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De-Kun Dong, Jia-Shu Cao, Kai Shi, and Le-Cheng Liu

overdominance plays an important role in the formation of heterosis. These two hypotheses share a common character in that they both were based on only single-locus analysis. Considering the multigenic nature of quantitative traits, epistasis should not be

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Samuel F. Hutton, Jay W. Scott, and Jeffrey B. Jones

significant homozygous × heterozygous {[j]} and heterozygous × heterozygous {[l]} interactions in Spring 2006 and Summer 2007 ( Table 2 ). Because the [h] and [l] parameters had opposite signs, duplicate dominance or recessive suppression type of epistasis was

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D.M. Shuh and James F. Fontenot

The inheritance of multiple flowers and leaf pubescence resulting from the crosses between accessions from pepper species Capsicum annuum L. and C. chinense Jacq. was examined. Hand cross- and self-pollinations were made in a glass greenhouse. Only eight normal F1 plants were obtained from crosses between the two species when C. annuum L. was the female parent. F2 and backcross generations obtained from the F, and the two parents were grown in the field. Two field studies indicated that multiple flowers and leaf pubescence were controlled by dominant genes. A three-gene model leading to an F2 segregation ratio of 45:9:10 and a two-gene model leading to an F2 segregation ratio of 13:3 were suggested for the inheritance of multiple flowers and leaf pubescence, respectively. Epistasis was evoked in the interpretation of the data. No linkage was found between the two characters. The inconsistencies between F2 and backcross data might be due to selective elimination of genes from one or the other parent in an Interspecific hybridization. Segregation ratios from intraspecific crosses for leaf pubescence supported a two-gene model and gave an F2 ratio of 13 pubescent leaf : 3 glabrous leaf progeny.

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Dennis J. Werner, Michael A. Creller, and José X. Chaparro

Inheritance of the blood-flesh (red-violet mesocarp) trait in peach [Prunus persica (L.) Batsch.] was investigated in S1, S2, F1, F2, F3, BC1P1, and BC1P2 families derived from `Harrow Blood', a clone showing anthocyanin accumulation in fruit about 45-50 days after anthesis. This trait invariably was associated with the red midrib leaf phenotype in `Harrow Blood', an S1 family from `Harrow Blood', and in green leaf F2 progeny derived from `Harrow Blood' × `Rutgers Red Leaf 2n'. A segregation ratio of about 3 blood-flesh : 1 wild-type was observed in the S1 family, but F1 progeny produced only wild-type fruit. Examination of F2 progeny segregating for the blood-flesh and red leaf traits revealed no evidence of epistasis. Based on segregation ratios in F1, F2, F3, BC1P1, and BC1P2 families from this cross, the F1 family from `Contender × (`Harrow Blood' × `Rutgers Red Leaf 2n'), and six additional F1 families from crosses between `Harrow Blood' and green leaf clones with wild-type fruit, we propose that blood-flesh is controlled by one gene, designated bf (blood-flesh). The blood-flesh phenotype was associated with reduced tree height in S1 and F2 progeny derived from `Harrow Blood'. Segregation for leaf blade color deviated significantly (P = 0.05) from the expected 3 red : 1 green ratio in six of the F2 families derived from selfing seven F1 trees from `Harrow Blood' × `Rutgers Red Leaf 2n'.

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Jason Prothro, Katherine Sandlin, Rattandeep Gill, Eleni Bachlava, Victoria White, Steven J. Knapp, and Cecilia McGregor

-recessive genotype has lower SOP than the heterozygous and homozygous-dominant genotype ( Fig. 5 ). The effect of the interaction in the overall population is small ( R 2 = 0.7%). Fig. 5. Epistasis plot ( Kao and Zeng, 2002 ; Kao et al., 1999 ) for the interaction

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Edward J. Ryder

Two new lettuce (Luctuca sativa L.) genes are described and named truncated leaf (tn), and sickly (si). A gene for reflexed involucre is identical to that previously described in wild lettuce (L. serriola L.). Mosaic reaction (me) and light green (lg) are linked, with P = 0.448. Six gene pairs tested for linkage are independently inherited. Sickly is epistatic to light green.

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H.T. Erickson

Indeterminate growth habit in lima bean is inherited as a single gene dominant. A qualitative short-day photoperiodic response for flowering appears to be controlled by duplicate dominant genes with coupling linkage to the gene for growth habit. Partial epistasis of the determinate growth habit on genes for short-day response is suggested.

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Rodomiro Ortiz

Virus-like symptoms (due to banana streak virus, cucumber mosaic virus, or both) have been observed in plants of Musa hybrids (TMPx) and local landraces included in multilocational trials in sub-Saharan Africa. Virus-like symptom incidence in these multilocational trials was analyzed using the additive main effect multiplicative interaction (AMMI) model. There were significant differences in virus-like symptom incidence among environments, which was highest in the cool, rainy season (14% to 42%) and lowest in the warm, dry season (<10%). Genotypes showed significantly different responses to virus(es), which depended on the environment. There were no plants of AA and AAA bananas showing virus-like symptoms (0% incidence), whereas ABB cooking bananas and a cooking banana hybrid (ABB × AA) seldom showed virus-like symptoms (<2% incidence). The AAB French plantains appeared to have a similar genotypic response to virus(es) (about 10% virus-like symptom incidence) and were regarded as less susceptible than the False Horn plantain `Agbagba', which showed virus-like symptoms in most of the environments (average 21% incidence). Hence, `Agbagba' should be considered a susceptible indicator host because it has a stable susceptible host response to Musa virus(es). Plantain hybrids (AAB × AA) showed virus-like symptoms; however, there were significant differences in genotypic response to the virus(es) among various hybrids (11% to 60%). Epistasis due to transgressive segregation may control the susceptibility of TMPx germplasm to Musa virus(es). The AMMI1 model revealed that an increase in clonal susceptibility resulted in a more unstable response to the virus. Similarly, phenotypic instability was associated with an increase in clonal resistance. Environments with very low (dry season) or very high (rainy season) incidence of virus-like symptoms had unstable virus expression. Scoring virus symptoms in cool environments with low rainfall and low potential evapotranspiration provided an unbiased assessment of genotypic response to Musa virus(es). The AMMI2 model showed that seasonal rather than locational diversity accounted for most of the interaction patterns. This finding may indicate a low level of strain differentiation in the region.

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Eduardo D. Munaiz and Michael J. Havey

Onion (Allium cepa) plants with lower amounts of epicuticular waxes on foliage suffer less damage from the insect pest Thrips tabaci (onion thrips). Glossy onion accumulates significantly less epicuticular wax compared with wild-type “waxy” onion, and a single recessive locus (gl) has been proposed to condition this phenotype. Genetic analyses of types and amounts of epicuticular waxes were completed using two segregating families from the cross of the glossy inbreds B9885 and B9897 (both originally selected from the onion cultivar White Persian) with waxy inbred B8667 and semiglossy (intermediate amounts of waxes) inbred B5351, respectively. F2 progenies were grown in greenhouses and scored visually for foliar phenotypes, and amounts and types of epicuticular waxes were determined using gas chromatography-mass spectrometry (GCMS). For one F2 family from the cross of glossy B9885 by waxy B8667, visually scored glossy vs. waxy foliage fit a 1:3 ratio and the phenotype mapped to chromosome 8 of onion. This same region on chromosome 8 was significantly associated with amounts of the ketone hentriacontanone-16 (H16) and fatty alcohols 1-octacosanol (Oct1) and 1-triacontanol (Tri1). Visually scored F2 progeny from the cross of glossy B9897 × semiglossy B5351 did not fit expected models for one or two recessive loci. Significant quantitative trait loci (QTL) were revealed on chromosomes 5 and 8 controlling amounts of H16. Epistasis was detected between regions on chromosomes 1 and 8, and a 100-fold increase of H16 was conditioned by homozygous genotypes for the B5351 region on chromosome 1 and the B9885 region on chromosome 8. The three QTL model explained 41% of the phenotypic variation for amounts of H16 at logarithm of odds of 16.6. Amounts of Oct1 and Tri1 in the B9897 × B5351 family were associated with a major QTL on chromosome 1, explaining 37% to 46% of the phenotypic variation, respectively. This research demonstrates that glossy foliage of ‘White Persian’ onion is conditioned by a recessive locus on chromosome 8 for which we propose the name gl wp. These results are important for selection of onion with unique profiles of epicuticular waxes to reduce losses resulting from onion thrips.

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N. Georgelis, J.W. Scott, and E.A. Baldwin

Small-fruited cherry tomato accession PI 270248 [Lycopersicon esculentum Mill. var. cerasiforme (Dunal) A. Gray] with high fruit sugars was crossed to large-fruited inbred line Fla.7833-1-1-1 (7833) (L. esculentum) that had normal (low) fruit sugars. The F1 was crossed to PI 270248 and 7833 to obtain BCP1 and BCP2, respectively, and self-pollinated to obtain F2 seed. The resulting population was used to study the inheritance of high sugars from PI 270248. Continuous sugar level frequency distributions of BCP1, BCP2, and F2 suggest that the trait is under polygenic control. Additive variation was significant, but dominance variation was not. There was a heterozygote × heterozygote type of epistasis present that likely caused the F1 sugar level to skew nearly to the level of the high sugar parent. The F2 mean sugar level was lower than the midparent level. Broad-sense heritability was 0.86. There was a significant line × season (fall, spring) interaction where lines with higher sugars were affected more by seasons than lines with lower sugars. Sugar level, in general, was higher in spring. Higher solar radiation in spring than in fall may explain the sugar level difference between the seasons.