Parental species and their compatibility. For hybridization with sunflower, we have used certain species of the genus Helianthus L., which differ markedly from the former in their morphological characters and general growth habit. In addition to tuberous species of this genus, such as H. tuberosus, H. macrophyllus, and H. subcanescens, we also introduced species with rhizomes or root suckers (H. Maximiliani, H. mollis, H. laetiflorus, H. tomentosus, and others) into the crosses.
Hybridization experiments showed that the group of rhizomatous species with a chromosome number equaling that of sunflower (2n = 34) did not cross at all with the sunflower, whereas the tuberous group with a chromosome number of 2n = 102 crossed relatively easily. H. subcanescens crosses particularly well with sunflower, and H. macrophyllus and H. tuberosus somewhat less easily. Crosses succeed if these species are used as seed parents, while sunflower used as seed parent has an adverse effect on the cross.
We had, and now have, large numbers of first-generation hybrids between sunflower and tuberous Helianthus species at our disposal. The varieties introduced into the crosses include sunflowers from the Don Oil Crop Station (Zhdanovskii 8281) and also from the All-Union Institute of Oil and Essential Oil Crops (Nos. 1646, 6540, and others). One of the Jerusalem artichokes used was Belyi Kievskii [White Kiev], which is distinguished from other varieties by a high fertility under the conditions of the central belt of the Ukraine. The hybrids from its cross with sunflower exhibit a high degree of heterosis, both in aerial mass (silage) and tubers. In recent years, other varieties of Jerusalem artichoke have been introduced into the crosses: Belyi urozhainyi [White Yielding] Ukrainskii 76, S-12-37, and G-7l-39, but these are poorly fertile and cross very badly with sunflower.
Form-creative process in hybridization of Jerusalem artichoke with sunflower. The first-generation hybrids are marked by a high variability in all morphological characters, particularly in stem branching, a cordate or ovate leaf shape, tuber formation or absence of it, anthocyanin coloring of the stem, etc.
Hybrid plants can be distinguished from non-hybrids already in the seedling stage by their cotyledons. In ordinary seed-grown Jerusalem artichoke these are dark green in color, more elongate, and without an abrupt transition to the petioles. The cotyledons of the hybrids are intermediate between those of Jerusalem artichoke and sunflower: they are wider, and their blades narrow abruptly where they join the petiole.
The first-generation hybrids between Jerusalem artichoke and sunflower exhibit an intermediate branching type, they are less branched than Jerusalem artichoke, and sometimes entirely unbranched. Among 931 hybrid plants, for example, which we studied in 1956, 61 or 6.6% were unbranched and 332 or 35.6% slightly branched, while 349 or 37.5% had a medium branching habit, and 189 or 30.3% were strongly branched.
The leaves of the hybrids are generally wider than those of Jerusalem artichoke, and vary greatly in size; frequently they are even larger than sunflower leaves. The leaf (petiole) base is usually pithed, a feature used for determining the hybrid nature of the plants.
The leaf petiole is thicker than in Jerusalem artichoke, and thinner than in sunflower. While the sunflower petiole is unwinged and that of Jerusalem artichoke winged to the base, that of the hybrids is almost invariably winged, but to varying degrees, generally to half-way down.
|* [Sic. This conclusion is not borne out by the figures quoted.]|
A distinguishing mark of Jerusalem artichoke, and in particular of variety Belyi Kievskii, is the red-brown anthocyanin coloring of the stem, particularly of its upper part. In sunflower, there is no anthocyanin coloring. Sunflower X Jerusalem artichoke hybrids segregate markedly for this character and range from intensely colored forms to others which have no coloration at all. Among 940 hybrids studied by us for this character, 379 or 40.3% were anthocyaninless, 142 or 15.1% were weakly colored, and 143 or 15.3% had a strongly colored stem. These data show that the majority of hybrids are intermediate for this character*, while there are few forms with an intense coloring of the stem.
The head diameter in Jerusalem artichoke is fairly small, reaching 1.2 to 1.5 cm, and the heads have no ligulate florets. In hybrids between Jerusalem artichoke and sunflower the head is considerably larger than in Jerusalem artichoke, but smaller than in sunflower; it usually has a diameter of 4 to 5 cm, and 8 to 10 cm in only single specimens. The number of ligulate ray florets is usually intermediate, about 20 to 24. They are intensely yellow, sometimes very large, and often even hang down on the disk.
Fasciations are of frequent occurrence in first-generation hybrids. In certain years, fasciated types are very numerous. Fasciations appear in the form of elongate, double and even triple heads, small heads around the stem, and groups of heads in the leaf axils.
In 1956, the fasciated types were particularly numerous. Among 940 F1 hybrids, 228 or 24.2% were fasciated plants.
In the second generation the formative processes are even more pronounced. Side-by-side with unbranched forms, there are strongly branching forms, moreover there are modifications in branching habit, and frequently plants appear which do not resemble their parents and are sometimes unlike any representative of the genus Helianthus L. in general growth-habit.
Segregation also becomes more pronounced in a number of other characters: leaf shape, anthocyanin coloring, increase in head size, appearance of ornamental forms, etc.
According to the heredity of morphological characters, and depending on the dominance of certain traits we divide all hybrids of the first and more advanced generations into five basic types.
|FIGURE 1. Hybrids between Jerusalem artichoke and sunflower; of the sunflower-Jerusalem artichoke type with a dominance of sunflower characters.|
In first-generation hybrids, plants with intermediate characters predominate, i.e., plants of types II and III. In the second and advanced generations, the number of plants resembling sunflower increased, i.e., types I and II and also the number of hybrids with new characters, i.e., type V.
The tuber-forming ability of Jerusalem artichoke X sunflower hybrids. Hybrids between Jerusalem artichoke and sunflower exhibit a varying tuber-formation ability. Together with high-yielding plants producing up to 4 kg of tubers each, there are others which only yield 100 to 200g. The tuber-formation character is dominant in F1 hybrids.
Only a small percentage (about 1%) of the large number of hybrid seedlings raised by us had an annual life cycle, i.e., the plants were without tubers and other perennial organs (stolons or root buds). A higher percentage of annuals only appeared in single years. In 1949, for example, we had 202 plants in the nursery of first-year hybrids. Among them there were only 8 plants, or 3.9%, with annual life-cycles. The remaining 194 hybrids were either tuberous or had perennial root buds. Seven plants, or 3.4 %, had such root buds.
Characteristically, a certain percentage of plants grown from hybrid tubers do not form tubers themselves, though they do not differ from tuber-forming plants in any other way. Twenty-three of 470 plants raised from tubers, or 4.8%, were non-tuberous, and 14 plants, or 29%, formed perennial root buds, or small stolons without tuber thickenings in the collar region.
In the second generation raised from a backcross of F1 hybrids to sunflower, there were fewer tuberous segregants and more annual types, i.e., the tuber trait appeared as a recessive character.
It has been demonstrated by experiments that the percentage of tuberous segregants can be increased to almost 100% by backcrossing F1 hybrids to a recurrent tuberous species. The tuber trait is closely linked with the growth habit of the tuberous species, and one can foretell in preliminary assessment whether a particular hybrid is likely to form tubers.
|FIGURE 2 Hybrids between Jerusalem artichoke and sunflower; of the "new forms" type.|
The shape of the tuber is highly variable and ranges from deformed stolon-like types to tubers of an even, potato-type shape. Irregularities in tuber shape constitute an undesirable character in most of the hybrids; the tuber becomes lengthened and develops variously sized outgrowths. We have tentatively established ten types of hybrid tubers.
Vegetative period and fertility of Jerusalem artichoke x sunflower hybrids. Under the conditions of the central belt of the Ukraine the Jerusalem artichoke does not flower at all. It forms buds or late flowers only in rare years with a long warm fall, but forms no seed. The sunflower has a relatively short vegetative period, flowers round about July, and ripens in August. The vegetative period of the sunflower from germination to flowering is 65 to 68 days, and from the seedling stage to ripening 112 to 115 days.
F1 hybrids have an intermediate vegetative period; most hybrids flower, but relatively few reach seed maturity.
Hybrids between the wild tuberous species H. subcanescens (Gray) Wats. and H. macrophyllus Willd. flower early and reach full maturity in the Ukraine.
The second generation segregates markedly for length of the vegetative period, and its hybrids range from extremely quick-ripening to non-flowering forms.
The hybrids have been divided by us into four groups by fertility, from highly fertile to sterile. The highly fertile group comprises hybrids from the cross between H. annuus and H. macrophyllus. This combination has yielded over 600 achenes per plant in certain years. Hybrids from the cross between H. subcanescens and H. annuus were less fertile. They gave an average of 80 to 100 achenes per plant. Hybrids between the cultivated Jerusalem artichoke (H. tuberosus L.) and sunflower were weakly fertile and almost sterile; on the average, they produced one achene per head or a fraction of one per plant.
The F2 hybrids from a backcross of F1 to sunflower or Jerusalem artichoke are completely sterile. We have examined some ten thousand heads, and only in some of them were single achenes formed. As an exception, we obtained a hybrid in 1954 which developed 700 achenes per plant. No cytological study of this hybrid was made, and we can give no reasons for its high fertility. Thousands of other plants from the same cross were totally sterile or produced 1 to 2 achenes per plant. The seeds of this hybrid served as starting material in breeding for rust immunity in sunflower (Figure 3).
Jerusalem artichoke x sunflower hybrids as valuable dual purpose fodder plants. In breeding work with hybrids between Jerusalem artichoke and sunflower we obtained two hybrid clones, No. 15 and No. 120, which have a considerable interest as highly productive fodder plants with a double use (tubers and herbage). Under favorable conditions, plants of both clonal lines reach a height of 3.4 to 4 m and give a high yield of green matter which is suitable for silage, as well as a high tuber yield suitable as fodder for all farm animals, especially pigs.
Under good growing conditions, clonal line No. 120 yielded 300 to 400 centners of tubers and 600 to 700 centners of green matter per hectare in favorable years. The tuber yield from clonal line No. 15 was usually equal to that from the parent variety of Jerusalem artichoke, which is 150 to 180 centners/ha. in the forest-steppe of the Ukraine. In herbage yield, the hybrid clonal line surpassed Jerusalem artichoke considerably. Under ordinary growing conditions, it yielded 600 centners/ha ha of green matter and, in low lying places, where there is no water shortage, 800 and 900 centners/ha.
|FIGURE 3. Achenes of parents and hybrids 1 - achene of Jerusalem artichoke; 2 - achene of F1 hybrid 3 - achene of F2 hybrid; 4 - achene of sunflower.|
The aerial mass of hybrid clone No. 120 is somewhat coarse, but the presence of high amounts of carbohydrates (up to 15% of the fresh weight) and other nutrient substances in the stems makes it a suitable raw material for silage.
|*[Poltavskii nauchno-issledovatel'skii institut svinovodstva.]|
N. F. Chebotarev (1952) made a comparative study of our hybrids with other crops of fodder importance at the Poltava Research Institute for Pig Breeding*. He gave the following sampling data of fodder units and digestible protein per hectare: hybrid clone No. 120 - 23,190 fodder units and 720 kg of digestible protein, potato - 7,030 fodder units and 120 kg of digestible protein, sunflower - 5,720 fodder units and 410 kg of digestible protein, corn (with cobs) - 6,550 fodder units and 160 kg of digestible protein.
The fodder value of these hybrids' green matter equals that of corn and is higher than that of sunflower greens used for silage. According to determinations made in the Biochemistry Laboratory of the former Institute of Genetics and Breeding of the Academy of Sciences of the Ukrainian SSR, the stems of the hybrids have a considerably higher sugar content than those of sunflower; their sugar content is the same as that of the stems of Jerusalem artichoke. The protein content of the stems of the hybrids is somewhat lower than in sunflower, but no lower than in Jerusalem artichoke; this is seen from the following data (in percentages of fresh weight):
|Sunflower Zhdanovskii 8281 Jerusalem artichoke Belyi||5.5||14.6|
|Hybrid clone No. 120||32.4||11.9|
The stems of the hybrids have a high carotene content - 106.8 mg per 1 kg of fodder - and constitute a good raw material for silage. The tubers of the hybrids have a higher fodder value than those of the ordinary Jerusalem artichoke; according to determinations of the same laboratory, the hybrid tubers contain almost 5% more fructoses (of the basic carbohydrate) than the parent variety of Jerusalem artichoke.
The protein content in the hybrid tubers was the same as in Jerusalem artichoke and amounted to 11.3% of the dry substance. The content of minerals in Jerusalem artichoke was 5.1% and in hybrids 4.85%. Because of this mineral content, young pigs fed on these tubers do not develop anemia.
Experiments carried out in the state farms of the Khar'kov and Poltava Regions have demonstrated the value of this crop for pig-breeding farms. The green mass of the hybrids was harvested and silaged by the state farms in the fall, and the tubers were left in the ground over winter and used for pig grazing in early spring.
In the pig-breeding State Farm No. 7 of the Khar'kov Region experiments were made on grazing pigs on an area of 18 hectares in the early spring period (second half of March, April, and the first half of May). These experiments showed that, in the case of non-hybrid varieties, various tuber remnants (tuber halves, eyes, stolons) amounting to 3,000 pieces per hectare were left in the soil; the hybrid tubers, on the other hand, form compact clumps that are wholly consumed by the pigs, no remnants being left. By virtue of their compact tuber clumps, hybrids between sunflower and Jerusalem artichoke are suitable culture for fodder and field-crop rotations; the difficulty of having to clean the fields, which troubles farmers in rotations with non-hybrid Jerusalem artichokes, does not exist here.
State and collective farms can harvest a high green matter yield from the hybrid varieties in the fall, and can use the tubers in the fall and spring as valuable juicy fodder for all kinds of farm animals, especially pigs. This is of great importance for agricultural production, as there is usually a shortage or a total lack of juicy fodder in the collective and state farms in spring. Besides, if pigs are grazed on plantations of hybrids in early spring, full use is made of the tubers without any expenditure in manpower for harvesting and storing, and hence large quantities of other feeding stuff are saved.
Jerusalem artichoke x sunflower hybrids and the problem of inulin and fructose. Another point to be dealt with is the utilization in the sugar industry of Jerusalem artichoke and its hybrids with sunflower. There are new, not yet widely known possibilities in this matter. A combined enterprise (processing plant and state farm has been established recently at our recommendation in the Tcherkass Region for the production of fructose from hybrid tubers.
Hybrids are a good raw material for the production of fructose. They have a compact clump of tubers, their tubers are large, fan-shaped, have short stolons which do not interfere with cutting during processing, and contain a high percentage of fructose amounting to 22-23% in certain years; the general yield of fructose per hectare is higher than in Jerusalem artichoke (Table 1).
The carbohydrate complex in hybrid tubers that had been stored in clamps during the winter was determined and compared with that of ordinary Jerusalem artichoke (Table 2).
HYBRIDS WITH SUNFLOWER, BASED ON EXPERIMENTAL DATA OF THE FORMER INSTITUTE OF
GENETICS AND BREEDING, ACADEMY OF SCIENCES OF THE UKRAINIAN SSR (AVERAGE FOR 1953 to 1955)
in tubers (%)
|Jerusalem artichoke Belyi Kievskii||187.0||17.1||32.0|
|Hybrid between Jerusalem artichoke and sunflower, clonal line No. 120||425.1||18.8||80.3|
|CARBOHYDRATE COMPLEX IN TUBERS OF JERUSALEM ARTICHOKE AND ITS HYBRIDS WITH SUNFLOWER (%)|
|Jerusalem artichoke Belyi Kievskii||0.66||3.09||0.69||1.59||10.95||15.35||71.33|
|Hybrid clone No. 120||0.50||2.48||0.16||1.70||15.61||18.75||83.25|
As seen from the above date, the hybrid between Jerusalem artichoke and sunflower has a 3. 4 % higher content of total sugars and contains 4. 66% more basic-carbohydrate fructose than Jerusalem artichoke.
|*[Laboratoriya sakharistykh veshchestv Instituta organicheskoi khimii Akademii Nauk Ukrainskol SSR.]
** [Tsentral'nyi nauchno-issledovatel'skii institut sakharnoi promyshlennosti.]
Analyses of hybrid stems made at the biochemical laboratory of the former Institute of Genetics and Breeding of the Academy of Sciences of the Ukrainian SSR and at the carbohydrates laboratory of the Institute of Organic Chemistry of the Academy of Sciences of the Ukrainian SSR* revealed the presence of 12 to 15% of sugars, and in some years of 18% (of the fresh weight).
The stem sugar content can, without a doubt, be increased considerably by breeding, so that hybrids with a twofold utilization by the sugar industry can be developed.
Small-scale production experiments at the Central Sugar Industry Research Institute** have shown that the syrup obtained from stems of hybrids raised by the author at the former Stavropol' Breeding Station has an agreable taste with a honey flavor. The use of such hybrid species for fructose production is very promising, as additional amounts of fructose (approaching those from the tubers in quantity) can be extracted from the stems.
|*[A pood (Russian weight) = 36.113 lb.]|
The susceptibility of Jerusalem artichoke x sunflower hybrids to diseases, and the possibility of using these hybrids in sunflower breeding. Jerusalem artichoke x sunflower hybrids are marked by a complete immunity to rust and broomrape. The problem of combating broomrape on sunflower is almost solved, as is known. Rust control still necessitates much work. None of the presently grown sunflower varieties are unaffected by rust; in some humid districts sunflower cannot be cultivated, because of the seriousness of attacks by this fungus. The raising of rust-immune sunflower varieties is an urgent problem, on which the breeder has to work. According to calculations by the known sunflower breeder V. S. Pustovoit, two million poods* in sunflower oil are lost by each degree of rust affection every year.
Jerusalem artichoke x sunflower hybrids can serve as starting material in the breeding for rust resistance. We studied the progeny of Jerusalem artichoke x sunflower hybrids during seven years and made selections for immunity to rust and broomrape. We found that F1 hybrids are entirely immune to Puccinia helianthi. In the second and the third generations, segregation into immune and susceptible forms takes place, with a considerable preponderance of the former.
We have done breeding work for rust immunity to the seventh generation, in which there is a vigorous segregation into immune and non-immune families. No cases were observed, where an entire family was immune, but the average degree of affection (in families described as immune) is very low. We have obtained families which are undergoing competitive tests and are being propagated at the Andreev State Farm of the Cherkassy Sugar Beet Trust; they are almost entirely free of rust, give a high seed yield, and surpass the standard varieties in oil yield. Test results of the most productive families are shown in Table 3.
|MOST PRODUCTIVE FAMILIES OF JERUSALEM ARTICHOKE x SUNFLOWER
HYBRIDS OBTAINED IN THE SEVENTH GENERATION
|Variety||Seed yield per plot||Husk||Oil||Oil yield per plot||Affection
|Thousand-seed weight (in g)|
|in g||in %||in %||in g||in %|
Seventh generation hybrids have also shown a high immunity to broomrape. Families grown in an environment which is favorable for infection were mostly resistant and about 30 % of them absolutely immune (Figure 4).
|FIGURE 4. Third-generation Jerusalem artichoke x sunflower hybrid, which served as starting form in the breeding of rust-immune sunflower|
Trial production test of Jerusalem artichoke x sunflower hybrids. For this test we sent planting material to 30 research institutions, 35 collective farms, and 90 state farms in different zones of the Soviet Union. In addition, hybrids of Jerusalem artichoke with sunflower were tested by many collective farm research workers and young naturalists on school plots.
The trial was made on a wide network stretching from the Far East (Magadan) and to the western Ukraine (Lvov) and from the extreme north (Kandalaksha, Murmansk Region) to the south (Kirovabad).
The following conclusions can be drawn from these tests:
In the Ukraine, the hybrids are grown more successfully; the best tuber and herbage yields are obtained in the more northern and western districts (Chernigov, Sumy Poltava, Kiev, Zhitomir and Vinnitsy Regions); in. these districts the tuber yield is between 300 and 400 centners/ha, with a similar yield of green matter.
On the cytology of the Jerusalem artichoke x sunflower hybrids. A cytological study was made of hybrids of the first and second generations, so as to clarify causes of their sterility. These hybrids are also of interest as offspring of parental forms with unequal chromosome numbers (sunflower 2n = 34, Jerusalem artichoke and wild relatives 2n = 102).
F1 hybrids of three combinations with different degrees of fertility were submitted to a cytological study:
In addition, we are beginning with a study of F2 backcrosses to clarify the causes of the particularly high sterility in these hybrids. We have to stress that we have made no detailed study of somatic mitosis, but have merely counted chromosome numbers on permanent preparations.
The chromosome count in the somatic cells of F1 hybrids showed the presence of 68 chromosomes; this is in accordance with hypothetical assumptions (51 chromosomes from Jerusalem artichoke and 17 from sunflower).
We have also made a study of the qualitative composition of pollen grains, in particular of their fertility or abortiveness, of the percentage of normal and degenerated pollen, and of variability in the size of pollen grains.
The species H. tuberosus L. has a high percentage (65.1) of abortive pollen grains. It also has the greatest quantity of degenerated pollen (16.1%) and of pollen deviating in size from the normal (macropollen - 1.7%, and micropollen - 2.2%). It has been proved by Kostoff (1934) that the reduction division in H. tuberosus L. is highly irregular; apparently it is a plant of hybrid origin. There were relatively few abortive pollen grains in the species H. subcanescens (Gray) Wats. (22.3%) and very few in H. annuus Willd. (1.6%).
F1 hybrids, too, have a high percentage of abortive pollen grains. The highest percentage was observed in the combination H. tuberosus x H. annuus (65.5); it was somewhat lower in hybrids from the cross H. subcanescens x H. annuus (37.2), and the combination H. annuus x H. annuus had the lowest percentage of pollen abortion (6.5). The first two combinations also have a higher percentage of degenerated pollen and pollen deviating from the normal size.
The high percentages of abortive and degenerated pollen, and also of that of pollen of a deviating size indicate an abnormal course of meiosis which generally leads to sterility in the hybrid. The F1 H. tuberosus x H. annuus hybrids, which have the highest percentage of abortive pollen grains and of pollen of deviating size, have an extremely low fertility and are almost sterile. F1 H. subcanescens x H. annuus, which have a lesser percentage of abnormal pollen grains, are more fertile than the combination H. tuberosus x H. annuus but less fertile than hybrids from the cross between H. annuus and H. annuus.
The F2 hybrids from the backcross of F1 to sunflower have an even greater variability of pollen grains. In the second generation, high percentages of abortive pollen (80 to 82), degenerated pollen (11.6 to 18.3) and micro- and macropollen (6 to 11) are noted. This is an indication of the exceptional sterility of the hybrids, which has been confirmed by our investigations. Of some thousands of F2 plants which we have studied, only single individuals produced some few achenes in their flower heads, while all the remaining plants were highly sterile.
While pollen grains of the parental forms are more or less evenly sized, the size of hybrid pollen is very variable, especially in both F1 and F2 sterile groups. This is particularly apparent in the F1 combinations H. tuberosus x H. annuus, F1 H. annuus x H. tuberosus, F1 H. annuus x H. annuus, and the F2 and F3 hybrids.
In the fertile group of first-generation hybrids (H. annuus x H. annuus) the formation of 34 bivalents was observed as well as a complete absence of univalent chromosomes. It has been established that there is a complete autosyndesis of chromosomes of species H. annuus Willd. in these hybrids.
In the group of partially fertile hybrids (H. subcanescens x H. annuus), the reduction division is somewhat disturbed as a result of three univalents failing to become included in the nucleus. During diakinesis the presence of univalents and bivalents together with other configurations (trivalents and multivalents) has been observed. In most cells there were one, and sometimes two or three univalents, which generally isolated themselves and formed micro-pollen grains.
The presence of three univalents in hybrids between sunflower and H. subcanescens (Gray) Wats. indicates that the basic haploid chromosome number of the species H. subcanescens (Gray) Wats. cannot be 17, but is 16 plus an odd chromosome which has its individual behavior in crosses. There is no full autosyndesis, as observed in the cross of the sunflower with H. annuus Wild, in this combination, but a partial one, leading to an incomplete fertility of hybrids (I. I. Marchenko, 1947).
We have not completed our investigations of the group of sterile hybrids H. tuberosus x H. annuus. From the preliminary study of pollen mother cells it is seen that the reduction division in these hybrids is markedly disturbed, with a large number of chromosomes failing to become included in the nucleus and with the formation of triads and even diads together with normal tetrads.
The genus Helianthus L. is one of the largest genera of the family Compositae. It numbers more than 100 species, which are of considerable interest for breeding. The majority of wild-growing species are not affected by rust, broomrape and other diseases of our cultivated sunflower. Many species of this genus grow on solonets and solonchak, on desert, stony and sandy soils, and withstand severe climatic and edaphic conditions. Tuberous and even nontuberous species are of interest for the improvement of Jerusalem artichoke, which has a fodder and industrial importance. By utilizing annual and perennial species of the genus Helianthus in hybridization, varieties of Jerusalem artichoke with a heightened content of inulin in the tubers can be developed, the tuber shape can be improved, the clump of tubers can be made more compact, and this plant can be rendered suitable for use in fodder and field-crop rotations.
Work in interspecific hybridization in the genus Helianthus has been done by only a few scientists (Cockarell, Thellung, Wagner, and others) on limited material of no practical value. Work with a practical application has only been carried out in the U. S. S. R. during the last decade. Hybridization has been done with a view to improving the basic oil crop — sunflower (Satsyperov, Plachek, Pustovoit), and also Jerusalem artichoke (Shibrya, Marchenko, Davidovich).
The first hybrid generation obtained by us is marked by a high variability in all morphological-physiological characters, such as length of the vegetative period, tuber-forming ability, branching characters, leaf shape, stem pigmentation, etc.
The fertility of the first-generation hybrids depends on the parental pairs taken for the cross. The first generation from the cross between cultivated Jerusalem artichoke (H. tuberosus L.) and sunflower proved to be almost sterile; a group of hybrids of medium fertility was obtained from crosses of sunflower with the wild relative of Jerusalem artichoke H. subcanescens (Gray) Wats.; highly fertile hybrids resulted from the cross of sunflower with another wild relative of Jerusalem artichoke — H. annuus Willd., especially if sunflower was taken as seed parent. In the second generation, a complete sterility of the hybrids was observed in all cases.
|*[Vsesoyuznyi nauchno-issledovatelskii institut maslichnykh kul'tur -- All-union Research Institute of Oil and Essential Oil Crops.]|
The hybrids between Jerusalem artichoke and sunflower are characterized by a complete immunity to rust and broom rape and also to other diseases, with the exception of sclerotinia. The hybrids served as our starting forms in sunflower breeding. In the F7, families having an entire or almost entire immunity to these diseases were obtained; these families also surpassed such standard varieties of sunflower as Zhdanovskii 8281, VNIIMK* 6540, and others in seed yield, thousand-seed weight, and oil yield.
The majority of first-generation hybrids are considerably more vigorous in their development of green matter than the starting forms. In tuber-forming ability, Jerusalem artichoke characters dominate in first-generation hybrids; the tuber yield varies between 100 to 200 g to 4 kg per plant. There are a few segregants with an annual life cycle.
Hybrids between Jerusalem artichoke and sunflower which have been obtained and introduced in the collective and state farms of the Ukrainian SSR and other republics of the Soviet Union belong to two hybrid clonal lines - No. 15 and No. 120. Both these clones are intermediate between
Jerusalem artichoke and sunflower in their external characters. They give high yields of tubers and green matter valuable for silage; this is owing to their pronounced heterosis which is fixed by vegetative propagation.
In the forest-steppe zone of the Ukrainian SSR, clonal line No. 120 yields 30 to 40 tons of tubers and 60 to 70 tons of green matter per hectare under favorable conditions. The hybrid No. 15 yields 15 to 18 tons of tubers and 75 to 80 tons of green matter per hectare. These green-matter yields are one-and-a-half times to twice as high as those from ordinary varieties of Jerusalem artichoke.
The hybrids between Jerusalem artichoke and sunflower also possess very good qualities as fodder plants: their green matter contains up to 12% of sugars and up to 3% (of the fresh weight) of digestible protein; the hybrids are on a level with corn in fodder value and are superior to sunflower grown for silage. The nutritional value of the hybrid tubers is much higher than that of such crops as fodder beet, fodder carrot, or swede.
Hybrid clonal line No. 15, which produces high yields of tender green mass and has a somewhat lower tuber yield, is being introduced by us to large meat-milk stockbreeding farms, where greens rather than tubers are required. Clonal line No. 120, the asset of which lies in its tuber yield, is being introduced mainly in pig-breeding farms and pig farms of the collective farms.
Hybrid clone No. 120 has a compact clump of tubers; it can be lifted from the soil easily, without any small tubers being left behind. This property makes line No. 120 a suitable culture for field and fodder-crop rotations without any necessity for the fields to be weeded.
Jerusalem-artichoke x sunflower hybrids have high contents of inulin in their tubers (20 to 22%) and may be of interest as a new industrial crop for fructose production. Crystaline fructose obtained by laboratory and semiindustrial methods at the Institute of Organic Chemistry of the Academy of Sciences of the Ukrainian SSR is of interest for the cake industry and medicine. In view of this desirable raw material, a combined fructose-producing enterprise has been set up in the Cherkassy Region.
In stems of the hybrids, 12 to l5% of total sugars have been found, so that these plants may possibly find use in the sugar industry together with cane sugar.
The hybrids between Jerusalem artichoke and sunflower have passed production tests in recent years in 200 collective and state farms and have also been investigated by collective farm research workers in different parts of the Soviet Union. On the whole they have shown themselves commendable.