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C.M. Ronning, S.P. Kowalski, L.L. Sanford, and J.R. Stommel

The Colorado potato beetle is a serious pest of the cultivated potato. Natural resistance has been found in a few wild species, including Solanum chacoense Bitter, in which resistance is attributed to the presence of foliar specific leptine glycoalkaloids. Production and accumulation of these compounds within S. chacoense varies widely and appears to be inherited in a quantitative fashion, but high leptine producing clones occur rarely. In the present study, 15 different accessions from various locations and altitudes of origination were analyzed for foliar glycoalkaloid content in order to determine the frequency and distribution of genes for leptine production/accumulation, and to see if we could find a center, or core, of leptine production. Leptines were detected in eight of the 15 accessions, and the amounts within each accession varied widely, but none of the individuals produced high amounts of leptine (defined as greater than 62% of total glycoalkaloids). All of the leptine-containing accessions originated from western Argentina. There was no relationship between elevational level and leptine, but there was a negative trend with total glycoalkaloids and elevation; this was due to levels of solanine and chaconine decreasing with increasing elevation. In addition, nine unidentified glycoalkaloids were detected, in very high proportions in some individuals and accessions. AFLP marker frequency and diversity were used to compare subpopulations of these accessions. AFLP markers revealed substantial diversity among clones. The relationship of marker distribution to glycoalkaloid content is discussed. The results raise interesting questions about glycoalkaloid biosynthesis and inheritance, and point the direction for new avenues of leptine and glycoalkaloid research.

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Swee-Suak Ko, Woo-Nang Chang, Jaw-Fen Wang, Shin-Jiun Cherng, and S. Shanmugasundaram

In the tropics, onion (Allium cepa L.) bulbs are usually stored in shelters under ambient conditions resulting in severe storage losses. This study was aimed at determining whether variation in bulb storability exists among short-day onion cultivars and whether the trait can be improved through conventional breeding. Twelve onion cultivars with different degrees of storability were selected from preliminary experiments. Bulbs of selected cultivars were grown and stored for 3 months under ambient conditions. Observations were made on disease incidence at harvest, percentage diseased bulbs, and storage disease incidence of bacterial soft rot [BR (Pseudomonas gladioli pv. alliicola Burkholder)], black mold [BM (Aspergillus niger Tiegh.)], and fusarium basal rot (Fusarium oxysporum Schlechtend.:Fr. f. sp. cepae) after 3 months of storage. Data on bulb characteristics such as bulb fresh weight (FW), dry matter (DM) content, total soluble solids (TSS), and pyruvic acid content were recorded at harvest. Mean storage losses of cultivars ranged from 21% to 99% over 3 years. Diseases were the major causes of storage losses, with BR and BM being the most predominant. Performance of most traits (including storage losses) was significantly influenced by year (Y), cultivar (G), and Y × G interaction. Heavy rainfall during bulb development in 1997 may have contributed to higher disease incidence at harvest, higher percentage of diseased bulbs during storage, and lower DM, and TSS of the cultivars. Cultivars with good storability, such as `Red Pinoy' and `Serrana', were less sensitive to stressful environments and high disease pressure. Incidence of storage diseases was significantly correlated with DM (r = -0.65 to -0.84) and TSS (r = -0.66 to -0.87), as well as incidence of BR (r = 0.57 to 0.94) in each year. Thus, they could be good indicators for evaluating storability. Cultivars with good storability tended to have small bulbs, as average bulb FW was positively correlated with incidence of storage diseases. Disease incidences on `Red Pinoy' and `Serrana', both in the field and in storage, were significantly lower than in the other cultivars, indicating they are tolerant to major storage diseases and that they could be used as donor parents for genetic improvement of onion storability.

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Taryn L. Bauerle, William L. Bauerle, Marc Goebel, and David M. Barnard

( Bilderback, 2002 ). However, containerized plants have a limited substrate volume, often times requiring several irrigation events per day. Moreover, variability in substrate moisture within a container can be substantial, making characterization of available

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Ed Etxeberria, Pedro Gonzalez, Ariel Singerman, and Timothy Ebert

., 2011 ) adds to the inconsistency and inexactitude of the results. To overcome the ambiguities in C Las titer determinations by using a different set of leaves for every test and to lower the numerical variability between samples, we developed a

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Babak Talebpour, Maksut Barış Eminoğlu, Uğur Yegül, and Ufuk Türker

necessary to map yields for each tree in an orchard and use these data to determine the cause of variability in the orchard, and also optimize input applications on a site-specific basis ( Brown and Rosenstock, 2006 ). Initial investigations have been

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Hrvoje Rukavina, Harrison Hughes, and Randy Johnson

environments. Environmental factors are commonly measured directly as climatic or indirectly as geographical variables ( St Clair et al., 2005 ). It is generally thought that adaptation to local environments has generated variability within grass species

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Uttara C. Samarakoon, Keith A. Funnell, David J. Woolley, and Edward R. Morgan

distribution detected more variability among cultivars than standard deviation, hence was used in most of the subsequent analyses. There was no significant difference in the 10th to 90th percentile distribution of time (days) from the emergence of the first

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Mobashwer Alam, Craig Hardner, Catherine Nock, Katie O’Connor, and Bruce Topp

differences in leaf, stem, and growth parameters were identified ( Table 1 ). Both cultivars showed variability in nut and kernel size ( Fig. 3 ). There was no significant differences for average nut and kernel weight, but significant differences were detected

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Zahra Noormohammadi, Mehdi Hosseini-Mazinani, Isabel Trujillo, Luis Rallo, Angjelina Belaj, and Majid Sadeghizadeh

. Allelic composition of studied olive accessions for thirteen microsatellite markers. High variability in average number of alleles per locus in olive cultivars has been also reported by other workers ( Belaj et al., 2004 ; Carriero et al., 2002

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Ossama Kodad, José M. Alonso, María T. Espiau, Gloria Estopañán, Teresa Juan, and Rafel Socias i Company

heterozygosity in this species ( Kester et al., 1990 ; Socias i Company and Felipe, 1992 ). This large variability has provided a useful genetic pool for almond evolution, allowing in each growing region the selection of almond cultivars well-adapted to this