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  • 1
    Electronic Resource
    Electronic Resource
    A comparison of apple and pear seedlings with reference to the juvenile period. II. Mode of inheritance (1976)
    Springer
    Euphytica 25 (1976), S. 339-342 
    Details
    ISSN: 1573-5060
    Keywords: Malus ; apple ; Pyrus ; pear ; seedlings ; inheritance of juvenile period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Analysis of two incomplete half-diallel schemes of crosses, involving 22 apple and 33 pear progenies with 2500 and 5400 seedlings respectively, showed a highly significant GCA and an insignificant SCA variance for the juvenile period (J.P.). This indicates that the inheritance of the J.P. is of an additive nature, a mode of inheritance which is a function of the inheritance of a complex of factors governing ‘growth’. The mean J.P. of apple progenies varied between 3.4 and 5.0 years, that of pear progenies between 4.7 and 7.0 years. The implications for breeding are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041565
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of apple and pear seedlings with reference to the juvenile period I. Seedling growth and yield (1976)
    Springer
    Euphytica 25 (1976), S. 343-351 
    Details
    ISSN: 1573-5060
    Keywords: Malus, apple ; Pyrus ; pear ; seedlings ; juvenile period ; stem diameter ; precocity ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Several thousand apple and pear seedlings of many progenies were studied in connection with their juvenile period (J.P.). The initially significant inverse relation between the vigour (stem diameter) and the J.P. of the seedlings became insignificant as the trees grew older, due to a retardation of growth occurring when the seedlings become generative. This relation can be used effectively in pre-selecting for vigour in the nursery. Cumulative yields were higher when the J.P. was shorter, but there was no evident link between the J.P. and annual yield in full bearing, that is to say, precocity and preductivity are not directly connected. Better growing conditions and pre-selection have shortened the mean progeny J.P. of either crop by three years since the 1950's. Generally, the pear seedlings appear to grow faster, to become generative slower and to yield lower than comparable apple seedlings. The mean J.P. of apple and pear progenies averaged 4.2 and 6.0 years respectively. The difference between apple and pear may be attributable to a greater selection pressure on both precocity and productivity with apple than with pear. This possibly also led to a smaller tree in the productive phase on the assumption that tree size at first flowering-small at a short, large at a long J.P.-expresses reproductive efficiency and as such is reflected in the size of the adult tree.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041566
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  • 3
    Electronic Resource
    Electronic Resource
    Embryo development and fruit-set in pear induced by untreated and irradiated pollen (1987)
    Springer
    Euphytica 36 (1987), S. 287-294 
    Details
    ISSN: 1573-5060
    Keywords: Pyrus ; pear ; irradiated pollen ; embryogenesis ; fruit-set ; haploids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Flowers of the pear cultivars Conference, Doyenné du Comice and Gieser Wildeman were pollinated with untreated and 50-krad-irradiated pollen. Fruitlets were sectioned at regular intervals up to 6 weeks after pollination. Tubes of the irradiated pollen grew slower, but within two weeks nearly as many embryos were initiated as in the case of untreated pollen. Thereafter, the proportion of degenerated embryos increased, although the endosperm sometimes persisted. Six weeks after pollination only about 21% of the seeds induced by the irradiated pollen still contained normal embryos. At or before that time in-vitro culture of the immature seeds will be necessary because few embryos survive until harvest. The irradiated pollen stimulated a rather large ‘parthenocarpic’ fruit-set, presumably associated with endosperm rather than embryo development during the first 4–6 weeks after pollination. The possibilities of haploid production are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730675
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  • 4
    Electronic Resource
    Electronic Resource
    Pollen and pollination experiments. IV. ‘Mentor pollen’ and ‘pioneer pollen’ techniques regarding incompatibility and incongruity in apple and pear (1981)
    Springer
    Euphytica 30 (1981), S. 363-369 
    Details
    ISSN: 1573-5060
    Keywords: Malus ; Pyrus ; apple ; pear ; incompatibility ; incongruity ; mentor pollen ; pioneer pollen ; fruit set ; seed set
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It was attempted to overcome self-incompatibility in apple and pear and incongruity between these species with the aid of compatible ‘mentor’ or ‘pioneer’ pollen. The mentor pollen was applied in a mixture (1:1) with the incompatible/incongruous pollen and the pioneer pollen was applied one day in advance of the other pollination. Two trials in 1976 with dead methanol-treated mentor pollen on apple were moderately successful, probably because of the hot spring weather. In the apple and pear trials of 1979 neither the methanol-treated nor the viable irradiated (100 krad) mentor or pioneer pollen significantly improved the seed set by self pollen or that after intercrossing. Competition and early embryo abortion after selfing or intercrossing probably contributed to the lack of success of these methods. The viable irradiated pollen induced a rather high ‘parthenocarpic’ fruit set, whether applied on its own or mixed with or in advance of the incompatible pollen; the inviable methanol-treated pollen had no such stimulating influence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033998
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  • 5
    Electronic Resource
    Electronic Resource
    Pollen and pollination experiments. VIII. The effect of successive pollinations with compatible and self-incompatible pollen in apple and pear (1983)
    Springer
    Euphytica 32 (1983), S. 57-64 
    Details
    ISSN: 1573-5060
    Keywords: Malus ; apple ; Pyrus ; pear ; self-pollination ; cross pollination ; self-incompatibility ; mentor pollen ; pioneer pollen ; fruit set ; seed set
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In compatible pollen combinations, viable but infertile irradiated pollen Cr appears to compete much more in a mixture (the mentor pollen situation: C+Cr), than when used one day in advance (the pioneer pollen situation: Cr/C). Seed set of Cr/C was usually also greatly superior to that of C/Cr and, using, self, incompatible pollen S instead of Cr, S/C was nearly always much better than C/S. This is in accordance with the promotion of the second by the first (pioneer) pollen. Hence, when Cr or S are applied second in C/Cr or C/S, more ovules are rendered ineffective (blocked or aborted) than in the reverse combination when Cr or S act as pioneer pollen. These observations are consistent with the trend that the combinations C/ C+S, C+S, C/S tended to produce more selfed seeds in that order. Although mentor or pioneer pollen assist in removing the style barrier for self pollen, embryo abortions appears to be a second obstruction towards seed formation. Indications are that high spring temperature during pollination promote the production of selfed seeds in the presence of compatible pollen. The surfeit of self pollen in orchards with a minority of pollinators is not necessarily an unfavourable factor, it may both directly and indirectly contribute to fruit and seed set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00036864
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  • 6
    Electronic Resource
    Electronic Resource
    Pollen and pollination experiments. IX. The pioneer pollen effect in apple and pear related to the interval between pollinations and the temperature (1983)
    Springer
    Euphytica 32 (1983), S. 703-709 
    Details
    ISSN: 1573-5060
    Keywords: Malus ; apple ; Pyrus ; pear ; double pollination ; pollination interval ; temperature ; pioneer pollen ; seed set first pollen ; seed set second pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Double pollinations of apple and pear may double the seed production, to which the second pollen can contribute 3 times as many seeds as the first (pioneer) pollen, when the interval between pollinations is long enough (48 h) at low (≃ 10°C) or short enough (7 h) at high (≃ 20°C) temperatures. With shorter or longer intervals, the contribution of the second pollen to seed production diminishes. The dominance of the second pollen was attributed to promotion by the first one, the second pollen probably being optimally stimulated when the tubes of the first have passed about 1/3rd of the style. It is concluded that the effectiveness of the pioneer pollen method to overcome incompatibility, depends on whether the interval between pollinations can be usefully adjusted to both the environmentally (temperature) and inherently determined rate of pollen tube growth of the species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042150
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  • 7
    Electronic Resource
    Electronic Resource
    The interaction between compatible and self-incompatible pollen of apple and pear as influcenced by their ratio in the pollen cloud (1984)
    Springer
    Euphytica 33 (1984), S. 699-704 
    Details
    ISSN: 1573-5060
    Keywords: Pyrus ; pear ; Malus ; apple ; self-incompatibility ; mentor/pioneer pollen ; double pollination ; mixed pollination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The production of self-seed was investigated in apple and pear with the aid of viable and compatible mentor/ pioneer pollen in relation to the proportion of self-imcompatible pollen present in the pollen cloud. Treatments consisted of mixtures of compatible and self-incompatible pollen at ratios of 1:1, 1:2 and 1:9 applied once or twice or followed by self-pollination. Selfing only, whether once or twice, produced virtually no fruits or seeds, while mixed pollinations did. Generally, fruit set tended to decrease and the self-seed to increase with increasing amounts of self pollen in the pollinations. The pioncer-pollen method (compatible in advance of self pollen) appeared more effective than the mentor pollen method (compatible and self pollen mixed). The use of viable instead of dead mentor/pioneer pollen causes competition for the ovules with the self pollen, but has the advantage that, in addition to some self-seed, other seeds are formed which, e.g. in apple, are necessary to keep the fruits on the tree until harvest. Fruit set was moderately reduced at ratios of compatible pollen to self pollen not exceeding 1:9 with pear and 1:5 with apple which constitute maximal ratios in practice as regards pollinator trees: trees of the main cultivar. In fruit orchards and probably in nature with other species, the interaction between compatible and self pollen may result in more self-seed, and so suggests that inbreeding played a greater part in the evolution of self-incompatible species, than the meager results of articial self-pollination imply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021897
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  • 8
    Electronic Resource
    Electronic Resource
    Pollen and pollination experiments. III. The viability of apple and pear pollen as affected by irradiation and storage (1981)
    Springer
    Euphytica 30 (1981), S. 65-70 
    Details
    ISSN: 1573-5060
    Keywords: Malus ; Pyrus ; apple ; pear ; pollen ; irradiation ; storage ; rehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Apple and pear pollen was irradiated with doses of 0, 50, 100, 250 and 500 krad (gamma rays) and stored at 4°C and 0–10% r.h. From the in-vitro germination percentages an average LD 50 dose of about 220 krad was estimated. For both irradiated and untreated pollen a close and corresponding lineair relationship existed between germination percentage and pollen tube growth. Irradiated pollen was much more sensitive to dry storage conditions than untreated pollen, resulting in less germination and more bursting. Apparently, irradiation caused the pollen cell membrane to lose its flexibility faster than normal. Rehydration of dry-stored, irradiated pollen in water-saturated air restored germination percentages up to their initial levels. The importance of this procedure in germination trials is stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033660
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  • 9
    Electronic Resource
    Electronic Resource
    Pollen and pollination experiments. VI. Heat resistance of pollen (1982)
    Springer
    Euphytica 31 (1982), S. 287-290 
    Details
    ISSN: 1573-5060
    Keywords: Lilium ; Malus ; Pyrus ; Rosa ; pollen treatment ; heat resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pollen of dry apple, pear, lily and rose pollen was heated up to 48 h at a range of temperatures. About half or more than half of the pollen grains survived 48 h at 40 C, 24 h at 50 C, 8 16 h at 60 C. 4 8 h at 70 C, more than one hour at 80 C. and between 10 and 20 min at 90 C. Presumably, pollen able to withstand low humidity is also heat resistant, a property which may be usable to make pollen virus free through heat treatment and perhaps to overcome incompatibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021642
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  • 10
    Electronic Resource
    Electronic Resource
    The performance of double or mixed pollinations with compatible and self-incompatible or incongruous pollen of pear and apple (1986)
    Springer
    Euphytica 35 (1986), S. 1011-1015 
    Details
    ISSN: 1573-5060
    Keywords: Pyrus ; pear ; Malus ; apple ; pollination ; interaction ; compatible ; self-incompatible ; incongruous pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Six pear and five apple trials were carried out to ascertain the outcome of combinations of compatible pollen (C) with self (S) or incongruous pollen (I) as to the pollination index (PI=seeds/pollinated flower). The PI of the mixture C+I (1:5) was consistently depressed as compared to that of the control C. The results of the double pollinations S/C and I/C were affected by the temperature at pollination; their PI's at 〈15°C were twice as high as those at 〉15°C, being well above and below the PI of C in the former and latter case respectively. The opposite was true for the C/S combination, the PI of which increased with the pollination temperature; the PI of C/I did not differ much from the PI of C, irrespective of temperature. The conclusion was reached that the interaction previously and presently found between compatible and self-incompatible pollen also exists to a fair extent between compatible and incongruous pollen. However, in pear neither the mentor nor the pioneer pollen technique proved to aid its hybridization with apple, the formation of self seed was not observed either. In apple the production of apple × pear hybrids was likewise doubtful, but the double pollinations S/C and C/S formed 4–10% self seed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028612
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