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Shuyin Liang, Xuan Wu, and David Byrne

of the most significant abiotic stresses which negatively affects landscape performance by causing leaf damage, flower abscission, and decreased flower size and quality. These effects greatly reduce the market value of garden roses. Heat or high

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Jack E. Staub, Fenny Dane, Kathleen Reitsma, Gennaro Fazio, and Anabel López-Sesé

Genetic relationships among 970 cucumber (Cucumis sativus L.) plant introductions (PIs) in the U.S. National Plant Germplasm System (NPGS) were assessed by observing variation at 15 isozyme loci. Allozyme frequency data for these PIs were compared to allozyme variation in heirloom and modern (H&M) cultivars released from 1846-1985 (H&M cultivars; 178 accessions), and experimental commercial (EC) germplasm (EC germplasm; 82 accessions) in use after 1985. Multivariate analysis defined four distinct groups of accessions (Groups A-D), where Group A consisted of PIs received by the NPGS before 1992, Group B contained PIs from India and China obtained by NPGS after 1992, Group C consisted of EC germplasm, and Group D contained H&M cultivars. Morphological, abiotic stress (water and heat stress tolerance) and disease resistance evaluation data from the Germplasm Resources Information Network (GRIN) for the PIs examined were used in conjunction with estimates of population variation and genetic distance estimates to construct test arrays and a core collection for cucumber. Disease resistance data included the evaluation of angular leafspot [Pseudomonas lachrymans (E.F. Smith) Holland], anthracnose [Colletotrichum lagenarium (Ross.) Ellis & Halst], downy mildew [Pseudoperonospora cubensis (Berk. & Curt) Rostow], rhizoctonia fruit rot (Rhizoctonia solani Kuhn), and target leafspot [Corynespora cassiicola (Berk. & Curt) Wei] pathogenicity. The test arrays for resistance-tolerance to angular leafspot, anthracnose, downy mildew, rhizoctonia fruit rot, target leafspot, and water and heat stress consisted of 17, 16, 17, 16, 17, 16, and 16 accessions, respectively. The core collection consisted of accessions in these test arrays (115) and additional 32 accessions that helped circumscribe the genetic diversity of the NPGS collection. The core collection of 147 accessions (115 + 32) represents ≈11% of the total collection's size (1352). Given estimates of genetic diversity and theoretical retention of diversity after sampling, this core collection could increase curatorial effectiveness and the efficiency of end-users as they attempt to identify potentially useful germplasm.

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Aneela Nijabat, Adam Bolton, Muhammad Mahmood-ur-Rehman, Adeel Ijaz Shah, Rameez Hussain, Naima Huma Naveed, Aamir Ali, and Philipp Simon

physiological responses to abiotic stress among and within plant species suggests that the genetic improvement of the stress tolerance response may be effective in breeding programs, and membrane stability response to heat stress has been used to identify

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Vicente Gimeno, James P. Syvertsen, Inma Simon, Vicente Martinez, Jose M. Camara-Zapata, Manuel Nieves, and Francisco Garcia-Sanchez

-sensitive. Citrus tolerance to the abiotic stresses can depend on several factors including type of rootstock, N fertilization, soil, and climate conditions ( García-Sánchez and Syvertsen, 2009 ; Gimeno et al., 2009a ; Saleh et al., 2008 ). In addition, an

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Sanalkumar Krishnan and Emily B. Merewitz

involved in the responses to biotic pathogens in the systemic acquired resistance and induced systemic resistance pathways. SA and JA have also been associated with critical responses to abiotic stresses including salt stress ( Clouse and Sasse, 1998

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Mark W. Farnham and Thomas Bjorkman

Breeding is one of the most efficient methods for managing abiotic stress. Some abiotic stresses directly reduce growth. Others affect development in a way that reduces or eliminates the crop's value. An example of the latter is superoptimal

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Yanxia Zhao, Guimei Qi, Fengshan Ren, Yongmei Wang, Pengfei Wang, and Xinying Wu

response of plants to abiotic stress ( Fan et al., 2016 ; Fujita et al., 2011 ; Zhu, 2002 ). A previous study has shown that the application of ABA may be a suitable strategy to enable grape ( Vitis vinifera ) to manage stress, thereby increasing the

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Richard L. Hassell, Frederic Memmott, and Dean G. Liere

water, and then treated with fungicides or disinfectant, e.g., Physan 20 or peroxyacetic acid/hydrogen peroxide, to minimize the microorganism damage to the graft. The rootstock should have good tolerance to abiotic stress, resistance to soilborne

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Parthiba M. Balasubramanian, Albert Vandenberg, and Pierre J. Hucl

Suboptimal seedbed temperatures in early spring limit common bean (Phaseolus vulgaris L.) seedling emergence. This field study evaluated emergence of cultivated and wild common bean when subjected to suboptimal seedbed temperature. One hundred and eighty common bean accessions and three control cultivars were planted on 3 May at Saskatoon, Sask., in 2000 and 2001. Percent emergence, cumulative thermal units to 50% anthesis and to 50% maturity, and seed yield were determined. The seedbed temperature during the 2 weeks after planting ranged between 1 and 18 °C in 2000, and 5 and 17 °C in 2001. At 20 days after planting, emergence in accession G8823 was significantly greater than the control cultivars in 2000. `CDC Nighthawk', a black bean control cultivar was comparable in emergence to G8823 at 30 days after planting. A similar trend was observed in 2001 with the exception that emergence was greater at 30, 40, and 50 days after planting due to a warmer seedbed. `CDC Nighthawk' was among the earliest to mature, although it required a significantly higher cumulative thermal unit to anthesis compared to most other accessions. G8823 could serve as a parent to develop elite bean cultivars with emergence at suboptimal seedbed temperatures.

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Monica Ozores-Hampton, K.E. Cushman, F. Roka, and R.D. French-Monar

Several experiments were conducted in commercial tomato (Solanum lycopersicum) plantings during the 2004–05 and 2005–06 seasons in Immokalee, FL, to understand types of plant damage and potential yield reductions caused by hurricanes. Expt. 1 involved ‘Florida 91’ tomato seedlings damaged during 2004 by hurricane Frances, 15 days after transplanting (DAT). Individual plants were rated and categorized as best, good, or fair, 34 DAT according to plant size and vigor/severity of injury. Ten plants from each category were removed with roots intact, and dry weights were recorded. During 2005, 23 DAT or 8 days after hurricane Wilma, Expt. 2 was conducted to compare rescued and replanted ‘Soraya’ tomato seedlings. Rescued seedlings were left in place after the hurricane and others were removed and replaced with new transplants of the same variety. Expt. 3 (‘Florida 47’) and 4 (‘BHN 586’) involved the contrast of two yield seasons without a hurricane (2004–05) and with hurricane Wilma (2005–06) to estimate the effect of the hurricane damage on tomato 65 and 45 DAT. Fruit was counted, graded by size, and weighed for each experiment from 10 plants/plot. Injury caused by hurricane winds was most evident in Expt. 1 mostly in stem damage below the soil surface showed callous tissue at the site of injury due to plants being whipped around in the planting hole. Plants rated “best” showed greater plant and root dry weight, stem diameter below the injury point, and higher yield of extra large and total marketable fruit at first harvest than plants rated good or fair. Total marketable yields from rescued plants in Expt. 2 were double than that from replanted plants, and fruit matured 20 days earlier for rescued plants indicating that plants injured by Wilma recovered quickly. Hurricane-damaged crops during 2005–06 in Expts. 3 and 4 yielded 60% lower than that of undamaged crops during 2004–05. In the extra large size category, the yields were reduced between 34% and 12% from the previous season. However, hurricane-damaged loss of yield in the extra large category was offset by increased yield in the medium category. It appears that hurricane-damaged plants, when young, were capable of full recovery and normal yields, whereas hurricane-damaged plants, when older at the time injury occurred, were not able to fully recover and eventually produced only half the normal yield.