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James F. Hancock

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James F. Hancock

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James F. Hancock

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James F. Hancock and Charles Stuber

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James F. Hancock and Barbara Goulart

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Luping Qu and James F. Hancock

A tetraploid blueberry population resulting from a cross of US 75 {a tetraploid hybrid of Fla 4B [a selection of Vaccinium darrowi Camp (2n = 2x = 24) × `Bluecrop' [(V. corymbosum L. (2n = 4x = 48)]} × `Bluetta' (4x) was used to generate a genetic linkage map of US 75 by randomly amplified polymorphic DNA (RAPD) analysis. One hundred and forty markers unique for Fla 4B that segregated 1:1 in the population were mapped into 29 linkage groups that cover a total genetic distance of 1288.2 cM, with a range of 1.6 to 33.9 cM between adjacent markers. The map is essentially of V. darrowi because US 75 was produced via a 2n gamete from Fla 4B and only unique markers for Fla 4B were used. Therefore, all the chromosomes of V. darrowi could be represented in the map.

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James F. Hancock and John Nelson

Abstract

Commercial blueberry fields in Michigan were treated with K at either 0 or 67.5 kg·ha–1 for 3 years. Soil and foliar levels of K at harvest were determined. There were no significant associations between soil K and yield, even though many values were below 25 ppm. Leaf K was significantly correlated with yield in only 1 year and the optimum was about 0.43%.

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Sedat Serçe and James F. Hancock

The inheritance of day-neutrality in octoploid Fragaria L. was investigated in crosses between day-neutral (DN) × short day (SD) and DN × DN types using F. ×ananassa Duchesne in Lamarck cultivars and elite selections of F. virginiana Miller and F. chiloensis (L.) Miller. Genotypes were considered as DN if they flowered under both the SDs of spring before 30 May (<14 hours) and the long days of summer after 24 July (>15 hours). Wide ranges in the percentage of DN progeny were found among the families regardless of species background (30% to 87% in DN × SD and 22% to 93% in DN × DN crosses). None of the families fit the segregation ratios expected if DN was regulated by recessive alleles at one locus, and only about half of the families fit the segregation ratios expected if a single dominant allele regulated DN. Several two-gene models fit the segregation data better than the single locus ones, but none of the genetic models tested fit the DN segregation ratios at the ends of the distribution range. The wide range observed in the percentage of DN progeny across all the families is most consistent with a polygenic model. Several other kinds of observations supported the multigenic regulation of DN: 1) Different DN parents crossed to the same SD genotype often produced different percentages of DN progeny, 2) Some of the day-neutrality sources were more powerful than others in producing of DNs, and 3) None of the DN parents produced 100% DN progeny, which would be expected if there were homozygous dominant DN individuals. Specific combining abilities for DN and flowering strength were significant, while general combining abilities for these traits were not. Our results suggest that parental combinations can be selected that will generate very high proportions of DN progeny that bloom for long periods of time.

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James F. Hancock and James H. Siefker

Abstract

Inbreeding coefficients were calculated for the 63 cultivars of blueberry (Vaccinium corymbosum L.) released by public agencies in the United States. A steady increase in coefficients was noted from the period of 1910−1920 (F=0.00) to 1960−1970 (F=0.13). ‘Lateblue’ and ‘Flordablue’ had the highest coefficient of 0.25. Most of the genes in the cultivars came from the wild selections ‘Brooks’, ‘Sooy’ and ‘Rubel’.