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Nathalie Delhomez, Odile Carisse, Michel Lareau, and Shahrokh Khanizadeh

Seventeen strawberry (Fragaria ×ananassa Duchesne) cultivars and six selections were tested under greenhouse conditions for susceptibility to leaf spot induced by Mycosphaerella fragariae (Tul.) Lindau. The level of susceptibility was evaluated based on maximum disease severity and area under the disease progress curve (AUDPC). The 23 genotypes were ranked based on AUDPC and grouped according to their susceptibility. Cluster analysis for AUDPC gave four groups corresponding to low, moderate, high, and very high susceptibility to leaf spot. `Annapolis', `Chambly', `Glooscap', `Redcoat', and `Veestar' consistently showed a low level of susceptibility. The selections SJ89700-1 and SJ8518-11 and `Tribute' showed a very high level of susceptibility, and the remaining cultivars were grouped as either moderately or highly susceptible.

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Masahiko Yamada, Akihiko Sato, and Yasuo Ukai

Environmental variance components were estimated for calyx-end fruit cracking in pollination-constant and nonastringent cultivars and selections of Japanese persimmon (Diospyros kaki Thunb.). The cracking value of a tree in a cultivar or selection (genotype) (X) was evaluated as the number of fruit that cracked divided by the total number (25) of fruit evaluated from each tree. Because the mean value of X was correlated with the variance of X, analyses of variance were performed using its square root value. The variance associated with genotyp× year interaction was the largest of environmental variance components. The variances associated among years and among trees within genotypes were very small. The mean percentage of cracked fruit in evaluation for 10 years was 3% for `Fuyu', 11% for `Matsumotowase-Fuyu', and 12% for `Izu'. On the basis of the environmental variance components obtained, it is proposed that all offspring genotypes exhibiting a phenotypic cracking incidence of less than 20% and 11% should be selected in single-year and three-year evaluations, respectively, when those genotypes are evaluated using 25 fruits from a single tree, in order to successfully select all genotypes with an genotypic incidence of less than 3%.

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Alfred Jones and P. D. Dukes

Abstract

Thirty random seedlings from each of 50 random parents of a sweet potato (Ipomoea batatas (L.) Lam.) mass selected population were evaluated in the greenhouse and their subsequent field performances were recorded. Simulated selection sequences were also studied. A sequence with mass selection first on maternal hill weight, high seed set, and high seed weight followed by a 50% culling level within families on the basis of low greenhouse seedling vigor resulted in average progeny field yields 45% above that of no selection. The results showed seed weight to be a potentially useful selection criterion for root yield. Individual seedling root weight in the greenhouse was not a good predictor of field yield.

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I.L. Goldman

input and hard work on this recurrent selection project, and four anonymous reviewers for their suggestions to this manuscript. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper

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Katrina J.M. Hodgson-Kratky, Olivier M. Stoffyn, and David J. Wolyn

-producing desert plant ( Dierig et al., 1989 ; Ray et al., 1993 ; Thompson et al., 1988 ); consequently, selection for only one parameter may not always improve rubber yield. In guayule, single-plant selection for both root weight and rubber percentage increased

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Y.L. Qian, J.M. Fu, S.J. Wilhelm, D. Christensen, and A.J. Koski

selected as parental breeding materials. No information is available about the relative salinity tolerance of these elite, turf-type saltgrass selections. The objective of this study was to screen salinity tolerance and determine the level of salinity

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Renjuan Qian, S. Brooks Parrish, Sandra B. Wilson, Gary W. Knox, and Zhanao Deng

selections in Florida and found three of them to be highly female sterile. Female sterile porterweed included the following: ‘Violacea’ porterweed ( Stachytarpheta mutabilis ), ‘Naples Lilac’ porterweed ( S . cayennensis × S . mutabilis ‘Violacea’), and

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Mark K. Ehlenfeldt and Chad E. Finn

inquiries from the landscape and nursery industry regarding two pink-fruited blueberry selections in its test plots. Because of this interest, the U.S. Department of Agriculture, Agricultural Research Service has released these selections for evaluation

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Omar Carrillo-Mendoza, José X. Chaparro, and Jeffrey Williamson

higher branch production and lower blind node incidence than FG × ‘Tardy Nonpareil’ almond (TNP) hybrids. Two selections from P. kan F 1 : seedling number 3 [chilling requirement 300 chill units (CU)] and seedling number 6 (300 CU), and one selection from

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Neel Kamal and Christopher S. Cramer

that variation exists in onion germplasm for resistance to onion thrips and IYS. By performing selections on this germplasm, it may be possible to enhance the level of IYS resistance. This study was undertaken to determine if selected onion populations