Heterodera schachtii Schmidt, in Southern Alberta
1A. M. HARPER2, C. E. LILLY-, AND E. J. H A W N3
Received for publication February 19, 1962
T h e sugar beet nematode, Heterodera schachtii Schmidt, is a serious pest of sugar beets in Europe (2)4 and is present in 15 beet-producing states of the U. S. A. (1). T h e plant parasite was first discovered in Canada in 1931 near St. Catharines, Ontario (4). In 1939 it was found on sugar beets near Sarnia, Ontario (3).
In June 1961, an unthrifty stand of beets 13 acres in size was found near Taber, Alberta. T h e plants in approximately one- quarter of the field were severely stunted, the leaves were badly wilted, and there was considerable root proliferation (Figures
1 and 2). Numerous white cysts were found on the roots of the stunted plants as well as on the roots of other sugar beets throughout the field (Figures 3 and 4). Cysts were also found on flixweed, Descurainia sophia (L.) Webb, and on oak-leaved goosefoot, Chenopodium glaucum. L., in the same field. T h e cysts were identified as H. schachtii by Dr. A. D. Baker and R. H.
Mulvey of the Nematology Section, Entomology Research Insti- tute, Ottawa, Ontario.
Although beets were first grown commercially in Alberta in 1903 and have been grown since 1925 in the district where the infested farm is located, this was the first time the sugar beet nematode had been found in western Canada.
Until 1950 the infested field was flood irrigated but since that time it has been sprinkler irrigated. T h e area where damage was evident in the field was previously a knoll that had been levelled. T h e farmer had noted stunting of the beets in this area in 1957, which suggests that the infestation may have been present
•for at least 4 years.
Although the average yield on this farm was generally higher than that of the surrounding area, the farmer used a very short cropping sequence, in which he grew beets in 10 of the last 17 years. This sequence would be expected to favor a rapid in- crease in the numbers of nematodes once the field became infested.
1 Contribution from the Entomology Section and the Plant Pathology Section, Canada Agriculture Research Station, Lethbridge, Alberta.
2 Entomologist
3 Plant Pathologist
4 Numbers in parentheses refer to literature cited.
Figure 5.—(lower left) Photomicrograph of a cyst of H. schachtii opened to show the eggs (X30).
Figure 6.—(lower right) Enlargement of the nematode eggs shown in Figure 5 (XI30).
VOL. 12, .No. 2, JULY 1962
Figure 1.—(upper left) Sugar beet field near T a b e r , Alberta, severely infested with Heterodera schachtii Schmidt. T h e beets were wilted, stunted, and chlorotic.
Figure 2.—(upper right) Comparison of a normal beet (right) with three beets severely stunted by H. schachtii. "Hairiness", exhibited by the beet at the left, is often indicative of the presence of the sugar-beet nematode.
Figure 3.—(center left) A portion of a heavily infested beet. Arrow points to one of the cysts (X10).
Figure 4.—(center right) Photomicrograph of one of the secondary roots of a beet with adhering lemon-shaped cysts of H. schachtii (X30).
Cysts ranged in color from white to brown.
Survey
In early July, sugar beets and soil from the most unthrifty areas of 721 sugar beet fields throughout southern Alberta were examined by the authors in the laboratory for cysts of H.
schachtii. No other infestations were discovered, [ones (2) found, in England, that with a population of cysts under one million per acre there were no crop symptoms and the infestation was not detectable. It is possible, therefore, that there may be light, undetectable infestations of the nematode in southern Alberta.
Some beets examined during the survey had an abnormally large number of lateral rootlets. In most cases this abnormal growth appeared to result from damage by the sugar-beet root aphid, Pemphigus betae Doane, the sugar-beet root maggot, Tetanops rnyopaeformis (Roder), or the wireworms (Ctenicera destructor (Brown) and Hypolithus bicolor Esch.
In the infested field, soil samples taken from around beets contained 135 cysts per 200 grams of soil. Both old and young cysts were present in July, the latter full of eggs and second-stage larvae (Figures 5 and 6). T h e presence of old cysts and the degree of infestation indicated that this pest had probably been present in the field for more than one year.
On July 14 several small beets from the infested field were lifted with adjacent soil and planted in 6-inch pots in a green- house. Approximately 170 days later one 100-gram sample of soil was taken from an area immediately adjacent to the beet in each of 8 pots. T h e average number of cysts obtained from the soil samples was 1,192.
Control measures
T h e ability of H. schachtii to increase rapidly and spread made it desirable to reduce this infestation as quickly as possible.
T h e field was plowed and fumigated on August 14 by applying approximately 25 gallons per acre of the nematocide Shell DD at a depth of 6 to 8 inches. Forty-five days later beets were planted in 8 pots containing soil from the fumigated field.
Approximately 95 days after planting, the pots contained an average of 170 nematodes per 100 grams of soil. Although the nematocide appeared to greatly reduce the number of nematodes in the field the residual population could still cause serious dam- age to beets.
It was recommended that alfalfa, which is not a host of H. schachtii, should be grown on this land for at least 6 years and that on the remainder of the farm sugar beets or other susceptible crops should not be grown oftener than once every 4 years. To prevent serious infestations of this pest from developing in sugar-
VOL. 12, No. 2, JULY 1962 151 beet-growing areas of A l b e r t a , officials of the sugar beet growers'
association a n d the C a n a d i a n Sugar Factories L i m i t e d have agreed to a d h e r e to these r e c o m m e n d a t i o n s a n d also to a general recom- m e n d a t i o n t h a t susceptible crops should n o t be g r o w n oftener than once every 4 years.
Literature Cited
(1) GOLDEN, A. M., and E. C. JORGENSON. 1961. T h e sugar beet nematode and its control. U.S.D.A. Leaflet No. 486. p p . 1-8.
(2) JONES, F. G. W. 1957. Beet eelworm. In Sugar-beet Pests. Ministry of Agriculture, Fisheries and Food, London, England. Bull. No. 162.
p p . 39-51.
(3) MULVEY, R. H. 1957. Susceptibilities of cultivated and seed plants to the sugar beet nematode, Heterodera schachtii Schmidt, 1871, in southwestern Ontario. J. Helminthology. 31 (4) : 225-228.
(4) STIRRETT, G. M. 1935. A contribution to the knowledge of sugar-beet insects in Ontario. Scientific Agriculture. 1 6 ( 4 ) : 180-196.
Selection for Low and High Aspartic Acid and Glutamine in Sugar Beets
R. E. FlNKNER, C. W. DOXTATOR, P. C. HANZAS
AND R . H . H E L M E R I C K1
Received for publication February 20, 1962
In recent years there has been an increasing widespread and copious use of nitrogen fertilizer in sugar beet production. In most cases this has resulted in an increase in beet yield along with low sucrose content. Impurities "or nonsugars" have in- creased, causing a low extraction of sugar per ton of beets and an increased production of molasses. T h e increases of amino acids and of other nitrogenous compounds in the beet are the major factors contributing to the reduction of the quality of beet juice for sugar extraction.
T h e objectives of the present investigations were: To deter- mine if certain amino acids could be increased or decreased by ordinary mass selection; to ascertain if these selections reacted the same under different nitrogen levels of fertility; and to determine how these selections affected other chemical com- pounds in the beets.
T h e classical protein and oil selection experiments on corn conducted at Illinois have demonstrated that chemical composi- tion of plants was in part under genetic control (10)2. Selections in sugar beets for high and low quantities of chemicals such as sucrose, sodium, potassium, galactinol, raffinose, and purity have been successful as determined by progeny tests. Many in- vestigators (1, 2, 3, 4, 17, 19) have applied selection pressure for low sodium content of individual roots. All have shown that the sodium content was significantly correlated with sucrose but in a negative relationship. All have shown by progeny tests that significant reductions or increases in sodium content could be accomplished by mass selection. Wood (17) reported on progeny tests of roots selected for high and low ramnose content. He concluded that the ramnose content of beets could be significantly reduced by mass selection. Later Wood et al. (18) studied the inheritance of raffinose production in sugar beets and reported that the number of effective factor pairs involved in the oro- duction of raffinose between the two parents used was about five;
at least one was isodirectional and all were equal in magnitude.
In the crosses studied neither dominance, nor heterosis, nor link- age appeared to be involved. Quantitatively, the factors for ramnose production in the two parents followed an arithmetic
1 M a n a g e r Research Station. P l a n t Breeder, Research Chemist and P l a n t Breeder, re- spectively, American Crystal Sugar C o m p a n y , Rockv Ford, Colorado.
2 N u m b e r s in parentheses refer to l i t e r a t u r e cited.
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scale a n d consequently were additive. F i n k n e r et al. (4, 6) also studied beets selected for high a n d low raffinose content. T h e y found t h r o u g h progeny tests that these selections bred t r u e for high or low raffinose content. T h e y also studied these selections under different harvest dates and storage conditions. Again it was found that the high selections r e m a i n e d high a n d the low selections stayed low.
Powers et al. (14) summarized m u c h of the recent data con- cerning selection for high a n d low sodium a n d raffinose contents.
They also reported on selections for thin juice purity and sucrose content. T h e data for thin juice purity showed that selection for greater purity has resulted in an increase in this character.
Agricultural scientists are aware that the soil has long been recognized as the basis of agricultural production. In the elucida- tion of the chemodynamics of soil plant complex it has been shown by several investigators on several crops that the addition of fertilizer to the soil can change the chemical composition of plants. H a c et al. (7) a n d W a l k e r et al. (15) studied the effect of nitrogen fertilizer on the glutamic acid c o n t e n t in sugar beets.
T h e y found that the application of nitrogen fertilizer caused an increase in glutamic acid of beets. W a l k e r and Hac (16) observed that as the soil moisture increased u n d e r both furrow a n d sprinkler irrigation, nitrogen fertilizer increasingly stimulated yield and glutamic acid content of beets. Haddock et al. (8) showed that several nitrogen constituents, especially g l u t a m i n e , increased with nitrogen fertilizer applications. F i n k n e r et al. (5) presented data using three different levels of nitrogen applica- tions and found that the a m i n o acid content of the beets increased as the rates of nitrogen increased. In a study of n i n e different amino acids a n d the total a m i n o acid content F i n k n e r et al. (5) showed a significant linear increase response to nitrogen appli- cation.
Payne et al. (11, 12) m a d e p o p u l a t i o n genetic studies per- taining to nitrogen c o m p o u n d s in sugar beets a n d concluded that varieties of beets could be b r e d which would contain lower amounts of nitrogen constituents even when grown on high fertility soils.
Materials and Methods
T h e variety used in this e x p e r i m e n t was SLC 24, a self-sterile monogerm. A total of 2,272 beets was selected in 1958 by t h e unit block m e t h o d similar to that developed by Powers (13).
The selection u n i t block was 35 feet long a n d 11 feet wide.
It differed from Powers' m e t h o d in that no inbreds or F, hybrids were planted to measure the e n v i r o n m e n t a l variation.
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Each individual beet was weighed, sampled and analyzed for sucrose, aspartic acid and glutamine. T h e n u m b e r of roots selected from each unit was recorded and the range and mean calculated. T h e standard deviation of each unit block was estimated by utilizing the formula, Range/s = mean ratio, a short-cut method described in Snedecor's "Statistical Methods", 5th Edition, T a b l e 2.2.2, page 38.
Based on these estimated standard deviations, selections were made within the unit block for beets which were higher or lower than the block mean for aspartic acid and glutamine.
Beets selected for high aspartic acid were at least twice the standard deviation higher than the block mean and the beets selected for low aspartic acid were at least 1.3 times the standard deviation below the block mean. T h e selection deviation values used for glutamine were 2.3 times the standard deviation for the high selection and 1.1 times the standard deviation below the block means for the low selection. A random selection of approximately every 25th root from the total population was saved and considered the check.
Although sugar and weight were recorded for the individual roots, selections were based on the amount of the two amino acids. T h e amino acids were determined by a paper chromato- graphic procedure reported by Hanzas (9). All paper chromato- graphic determinations are reported as percent on dry substance.
T h e n u m b e r of roots selected for each group, the pedigree numbers, the general means for each character studied for each group, and for the entire population, are shown in T a b l e 1.
Table 1.—Means of weight, chemical characteristics and number of roots for five amino acid selections.
Individual root data
From the above table it will be seen that the high and low selections for aspartic acid and glutamine were greatly different, but in weight and sucrose percents they were similar.
Roots of each of the five groups were space isolated in the spring of 1959 and produced seed that fall. Tn 1960 the five seed lots were planted in a split plot replicated test at Rocky Ford, Colorado, and at East Grand Forks, Minnesota. Tn these
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tests the three m a i n plots were the levels of nitrogen, a n d the selections were the subplots. T h e plots were single rows with a commercial variety planted on each side to give uniform com- petition for each selection. T h e selections were replicated six times in each test.
Plots were harvested for weight, sucrose a n d other juice quality characters. P a p e r chromatography was used to d e t e r m i n e amino acids, total a m i n o acid, galactinol4, a n d raffinose. T o t a l nitrogen was d e t e r m i n e d by a modified micro-Kjeldahl nessler- ization (11)- Sodium a n d potassium were d e t e r m i n e d by the flame spectrophotometer. Sugar and purity were analyzed by standard sugar analysis procedures.
Experimental Results
R e m a r k a b l e differences were obtained in the progeny tests of the five a m i n o acid selections. Very reliable differences be- tween the high a n d low a m i n o acid selections were o b t a i n e d for all characters tested at one or the other, or both locations, except for sucrose percent. T h e results of these progeny tests u n d e r different n i t r o g e n levels are shown in T a b l e 2 for the Rocky Ford test and T a b l e 3 for the East G r a n d Forks test. It should be noted that the levels of nitrogen fertilizer used were different for each test as the soils at East G r a n d Forks contained m u c h more organic m a t t e r t h a n the Rocky Ford soils.
T h e r e was a total of four significant variety X nitrogen interactions in b o t h tests. Only one of these was highly sig- nificant; the others were possibly chance deviations. T h e results indicate that the varieties, in general, reacted similarly in the three different soil nitrogen e n v i r o n m e n t s . In the Rocky Ford test the a d d i t i o n of n i t r o g e n had only m i n o r effects on the cliaracters studied, as significant differences between rates were detected for only seven characters from a total of twenty. T h e s e differences also were significant only at the five percent level.
In the East G r a n d Forks test the a d d i t i o n of nitrogen had a greater effect on these characters t h a n the test at Rocky Ford as ten significant differences were detected a n d many of these were highly significant. T h e a d d i t i o n of nitrogen significantly de- creased the percent sucrose a n d increased the total a m i n o acid content in each test.
Selections for high a n d low aspartic acid a n d g l u t a m i n e con- tents significantly separated the original p o p u l a t i o n s i n t o distinct groups. In sugar per acre, tonnage, sucrose a n d purity, the selections gave varying results. T h e low aspartic acid selection
(59-407) increased root yield in both tests, b u t the stands also
3 Recent improvements in technique indicate that the galactinol values may be too high.
Table 3.—Stand, yield and chemical results of five amino acid selections planted at East Grand Forks, Minnesota, at three different nitrogen fertility levels.
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were at least ten percent higher than the check (59-411) in both tests. T h i s increase in stand may have helped to increase the yield. T h e low glutamine selection (59-409) with a slight increase in stand, showed only slight increases in yield and sugar per acre, and was not significantly above the check for any of these characters. T h e low selections were higher in all of these desir- able characters than the high amino acid selections. Selecting for high or low aspartic acid or glutamine did not affect the percent sucrose. Purity of juice was significantly improved by low glutamine selection in both tests, and to a lesser degree by the aspartic acid selection.
T h e raffinose and galactinol contents were changed by the selection for low and high amino acids. In the East Grand Forks test, the high selection of both amino acids significantly decreased the raffinose content. In the Rocky Ford test the selections were not significantly different for raffinose content. T h e galactinol content was significantly increased in the East Grand Forks test by selecting for low aspartic acid, however in the Rocky Ford test the high selection significantly lowered the galactinol amount.
Therefore it appears that selections for high and low aspartic acid decreased and increased the galactinol content, respectively, in these varieties. T h e glutamine selections were not significantly different from each other for galactinol content but the results for the East Grand Forks test were similar to the trend mentioned above for the aspartic acid selections. In the Rocky Ford test the glutamine selections were not significantly different for galactinol content but the general trend was reversed.
T h e sodium and potassium results were different for the two amino acid selections. T h e low glutamine selection reduced the potassium content significantly in both tests, but did not affect the sodium content. T h e low aspartic acid selection increased the sodium content significantly while the high aspartic acid decreased the sodium content significantly, but did not affect potassium. These results were obtained in both tests.
T h e r e were nine amino acids evaluated plus total amino acids and total nitrogen in the progeny tests. T h e selections for low and high aspactic acid contents shifted all nine amino acids in their respective directions of selection, i.e., all amino acids had a tendency to increase in the high selection and to decrease in the low selection. T h e same was true for the glutamine selection except that the separations were greater in magnitude. T h e r e were slight variations from these results but none reached the significant level. It can be concluded therefore, that selection for a reduction or an increase of these two amino acids, reduced
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or increased all a m i n o acids. T h e g l u t a m i n e selections were more effective than the aspartic acid selections in shitting the populations. F u r t h e r m o r e , total n i t r o g e n in the beet juices of these low selections was significantly lower than the check, while the total nitrogen in the high g l u t a m i n e selection was significantly higher than the check.
Discussion of Results
It is evident from the data that the aspartic acid a n d / o r glutamine c o n t e n t can be increased or decreased in the root by selection pressure. Such pressure affected the nitrogen meta- bolism of the plants as there was a general increase or decrease of the total a m i n o acid content a n d the total nitrogen content, depending on the direction of the selection pressure.
T h e effects of the selection pressure applied in these tests were not completely confined to the nitrogen-containing com- pounds. Selection of aspartic acid significantly affected the sodium c o n t e n t while the selection applied to g l u t a m i n e sig- nificantly changed the potassium content. T h e s e were the only two mineral elements studied. Shifts in a m o u n t s of other elements also probably occurred.
Changes were noted in the carbohydrates studied. T h e high amino acid selections significantly decreased the raflinose c o n t e n t and a similar t r e n d was a p p a r e n t for galactinol. Sucrose c o n t e n t remained u n c h a n g e d .
T h e general t r e n d was for purities to increase with the lower- ing of a m i n o acid content. T h i s Avas to be expected, as a large part of the nonsugars are n i t r o g e n o u s c o m p o u n d s . C o n s i d e r i n g all the characters studied in these tests, the selection for low a m i n o acid c o n t e n t was beneficial by increasing sugar yield a n d juice quality, b u t not beneficial by causing an increase in raffinose, galactinol a n d sodium. T h e s e three latter constituents have a tendency to lower beet juice quality. T h i s was over- balanced however, by the beneficial effects of the lower a m i n o acid c o n t e n t as reflected in the purity data.
Considering the aspartic acid selections a n d the g l u t a m i n e selections, it appears that e i t h e r one could be used satisfactorily to improve beet varieties, although the g l u t a m i n e selection was slightly m o r e effective in spreading the populations i n t o separate groups. In a b r e e d i n g p r o g r a m the selection pressure applied against g l u t a m i n e would be just as effective as selecting against both aspartic acid a n d g l u t a m i n e at t h e same time. T h e low glutamine selection also had lesser d e t r i m e n t a l effects as it did not significantly change the sodium, raffinose or galactinol c o n t e n t