolius) plant showing early-phase systemic necrotic shoot symptoms typical of infection with its necrotic strain (prior to killing the plant) (at The Lakes in 1993). (B) Narrow-leafed lupin plant showing upper leaf symptoms typical of infection with its non-necrotic strain consisting of mosaic, accompanied by leaflet downcurling and size reduction (at Avondale in 1999). (C) White lupin (L. albus) cv. Lutop plant with typical leaf symptoms caused by BYMV infection consisting of mosaic, deformation and size reduction (at South Perth in 1990). (D) Lentil (Lens culinaris) cv. Digger plant with typical leaf symptoms caused by BYMV infection consisting of leaf mosaic, leaflet chlorosis, downcurling and reduction in size and plant dwarfing (at South Perth in 1996). (E) Apical portion of faba bean (V. faba) plant showing typical leaf mottle symptoms caused by BYMV infection (at South Perth in 1996). (F) Apical portion of field pea plant (Pisum sativum) showing typical leaf symptoms of mosaic and leaflet deformation caused by BYMV infection (at Medina in 1988). (G) Apical portion of chickpea (Cicer arietinum) cv. Heera shoot showing leaflet reddening symptoms caused by BYMV infection (at South Perth in 1998).

Figure 3

Images of disease symptoms caused by infection with bean yellow mosaic virus (BYMV) in species of alternative pasture hosts and screening procedure used to evaluate alternative host species for their susceptibilities and sensitivities to BYMV infection. (A) Subterranean clover (Trifolium subterraneum) cv. Karridale pasture with patch of stunted BYMV-infected plants indicated by white arrow (at Manjmup in 1990). (B) Close up of plants from stunted BYMV-infected subterranean cover patch in A showing leaflet symptoms of mottle, palor and deformation. (C) Individual plants within single-row plot of crimson clover cv. Caprera (T. incarnatum); BYMV-infected plant showing chlorosis and stunting (front) and normal-looking healthy plant (behind) (at Medina in 1996). (D) Plant of Moroccan clover (T. isthmocarpum) with obvious leaf-vein-clearing symptoms in young leaves caused by BYMV infection at (at Narikup in 1998). (E) Early phase of potential alternative host genotype susceptibility/resistance screening process showing stunted BYMV-infected subterranean clover transplants placed at both ends of each row to provide a uniform BYMV infection source for naturally occurring aphid vectors to spread the virus to the test rows. After they became BYMV infected, originally healthy clover transplants placed in between the infector transplants boosted the virus inoculum source for BYMV spread to the test rows. Sticky yellow traps used to monitor aphid flights (at South Perth in 1990). (F) Single-row plots of potential alternative host genotypes (mainly pasture legume species) surrounded by a non-host oat (Avena sativa) barrier undergoing BYMV susceptibility/resistance screening (at South Perth in 1990).

Figure 4

Images of disease symptoms caused by infection with bean yellow mosaic virus (BYMV) in different crop and potential crop lupin species. (A–E) Different phases of symptom development elicited by early infection of narrow-leafed lupin (Lupinus angustifolius) with BYMV necrotic strain. (A) Initial systemic ‘Shepard’s crook’ symptom consisting of bending over of the shoot tip caused by recent infection (at South Perth in 1986). (B) Next phase of early systemic symptom consisting of apical shoot necrosis (at The Lakes in 1993). (C) Later phase of infection spread consisting of apical systemic necrosis having spread to all shoots (at Woogenellup in1988). (D) Final phase of infection spread resulting in death of all shoots (at South Perth in 1992). (E) Situation where both the necrotic BYMV strain (left) and cucumber mosaic virus (right) were spreading within the same young narrow-leafed lupin cv. Gungurru stand; plant on left shows early phase of systemic necrosis symptoms whereas youngest leaves of plants on right show symptoms of leaflet chlorosis, downcurling and size reduction (plants at back healthy) (at Wongan Hills in 1995). (F) Late-infection BYMV necrotic strain occurring after flowering eliciting ‘black pod syndrome’ (at South Perth in 1995). (G–I) Different symptoms elicited by infection of narrow-leafed lupin with BYMV non-necrotic strain. (G) Early systemic symptom in upper leaves consisting of leaflet chlorosis, downcurling and size reduction (at Avondale in 1999). (H) Later phase of symptom development where upper portion of infected plant shows symptoms of leaf mosaic, chlorosis, deformation and size reduction, whereas lower down the leaf, appearance remains unaffected (at Avondale in 1999). (I) Later phase of infection occasionally observed where the only symptoms visible were upper fleshy, expanded and downcurled leaves and plant dwarfing (at The Lakes in 1993). (J) Glasshouse aphid transmission test with narrow-leafed lupin cv. Danja showing 2 plants killed by inoculation with necrotic strain isolate MI (right), with stunted growth caused by inoculation with non-necrotic isolate La-NN (middle) and healthy controls (left) (at South Perth in 1994). (K) Plant of white lupin (L. albus) cv. Ultra showing BYMV foliage symptoms consisting of severe leaf mottle and deformation and plant dwarfing (at South Perth in 1990). (L) Plant of yellow lupin (L. luteus) cv. Reda showing foliage symptoms of leaflet chlorosis, narrowing and reduced size (front) contrasting with larger darker green healthy leaves of neighboring plant (behind on left side) (at South Perth in 1990). (M) Plant of the rough-seeded lupin species, sandplain lupin (L. cosentinii). cv. Eragulla, showing foliage symptoms of severe leaf mottle, deformation and size reduction and plant dwarfing (front) contrasting with normal foliage of a healthy plant (behind) (at South Perth in 1989). (N) Plant of the rough seeded lupin species L. pilosus showing foliage symptoms of severe leaf mottle, deformation and size reduction in its upper leaves (center) contrasting with the foliage of heathy plants (on both sides) (at South Perth in 1987). (O) Plant of the rough-seeded lupin species L. digitatus showing foliage symptoms of severe leaf mottle, deformation and size reduction in its upper leaves and stunting (center) contrasting with the foliage of heathy plant (behind) (at South Perth in 1993).

Figure 5

Images of cultural control experiments examining the effects of reflective mulch, non-host barriers, admixture with a non-host and different plant densities upon spread of bean yellow mosaic virus (BYMV) necrotic strain from an external source into narrow-leafed lupin (Lupinus angustifolius) stands. (A) Small-scale field experiment evaluating the effectiveness of reflective mulch in reducing BYMV and cucumber mosaic virus spread into single-row plots of narrow-leafed lupin by reducing aphid landing rates (at South Perth in 1988). (B) Typical design of large-scale field experiments used to study the effectiveness of different cultural control measures at reducing BYMV spread into narrow-leafed lupin crops from a nearby virus source. The plots were arranged in single file at the crop edge and were separated from the pasture by a cultivated fallow strip (at Badgingarra in 1994). (C) Non-host oat barrier plots of 30 m long × 15 m wide trip (front) that diminished BYMV spread to a narrow-leafed lupin cv. Danja crop (behind). These were alternated with fallow plots 30 m long × 15 m wide (not shown are images of fallow plots that failed to diminish BYMV ingress into the crop) (at Narrogin in 1987). (D) Design of large-scale field experiment used to study admixture with a non-host (oats) upon the spread of BYMV into lupin crop (behind). Plots of each type were alternated and numbers of BYMV-affected lupin plants were counted within a central 10 m × 10 m square within each plot (at Mount Barker in 1989). (E) Appearance of plants within an oat–lupin admixture plot (at Mount Barker in 1989). (F) Example of a field experiment examining the effect of plant density upon the spread of BYMV into narrow-leafed lupin plots arranged in a single file at the crop edge. Plots were sown at seedling rates of 25, 50, 75, 100 and 125 kg/ha in a randomized block design and were separated by a 1.5 m wide non-host (wheat) buffer (at Avondale in 1991).

Figure 6

Images of cultural control experiments examining the effects of different plant densities (1990–1991) or plant densities, row spacings and stubble retention (1992), upon spread of bean yellow mosaic virus (BYMV) necrotic strain from an external infected subterranean clover pasture source into narrow-leafed lupin (Lupinus angustifolius) stands. (A) Appearance at end of growing season of plot originally sown at the low seeding rate of 25 kg/ha in which many plants had been killed or were being killed by infection with BYMV necrotic strain (due the lack of any groundcover or canopy cover that would reduce aphid vector landings) (at Avondale in 1991). (B) Appearance at end of growing season of plot originally sown at the high seeding rate of 125 kg/ha lacking visible damage from BYMV infection (because the high plant density prior to canopy closure and resulting rapid canopy development had helped repel incoming aphid vector landings) (at Avondale in 1991). (C) Small-scale field experiment in which centrally placed yellow water traps caught aphids flying over plots with or without straw added at 2 t/ha (at South Perth in 1992). (D) Close up of soil surface within the small-scale field experiment showing yellow water trap placement and distribution of added straw (at South Perth in 1992). (E) Close up of soil surface showing distribution of added straw within a plot with recently germinated lupin seedlings from a field experiment examining the effects of straw mulch (2 t/ha), row spacing and plant density upon BYMV spread; plot sown at low seeding rate of 30 kg/ha and narrow row spacing of 17.5 cm (at Badgingarra in 1992). (F) Appearance of plot without added straw originally sown at the low seeding rate of 30 kg/ha with wide row spacing of 35 cm with many plants being killed by infection with necrotic BYMV (due lack of sufficient groundcover or adequate canopy cover that would reduce aphid vector landings) (at Badgingarra in 1992). (G) Appearance of plot with added straw at 2 t/ha originally sown at the low seeding rate of 30 kg/ha with wide row spacing of 35 cm in which fewer plants were being killed by infection with necrotic BYMV (due to reduced aphid vector landings resulting from straw groundcover presence) (at Badgingarra in 1992). (H) Appearance of plot with straw mulch added at 2 t/ha originally sown at the normal seeding rate of 60 kg/ha with wide row spacing of 35 cm in which few plants were being killed by infection with necrotic BYMV (due to reduced aphid vector landings resulting from presence of straw groundcover and the greater plant density within rows) (at Badgingarra in 1992). (I) Appearance of reference plot without added straw originally sown at the high seeding rate of 100 kg/ha with narrow row spacing of 17.5 cm in which very few plants were killed by infection with necrotic BYMV (due to reduced aphid vector landings resulting from greater plant density within rows and rapid plant canopy development covering the bare ground in between narrowly spaced rows) (at Badgingarra in 1992).

Figure 7

Images of bean yellow mosaic virus (BYMV) symptoms from host resistance studies with narrow-leafed lupin (L. angustifolius) and other lupin species. (A) Annual lupin BYMV resistance screening employing single row plots containing cultivars, breeding lines and germplasm accessions of different lupin species. Subterranean clover transplants infected with BYMV necrotic strain isolate MI placed at both ends of each plot to ensure a uniform inoculum source for spread by naturally occurring aphids to the lupin rows (at South Perth in 1993). (B) Recording spread of BYMV infection in annual lupin BYMV resistance screening focused on cultivars, breeding lines and germplasm accessions of narrow-leafed lupin. Note smaller BYMV-infected subterranean clover virus source plants at both ends of each row with larger initially healthy source subterranean clover source plants in between each of them that, once infected, increased virus source potency for spread to the lupin rows (at South Perth in 1997). (C) BYMV necrotic strain spread within a plot of narrow-leafed lupin causing systemic necrotic symptoms at different stages of development in infected plants (at South Perth in 1992). (D) BYMV necrotic strain spread along an entire single-row plot of sandplain lupin (L. cosentinii) cv. Eragulla causing non-necrotic symptoms of severe leaf mosaic, deformation, reduction in size and plant stunting (at South Perth in 1995). (E) BYMV necrotic strain spreading within a plot of narrow-leafed lupin causing systemic necrotic symptoms at different stages of development within infected plants (at South Perth in 1992). (F) BYMV necrotic strain spreading within a plot of narrow-leafed lupin causing systemic necrotic symptoms at different stages of development within infected plants (at South Perth in 1997). (G) BYMV necrotic strain symptoms within a plot of narrow-leafed lupin germplasm accession P26697 in which, instead of causing necrotic symptoms, this strain elicited non-necrotic symptoms consisting of systemic mosaic and leaf deformation (central row) contrasting with rows of other accessions in which the plants were killed (rows in front in bottom right position and behind in top left position) (at South Perth in 1995). (H) Aphid transmissions with BYMV to plants of narrow-leafed lupin cv. Danja, uninoculated control plant (left), necrotic isolates MI (center left) and LP (center right) causing systemic necrosis and plant death, and non-necrotic isolate LKtg2-NN causing upright habit, decreased leaf size and stunting (right). (I) Aphid transmissions with BYMV to plants of narrow-leafed lupin accession number P26697, uninoculated control plant (left), necrotic strain isolate MI (center) causing upright habit, decreased leaf size and stunting, necrotic strain isolate LP (right) causing the necrotic symptoms systemic necrosis and plant death. (J) Aphid transmissions with BYMV to plants of white lupin (L. albus) cv. Kiev Mutant: uninoculated control plant (left), non-necrotic strain isolate LKtg1-NN (center) causing mild upright habit and decrease in leaf size, and non-necrotic strain isolate LEsp-NN (right) causing severe upright habit, pallor and decrease in leaf size. (K) Aphid transmissions to F2 narrow-leafed lupin progeny plants from the cross P26697 × Merrit demonstrating non-necrotic plant dwarfing (center) and plant death (right) caused by necrotic BYMV strain isolate MI; healthy plant (left).

Figure 8

Images from studies on the temporal and spatial spread patterns of necrotic and non-necrotic bean yellow mosaic virus (BYMV) strains in narrow-leafed lupin (Lupinus angustifolius) (A–D,F–J) or both narrow-leafed and yellow (L. luteus) lupin (E). (A) Commercial crop of lupin cv. Merrit at site 1 into which BYMV necrotic strain was spread from an adjacent BYMV-infected subterranean clover pasture across a 10 m wide dirt track by naturally occurring aphid vectors (at The Lakes in 1993). (B) Close up of the cv. Merrit crop margin at site 1 showing high incidence of plants with necrotic BYMV symptoms moving from shoot apices to the rest of the infected plant (at The Lakes in 1993). (C) Gradient of plants symptomatic for BYMV necrotic strain in the cv. Merrit crop at site 1, starting at the crop edge closest to the BYMV-infected pasture source with fitted exponential line 7.76 + 43.7 (0.8406x) (at The Lakes in 1993). (D) Gradients of plants symptomatic for BYMV necrotic strain in a commercial lupin cv. Gungurru crop at site 2, starting from the crop edge bordering either a perimeter oat barrier 20 m wide that separated adjacent infected pasture from the crop with fitted linear line 6.561 − 0.1511x (red line) or internal tracks containing BYMV-infected clovers with fitted exponential line 7.308 + 37.7 (0.27x) (black line) (at West Dale in 1994). (E) Disease progress curves for BYMV comparing the spread of its necrotic (N) and non-necrotic (NN) strains in plants within replicated single-row (2.5 m) plots of cv. Merrit (a), breeding line 90L423-07-13 (b) or of both strains combined in Merrit, breeding line 90L423-07-13 or yellow lupin cv. Wodgil (c) (at South Perth in 1998). (F) Example of field experiment examining spread of necrotic and non-necrotic BYMV strains from introduced BYMV-infected subterranean clover (Trifolium subterraneum) infector plants within replicated cv. Gungurru lupin plots (17 × 18 m) arranged in a randomized block design and each surrounded by 5 m wide non-host canola (Brassica napus) buffers (at Avondale in 1998). (G) Early phase of BYMV spread by naturally occurring aphid vectors from a focus of subterranean clover transplants infected with necrotic strain isolate MI either killing or in the process of killing surrounding plants, each of which were tagged with different colored tapes; tape color indicated tagging date (exp 2, at Avondale in 1998). (H) Early phase of BYMV spread by naturally occurring aphid vectors from a focus of subterranean clover transplants infected with non-necrotic strain isolate LKoj1-NN causing apical chlorosis and stunting in surrounding plants, each of which were tagged with different colored tapes; tape color indicates tagging date (exp 2, at Avondale in 1998). (I) Intermediate phase of BYMV spread by naturally occurring aphid vectors causing plant death, or in the process of killing plants, growing in the vicinity of the original necrotic strain isolate MI infection focus; color-coded wooden stakes positioned next to each infected plant indicate tagging date (exp 3, at Avondale in 1999). (J) Intermediate phase of BYMV spread by naturally occurring aphid vectors causing leaf mosaic, chlorosis and size reduction and smaller sized plants growing in the vicinity of the original non-necrotic strain isolate LKoj1-NN infection focus; color-coded wooden stakes positioned next to each infected plant obscured by infected plant foliage growth (exp 3, at Avondale in 1999).

Figure 9

Images from studies on spatial patterns of spread of necrotic and non-necrotic bean yellow mosaic virus (BYMV) strains (A–D) or quantifying seed yield losses caused by its non-necrotic strain in narrow-leafed lupin (Lupinus angustifolius) (E–G). (A) Late phase of BYMV spread by naturally occurring aphid vectors causing plant death or in the process of killing lupin plants over a wider area around the original necrotic strain isolate MI infection focus; color-coded wooden stakes positioned next to each infected plant indicate tagging date (exp3, at Avondale in 1999). (B) Late phase of BYMV spread by naturally occurring aphid vectors causing leaf mosaic, chlorosis and size reduction and smaller sized plants affecting most of the lupin plants after spreading from the original non-necrotic strain isolate LKoj1-NN infection focus; color-coded wooden stakes positioned next to each infected plant now obscured by infected plant foliage growth, so late-infected plants are tagged with colored tape (exp 3, at Avondale in 1999). (C) Maps of clustering indices (v) for cumulative numbers of narrow-leafed lupin cv. Gungurru plants with BYMV symptoms at the ‘natural spread site’ in an area defined by (5 < x axis < 20, 15 < y axis < 20), comparing necrotic (270 infections) with non-necrotic (269 infections) BYMV at 137 days after sowing. Non-necrotic strain (map below) spread more widely than necrotic strain (map above). Axes show distances in meters and top axis, the boundary with adjacent BYMV-infected pasture. Red and blue spots and circles represent units denoting infection patches with ν > 0 (red) and infection gaps with ν < 0 (blue), respectively. Circles represent clustering indices of 0 to +/− 0.99 (clustering below expectation), small spots +/− 1 to +/− 1.49 (clustering exceeds expectation) and large spots > 1.5 or <−1.5 (half as much again as expectation). Red lines enclosing patch clusters are contours of ν = 1.5 and blue lines enclosing gap clusters are of ν = −1.5. Black lines are zero-value contours, representing boundaries between patch and gap regions where the count is close to the sample mean (natural spread site, at Mount Barker in 1998). (D) Maps of clustering indices at 144 days after sowing for cumulative numbers of narrow-leafed lupin cv. Gungurru plants with necrotic (left map) and non-necrotic (right map) BYMV symptoms in plot without introduced foci. Non-necrotic strain spread much more widely than necrotic strain. Symbols, contours and axes as for Figure 9C (exp 3, at Avondale in 1999). (E) Overview of field experiment with a randomized block design quantifying seed yield losses caused by BYMV non-necrotic strain in 5.6 × 15 m cv. Tanjil plots (green) surrounded by 5 m wide non-host canola buffers in flower (yellow) (at Avondale in 2001). (F) Initial BYMV spread from infected subterranean clover transplant to nearby plants in central row within plot of field experiment quantifying seed yield losses caused by BYMV non-necrotic strain (at Avondale in 2001). (G) Patch of shorter plants with non-necrotic BYMV symptoms (paler foliage, mostly not flowering yet) surrounding introduced BYMV infection focus within plot of field experiment quantifying seed yield losses caused by BYMV non-necrotic strain in narrow-leafed lupin (at Avondale in 2001).

Figure 10

Images from aphid vector, epidemiology and forecasting studies with bean yellow mosaic virus (BYMV) in narrow-leafed lupin (Lupinus angustifolius). (A) Net employed to trap and collect flying airborne winged vector aphids downwind of virus-infected lupin stands for use in virus transmission studies (at South Perth in 1996). (B) Dense population of critical BYMV vector aphid Myzus persicae (green peach aphid) colonizing lupin shoot. (C) Example of alate and apterous BYMV vector aphid Acyrthosiphon kondoi (bluegreen aphid) colonizing a leaf petiole. (D) Example of apterous adult and nymphal growth stages of BYMV vector Rhopalosiphum padi (oat aphid) colonizing a cereal leaf. (E) Diagrammatic overview summarizing the four main components of the overall forecasting model for BYMV infection of lupin crops (pasture biomass, background aphids, crop aphids and crop BYMV infection) and how they are inter-related. Solid outlines represent parameters and variables for perimeter populations of aphid vectors and lupins or those that are equal for both perimeter and interior populations; dashed outlines represent variables from the interior populations of aphid vectors and lupins. (F) BYMV-lupin pathosystem risk map produced for 1999 by the modeling framework for different districts in the southwest Australian grainbelt. Colors represent 90–100% to 0–10% BYMV incidence in lupin crops. (C) Image credit @Department of Primary Industries and Rural Development/Deborah Thackray.

Figure 11

Images showing symptoms caused by bean yellow mosaic virus (BYMV) infection in foliage of minor cool-season pulses (A–E) and seeds of faba bean (Vicia faba) (F,G). (A) Plant of common vetch (Vicia sativa) with symptoms of yellow mosaic in leaflets of young leaves infected with BYMV (at South Perth in 1998). (B) Plant of narbon bean (V. narbonensis) with severe foliage symptoms consisting of leaf chlorotic mosaic, deformation and reduced size and plant stunting (at South Perth in 1998). (C) Plants of grass pea (Lathyrus sativus) with severe symptoms consisting of leaf chlorosis, deformation and reduced size, and plant stunting (at South Perth in 1998). (D) Plant of dwarf chickling (L. cicera) with severe symptoms consisting of leaf chlorotic mosaic, deformation and reduced size and plant stunting (center) and healthy plant within same row (upper left) (at South Perth in 1997). (E) Plant of L. ochrus with severe foliage symptoms in young leaves consisting of leaf palor, deformation and reduced size (at South Perth in 1997). (F) Row of faba bean cv. Fiesta seeds from BYMV-infected plant with surface necrotic markings, malformation and size reduction (right) and row of seeds from healthy plant (left) (at Avondale in 1999). (G) Seeds harvested from BYMV-infected faba bean plants growing in the Middle East with surface necrotic markings, malformation and size reduction (right) or from healthy plants (left). (G) Image credit@International Center for Agricultural Research in the Dry Areas/Khaled Makkouk.

Figure 12

Images showing foliage symptoms caused by bean yellow mosaic virus (BYMV) infection from host resistance studies with cool-season pulses other than lupin. (A) BYMV resistance screening employing single-row plots containing cultivars, breeding lines and germplasm accessions of different cool-season pulses excluding lupin (Lupinus spp.). Subterranean clover (Trifolium subterraneum) transplants infected with BYMV necrotic strain isolate MI placed at both ends of each plot to ensure a uniform inoculum source for spread by naturally occurring aphids to the test rows (at South Perth in 1994). (B) BYMV resistance screening employing single-row plots containing lentil (Lens culinaris) cultivars, breeding lines and germplasm accessions; two healthy breeding line ILL7 136 rows visible and all other rows infected, showing leaf chlorosis, size reduction and premature senescence (at South Perth in 1997). (C) Single row of BYMV-resistant lentil breeding line ILL7 136 plants with healthy appearance (left) compared with susceptible plant row showing BYMV symptoms consisting of leaf chlorosis and plant stunting (right) (at South Perth in 1997). (D) Leaf of faba bean cv. Barkool (Vicia faba) plant sap inoculated with BYMV isolate LP showing severe mosaic symptoms (right) and uninocuated healthy leaf (left) (at South Perth in 1998). (E) Leaf of faba bean cv. Icarus sap inoculated with BYMV isolate MI causing necrotic local lesions without further virus spread, representative of localized hypersensitive resistance (at South Perth in 1998). (F) Lentil seedlings aphid inoculated with BYMV isolate MI showing symptoms of leaf pallor and premature senescence and severe plant stunting in susceptible cv. Digger (left) compared with healthy growth in breeding line ILL 7163 (right) (at South Perth in 1998). (G) Upper portion of chickpea (Cicer arietinum) cv. Heera shoot showing symptoms of apical necrosis from a plant that was aphid-inoculated with BYMV isolate LEsp-NN (at South Perth in 1998). (H) Upper portion of narbon bean (V. narbonensis) shoot showing leaf symptoms of severe mosaic, deformation and size reduction from a plant sap inoculated with BYMV isolate MI (at South Perth in 1998). (I) Upper portion of dwarf chickling (Lathyrus cicera) breeding line Lath-BC shoot showing leaf symptoms of severe mosaic, pallor, downcurling and size reduction from a plant aphid inoculated with BYMV isolate LWh-NN (at South Perth in 1998). (A,B) image credit@Department of Primary Industries and Rural Development/Simon McKirdy. (E,G,H) image credit@Department of Primary Industries and Rural Development/Yvonne Cheng.