Re: Nicotra Fan Selection Software 33
Celena Holtzberg
Phenotypic plasticity is frequently assumed to be an adaptive mechanism by which organisms cope with rapid changes in their environment, such as shifts in temperature regimes owing to climate change. However, despite this adaptive assumption, the nature of selection on plasticity within populations is still poorly documented. Here, we performed a systematic review and meta-analysis of estimates of selection on thermal plasticity. Although there is a large literature on thermal plasticity, we found very few studies that estimated coefficients of selection on measures of plasticity. Those that did do not provide strong support for selection on plasticity, with the majority of estimates of directional selection on plasticity being weak and non-significant, and no evidence for selection on plasticity overall. Although further estimates are clearly needed before general conclusions can be drawn, at present there is not clear empirical support for any assumption that plasticity in response to temperature is under selection. We present a multivariate mixed model approach for robust estimation of selection on plasticity and demonstrate how it can be implemented. Finally, we highlight the need to consider the environments, traits and conditions under which plasticity is (or is not) likely to be under selection, if we are to understand phenotypic responses to rapid environmental change. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.
Technical selection software program that enable you to configure your own individually designed fan. It provides you with the opportunity of choosing from the entire range of fan types and their associated equipment options.
The singling out and selection of natural improved mutants have always carried out a fundamental role in the development of the Citrus industry in the world. Meaningful examples of mutants are the satsuma varieties "Ueno" and "Miyagawa", the mandarin varieties, "Tardivo di Ciaculli" and "Avana seedless" and the clementine varieties "Arrufatina", "Clemenpons", "Hernadina", "Marisol", "Nour", "Nules", "Oronules" "Comune ISA", "Fedele", "Spinoso", "Rubino" e "Tardivo.
If poly-embryonic genotypes are used in crossing as female parent, several nucellar seedlings similar to the mother plant are produced and very few or no hybrids. This characteristic, which is very frequent in most of the cultivated citrus species, allows to obtain virus free seedlings similar to the mother plant (even if infected) and also to select improved mutants which can be obtained by the nucell. The citrus improvement by nucellar selection takes a lot of time because of the very long juvenile phase, the late start into bearing and the high thorniness. The wait is often repaid with the singling out of some seedlings better than the parent both for yield efficiency and fruit quality. The satsuma varieties "Mihu" and "Okitsu" are nucellar selections of "Miyagawa". In Italy, the Istituto Sperimentale per l'Agrumicoltura of Acireale (ISA) obtained several nucellar selections from different citrus species or clone and, as regards mandarin, the most diffused originated from "Mandarino tardivo di Ciaculli" (nuc.60-22A-2, nuc.60-22A-7, 19 CN. L, 18 CN. L, 3DN6 N L.) and "Mandarino Avana apireno" (nuc. 62- Ap-9, nuc.-62-Ap-14).
The hybridisation to create new genotypes is conditioned by the heterozygous, which causes a strong variability of the characters in the progeny, by the nucellar embryony and by the long non productive juvenile phase which prevents carrying out the selection of the seedlings before they are 5 - 7 years old. In any case the best results of hybridisation in the Citrus species were obtained by artificial cross of various mandarin-like species. Important examples of hybrid selections are: In Italy "Palazzelli", "Primosole", "Simeto", "Desiderio", "Bellezza" and "Sirio"; In U.S.A. "Kara", "Wilking", "Kinnow", "Sunburst" and "Fortune"; In Israel "Yafit", "Norit" and "Edit"; in Japan "Nankou", "Hakaya", "Tsunokaori", "Benimadoca", "Ariake", "Amakusa", "Hareyaka", "Mihocore", "Yoku" and "Shiranuhi", which are almost all hybrids between satsuma, clementine or mandarin-like. Other important hybrids are those which can be obtained by the crossing between mandarin-like and grapefruit, that is the tangelos, and by mandarin-like and sweet orange which are called tangors. These hybrids have been largely cultivated and it is sufficient to mention the tangelos "Orlando", "Minneola", "Nova", "Mapo" and "Cami"; the latest two diffused in Italy. As regards the tangors, only the Japanese "Kiyomi" variety, obtained by artificial cross, was diffused, while much more important are those ones considered natural hybrids such as "Ellendale" in Australia, "Temple" in U.S.A., "Iyo", "Miyauki Iyo" and "Otani Iyo" in Japan, "Murcott" in Brazil, "Ortanique" in Morocco and more recently also in Italy and other Mediterranean countries.
The use of modern biotechnologies based on in vitro culture of individual cells, of protoplasts, of tissues and on recombining DNA, allows to overcome some of the limiting factors of conventional breeding. In fact it gives the possibility of creating new genotypes by the direct transfer of useful genes and of carrying out the selection at cellular and molecular level.
Through the in vitro culture of undeveloped ovules extracted from ripe fruits, (in vitro) embryogenic callus, embryos and plantlets from polyembryonic citrus species and varieties which produce seedless fruits can be obtained . These ovules are a first phase of the seeds that later on are not able to grow due to lack of fertilisation. They contain several nucellar embryos in the first phase of development, which if cultivated in vitro in proper substrates, originate the cycle of regeneration ovule-callus-embryo-plant. Through this technique, utilised especially in Italy (ISA), Japan, USA, several somaclonal varieties and selections of different citrus species were obtained.
A programme for developing seedless mutants of existing cultivars is carried out at the University of California - Riverside (UCR) by irradiating buds of seedy but promising cultivars. UCR identified six low seedy very promising mutant selections, actually under evaluation in mixed plantings. Same kind of programme are carried in China at the Cash Crop Station, Xiangxi, where "Fuyu 28" selection was obtained from irradiated (gamma rays) buds of "Ponggan"; at Guandong Fruit Research Institute which identified some promising seedless selections and at Changqing Fruit Farm, Guandong, which recently released the "Huaqing Seedless" and "Huaqing Few Seeded" varieties.
The potential of conventional methods of improvement of citrus rootstock is limited by biological factors that inhibit breeding and selection, such as heterozygous and inbreeding depression, pollen and ovule sterility, sexual incompatibility, apomixes and nucellar polyembryony, juvenility. However the USDA, ARS, US Horticultural Research Laboratory has carried out over time a programme for new rootstock development that focused on sexual hybridisation at the diploid level to produce improved genetic combinations. It recently released two hybrids "US-852" [Changsha mandarin (C. reticulata) x English Large Flowered Trifoliate Orange (Poncirus trifoliata)] and "US-812" (Sunki mandarin x Benecke trifoliate orange), which make healthy trees, excellent fruit quality and are very productive.
83. Arnold, P.A., Nicotra, A.B. & Kruuk, L.E.B. (2019b). Sparse evidence for selection on phenotypic plasticity in response to temperature. Philosophical Transactions of the Royal Society B: Biological Sciences, 374, 20180185. [pdf]
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The number of children produced by a modern woman is usually below her total reproductive capacity and is determined by circumstances other than natural selection. It is, therefore, practically impossible to detect differences in natural fertilities associated with different types (e.g. phenotypes, genotypes) of women. This does not mean, however, that natural selection at the reproductive level cannot at all be detected today. If women of a particular type have high natural fertility, this usually means that they reproduce (become pregnant) at a higher rate than women of a type with lower natural fertility. Hence, when there is a limit on the number of children, women of the first type will reach the limit at an earlier age than women of the second type. As a result, types that have a higher natural fertility should be overrepresented among pregnant women of younger ages and, consequently, underrepresented among older ones, as compared to types with a lower natural fertility. Based on this notion, a model of age-related differences between distributions of types among pregnant women is suggested. The model is applied to data on MNSs-blood group and PGM1 (phosphoglucomutase) types in a sample of pregnant women and an evidence of natural selection at the reproduction level associated with these genetic markers is obtained.
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