STUDIES IN BULK CROSSES BETWEEN SOME BEET STRAINS Rolf Manner Linköping, Sweden Received June 30, 1960 In a number of cultivated plant species hybrids have been produced of value to pracitical cultivation during the last decades. These have been planned for hybrid seed production on an experimental or even on a practical scale in a large number of other plant species in different parts of the world. The present author, during his time as plant-breeder of fodder-beets, has often observed a considerable inbreeding depression in crosses. Further, he has gained the impression that in special cases the hybrids are more luxuriant than the parents. These observations are in full agreement with the observations published by Stewart, Gaskill and Coons (11), Doxtator and Skuderna (2), Sedlmayr (9) and Boon (1). Under these circum- stances the author found it to be of value to ascertain to what extent this heterosis can be exploited without using male-sterile material in bulk crossing between dif- ferent fodder and fodder sugar-beet strains. The use of male-sterile material would naturally have been still more interesting and a step closer to the practical realization of the hybrid-seed production and usage. This would, however, have proved much more expensive in terms of time, money and work than the present investigation, which is performed with marketed strains. Further, the genetical and practical value of the parents used would have differed greatly if the strains had first been crossed with male-sterile material, and this would have made it impossible to compare the hybrids with the marketed strains used in the crosses. The present investigation con- cerning bulk crosses between marketed strains gives an idea of the practical value and the results of the crosses. The present investigation also deals with an additional problem, namely, the effect on seed cultivation of different strains grown close together. It should be of considerable interest for seed growing and seed control to know to what extent the bulk crosses between strains differ in their performance or are better than the pure strains. The possibilities of using the polycross method in beet breeding is investigated (1) and the exploitation of heterosis is discussed (13). https://www.c-info.fi/en/info/?token=Sr94pdliZ-a7a5RO.KlJEP7pOtsE1Ddo1fM9vig.pXZ2G89tY4NR3Qk6MkoLhM_gIU2QCJhMVC3vleIugHzwqny29B451fluYKSF98BTRqEwmefqRMYhvWzXNNUtlFwqUzFeF-5T9Nr1sQOWo4mxZs6_diCHDHPcvhy2JH4DepW8w5tgJk8rq7G_dXfjhsNAiynDnjFiuA 200 Material and methods The present study was conducted during the years 1952—1957 at the Gulläker Plant Breeding Institute, Hammenhög, Sweden being carried out in connection with the practical plant-breeding work there. During the year 1952 only bulk crosses were performed whereas the yield trials were carried out in the years 1953—1957. The following bulk crosses were investigated: Colour of Number of strains taking part in the cross the roots 2 3 >3 White Milka x Solid Gulläker x (Milka + Solid) Gulläker x (Vwhite) Gulläker x Triumf Solid X (Gulläker -f Milka) Vit Gröntoppig x (2,’white) Gulläker x Milka Milka x (Gulläker -(- Solid) Monark x white) Gulläker x Solid Vit Gröntoppig x (Gulläker -f- Triumf x (2?white) Solid) Triumf x Miika Solid X (£\vhite) Solid X Triumf Triumf x Vit Gröntoppig Gulläker x Monark Milka X Monark Triumf x Monark Solid X Monark Hg 2083 x Triumf Solid X Vit Gröntoppig Light red Ljusröd x (Bacon + Rubra) (Bacon x (Rubra + Ljusröd) Yellow B. Kofor x B. Slättbo II B. Svea x (£Barres) B. Kofor x B. Halvläng B. Ferritslev (£"Barres) B. Kofor X B. Svea ötofte Nova x (.Z’Barres) B. Koforx Hg 50-627: 1 B. Kofor x (1 Barres) B. Halvläng X (2,'Barres) B. Slättbo II x (EBarres) The Breeding Institutes of the strains used for crossing as are follows: Solid, Ruba and Barres Halvläng are bred at The Swedish Seed Association, Svalöf, Sweden; Triumf, Bacon and Barres Slättbo II at the Weibullsholm Plant Breeding Institute, Landskrona, Sweden; Gulläker, Vit Gröntoppig, Ljusröd, Barres Kofor, Hg 2083 and Hg 50 627 :1 at the Gulläker Plant Breeding Institute, Hammenhög, Sweden; Milka, Monark and Barres Svea at Pajbjergfonden, Borkop, Denmark, These three strains are however represented in Sweden by Algot Holmberg & Sons Ltd., Norrköping; otofte Nova at otofte, Denmark; and Barres Ferritslev at Ferritslev, Denmark. The trials were sown on the following dates, the dates of thinning are in brackets: 21st—22nd April 1953, 3rd May 1954, sth—l3th May 1955, 9th—ll May 1956 and 30th April 1957 (30th May, 31st May, 20th—-22nd June, 4th—sth June and 31st May). 201 The bulk crosses were performed in the following manner. The roots of the strains to be crossed were planted in alternate rows: in most cases in 5—6 replicates. The same number of roots of the strains was used. Open-pollination was then expected to yield theoretically ± 50 per cent crosses between both the planted strains if two strains were planted together, about 65—70 per cent if three strains were crossed together and more if the number of strains crossed was more than three. The present author found this percentage fluctuating in different cases. Cases were found in which the percentage was only 25, which possibly depended on differences in the flowering time. The seed from different planted strains was harvested separately and used in subsequent trials. In the trials the following characteristics were investigated: 1. mean height of the neck of beets in centimetres: 2. the plumpness of the roots was ocularly estimated in the field on a o—lo0—10 scale, in which 0 = very thin roots and 10 = round roots; 3. the branchiness of the roots was ocularly estimated in the field on a o—lo0—10 scale, in which 0 = none of the roots branched, and 10 = all roots are very much branched: 4. root yield is given in kilograms per hectare: 5. the average percentage of dry matter in the roots 6. dry matter yield in kilograms per hectare: 7. percentage of bolters, counted at harvest: 8. percentage of crosses is the percentage of roots with aberrant colour; The distance between the rows has been 45 centimetres. The plots have in all cases been ten square metres. The number of replicates has in most cases been four, but in some cases five and in a few cases less than four. As always in trials with root crops the number of roots per trial has varied somewhat (< ± 4 %). 90 plants per 10 square metres is the number of plants left, if possible, at the thinning. The Xvallies have been calculated in conformity with Finney (3) and the significance has been estimated in accordance with Fisher and Yates (4), being denoted by asterisks as follows: *** = P 0.001 (highly significant), ** = ?;£ 0.01 but > 0.001 (satisfactorily significant) and *= P 0.05, but > 0.01 (signifi- cant). Pollination Beta vulgaris is a typical cross-fertilizing plant (7), which is also true of the forage beets (5, 12). According to Schneider (8), each seed plant of the beets pro- duces nearly one milliard pollen grains, which spread in every direction to a distance of 2000 m and more (6). The quantity of pollen is inversely proportional to the dis- tance from thebeet plant or thebeet cultivation, according to Stewart and Campbell (10). On the basis of these experimental results it may be assumed that in the present investigation, where the beet strains were grown in alternating rows, conditions must have been good for crossing and the fact that ± 50 per cent of the seeds developed must have been the result of cross-pollination a statement that is in 202 full agreement with Knapp (7). No reason for considering that differences between sugar and forage beets may have influenced the results can be found. If the number of families, lines or strains is n, the percentage of crosses generally seen will be: - %, according to Knapp (7). This is valid only if the fertilization is free n and not influenced by sterility, differences in the number of plants or differences in flowering time. Table 1. The characteristics of the check Barres Kofor and of the parents on an average in the experiments. Barres The parents The white The light The Barres Kofor on anaverage parents red parents parents Number of strains and crosses .. 1 18 8 3 7 Number of trials 35 84 27 4 53 Mean height of the neck, centimetres 12.2 7.8 5.1 8.7 10.6 The plumpness of the roots (0-10) 5.0 4.8 4.7 4.5 5.2 The branchiness of the roots (0—10) 2.4 3.8 5.0 3.3 2.6 Root yield, kilograms per hectare 78590 72900 68890 71450 78040 Percentage of dry matter 13.7 15.6 17.1 15.6 13.9 Dry matter yield, kilograms per hectare 10750 10290 9930 10360 10680 Percentage of bolters 1.0 1.1 0.9 2.0 0.9 Percentage of aberrant roots .. 0.2 0.5 0,2 0.0 1.2 The standard performance of the material used As it has been found more convenient to give the values in this paper as ± the mean of the parents and ± the mother, it is of interest to obtain an impression of the standard performance of the material used. The values for the check Barres Kofor and the average values for the parents are given. Further, the values for the parents of different root types are given in Table 1. Generally it can be said that the yields have been rather large both as to root yield and dry matter yield. The percentage of bolters has been rather small, I—21 —2 per cent. Comparisons between the hybrids and the mean of the parents Altogether 32 different bulk crosses, which have been tried in 138 comparisons, are studied in the present investigation. The results of these comparisons are given in Table 2. 203 Table 2. The hybrids in comparison with the mean of the parents and in comparison with the mothers. Mean of all crosses in comparison with the mean of the parents the mothers Number of combinations 32 49 » » trials of the crosses 138 119 Mean height of the neck, centimetres 4- 2.0 + 1.3 The plumpness of the roots (0—10) 4- 0.9 + 0.8 The branchiness of the roots (0—10) 1.3 0.8 Root yield, kilograms per hectare 390 940 Percentage of dry matter 0.6 0.5 Dry matter yield, kilograms per hectare .... 340 250 Percentage of bolters 0.1 0.3 » * aberrant roots + 0.6 + 1.0 On an average the roots have not beet more branched than the average of the parents in every individual cross. The difference is considerable or about 15 per cent. The root yield is on an average 390kg smaller per hectare than the mean of the parents. This is only about 0.5—0.6 per cent of the average root yield of the parents used. The dry matter content is on an average about 0.6 per cent lower than the av- erage of the parents. This is about 4 per cent of the dry matter content. This results in the fact that the performance of the hybrids is not as good in dry matter yield as in root yield. On an average the dry matter yield has been 340 kilograms smaller in the hybrids than the mean of the parents. This means that the dry matter yield has been nearly four per cent smaller in the hybrids than the mean of the parents. The percentage of bolters has not on an average been increased in the hybrids in comparison with the mean of the parents. The percentage of aberrant plants or crosses has been larger about double in comparison with the mean of the parents. The difference between the hybrids and the mean of the parents must be considered to be considerable. Table 3. The hybrids in comparison with the mean of the parents. Mean of all Number of strains involved in the crosses crosses 2 3 >3 Number of combinations 32 17 5 10 Number of trials of the crosses 138 104 14 20 The branchiness of the roots (0—10) 1.1 1.1 1.6 1.0 Root yield, kilograms per hectare 390 1250 690 + 1230 Percentage of dry matter 0.6 0.3 1.5 0.7 Dry matter yield, kilograms per hectare .... 390 280 500 280 Percentage of bolters 4: 0.0 0.5 0.6 4- 10 I * aberrant roots + 0.6 + 0.5 + 1.6 + 0.2 204 On the basis of these comparisons it may be assumed that the yield performance, especially the dry matter yield, in the present material has been smaller, than in the parents. The roots have not been more branched and the percentage of aberrant individuals has been larger than for the parents on an average. The percentage of bolters has been on an average the same for the hybrids as for the parents. The corresponding comparisons between the hybrids and the mother strain of the crosses are given in Table 2. The results largely agree with the comparisons of the mean of the parents given in Table 2. The most striking difference was found in the root yield, which was much smaller (940 kilograms) on an average than in the cor- responding mother strains. Both in comparison with the parental mean and with the mothers the hybrids have the neck of the root higher over the surface of the soil than the parents. The plumpness of the roots was more noticeable in the hybrids than in the parents (Table 2). The influence of the number of strains used in the crosses In this connection it must be considered of importance whether or not there are differences between hybrids with a different number of strains involved in the cross- ing system. Such a comparison is given in Table 3. The differences as to the branchi- ness of the roots were not large. It is interesting to note that the branchiness shows a tendency to be smaller in the hybrids than on an average in the parents. Table 4. The hybrids in comparison with the mothers. Mean of all Number of strains involved in the crosses o 3 > 3crosses Number of combinations 49 32 5 12 » » trials of the crosses 119 90 8 21 Mean height of the neck, centimetres .... + 1.3 + 1.4 1.3 The plumpness of the roots (0 10) + 0.8 -f 1.1 0.3 The branchiness of the roots (0 —10) .... 0.8 1.3 + 1.1 0.3 Root yield, kilograms per hectare 940 1630 3050 + 1810 Percentage of dry matter 0.4 0.5 0.3 0.3 Dry matter yield, kilograms per hectare .... 250 330 470 + 40 Percentage of bolters 0.3 0.9 + 0.7 + 0.8 Percentage of aberrant roots + 1.0 + 0.9 + 3.1 + 0.5 The root yield performance of the hybrids with a higher number of strains than three involved has been much better than that of hybrids with only two parental strains involved. The difference was higher than three per cent of the average yield. The dry matter percentage was, however, in the present material considerably better for hybrids with only two strains involved in the crosses than for the hybrids with more than three strains involved in the crosses. The dry matter yield in both groups was consequently 280 kilograms smaller than that of the mean of the parents. 205 The comparisons in Table 4 between groups of hybrids with different numbers of strains involved in the crosses show about the same differences between groups of 2 and > 3 strains as in Table 3, but the yield values are more negative for the first- mentioned group and more positive for the group with hybrids in which more than three strains are involved in the comparisons with the mother than in the comparisons with the parental mean. Differences between different materials It is further of interest to see to what extent there are differences between dif- ferent types. In Tables 5 and 6 the values are given for crosses between different white beets and crosses between different beets of the Barres type, in Table 5 the values in comparison with the parental mean and in Table 6 the values in comparison with the mothers are given. The differences between the progeny and the parents show a tendency to be larger in the group of white beets than in the Barres beets. In comparison with both the mean of the parents and with the mothers the hybrids have not been branched as much. This is especially striking in the group of white beets in which only two strains are crossed. In both the comparisons in Tables 5 and 6 the root yields of the crosses in which more than three strains are Table 5. The hybrids in comparison with the mean of the parents for different types. White Barres Two strains > 3 strains Two strains > 3 strains crossed crossed crossed crossed together together together together Number of combinations 13 4 4 6 Number of trials of the crosses 76 8 28 12 The branchiness of the roots (0—10) .... 1.6 1.0 0.1 1.2 Root yield, kilograms per hectare 2410 1180 4- 2520 + 2830 Percentage of dry matter 0.4 0.9 0.0 0.5 Dry matter yield, kilograms per hectare .... 410 540 -f* 120 110 Percentage of bolters 0.9 -f 0.3 + 11 + 1-4 Percentage of aberrant roots + 1.2 0.5 1.6 -f 0.7 involved have been larger than the crosses in which only two strains are used. It it also interesting to observe that the effect of crossing as regards the root yield has been on an average negative in the group of white beets and positive in the Barres group. The dry matter percentage shows a greater tendency to increase in the group of the white beets than in the group of the Barres beets. Consequently, the Barres 206 Table 6. The hybrids in comparison with the mothers. White Barres Two strains > 3 strains Two strains > 3 strains crossed crossed crossed crossed together together together together Number of combinations 24 6 8 6 » i> trials of the crosses 63 9 26 12 Mean height of the neck. Centimetres .... + 2.6 + 5.1 3.3 The plumpness of the roots (0 10) -f 1.1 + 0.6 The branchiness of the roots (0—10) .... 1.7 0.2 i 0.0 0.4 Root yield, kilograms per hectare 3070 -f- 800 -j- 2680 + 2840 Percentage of dry matter 0.7 0.1 0.2 0.5 Dry matter yield, kilograms per hectare .... 500 + 220 + 180 130 Percentage of bolters 1.3 + 0.3 -f 0.4 + 1.3 Percentage of aberrant roots + 1.7 + 0.2 1.6 + 0.8 crosses gave relatively larger dry matter yields than the white beets. This was abun- dantly clear in the comparisons between the hybrids and the parental mean. The percentage of bolters has shown a clear tendency to increase in the Barres group. A small increase was shown in the white crosses in which more than three strains are crossed. In the group of strains with white root, in which only two strains are crossed, the percentage of bolters is much smaller in the progeny generation than in the parental generation. Table 7. Comparison between the yield characteristics in some reciprocal crosses. Cross Number Root yield Dry matter Dry matter of trials kilograms percentage yield kilograms ± the mother i the mother ± the mother Gulläker x Solid 4 3260 2.3 480 Solid x Gulläker 4 - 5590 -J- 0.0 - 630 Gulläker x Miika 4 4900 1.1 1340 Miika x Gulläker 5 2350 -f- 0.7 160 Miika x Solid 5 3870 + 0.5 120 Solid x Miika 5 1150 0.7 530 Gulläker x Monark 3 6880 0.2 1160 Monark x Gulläker 4 3940 0.3 740 Miika x Monark 3 5530 + 0.7 150 Monark x Miika 3 380 1.8 900 Solid x Monark 4 2700 0,3 400 Monark x Solid 3 1650 2.4 1370 B. Kofor xB. Svea * 3 + 2400 0.1 -f- 210 B. Svea xB. Kofor 3 2500 0.5 840 207 A detailed examination of certain reciprocal crosses In Table 7 are given the yield characteristics for nine reciprocal crosses, which involve the highest number of experiments of the crosses investigated. Characteristic of the six firstmentioned (all crosses between white strains) is that they have in all cases given smaller root and dry matter yields than the mother variety. On an average, in these crosses the dry matter percentages of the reciprocals counted together were lower than those of the mother-strains. The results for the best grosses, that possibly can be commercially exploited, are given only as averages in the tables, but neither the names of the parents nor the results of them are individually given in this ■paper. On the basis of the presented material (Table 7) it can be expected that there are differences in the combining abilities between different strains (cp. Table S. The effect of crossing between five fodder sugar beet strains. The mean of reciprocal crosses ± the mother Strain Number Root yield Percentage of Dry matter of trials per hectare dry matter yield per hectare Solid 36 - 2443 - 0.5 875 Milka 36 - 2865 - 0.3 - 655 Gulläker 31 - 3838 - 0.4 - 895 Monark 23 2655 0.3 568 Triumf 14 - 3985 - 0,1 - 868 Milka X Solid and Gulläker X Monark). This is still more emphasized in the data given in Table 8, which shows that considerable differences were found. Further the large differences between the material of white and that ofBarres beets should be pointed out. Table 9. Direct comparisons between and Fi . Fi F 2 Number of combinations investigated 7 7 » » trials of the crosses 11 9 The branchiness of the roots (0—10) + 0.3 + 0.3 Root yield, kilograms per hectare 2790 3060 Percentage of dry matter 0.4 0.3 Dry matter yield, kilograms per hectare .. 270 650 Percentage of bolters + 2.1 + 0.5 » » aberrant roots + 5.4 0.6 9 208 Comparison between Fl and F 2 It was possible to compare the first and second progeny generation in 7 diffe- rent combinations (Table 9). The branchiness of the roots was the same in both generations. Both the root yields and the dry matter yields per hectare were,relative- ly seen, smaller in F 2 than in the first progeny generation. It must be considered possible that the differences between both these generations in the yield characteris- tics mentioned would have been still larger if the number of plants had been as large for Fx as for F 2. The percentage of bolters was much larger in the first progeny generation than in the second progeny generation. The difference was satisfactorily significant ( x2 = 10.47**). Discussion On an average the root yields, the dry matter content and the dry matter yieldshave been smallerfor the progeny than for the parents. It can therefore be stated as regards the present material that it is not possible to produce practically usable hybrids without knowing the combining abilities of the parents and the perform- ance of the progeny. Further, it can be concluded that crossings between marketed beet strains during seed cultivation must be avoided. Consequently, rather large distances between different strains of the same beet type to avoid crossings must be considered a justifiable demand and one that should be observed by the seed testing representatives in field control. It must, however, be stated that on an aver- age neither the root form nor the height of the neck have been negatively influenced by the crossing of the strains. The above-mentioned points and the fact that the roots have not been more branched in the hybrids than in the parental strains must be considered both important and striking. Of further interest is the fact that the percentage of bolters has not increased on an average. That the percentage of aber- rant roots of strange colour has been higher in the hybrids than in the pure parental strains cannot be considered to be of any practical consequence. The hybrids in which more than three strains have been used have on an average shown somewhat better results in root yields than the hybrids between only two strains, but the differences are non-significant and must be considered dependent on the fact that the proportion between different materials has varied in the different groups. Further, the dry matter yields for both the groups are on an average the same in the comparisons with the means of the parents. Upon the whole, the performance of the Barres strains has been better in root yield, percentage of dry matter and dry matter yield per hectare than that of the white strains in the crosses. This is naturally very interesting and indicates that the combining ability of the Barres strains has been better than that of the white strains on an average. Of considerable interest are also the data showing that F x seems to be more favourable as to the yield features than F 2. The greatest disadvantages as regard the Fj-generation have been the facts that in the actual material the percentages of 209 bolters and crosses have been much higher than in the Regeneration. These results indicate that the greatest possibilities for getting favourable combinations in the present material seem to be found in the group of Barres strains, the best generation appearing to be the first progeny generation ; and that possibly a larger number of strains involved than three is somewhat more favourable than only two or three strains. The author does, however, suggest that it is possible to get much better combinations than those described in the present paper if, on the one hand, a larger amount of material with more marketed and theoretical strains is used, and, on the other, families of different strains and crosses; and the strains and families possessing the best combining-ability features are used for building hybrids and strains. Further, if it is possible to use the strains and families, with the best combining-ability features, in more extensive crossing systems the results will be still better than the average results obtained in the present experiments. Summary In the years 1952—56 the present author allowed different beet strains at the Gulläker Plant Breeding Institute to hybridize. In the years 1953—57 these hybrids were compared in trials with regard to their yield performance and some other practical features with the parents. Altogether 34 hybrids were compared in 138 comparisons with the parents. The progeny generations gave on an average smaller root and dry matter yields than the parents. The dry matter percentage was lower in the progeny generation than in the parental generation. The roots were not much more branched in the progeny generation than in the parental generation. The position of the roots in the soil and the form of the roots were not negatively influenced by crossing. Nor was the percentage of bolters larger than in the parental generation. The hybrids in which more than three strains were involved showed a tendency to give larger root yields than the strains in which only two strains were crossed. A corresponding increase in dry matter was not obtained. Considerable differences were found in the combining abilities between differ- ent types and strains and it seems to be possible to find combinations which have better yield performances than the parents. The consequence of crossing for the seed testing in field is discussed. REFERENCES (1) Bogh, H. 1952. Züchtungsarbeit mit Futterrüben. Pajbjergf. Forsogs- og Foraedlingsarbejde 1952: 21-59. (2) Doxtator, C. W. & Skuderna, A. W. 1947. Crossing Experiments in sugar beet lines. Proc. Amer. Soc. Sugar Beet. Technol. 1946: 230—236. (3) Finney, D. J. 1953. An introduction to statistical science in agriculture. 179 pp. Copenhagen. (4) Fisher, R. A. & Yates, F. 1953. Statistical tables for biological, agricultural and medical research. 126 pp. Edinburgh. 210 (5) Frandsen, K. J. 1956. Breeding of Forage Beets. Handbuch der Pflanzenzüchtung 3: 284 311, (Begr, Th, Roemer und W. Rudorf, 2 Aufl. hrsgb. H. Kappert und W, Rudorf) Berlin & Hamburg. (6) German, I. V. 1939. Transference of sugar-beet pollen by air currents in vertical direction. C. R. Acad. Sei. URSS 24: 77-80 (Ref. Knapp 1956). (7) Knapp, E. 1956. Beta-Rüben. Bes. Zuckerrüben. Handbuch der Pflanzenzüchtung 3: 196 284 (Begr. Th. Roemer und W. Rudorf. 2 Aufl. hrsgb. H. Kappert und W. Rudorf), Berlin & Hamburg. (8) Schneider, F. 1944. Züchtung der Beta-Rüben. Handbuch der Pflanzenzüchtung 4: 1— 95 (1 Aufl. hrsgb. Th. Roemer und W. Rudorf). Berlin. (9) Sedlmayr, R. 1947. Inbreeding of sugar beets. (Hung.) Hungarian Rev. Agrar. Sei. 1: 15 22. Abstr.: Biol. Abstr. (1949) 23: 1685. (10) Stewart, D. & Campbell, S. C. 1952. The dispersion of pollen in sugar-beet seed plots. Proc. of the 7th General Meeting of the Amer. Soc. of Sugar Beet Technologists 7: 459 469. (11) Stewart, D. & Gaskill, J. 0., Coons, G. H. 1947. Heterosis in sugar beet single crosses. Proc Amer. Soc. Sugar Beet Technol. 1946: 210 222. (12) Sundelin, G. 1934. Självfertilitet och självsterilitet hos Beta (with Engl, summ.) Sv. Utsädesföre- nings tidskr. 44: 329 352 och 363 385. (13) Wichmann, W. 1957. Leistungsanlagen und züchterische Probleme der Futterrüben und Kohl- rüben unter besonderer Berücksichtigung deutscher Verhältnisse. Z. Pflanzenz. 37: 27-40. SELOSTUS: JUURIKASKANTOJEN VÄLISISTÄ RISTEYTYMISTÄ Rolf Manner Linköping, Ruotsi Vuosina 1952 —56 tekijä on Gulläkerin kasvinjalostuslaitoksella suorittanut juurikaskantojen välisiä risteytyksiä, joista saatuja risteytymiä on kokeiltu ja tutkittu vertailevissa kokeissa mainitun kasvinjalostuslaitoksen koekentillä vuosina 1953 57. Näitä risteytymiä on verrattu vanhempiinsa, minkä lisäksi risteytymien Fr ja F - sukupolvia on verrattu toisiinsa. Yhteensä on kokeiltu 34 erilaista risteytysyhdistelmää. Tutkimustuloksista ilmenee mm., että käytetyn aineiston risteytymät ovat keskimäärin antaneet pienemmän juurikas- ja kuiva-ainesadon kuin niiden vanhemmat. Myös kuiva-ainepitoisuus on ollut risteytymissä keskimäärin pienempi kuin vanhemmissa. Juurikkaiden haarakkuus ei keskimäärin ole ollut suurempi risteytymissä kuin vanhemmissa. Risteytys ei ole vaikuttanut epäedullisesti juurikkaiden muotoon eikä niiden kasvutapaan. Sama koskee myös ensimmäisen vuodenaaluvien lukumäärää. Huomattavia eroja eri risteytymien välillä on havaittu varsinkin juurikkaiden ja kuiva-aineen hehtaarisatoihin nähden. Niinpä esimerkiksi barreskantojen väliset risteytymät ovat olleet vanhempiinsa verrattuina huomattavasti paremmat kuin käytettyjen valkoisien rehusokerijuurikaskantojen väliset risteytymät. On luultavaa, että voidaan löytää näitä vielä paljon parempiakin risteytysyhdistelmiä, mikäli käytetään hyväksi suurempaa aineistoa sekä etsitään ja kokeillaan kaikkein parhaiten yhdisty- miskykyisiä perheitä. F l -sukupolvion antanut suuremman sekä juuri- että kuiva-ainesadon kuin F 2-sukupolvi.Väriltään vanhemmista poikkeavien taimien ja aaluvien lukumäärä on ollut huomattavasti suurempi F,-sukupol- vessa kuin F 2-sukupolvessa. Kokeissa on vertailtu keskenään risteytymiä, jotka on rakennettu risteyttämällä keskenään eri määriä kantoja (2, 3 tai > 3). Vertailuista ilmenee, että tutkitut risteytymät eivät eroa toisistaan pal- joakaan kuiva-ainesatoon nähden. Toisaalta juurisato näyttää olleen suurempi sellaisilla risteytymillä, joita rakennettaessa on risteytetty useampia kuin kolme kantaa keskenään, kuin sellaisilla, joiden valmistukseen on käytetty vain kahta kantaa.