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  • Author or Editor: Sadanand A. Dhekney x
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Dennis J. Gray, Zhijian T. Li, Sadanand A. Dhekney, Donald L. Hopkins and Charles A. Sims

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Dennis J. Gray, Zhijian T. Li, Sadanand A. Dhekney, Donald L. Hopkins and Charles A. Sims

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Viji Sitther, Dapeng Zhang, Sadanand A. Dhekney, Donna L. Harris, Anand K. Yadav and William R. Okie

Information on genetic relationships and pedigree structure in germplasm collections is vital to breeders in crop improvement programs. In this study, we assessed genetic identity, kinship distance, and parentage–sibship relationships among 37 peach (Prunus persica) accessions and breeding lines using simple sequence repeat (SSR) markers. Pairwise comparisons based on multilocus SSR profiles led to the identification of two synonymous groups including five accessions. Two pairs of parent–offspring and one full sibling relationships were identified using the likelihood method, and Bayesian cluster analysis partitioned the accessions into groups that were partially compatible with the known pedigree, origin, and flesh color. The 37 accessions were grouped into four clusters, which were largely supported by the known pedigree and origin of these accessions. Although the observed mean heterozygosity was 0.219, mean inbreeding coefficient was 0.635, indicating a high degree of inbreeding among the accessions. Eleven of the 15 SSR markers (73.3%) tested were transferable to nine related Prunus species. Results of the study demonstrate that these SSRs could facilitate the assessment of genetic identity and pedigree structure.

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Sadanand A. Dhekney, Zhijian T. Li, Michael E. Compton and Dennis J. Gray

Stamens and pistils from mature grapevines and leaves from in vitro micropropagation cultures were used to optimize parameters influencing somatic embryogenesis in Vitis. Embryogenic competence was dependent on species/variety, explant type and developmental stage, medium composition, and growth regulator concentration. Of varieties evaluated, a greater number produced embryogenic cultures from stamens and pistils (26) compared with leaves (six). Among the different stamen and pistil stages, Stage II and III explants produced the maximum embryogenic response regardless of genotype and medium composition. Of seven culture media tested, the highest embryogenic response was recorded from varieties cultured on MSI (18) and PIV (16) media. Experiments annually repeated over 3 to 10 years demonstrated reproducible results. Highly reliable protocols for somatic embryogenesis were obtained for 29 Vitis species and varieties, including 18 Vitis vinifera varieties, Vitis riparia, Vitis rupestris, Vitis champinii, and eight Vitis hybrids. Embryogenic cultures were maintained on X6 medium for a period of 6 months to 2 years depending on the variety and used in studies involving genetic transformation and transgenic plant regeneration.