Search Results

You are looking at 101 - 110 of 955 items for :

  • Refine by Access: All x
Clear All
Free access

J.A. Mortensen, J.W. Harris, and D.L. Hopkins

Free access

B.I. Reisch, R.M. Pool, M.H. Martens, R.S. Luce, G. Remaily, and T.J. Zabadal

Free access

B.I. Reisch, R.M. Pool, W.B. Robinson, T. Henick-Kling, J.P. Watson, K.H. Kimball, M.H. Martens, G.S. Howell, D.P. Miller, C.E. Edson, and J.R. Morris

Free access

John R. Clark and James N. Moore

Free access

B.I. Reisch, R.M. Pool, W.B. Robinson, T. Henick-Kling, B.K. Gavitt, J.P. Watson, M.H. Martens, R.S. Luce, and H.C. Barrett

Free access

J.A. Mortensen, J.W. Harris, D.L. Hopkins, and P.C. Andersen

Free access

M. Andrew Walker, Lloyd A. Lider, Austin C. Goheen, and Harold P. Olmo

Free access

László G. Kovács, Guoqiang Du, and Pinghai Ding

Grapevine cold hardiness is often assessed with differential thermal analysis (DTA) of excised dormant buds. Such small tissues are prone to rapid dehydration when exposed to air during sample preparation. We show that excised buds of grape cultivars `Vignoles' and `Norton' lose as much as 6.3% and 2.9% of their total water content, respectively, during a two-minute exposure to air at 24 °C. In order to assess the impact of moisture loss on cold hardiness measurements, we prepared dormant bud samples with reduced water content and subjected them to DTA. The results demonstrate a positive correlation between average gross bud water content and median low temperature exotherm (LTEmean). In `Vignoles' and `Norton' buds, a 6.5% and a 4.3% reduction in gross water content, respectively, were sufficient to result in lower LTE temperatures (P < 0.001). The data suggest that even moderate dehydration of excised grape buds may influence the results of cold hardiness assessment by DTA. It is important that investigators be vigilant to the potential artifacts that can arise during sample preparation in order to ensure that the LTE temperatures of samples reliably characterize the cold hardiness of field populations.

Free access

John R. Clark and James N. Moore

Free access

Xia Xu, Jiang Lu, and Zhongbo Ren

Ploidy level in grapevines varies, especially since in vitro techniques are employed in the breeding process and after plants are treated with either chemicals or radiation. Detection of ploidy level in grapevines by microscopic chromosome counting is complicated by their high number and the small size of chromosomes. Flow cytometry provides an accurate and rapid method in determining the ploidy level in plant tissue by measuring the nuclear DNA content in living cells and thus is a very useful tool in plant breeding or genetic studies. The objective of this research was to analyze the ploidy level of a selected group of muscadine vines that were different from normal diploid vines in morphology. These grapes were derived from either chemical treatment of known varieties or from controlled/open pollinations. Among the 26 grapevines investigated, 8 were found to be diploids, 11 were tetraploids, and 7 were chimeric aneuploids. Results of this study indicate that flow cytometry is a quick, reliable tool for determining ploidy levels of grapevines.