Volume 14 N u m b e r 2 J u l y 1966
Published quarterly by
American Society of Sugar Beet Technologists Office of the Secretary
P. O. Box 538 Fort Collins, Colorado 80521
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T A B L E OF C O N T E N T S
Title Author Page Sugar beet and purified juice quality in
relation to non-sugar constituents R. M. McCready A. E. Goodban Rachel Ratner
Albert Ulrich ....91 A severe necrotic disease of sugar beet
caused by a strain of the beet mosaic
virus R. J. Shepherd B. B. Till
Norman Schaad 97 Distribution of nitrate nitrogen in the blades
and petioles of sugar beets grown at de-
ficient and sufficient levels of nitrogen James D. Kelley
Albert Ulrich 106 Aphid control and planting date for the
control of yellows of sugar beet F. J. Hills W. H. Lange J. L. Reed
R. S. Loomis 117 Preparation of galactinol and myoinositol
from sugar beet sirup by chromatography
on a cation exchange resin R. M. McCready J. B. Stark
A. E. Goodban 127 A simple method for the determination of
the relative concentration of total amino acids in juice expressed from sugar beet
plant tissues /. M. Fife 133 Maleic hydrazide and topping of over-
wintered sugar beets—a potential means
of reducing the beet virus reservoir R. J. Shepherd
B. B. Till 138 Some substances adsorbed on granular carbon
from beet thick juice H. G. Walker, Jr.
R. M. McCready 142 T h e effect of low, medium and high nitro-
gen fertilizer rates on the storage of sugar
beet roots at high and low temperatures 5. T. Dexter M. G. Frakes
Grant Nichol 147 Control of cercospora leaf spot by aerial
and ground applications of fungicide L. Calpouzos G. F. Stallknecht
H. G. Johnson 160 Selecting sugar beet seedlings for resistance
to Aphanomyces cochlioides Gerald E. Coe
C. L. Schneider 164
T A B L E O F C O N T E N T S — ( C o n t i n u e d )
Title Author Page Effect of aphid-borne beet yellows and beet
western yellows on sugar beet seed pro- duction under conditions of varying fer-
tility Orin A. Hills H. K. Jewell C. W. Bennett
R. W. Brubaker 168 T h e effect of six different soil temperatures
on infection and development of Nacob-
bus batatiformis in sugar beets M. L. Schuster Eric D. Kerr
Robert Sandstedt 174
Sugar Beet and Purified Juice Quality in Relation to Non-Sugar Constituents
R. M. M C C R E A D Y1, A. E. GOODBAN1, R A C H E L R A T N E R2
AND A L B E R T U L R I C H3
Received for publication September 3, 1965
All soluble chemicals present in thin juice after carbonation lower juice quality. T h e s e include ash, nitrogen compounds, some organic acids, alkali metal ions, and others. T h e actions of these substances are additive b u t not necessarily equal in effect.
Carruthers and Oldfield developed a method to assess beet quality (l)4. T h e y prepared a clarified extract from brei, determined some of the specific non-sugars, and summarized the non-sugar effects in a "purity value." H e i m a n n and R a t n e r studied the influence of sodium and the sodium-potassium ratio on the quality of Israeli beets (3). Powers and Payne studied the relation be- tween nitrogen, sodium, and potassium in both petioles and purified juice (5). O t h e r reports, too n u m e r o u s to summarize, have dealt with effects of genetics, climate, salts, fertility levels, a n d other factors and their interactions on over-all beet quality (2).
It seemed worthwhile to attempt to evaluate separately and interrelate some effects of sodium and potassium with nitrogen, chloride, and other specific chemicals of purified beet juice pre- pared from individual beets selected for a wide range of petiole nitrate content grown in the same field. Data from Israel offer a comparison with beets grown in another climate in a more saline soil.
Collection of Sugar Beets—A fertilizer test plot at Davis, California, had been planted on J u n e 7, 1963, with variety 202-H sugar beets (Spreckels Sugar Company) with application of 200 pounds of nitrogen per acre as a m m o n i u m sulfate. On October 10, 1963, beets within a few feet of each other were selected to represent a wide range of size and petiole nitrate contents (as indicated by the diphenylamine-sulfuric acid test (4)). T h e tops were removed immediately, and the beets and tops were taken to the laboratory for analysis.
1 Principal chemists, Western Regional Research Laboratory, Western Utilization Re- search and Development Division, Agricultural Research Service, U. S. Department of Agriculture, Albany, California.
2 Research Associate, present address, Senior Lecturer, Technion, Israel Institute of Technology, Haifa, Israel.
3 Plant Physiologist, University of California, Berkeley, California.
4 Numbers in parentheses refer to literature cited.
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Preparation and Analysis—Petiole nitrates were d e t e r m i n e d by the m e t h o d of Johnson and Ulrich (4). T h e beets were scrubbed free of soil, the crowns were removed, a n d each beet was n u m b e r e d for identification. Brei was prepared in a vege- table chopper and two samples taken for analysis, for sugar by polarization (Pol), and for sodium a n d potassium by flame photo- metry. Juice was pressed from the brei t h r o u g h a nylon cloth in a hydraulic press. Sucrose in the juice was measured by polarization and total solids by refractometer (RDS). T h e re- m a i n d e r of the juice was purified by the lime-phosphoric acid m e t h o d of Carruthers and Oldfield (1) a n d preserved for analy- sis by quick freezing.
Pol sugar of the purified juices was measured on 26 g of clarified juice d i l u t e d to 200 ml with water. A p p a r e n t purity was calculated from R D S and Pol sugar. T o t a l nitrogen including nitrate was measured by the Kjeldahl m e t h o d . Chloride was d e t e r m i n e d with an Aminco-Cotlove chloride titrator. Betaine isolated by ion exchange according to the m e t h o d of C a r r u t h e r s and Oldfield was precipitated as the reinickate a n d d e t e r m i n e d colorimetrically (1). Sodium a n d potassium were measured by flame photometry.
Measurements of " a n i o n s " to include pyrrolidone carboxylic acid (PCA) were as follows: After the limed-phosphated juice at pH 11.2 was heated a n d filtered, a sample was heated in a boil- ing water bath for 1 h o u r to convert g l u t a m i n e to PCA. " A n i o n s "
were d e t e r m i n e d on this converted juice by passing 20 ml t h r o u g h a c o l u m n containing 20 ml of Dowex 50 (H) ion exchange resin then titrating to pH 8.6 with 0.05 N sodium hydroxide. " A n i o n s "
should be d e t e r m i n e d after conversion of g l u t a m i n e to PCA because this conversion is usual in factory operation.
Results and Discussion
T a b l e 1 shows the results on beets a n d press juices for in- dividual roots, arranged in o r d e r to decreasing sugar c o n t e n t of the press juice. Samples with plus signs showed a positive reaction to the petiole n i t r a t e test. Low petiole n i t r a t e is associ- ated with high sugar content. T h e r e is usually a positive relation between beet weight a n d nitrogen fertilization, b u t in this case, beets were selected to have a wide range in sizes w i t h i n a selected nitrate classification. T h e wide range of petiole n i t r a t e is typical when beets are sampled by the petiole n i t r a t e test.
T a b l e 2 shows analyses of the purified juices. T h e s e samples are also arranged in decreasing order of the sugar content of the press juice. T h e purity values of the low nitrogen beets, samples 1 to 9 a n d 11, are unusually high a n d may reflect careful t o p p i n g
V O L . 14, N o . 2, J U L Y 1966 93 in the laboratory. Sample 12, one of the g r o u p of low-nitrogen beets, falls into the grouping of high nitrogen samples; it is not unusual to have overlapping in sample groups like these.
T a b l e 1.—Analyses o f beets for w e i g h t , P o l , a n d R D S a n d p e t i o l e s for n i t r a t e1.
a m p l e 1 2 3 4 5 6 7 8 9 1 0 + 11 + 12 13 + 14 + 15 + 1 6 + 1 7 + 1 8 + 1 9 + 2 0 +
R o o t wt, g 633 513 693 965 681 721 752 1,017 875 1,042 915 868 732 1,626 1,673 691 467 2,099 1,478 1,782
P e t i o l e N O3 - N ,
p p m 211 177 253 211 422 177 270 160 245 1,820 4,480 118 6,550 7,640 4,940 8,990 10,900 9,160 13,800 7,260
B e e t P o l ,
%
16.69 16.50 15.70 15.42 15.27 15.14 15.08 15.07 14.92 14.96 14.79 14.02 12.72 12.94 12.94 12.48 11.40 11.70 10.75 10.34
P o l ,
%
18.26 17.90 17.43 16.77 16.76 16.36 16.28 16.24 16.22 16.07 16.00 15.02 14.10 13.85 13.78 13.54 12.45 12.19 11.60 10.95
Press j u i c e R D S ,
%
19.84 19.81 19.29 18.51 18.51 17.72 17.74 17.83 17.76 18.48 18.08 16.89 16.60 16.14 16.70 15.84 14.76 15.37 13.71 13.13
Purity,
%
92.0 90.4 90.4 90.6 90.5 92.3 91.8 91.1 91.3 87.0 88.5 88.9 84.9 85.8 82.5 85.5 84.3 79.3 84.6 83.4
1 Arranged in order of sugar content of press juice.
T a b l e 2 . — C o m p o s i t i o n of purified juice.1
N , m i l i g r a m s M i l l i e q u i v a l e n t s
S a m p l e 1 2 3 4 5 6 7 8 9 1 0 + 11 + 12 1 3 + 1 4 + 1 5 + 1 6 + 1 7 + 1 8 + 1 9 + 2 0 +
Sugar 14.15 14.01 13.80 13.30 12.83 12.99 13.10 13.12 12.59 12.75 12.63 11.86 11.26 10.83 10.92 10.47 9.51 9.74 9.04 8.30
P e r c e n t R D S 14.66 14.68 14.34 14.04 13.41 13.60 13.61 13.81 13.31 13.94 13.50 12.82 12.35 11.82 1 2 2 8 11.51 10.66 10.97 10.00 9.48
Purity 96.5 95.4 96.2 94.7 95.7 95.5 96.3 95.0 94.6 91.5 93.6 92.5 91.2 91.6 88.9 91.0 89.2 88.8 90.4 87.6
per 100 T o t a l
36 49 50 42 34 30 28 44 36 94 78 75 116 89 155 82 86 123 93 91
g b e e t B e t a i n e
24.4 26.1 30.2 24.4 21.4 20.3 20.7 20.6 30.6 24.1 24.3 26.2 37.2 23.2 18.3 30.8 19.1 20.2
A n i o n s 1.77 2.85 3.24 3.00 2.48 2-85 1.90 2.92 2.88 2.75 4.56 3.36 4.79 5.31 3.86 4.33 5.89 7.55 7.47 9.00
per 100 CI 1.03 1.62 1.29 1.50 0.87 1.38 0.71 1.00 1.49 0.63 0.56 1.88 1.13 1.54 1.29 0.79 0.99 1.99 1.10 3.20
g beet N a 0.35 0.56 0.69 0.86 0.61 0.30 0.71 0.45 0.78 1.29 1.27 0.72 3.14 3.58 1.19 3.84 6.59 4.15 4.74 5.31
K 3.75 5.40 2.78 4.38 4.48 4.12 3.12 4.82 4.98 4.08 4.79 6.78 4.75 6.45 6.60 4.15 3.62 6.70 3.40 6.83
1 A r r a n g e d in order of sugar c o n t e n t of press juice.
94 JOURNAL OF THE A. S. S. B. T.
Table 3.—Correlations between some constituents of beets, press juice, and purified juice.
a b c d e f g h i
i k 1 m n o P q r s t
y1
Juice purity Juice purity Juice purity Juice purity Juice purity Juice purity Juice purity Juice purity Juice purity Juice purity N a K Na + K N a K N a K Beet Pol Beet Pol Press juice sugar3
xl
Beet Pol Press juice N a K Na + K K/Na Cl Anions Betaine Total N Total N Total N Total N Anions Anions Petiole N O J C I Press juice Petiole NOs P o l
—N R D S - N 2(Na + K) + N
r2
0.910 0.922
—0.813 -0.518 -0.912 0.680 -0.404 -0.898 N.S.
-0.871 0.550 0.509 0.694 0.935 0.398 0.922 0.668 0.979 -0.897 -0.902
Regression equation y = 1.39x + 74.5 v = 1.24x 4- 74.1 y = -1.20x + 95.3 y = 1.06x + 100.1 y = 1.30x + 98.2 y = -0.071x + 97.90
y = 0 . 9 1 5 x - 1.73 y — 0.000405x + 0.48 v = 0.995x — 3.08 y = —0.000383x + 15.43 V = -0.809x + 648
1 Expressed in the units used in Tables 1 and 2.
2r = 0.378 for 10%, 0.443 for 5%, and 0.561 for 1% level of significance.
3 Millimoles per liter in the press juice.
T a b l e 3 shows some correlation coefficients a n d regression equations derived from the variables analysed in this study. T h e concentrations of individual constituents in the purified juices were calculated back to their concentration in the original beet by assuming no loss of sugar in the purification procedure. If concentrations are expressed relative to the sugar content, spuri- ous negative correlations may be found which are d u e only to variations in sugar content. If a constituent B occurs in the beet at a constant concentration, a n d the p u r i t y of the juice is c o m p a r e d with B per u n i t of sugar, there is a built-in negative correlation between S/A a n d B / S . For the beets in this study, if betaine is expressed per u n i t of beet, the correlation with p u r i t y is —0.15, b u t if betaine is expressed p e r u n i t of sugar, t h e correlation rises to —0.67, which is significant at the 1% level.
As expected, purified juice p u r i t y correlates highly with the sugar content of beets (a) a n d press juice (b). J u i c e p u r i t y cor- relates negatively with the non-sugars, Na (c), Na + K (e), anions (h), a n d total N (j). In this series of beets, Na correlates with anions (n) a n d with petiole n i t r a t e (p), potassium with chloride (q), a n d Na + K with total N (m). T h e high negative correlation of petiole n i t r a t e with beet Pol (s) has been observed in all o t h e r tests. T h e high positive correlation between sugar in beets and R D S of press juice, 0.979 (r) suggests that for some purposes an R D S m e a s u r e m e n t of beet press juice used with the regression
VOL. 14, No. 2, JULY 1966
equation would serve as an adequate measurement of the sugar content of beets. F u r t h e r attention should be given to this pos- sibility. Item (t) shows that the calculated total moles of non- sugars is negatively correlated with the moles of sugar. Further- more, the regression equation indicates a reduction of one mole of sugar for each increase of 1.2 moles of non-sugar. T h i s indi- cates that the total solute content of beet press juice is relatively constant, when expressed as the n u m b e r of particles in solution.
If beet cells have a constant n u m b e r of molecules and ions per u n i t volume, and thus a constant osmotic concentration, the accumulation of sucrose would be limited by the presence of non-sugars. O n e mole of sodium chloride (59 grams) would displace two moles of sugar (648 grams). T o t a l concentration of solutes (osmolality) of beet juices will be reported in a future communication.
Table 4.—Analytical values of pressed juice from Israeli beets compared with Davis, California beets.
Number of samples
13 31 26 33
4 7 8
Sugar
%
above 18.0 16.6-18.0 15.0-16.5 below 15.0
16.6-18.0 15.0-16.5 below 15.0
Haifa, Avg. sugar
%
19.0 17.5 15.8 13.8
Israel beets
Purity 86 6 82-0 Davis, California beets
17.2 16.0 12.9
90.5 90.1 84.2
Avg. milliequivalents/100 g N a
15.3 18.3 22.2 39.9 4.4 5.3 36.4
K 25.2 28.0 30.4 40.5 27.5 31.6 44.8
sucrose K/Na 1.6 1.5 1.4 1.0
6.3 6.0 1.2
T a b l e 4 compares the beets in T a b l e 1 with beets grown near Haifa, Israel, in an area of saline soil irrigated with saline waters. T h e purity of the factory juices from Israeli beets is lower than the purity of the laboratory juice from the Davis beets at comparable sugar contents. Israeli beets contain more sodium than the Davis beets, b u t the total Na + K values are similar. T h e ratio of K / N a for the various populations are very different although for each population sugar and purity decrease as the ratio decreases. T h e purity d r o p does not seem to be related directly to excess salts b u t appears to be d u e to some other factor.
Summary
Beets grown in the same field selected for high and low petiole nitrate contents and size within each population were processed into brei, pressed juice, and purified juice. Sugar and
9 6 JOURNAL OF THE A. S. S. B. T.
non-sugar constituents were d e t e r m i n e d , a n d t h e influence of these constituents on juice q u a l i t y was assessed. C o r r e l a t i o n s between some c o n s t i t u e n t s of the beets, pressed j u i c e a n d purified juice were highly significant. Data from Israeli beets, briefly r e p o r t e d , show some similarity a n d some v a r i a t i o n .
Reference to a company or product name docs not imply approval or recommendation of the product by the U. S. Department of Agriculture to the exclusion of others that may be suitable.
Literature Cited
(1 CARRUTHERS, A., and J. F. T. OLDFIELD. 1961. Methods for the assess- ment of beet quality. Int. Sugar J. 63: 72-74, 103-105, 137-139.
(2) COMMISSION INTERNATIONALE T E C H I Q U E DES SUCRERIE. 1960. Proceedings of the 11th session, Frankfurt, West Germany. T h e technological value of the sugar beet. Elsevier Publishing Co., New York, 1962.
(3) H E I M A N N , H., and R. RATNER. 1962. T h e influence of sodium and potassium-sodium ratio on the sugar content of beets and on their processing. Int. Sugar J. 64: 136-138.
(4) JOHNSON, C. M., and ALBERT U L R I C H . 1959. Analytical methods for use in plant analysis. University of California, Expt. Station Bull.
766, p. 25-78.
(5) POWERS, L E R O Y , a n d MERLE PAYNE. 1964. Associations of levels of total nitrogen, potassium, and sodium in petioles and in thin juice with weight of root per plot, percentage sucrose and percentage apparent purity in sugar beets. J. Am. Soc. Sugar Beet Technol.
1 3 (2 ) : 138-149.
A Severe Necrotic Disease of Sugar Beet Caused by a Strain of the Beet Mosaic Virus
R. J. SHEPHERD, B. B. T I L L AND N O R M A N SCHAAD1
Received for publication October 4, 1965
D u r i n g the summer of 1963, Dr. F. J. Hills, Department of Agronomy, University of California, Davis, called our attention to sugar beet plants in a field near Davis that were showing a severe necrotic disease which hitherto had not been observed in this area. As a certain a m o u n t of distortion and vein clearing accompanied the symptoms of necrosis on affected plants, it was postulated that the causal agent might be a virus not previously found infecting sugar beets. Tests with the extracted sap of in- fected plants showed that a mechanically-transmissible virus was present. F u r t h e r study of the disease and its causal virus showed that it was caused by an unusual strain of the beet mosaic virus.
T h e results of this study and a description of the disease are presented herein.
Symptoms on Sugar Beet
T h e disease as originally observed on naturally infected beets consisted of a p r o m i n e n t necrosis of the leaf veins. T h i s necrosis was associated only with the intermediate sized and smaller veins of partially developed leaves. These affected veins appeared as a dark necrotic network, while the rest of the leaf, with the exception of a small a m o u n t of inconspicuous mottling, appeared almost normal. Frequently the interveinal tissue of such leaves was puckered or blistered outward suggesting that there was no cessation of growth when the peripheral veinal tissue died. No necrosis, however, was observed on the larger veins, midribs, or petioles of affected plants. Vein-clearing and small necrotic flecks were present on the smaller i m m a t u r e leaves near the center of the crown on naturally infected plants.
Symptoms on mechanically inoculated beet seedlings in the greenhouse were somewhat different from those observed on naturally infected plants b u t the most conspicuous symptom was again necrosis. Generally the first symptoms developed about 3-5 days after inoculation and consisted of chlorotic or necrotic local lesions on the inoculated leaves (Figure 1, B & D). Initial systemic symptoms usually developed concurrently with the local symptoms or shortly thereafter and consisted of vein-clearing
1 Associate Plant Pathologist, Laboratory Technician II and Research Assistant, re- spectively, Department of Plant Pathology, University of California, Davis, California.
JOURNAL OF THE A. S. S. B. T.
Figure 1.—Symptoms of the necrotic strain of beet mosaic virus on various hosts. Systemic symptoms on a well developed leaf of sugar beet (A) and a tip leaf from the same plant (C); local lesions on inoculated leaves of sugar beet (B & D), Chenopodium quinoa (E), Bountiful bean (F), and New Zealand spinach (G); Systemic mottle on Nicotiana clevelandii (H) and systemic terminal necrosis on Dwarf Telephone peas (left in I, on the right is a healthy pea plant for comparison).
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VOL. 14, No. 2, JULY 1966
and necrotic flecks on the youngest developing leaves in the crown. As these leaves continued to develop they exhibited p r o m i n e n t necrotic patches usually associated with the smaller veins a n d the neighboring tissue. Due to lack of growth as the leaves expanded, these necrotic areas caused tearing of the tissues giving the leaves a shot-holed appearance (Figure 1, A). Prominent chlorotic ringspots accompanied the necrosis and the leaves were generally somewhat distorted with an abnormal serration of the leaf margins (Figure 1, A). Generally, the plants were severely stunted.
Symptoms on O t h e r Host Plants
T h e virus was inoculated to various other species of plants in the greenhouse in order to obtain some information on its host range. T h e plants were usually grown in 5-inch clay pots in a sterile composted greenhouse soil consisting of fine sand and peat supplemented with bone and blood meal. Generally, 4-10 plants of each species were mechanically inoculated by r u b b i n g phosphate-buffered homogenates of infected leaves of Nicotiana multivalvis over corundum-dusted leaves with a clean forefinger. After allowing a period of 8-15 days for symptom development, an attempt was made to recover the virus from each plant by mechanical inoculation to beet seedlings. Symptoms on various plants were as follows:
Beta vulgaris var. cicla (L.) Moq. - Swiss Chard - Circular brown necrotic local lesions on inoculated leaves followed by a p r o m i n e n t systemic mosaic mottle with necrotic areas.
Chenopodium amaranticolor Coste & Reyn. - Pale necrotic local lesions developing after 5-7 days on the inoculated leaves, followed shortly by stunting, yellowing, a n d down- ward curling of apical leaves, which together with the grow- ing point, soon died.
C. capitatum (L.) Asch. - Reaction similar to C. amaranticolor.
C. quinoa Willd. - Local necrotic lesions (Figure 1, E) as on C. amaranticolor b u t accompanied by systemic development of a severe mottle with distortion and necrosis resulting in eventual death of the plants.
Cucurbita pepo L., var. Buttercup squash - No symptoms b u t virus recovered from small terminal leaves.
Gomphrena globosa L. - Chlorotic local lesions w i t h p a l e necrotic centers after 7-10 days on inoculated leaves.
Hibiscus esculentus L. - A transient chlorotic line pattern on systemically invaded tissues; symptomless thereafter, b u t virus recovered.
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Montia perfoliata (Domn) Howell. - Reddish-brown necrotic local lesions developing after a b o u t 10 days on inoculated leaves; no systemic symptoms.
Nicotiana clevelandii Gray. - Occasionally c h l o r o t i c l o c a l lesions on inoculated leaves; systemic chlorotic mottle.
N. multivalvis L i n d l . - Reaction same as N. clevelandii (Figure 1) Phaseolus vulgaris L. var. Bountiful, Morse Pole, R e d Kidney a n d Sutter P i n k - Very small reddish-brown necrotic local lesions (Figure 1, F); no systemic symptoms.
Pisum sativum L., var. Dwarf T e l e p h o n e - Small local necrotic flecks on inoculated leaves; systemic t e r m i n a l necrosis with eventual collapse a n d death of the plants (Figure 1, I).
Tetragonia expansa T h u n b . - Dark necrotic local lesions on inoculated leaves (Figure 1, G); no systemic invasion by the virus.
Plants on Which No Infection was Obtained
No symptoms were observed or virus recovered from the following species after mechanical inoculation with the virus:
Althaea rosea L. Cav.; Antirrhinum majus L . ; Capsicum frutescens L., var. California W o n d e r , H u n g a r i a n Yellow;
Cyomopsis tetragonoloba (L.) T a u b . ; Dahlia variabilis (Willd.) Desf.; Datura stramonium L.; Dolichos lablab L.; Helianthus annuus L.; Ipomoea purpurea (L.) Lam.; Matthiola incana (L.) R. Br.; Melilotus indica (L.) AH.; Mirabilis jalapa L.;
Nicotiana tabacum L., var. Wisconsin H a v a n a 425; JV. gluti- nosa L.; Phaseolus mungo L.; Physalis exocarpa Brot.; P.
peruviana L.; Plantago lanceolata L.; Raphanus sativus L.;
Rumex acetosa L.; Sesbania exaltata (Raf.) Cory; Trifolium incarnatum L.; T. pratense L.; Vicia faba L.; Vigna sinensis ( T o r n e r ) Savi; Viola odorata L.; Zinnia elegans Jacq.
T h e host range of the virus is similar to that of the beet mosaic virus, although somewhat different than that r e p o r t e d by others (3,4)2.
Properties of the Virus In Vitro
T h e properties of the virus in vitro were d e t e r m i n e d by using the expressing sap from systemically infected sugar beet. After each treatment, the sap was r u b b e d over several y o u n g sugar beet seedlings to assay for infectivity. T h e following results were obtained: d i l u t i o n , infection at 10-3, n o n e at 10-4; longevity in vitro (ca. 20°C), infection after 2 days, n o n e after 3 days; t h e r m a l inactivation (10 m i n u t e d u r a t i o n ) ; infection after h e a t i n g at 60°C, n o n e after 65°C.
2 Numbers in parentheses refer to literature cited.
VOL. 14, No. 2, JULY 1966 101
T h e s e properties of the virus are similar to those reported by P o u n d (3) for the beet mosaic virus b u t also agree fairly well for those for the beet marble leaf (1), or ring mottle viruses (2).
Insect Transmission of the Virus
T h e virus was found to be readily transmissible by green peach aphids, Myzus persicae Sulz. Non-viruliferous insects were cultured on Chinese cabbage, Brassica pekinensis (Lour.) R u p r . W h e n starved for 2 or more hours, followed by an acquisition feeding period of approximately 2 minutes on infected beets, slightly over 10 percent of the insects transmitted the virus to healthy sugar beet seedlings when single aphids were used. T h u s , the green peach aphid is a fairly efficient vector of the virus.
Electron Microscopy of the Virus
Brandes' leaf d i p p i n g method (8) was used to prepare speci- mens for electron microscopy. Preparations from healthy and diseased Nicotiana clevelandii a n d sugar beet were shadowed with U r a n i u m at an angle of 1 to 3 in a Kinney H i g h Vacuum Evapo- rator and examined in an R C A E M U 3-G electron microscope.
Flexuous rods which were presumed to be virus particles were seen in preparations from diseased material. Particles from N.
clevelandii are shown in Figure 2.
Size determinations were made either by reference to poly- styrene latex spheres 264 mm in diameter which were included in the water droplets at the time of carrying out the leaf dips, or by reference to photographs of a diffraction grating, made at the same magnification as the virus. T h e two methods gave almost identical results. T h o u g h only a few particles were found, meas- urements were made of 25, the lengths of which varied between 641 mm and 787 mm. T h e mean particle length was determined to be 688 (+b 8) mm. A b o u t one-half of the total n u m b e r of particles measured were approximately 650 mm in length. T h i s particle length is somewhat shorter than that reported for the beet mosaic virus in d i p preparations (8).
Cross-Protection Tests
T h e various properties of the virus suggested it might be a strain of the beet mosaic virus although the symptoms it induced on beets were markedly different than the more commonly occurring strains of the virus. Several cross-protection tests were carried out to determine if infection with a conventional strain of the beet mosaic virus would immunize beets against infection by the necrotic virus. As the virus causes distinctive symptoms in beets, its presence in systemically infected plants would be readily discernible in plants previously infected with the beet mosaic virus.