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S. Severmutlu, N. Mutlu, R.C. Shearman, E. Gurbuz, O. Gulsen, M. Hocagil, O. Karaguzel, T. Heng-Moss, T.P. Riordan, and R.E. Gaussoin

available in the literature on warm-season turfgrass species adaptation and use in this region. Urbanization, tourism, intensive agricultural use, and global warming have strained available water resources on a worldwide basis ( Isendahl and Schmidt, 2006

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Mahmoud Panjtandoust and David J. Wolyn

asparagus hybrids bred in different climatic zones indicated varying levels of adaptation (D.J. Wolyn, unpublished data). ‘Guelph Millennium’, bred in southern Ontario, is highly adapted with sustained high yields over many years. ‘UC 157’, developed in a

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Xiang Wang, Rajeev Arora, Harry T. Horner, and Stephen L. Krebs

adaptations ( Anderson et al., 1995 ; Björkman, 1981 ; Walters et al., 2003 ). Photoacclimation can occur at two levels: 1) leaf level and 2) chloroplast level ( Murchie and Horton, 1997 ). The different anatomy of “sun” and “shade” leaves is an example of

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Jonathan Lynch

120 COLLOQUIUM 3 (Abstr. 1000-1005) Seedling Morphological and Physiological Adaptation to Abiotic Stress

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Stephen M. Southwick and Kitren G. Weis

Selection and propagation of rootstocks for apricot (Prunus armeniaca L.) varies worldwide in response to local climate, soils, and cultivars. In this paper we review published research focused on these local selective practices. Additionally, we review the current development of apricot rootstocks and suggest new research avenues to satisfy the needs of commercial apricot growers. Rootstocks are identified by their responses to biotic and environmental stresses, with specific adaptive characteristics that enable establishment and production under unique zonal ecologies. Desirable characteristics include scion compatibility, adaptation for heavy or wet soils, pest and disease resistance, ease of propagation, control of vegetative vigor, effects on dormant season physiology of the scion, precocity, fruit quality, and productivity. Interstocks that can overcome incompatible rootstock-scion combinations are covered. As worldwide consumer demand for apricots increases with improved apricot cultivars, rootstock selections and propagation must be developed for niche fruit with specific characteristics, intensive production systems, mechanized harvest, and marginal site selection.

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Alfonso Guevara, María Nicolás-Almansa, José Enrique Cos, Juan Alfonso Salazar, Domingo López, José Egea, Antonio Carrillo, Manuel Rubio, Federico García, and David Ruiz

‘lucía myrtea’ and ‘victoria myrtea’ are early-season cultivars of Japanese plum ( Prunus salicina Lindl.) typology, both characterized by their low chilling requirements, so their adaptation is ideal for warm growing areas in the current context

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Zhuangjun Zhao, Margaret Mukami Gitau, Tao Hu, Yan Xie, Longxing Hu, and Jinmin Fu

physiological mechanisms underlying plant adaptation to soil salinity at subsurface depth have not been adequately understood. The high soil salinity due to neutral salts, such as NaCl, has destructive effects on plant growth, development, and differentiation

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David B. Rubino and David W. Davis

This study was conducted to investigate the effects of mild mass selection for adaptation on the performance, genotypic variance, combining ability, S1 family-testcross correlation, and midparent heterosis of S1 families derived from a sweet corn (su) × tropical maize (Zea mays L.) composite (Composite 1R). Four cycles of random mating followed by 10 cycles of 10% stratified mass selection were conducted for earliness, plant and ear type, and freedom from pests. Selection significantly (P < 0.01) decreased plant height, ear height, percentage barrenness, and ear length, and significantly (P < 0.01) increased stalk breakage, earliness (Celsius heat units to 50% anthesis and silking), and kernel row number of both S1 families and their testcrosses. Juvenile plant height at 45 days after planting increased in testcrosses only. Percentage tip blanking and pericarp thickness did not change. For most traits, the greatest response occurred during the first five of 10 selection cycles. Cycle 10 testcrosses performed at least as well as elite check testcrosses for eight of 10 traits. The tropical parents improved combining ability for increased juvenile plant height and kernel row number, and decreased percentage of stalk breakage. As a result of selection, genotypic variance among S families decreased by >40% for heat units to 50% anthesis and silking, ear height, and percentage of barrenness, although for all traits measured, significant genotypic variation persisted following 10 cycles of mass selection for adaptation. S1-testcross correlations and percentage midparent heterosis tended to be consistent across selection cycles. Five cycles of mild stratified mass selection increased the adaptation of a temperate sweet corn × tropical maize composite to the temperate zone of the United States while maintaining significant genotypic variation.

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Svoboda V. Pennisi and Dennis McConnell

Variegated Dracaena sanderana plants were grown under 47%, 63%, 80%, and 91% shade cloth. Prior to that, plants were grown under uniform light levels in a greenhouse. Morphological changes which manifested the adaptation to different light levels were not evident until all four leaves present in the apical whorl had expanded. Changes first appeared in a leaf which was 5-15 mm long when plants were placed under the different shade levels. The changes were recognized as alteration in the amount of leaf variegation which gradually changed as new leaves unfolded. After development of four leaves no further morphological changes were apparent. The first `transition' leaf had variegation similar to the preceding leaf and the last `transition' leaf had variegation comparable to the next successive leaf. The amount of variegation was quantified and the changes under different light levels determined. The use of a variegated plant enabled us to readily observe the morphological changes related to light adaptation and showed that a plant is an integrated system which adapts to altered environment over an extended period of time.

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Philip Busey


Bermudagrass (Cynodon spp.) turf in subtropical Florida normally requires higher levels of N than other grasses and frequently requires pesticide applications. Three sequential 2-year cycles of clonal selection were performed in replicated field plots to recognize bermudagrass germplasm adapted to suboptimal fertilization and natural pest infestation. Low fertility, 19 to 25 g N·m−2, was applied yearly, including the establishment phase. No nematicides, fungicides, or insecticides were applied. Severely damaging mole cricket (Scapteriscus sp.) populations were left uncontrolled. Among 95 clones, 4 experimentals (FB-109, PI-291586, T-72-54, and FL-2400) survived repeated cycles with relatively high turfgrass coverage and quality. Among cultivars, only ‘Tifgreen-II’ and ‘Ormond’ performed well. African introductions and artificially-induced mutants of hybrid cultivars were the best sources of adapted germplasm. Although the mechanism of this adaptation is unknown, field tests were an effective prescreening method for clonal selection.