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  • Author or Editor: M.M. Thompson x
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Seeds and herbarium specimens of 47 accessions from 11 Rubus taxa native to the Andean Region of Ecuador were collected in October and November 1990 and deposited at the USDA/ARS Germplasm Repository in Corvallis, OR. Plants will be grown from these seeds and evaluated for taxonomic identity and potential breeding value. Characteristics of the plants will be discussed. Taxa obtained include: R. adenothallos Focke, R. acanthophyllus Focke, R. bogotensis Kunth, R. coriaceus Poiret, R. glabratus H.B.K., R. glaucus Benth., R. robustus C. Presl., R. roseus Poiret, R. urticifolius Poiret. These taxa will contribute unique genes to the improvement of Rubus crops by breeders throughout the world. Seeds may be requested from the curator, USDA/ARS NCGR-Corvallis.

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‘Blairmonf apple (Malus domestica Borkh.) has been released by the Agricultural Research Service, U.S. Department of Agriculture, to provide a solid-red, sub-conic shaped, marketable cultivar which will develop satisfactory color and finish when grown in areas of southeastern United States where high daytime and, especially, nighttime temperatures often prohibit satisfactory development of the usual appearance attributes of many non-adapted cultivars.

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The U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore., maintains Rubus germplasm representing worldwide diversity of the genus. Chromosome numbers were counted for 201 plants representing 124 taxa (species and varieties). There are new reports for 42 taxa, confirmation for 72 previously reported, and 10 counts for plants unidentified to species. The basic chromosome number was seven, and ploidy levels ranged from 2x to 12x.

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Chromosome numbers were counted for 90 Rubus cultivars and selections maintained at the U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository, Corvallis, Ore. To my knowledge, 37 of the counts are new, including five that are corrections of previously published counts, 30 that are confirmations of numbers that were previously published but assumed from their parentage rather than actually counted, and 23 that are confirmations of previous counts. The basic number was 7, and 2n numbers ranged from 2x to 14x, including odd-ploids and aneuploids.

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Why aren't there more women horticulturists in the United States? The large number of European women in this field always astonishes Americans traveling abroad. In certain Asian countries, e.g. Taiwan and Thailand, women are represented in horticulture classes in much larger numbers. (This may partly account for the extraordinarily high proportion of Oriental women graduate students in the U.S.) Recently, in our country there has been a noticeable increase in high school girls enrolled in agriculture and participating in FFA. There is also a substantial increase in number of college women majoring in horticulture. A poll of 43 Land Grant Institutions showed that women constitute 22% of undergraduate majors and 14% of our graduate students. A comparison of the present meager representation of women in academic positions (2%), employed by USDA (1.5%), and members of ASHS (1.7%) with the proportion of young women training for careers in horticulture demands a reevaluation of long-held assumptions that horticulture is a masculine occupation. Why such a high rate of attrition between undergraduate training and professional employment?

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Growth and development of the pistillate flower and fruit in Corylus avellana L. cv. Barcelona, was studied from anthesis (January) to maturity (September). Ovary growth is very slow for about 4.5 months, proceeds very rapidly for about 6 weeks, during which time 90% of the increase in diameter occurs, and then abruptly ceases. Ovule development, megasporogenesis, megagametogenesis, and fertilization are described. At the time of pollination (January) the pistillate flower consists of a pair of stigmatic styles joined at their bases by a minute ovarian meristem. Pollen tubes reach the base of the style in 4 to 7 days. The sperm nucleus remains in the pollen tube tip in a resting stage until mid-June (about 5 months). During this period the basal meristematic cells develop into a mature ovary. Multiple megasporocytes, derived directly from archesporial cells, give rise to several megaspores, partly developed embryo sacs, and one normal embryo sac. When the sac is mature a secondary pollen tube, bearing the sperm, grows basipetally from the resting site in the upper tip of the ovary. It proceeds through the funiculus of the anatropous ovule, along the single integument, enters the nucellus through the chalazal end, and penetrates the micropylar end of the embryo sac where the sperm is ejected. While pollination is necessary to initiate ovary development, only a small percentage of the pollinated pistils develop into a full size nut. Fertilization is necessary for the formation of normal nuts with embryos. Full size nuts which are empty at maturity result from pollination without fertilization or from embryo abortion.

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Abstract

Susceptibility ratings for big bud mite Phytocoptella avellanae (Nal.) are given for 144 clones of filberts (Corylus sp.) and for 1850 progeny between crosses involving 21 parents. There is genetic resistance as well as different levels of susceptibility. Susceptibility is highly heritable and appears to be determined by multiple genes with predominantly additive gene action.

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Abstract

Under conditions of natural infection in the third year of planting, fire blight disease caused by Erwinia amylovora (Burr.) Winsl. et al. was less severe on the same cultivars grafted on seedling roots than on ‘EM VII’, ‘MM 104’ and MM 106’. The most susceptible cultivars appeared to be ‘Tydeman's Red’ and ‘Raritan’. ‘Williams Red’ was the only cultivar that escaped fire blight entirely.

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Abstract

Initial fruit set in 6 ‘Italian’ prune orchards for 2 years was markedly influenced by post-bloom temperature. In the warm year initial sets ranged from 36 to 64%; in the cool year initial sets were 1 to 13%. Visible frost damage occurred in only 1 orchard and was not responsible for the general failure in the cool year.

Embryo sacs were studied in pistils from the same orchards in the 2 years. The cause of erratic fruit setting in ‘Italian’ prune is attributed to its genetically determined sensitivity to cool weather in the post-bloom period. Cool temperature delays pollen tube growth, fertilization, and early embryo and endosperm development so long that the ovule begins to degenerate. Ovule breakdown begins in the nucellus at the chalazal end, so that even if fertilization is finally accomplished, fruit set is not stimulated.

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Abstract

Erratic fruitfulness, reputedly characteristic of ‘Italian’ prune in many areas, was pronounced in this 2-year study. Supplemental pollination with self-pollen and with pollen of 2 other cultivars did not increase fruit set over that of open-pollination in any orchard regardless of whether yield was high or low. Controlled self- and cross-pollinations established that ‘Italian’ is self-fertile. The lack of differences in fruit set on caged trees with and without bees as well as the failure to increase set with supplemental self-pollinations demonstrated that bees are not necessary to transfer the self-fertile pollen. It was concluded that inadequate pollination, in terms of quantity or quality, is not responsible for the sporadic poor yields of this cultivar.

Open Access