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PVX has a wide natural server stove, occurring in at least 62 plant species of 27 families ( Edwardson and Christie, 1997 ). The virus is specially significant worldwide in potato ( Bode, 1968 ; Beemster and de Bokx, 1987 ) and in many countries in a few major solanaceous crops including peppers ( Paulus et al., 1960 ; Steepy et al., 1967 ; Fribourg and Fernandez-Northcote, 1972 ; Makkouk and Gumpf, 1974 ), tobacco ( Hansen, 1946 ; Bode, 1953 ; Bode and Klinkowski, 1968 ), and tomato ( Vanterpool, 1926 ; Ainsworth, 1934 ). Although many of its natural hosts are weeds, PVX besides occurs naturally in other crop species including winter cherry ( Nicandra physalodes ) and turnip ( Brassica rapa ) in India ( Sangar et al., 1980 ; Samad et al., 1991 ), artichoke ( Cynara scolymus ) and grapevine ( Vitis vinifera ) in Italy ( Chabbouh et al., 1990 ; Giunchedi, 1973 ), and crimson clover ( Trifolium pratense ) in Belarus ( Ambrosov and Bltoskaya, 1978 )
Earlier reports of the effects of PVX on the increase and move over of septic potatoes are inconsistent, credibly due to infection by virus strains of different virulence, the manipulation of cultivars differing in allowance and/or electric resistance, the happening of unsuspected virus mixtures, different environmental conditions ( particularly soil fertility and fertilizer treatments ), date of reap and the earlier lack of comparable virus-free plants necessary for critical comparative tests.
As most strains of PVX induce only inconspicuous or asymptomatic infections in many potato cultivars, mild strains were early thought to be of little economic importance ( Bald, 1944 ; Clinch and McKay, 1947 ). For case, no statistically significant yield reductions were recorded in curriculum vitae Up-to-Date, Arran Banner, Majestic or President in Eire ( Clinch and McKay, 1947 : McKay and Loughnane, 1953 ), curriculum vitae Kennebec and Katahdin in Maine, USA ( Murphy et al., 1966 ), and in one hundred five. Sebago in Ontario ( Rowberry and Johnston, 1975 ) and cv Netted Gem ( syn. Russet Burbank ) in British Columbia, Canada ( Wright, 1970 ). By contrast, commonly-occurring isolates of the virus have been reported to reduce tuber yields of many potato cultivars by 2-23 % ( Emilsson and Gustafsson, 1956 ; Sung, 1967 ; Bode, 1968 ; Mellor and Stace-Smith, 1977 ; Beemster and de Bokx, 1987 ). therefore, tuber yield losses of 2-7 % have been recorded in curriculum vitae Alpha and Up-to-Date, of 7-9 % in one hundred five Bintje in Denmark ( Hansen, 1963 ), and of 5-20 % in respective cultivars in Australia ( Norris, 1953 ). give way reductions of 12 % have been recorded in one hundred five Up-to-Date in Australia ( Bald, 1943 ) and one hundred five Russet Burbank ( from 40.6 to 35.7 t/ha ) in British Columbia, Canada ( Wright, 1977 ) and, in the USA, of 7.3 % in one hundred five Mohawk, 11.2 % in curriculum vitae Kennebec, 13.7 % in curriculum vitae Chippewa, 14.9 % in one hundred five Katahdin, 16 % in one hundred five Sebago, and 18.3 % in one hundred five Teton in Maine ( Bonde and Merriman, 1951 ), 17.5 % in one hundred five Sebago ( Lim et al., 1966 ), 21.9 % in one hundred five Red Pontiac ( Hoyman, 1964 ), and 9-32 % depending on year ( Davies and Allen, 1984 ) or 23 % ( from 353 to 272 cwt/acre ) in one hundred five Russet Burbank in Idaho ( Ohms et al., 1977 ). It has been estimated that from 1931-1951 PVX caused an annual render passing in the USA of 13 % ( 110,000 bushels ), a decrease two times greater than the blend effects of late blight and Rhizoctonia ( Chester, 1955 ).
More deadly strains can reduce yields of intolerant cultivars by up to 50 % ( Broadbent et al., 1962 ; Romanova and Reifman, 1978 ; Beemster and de Bokx, 1987 ). In England, PVX caused an modal annual give loss of three cultivars over three years of 30 % ( from 2.25 to 0.72 lb/plant ). similarly, a virulent stress in the USSR caused a render decrease of 43 % in the one-fourth year of production ( Romanova and Reifman, 1978 ). such yield losses normally result from the output of smaller tubers ( Broadbent et al., 1962 ; Sung, 1967 ; Manzer 1978, 1979 ; Davies and Allen, 1984 ).
In summation to reducing yield, PVX besides reduces the dry matter capacity of tubers which is specially important in the potato serve diligence ( Emilsson and Gustafsson, 1956 ; Hansen, 1974 ) ; in Denmark, PVX-infected one hundred five Dianella yielded 12.3 triiodothyronine dry matter/ha, 3 % less than virus-free standard ( Hansen, 1974 ). PVX besides reduces the number and burden of microtubers produced in vitro by septic plants derived from meristem tip culture ( El-Fiki et al., 1992 ).
PVX can besides have derived function effects on plants infected during the current grow temper ( elementary infection ) and those grown from infect seed potatoes ( secondary infection ). thus, although a mild tense had no effect on marketable yield ( i.e. of tubers > 3.5 centimeter in diameter ) of chiefly infected curriculum vitae Kerr ‘s Pink in Eire ( Dowley, 1973 ), secondary coil infection resulted in a give way reduction of 5.7 % ( from 47,910 to 45,170 kg/ha ).
environmental conditions can besides greatly affect the emergence of infect potato plants. therefore, in a comparison of virus free plants and those infected with a meek strive of PVX, a meaning concede loss was recorded at only one of three experimental sites ( Richmond ) in New York State, USA ( Teri et al., 1977 ) : bastardly annual yields of curriculum vitae Hudson, Katahdin and Bake King over three years were reduced by 8.5 %, i.e. from 44.39 to 40.64 lb/plot ( 20 foot individual row ). In Armenia, PVX-induced crop losses were 8.2 and 11.3 % from crops grown in unfavorable or favorable production areas, respectively ( Sgoyan, 1974 ). exchangeable results have been reported from the former USSR ( Bobryshev et al., 1972 ).
Fertiliser applications besides affected the comparative yields of goodly and infect one hundred five Russet Burbank plants in Idaho ( Ohms et al., 1977 ) ; thus, virus-free plants outyielded septic plants by 70, 78, 81 and 95 cwt/ha after applications of 0, 80, 160 and 240 lb/acre of nitrogen, respectively.
Yield loss of potato tubers is besides correlated with the incidence of infection in a snip ; frankincense, infection levels of 10, 50 and 100 % of curriculum vitae Bintje by a meek PVX stress in the Netherlands resulted in repress yields of ca 1, 4 and 10 %, respectively ( Beukema and van five hundred Zaag, 1979 ). In Idaho, infection levels of 36 and 88 % in one hundred five Russet Burbank resulted in output losses of 21 and 36 %, repectively ( Davis and Allen, 1984 ).
There are conflicting reports on the effects of virus infection on the susceptibility of potatoes to fungal pathogens. PVX-infected potatoes were reported to be less susceptible to Phytophthora infestans ( Muller and Munro, 1951 ) and Fusarium roseum in the USA ( Jones and Mullin, 1974 ; Mullen and Bateman, 1975 ; Manzer et al., 1978 ), but to be more susceptible to Rhizoctonia solani in eastern Europe ( Komkov, 1975 ). It has besides been reported that PVX-infection may increase the susceptibility of some cultivars to blight ( Pietkiewicz, 1974 ; Dowley, 1973 ) ; however, the increased susceptibility reported by Dowley ( 1973 ) occurred in tubers harvested from primary-infected, but not secondary-infected, plants.
PVX is of a lot greater importance when it occurs together with other viruses, specially potato virus Y ( PVY ), potato virus A ( PVA ) or potato virus S ( PVS ). It has farseeing been known that PVX and PVA in combination, but neither alone, cause the alleged wrinkle disease of potato in North America and Europe. Plants containing both viruses are hard stunted and bushy with pucker, brittle and diffusely chlorotic leaves ; some affected plants may die ( Murphy, 1921 ; Murphy and McKay, 1932 ; Clinch and Loughnane, 1933 ; Bode, 1968 ). In Italy, the bearing of both viruses caused a return reduction in one hundred five San Michele of 40 %, from 1.042 to 0.633 kg/plant ( Gregorini and Lorenzi, 1974 ).
PVX and PVYo together cause the unusually severe rugose mosaic disease of potato which, although originally described in the USA, besides occurs in S. America, Europe and elsewhere ( Smith, 1931 ; Bode, 1968 ; Guerrero-Guerrero and Martinez-Lopez, 1980 ). Mature leaves of septic plants have total darkness necrotic veins and younger leaves are mottled ; such plants are frequently dwarfed, produce smaller tubers and, if hard affected ( for model, one hundred five Green Mountain ) often die prematurely ( Brentzel, 1935 ). In such shuffle infections, PVYo induces a tenfold increase in the concentration of PVX in potato and tobacco plants ( Rochow and Ross, 1955 ; Ross, 1957 ). yield losses resulting from infection by PVY alone and with PVX were 57 and 71 %, respectively ( Corsini et al., 1983 ).
give losses induced by PVS are increased when PVX besides occurs in infect plants. Thus the tuber render of curriculum vitae Russet Burbank plants infected by PVS alone in Maine, USA was reduced by 3.8 %, but by 6.2 % and 6.8 % when co-infected with a meek and a reasonably severe tenor of PVX, respectively ( Manzer et al., 1978 ) ; concede losses in one hundred five Kennebec were 4 % ( PVS alone ), and 3.9 % ( PVS plus mild PVX ) and 8.1 % ( PVS plus chasten PVX ) and in one hundred five Katahdin were 1 % ( PVS alone ), 4.2 % ( PVS plus balmy PVX ) and 9 % ( PVS plus moderate PVX ).
Average tuber yields ( kg/plot* ) over 3 years of 3 potato cultivars infected with PVS and PVX
Russet Kennebec Katahdin
Virus-free 23.18 27.86 24.00
PVS 22.28 ( 3.8 % ) ** 26.74 ( 4.0 % ) 23.75 ( 1.0 % )
PVS + mild PVX 21.73 ( 6.2 % ) 26.78 ( 3.9 % ) 22.98 ( 4.2 % )
PVS + 21.59 ( 6.8 % ) 25.59 ( 8.1 % ) 21.84 ( 9.0 % )
tone down PVX
* Each diagram was a unmarried quarrel of 6.1 m
** move over loss ( % ) compared with virus-free plants.
In Bulgaria, PVS entirely reduced the yield of curriculum vitae Saskia by 4.3 % whereas infection by both PVS and PVX caused a loss of 22.3 % ( Asenov, 1986 ). In the USA, PVS alone reduced the render of one hundred five Sebago by 6 % whereas together with PVX the passing was 15 % ( Lim et al., 1966 ).
The duration of the growing season can besides influence the effect that infection has on give ( Manzer et al., 1979 ). thus, late harvested, but not early harvested, virus-free plants of curriculum vitae Kennebec in Maine, USA outyielded those infected with PVS and a mild strive of PVX by 5.9 % ( from 26.25 to 24.70 kg/plot of 6.1 m single row ; beggarly yields over three years ). Although the succumb of the virus-free plants was higher, those infected with both viruses produced more but smaller tubers ( i.e. a annual average over three years of 144 and 136 tubers from infected and healthy plants, respectively.
Peppers (Capsicum annuum and C. pendulum)
In C. annuum in the USA, PVX causes mottle and severe necrosis of leaves and stems and, finally, defoliation of some cultivars including curriculum vitae Yolo Wonder and Trueheart Perfection ( Paulus et al., 1960 ; Steepy et al., 1967 ; Makkouk and Gumpf 1974 ). PVX and Potato virus Y together are the cause of severe systemic leaf chlorosis and deformation of C. pendulum plants in Peru ( Fribourg and and Fernandez-Northcote, 1972 ). Although the effects of virus infection on the increase and output of peppers has not been determined, its severe effects on infect plants indicate that it would cause significant succumb reductions.
PVX causes hard leaf mottling and/or necrotic blemish in naturally infected tobacco plants, but the consequence of infection on render and quality has not been reported ( Hansen, 1946 ; Bode, 1953 ; Bode and Klinkowski, 1968 ).
PVX alone causes flick mosaic and slight stunt in naturally infected glasshouse-grown tomato plants in the UK, Germany, Crete and elsewhere ( Ainsworth, 1934 ; Klinkowski and Uschdraweit, 1968 ; Avgelis, 1986 ). A severe necrotic disease, designated tomato double virus streak, has long been known to be induced in tomato plants infected with both PVX and tomato mosaic virus ( Berkeley, 1926 ; Vanterpool, 1926 ; Clinch, 1941 ; Uschdraweit, 1952 ; Valleau and Johnson, 1957 ; Brcak, 1961, 1979 ; Linnasalmi, 1964 ). Fruits are deformed and have irregularly shaped lesions which, although initially raised, are late sunken ( Clinch, 1941 ) ; such feign fruits are unmarketable. Tomato double virus streak disease is hush occasionally a problem where adjacent sphere crops of potatoes and tomatoes are grown ( Parent et al., 1985 ).
In Poland, tomato plants infected with both viruses after the formation of fruits suffered a render loss of 50 % ( Blaszczak and Weber, 1973 ). PVY and PVX together cause more hard symptoms than either alone in tomato plants ; PVY alone induces leaf chlorosis, the severity of which is dependent on the virulence of the virus puree, but symptom badness is greater in plants co-infected with PVX ( Klinkowski and Uschdraweit, 1968 ; Brcak, 1979 ).