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Southern highbush blueberry, a hybrid of northern highbush (Vaccinium corymbosum) and southern-adapted Vaccinium species, has the potential to meet the need for an early-ripening blueberry in the southern U.S. southern highbush cultivars can ripen up to one month earlier than the earliest rabbiteye (Vaccinium ashei) cultivars currently grown in the southern U.S. However, chilling requirement and cold-hardiness are cultivar-dependent for southern highbush and cultivar testing has been necessary to determine the cultivars best adapted to specific hardiness zones. In a 4-year study at Hope, Ark. (hardiness zone 7b), several southern highbush cultivars were evaluated for productivity, fruit quality and reliability of cropping. Yields were based on 1089 plants/acre (2690 plants/ha) for southern highbush cultivars and 605 plants/acre (1494 plants/ha) for rabbiteye cultivars. `Ozarkblue' and `Legacy' showed the most adaptability at this location, yielding on average 11,013 lb/acre (12,309 kg·ha-1) and 10,328 lb/acre (11,543 kg·ha-1) respectively, compared to 4882 lb/acre (5456 kg·ha-1) for `Premier' (rabbiteye) over 4 years. `Ozarkblue' and `Legacy' also rated well for plant vigor and fruit quality. We would recommend `Ozarkblue' and `Legacy' for commercial planting in southwest Arkansas and believe these cultivars have production potential for other areas of the southern U.S. that have similar hardiness zones and soil type to southwest Arkansas.

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Abstract

Two cultivars and 2 experimental chilling-tolerant lines of tomato (Lycopersicon esculentum Mill.) were harvested mature-green and stored for 15 days at 5°, 20°, and 35°C with or without the introduction of ethylene; portions of the high and low temperature samples were moved to 20° for an additional 10 days. Samples were analyzed for firmness, sugars, and acids. Fruit of the chilling-tolerant tomato lines were firmer than the commercial cultivars in all temperature treatments. Ethylene enhanced softening in the chilling-sensitive cultivars only at 20°, while the chilling-tolerant lines showed an effect only at 35°. The chilling-tolerant lines appeared to be more heat-tolerant than the sensitive cultivars. Sugar and organic acid analyses were not as clear-cut, often revealing a tendency for the cherrysized fruit to behave similarly to each other and different from the normal-sized fruit. The chilling-tolerant lines held at 5° or moved from 5° to 20° had lower monosaccharide levels than the corresponding sensitive cultivars. This also was true when fruit were moved from 35° to 20°. ‘New Yorker’ tomato had low levels of malate after exposure to 35°, which resulted in a high citrate/malate ratio not evident in the other 3 cultivars. Phosphoric acid levels were higher in the chilling-tolerant tomato fruit and increased with increasing storage temperature. Line 281 deviated from the other 3 cultivars in that, in general, acids increased and sugars decreased with increasing storage temperature.

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The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal high temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on protein synthesis and degradation in creeping bentgrass (Agrostis palustris Huds.). Plants of the cultivar Penncross were subjected to two temperature regimes in growth chambers: 1) heat acclimation—plants were exposed to a gradual increase in temperatures from 20 to 25, 30, and 35 °C for 7 days at each temperature level before being exposed to 40 °C for 28 days; and 2) sudden heat stress (nonacclimation)—plants were directly exposed to 40 °C for 28 days from 20 °C without acclimation through the gradual increase in temperatures. Heat acclimation increased plant tolerance to subsequent heat stress, as demonstrated by lower electrolyte leakage (relative EL) in leaves of heat-acclimated plants compared to nonacclimated plants at 40 °C. Heat acclimation induced expression of some heat shock proteins (HSPs), 57 and 54 kDa, detected in a salt-soluble form (cystoplasmic proteins), which were not present in unacclimated plants under heat stress. However, HSPs of 23, 36, and 66 kDa were induced by both sudden and gradual exposure to heat stress. In general, total protein content decreased under both heat acclimation and sudden heat stress. Cystoplasmic proteins was more sensitive to increasing temperatures, with a significant decline initiated at 25 °C, while sodium dodecyl sulphate (SDS)-soluble (membrane) protein content did not decrease significantly until temperature was elevated to 30 °C. The results demonstrated that both a gradual increase in temperature and sudden heat stress caused protein degradation and also induced expression of newly synthesized HSPs. Our results suggested that the induction of new HSPs during heat acclimation might be associated with the enhanced thermotolerance of creeping bentgrass, although direct correlation of these two factors is yet to be determined. This study also indicated that protein degradation could be associated with heat injury during either gradual increases in temperature or sudden heat stress.

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not offer a clear illustration of accuracy in these heat tolerance claims ( Table 1 ; Fig. 1 ). ‘Donkey’, ‘Tyee’, and ‘Marabu’ were expected to maintain higher germination percentages at higher temperatures, but ‘Tyee’ had the lowest germination

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transpirational water loss, increasing water uptake, and/or adjusting osmotically to maintain photosynthesis and other metabolic functions ( Bonos and Murphy, 1999 ; Qian and Fry, 1997 ; White et al., 1992 ; Zhang and Schmidt, 1999 ). Heat tolerance in

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notably, how nutrient accumulation is associated with differences in heat tolerance and specifically heat-induced damage in leaves between warm-season and cool-season grass species is not well documented. In addition, different nutrient elements may differ

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Leaf gas exchange of six red raspberry (Rubus idaeus L.) and one blackberry (Rubus L. subgenus Rubus Watson) genotypes growing in 12-L containers was measured at four temperatures (20, 25, 30, and 35 °C) once a month for 3 months in growth chambers by infrared gas analysis. Measurements were taken on three successive leaves on the same primocane between the third and seventh nodes (≈75% to 85% of full leaf expansion). The plants were grown in ambient (field) conditions except when measurements were taken. Maximum daily ambient temperatures rose as high as ≈37 °C during this period. Net CO2 assimilation (A), evapotranspiration (ET), and stomatal conductance (gs ) were measured during June, July, and August. Significant differences (P ≤ 0.01) in A were found among the seven genotypes. 'Arapaho' blackberry displayed the highest mean A rate at all temperatures. Only in the raspberry cultivars Nova and Reveille did the rate of A drop significantly when temperature increased from 20 to 30 °C. 'Reveille' was also the only cultivar in which A significantly declined between 30 and 35 °C. The ET increased significantly over the four temperatures in four cultivars ('Arapaho', 'Heritage', 'Nova', and 'Southland'). The ET rate at 35 °C was higher for 'Arapaho' than for all other cultivars. 'Autumn Bliss', 'Dormanred', and 'Reveille' did not change significantly as the temperature rose from 20 to 35 °C. Stomatal conductance of 'Heritage' and 'Arapaho' did not change significantly between 20 and 35 °C, whereas that of 'Autumn Bliss' and 'Reveille' declined almost 50% when temperature increased to 30 or 35 °C.

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-temperature stress. The overall goal was to improve snap bean for rust resistance and heat tolerance to increase production in environments experiencing these challenges need to ensure that the optimal traits are combined in desired market types that are high

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