Search Results
Abstract
High temperature prior to controlled freezing increased inner bark and xylem injury in twigs of both ‘Siberian C’ and ‘Redhaven’ peaches (Prunus persica (L) Batsch). ‘Siberian C had a lower natural moisture content than ‘Redhaven’. Artificially increasing moisture content did not affect xylem injury, but increased inner bark injury. Significant temperature by cultivar and moisture by cultivar interactions were found with inner bark. We concluded that the superior hardiness of ‘Siberian C’ was not due solely to its lower moisture content.
Abstract
A single genotype peach (Prunus persica (L.) Batsch cv. Redhaven) was used to study non-genetic hardiness variation. Twigs from the upper southwest and lower northeast sectors of several randomly chosen trees were frozen on 4 dates from November to March. The basal, middle, and tip sections of each twig were examined, using tissue browning as an index of injury. An appropriate statistical model was used to separate the variance components. Trees and tree × sector interaction constitute only a small portion of the total random variation, while twigs and residual error accounted for the major portion. Variance estimates were used to determine sample sizes needed to detect browning differences of a desired magnitude. The lowest variance estimates were obtained when the basal section of twigs collected from the upper southwest sector were analyzed. Sample sizes between 6 and 21 twigs could be expected to detect important differences in injury as assayed via tissue browning.
Abstract
‘Siberian C’ was hardier than ‘Velvet’ or ‘Redhaven’ peach [Prunus persica (L.) Batsch.] on all 13 test dates during 2 winters. Within test dates, cultivar injury was positively correlated with twig moisture content. Moisture content of the bark was twice that of xylem; however, xylem suffered more injury than the bark. Changes in temperature response patterns of bark and xylem from late fall to winter indicated a shift in freezing processes occurred during acclimation. Differential response of fully acclimated bark and xylem to temperature decrease suggested that bark underwent equilibrium freezing while xylem deep supercooled. ‘Siberian C’ did not appear more susceptible than ‘Velvet’ and ‘Redhaven’ to fluctuating late winter and spring temperatures.
Abstract
Seven clones of peach (Prunus persica (L.) Batsch) varying in hardiness, and 5 progenies derived from them were used to study the inheritance of cambium, xylem, and vegetative bud hardiness. Mean progeny cambium and xylem hardiness could be predicted from average parental performance, but vegetative bud hardiness could not. Injury within dates and tissues was highly heritable and environmental variation was very low. Correlations among injury ratings for different tissues, temperatures, and dates were low when based on individual trees indicating poor repeatability of individual genotypes over time. Correlations based on family means were higher. The low correlations based on individual trees indicate that selection based on individual phenotypic performance in a single test might be ineffective.
Prunus accessions were screened in a greenhouse for suitability as hosts for Criconemella xenoplax (Raski) Luc and Raski. All 410 accessions examined were suitable hosts for the nematode. Included in this study were 266 Prunus persica L. Batsch cultivars and cultivars representing 25 other Prunus species: P. americana Marsh., P. andersonii A. Gray, P. angustifolia Marsh., P. argentea (Lam.) Rehd., P. armeniaca L., P. besseyi L. H. Bailey, P. cerasifera Ehrh., P. cistena N.E. Hansen, P. davidiana (Carriere) Franch., P. domestica L., P. dulcis (Mill.) D. Webb, P. emarginata (Dougl. ex Hook.) Walp., P. hortulana L. H. Bailey, P. insititia L., P. kansuensis Rehd., P. maritima Marsh., P. munsoniana W. Wright & Hedr., P. pumila L., P. salicina Lindl., P. simonii Carriere, P. spinosa L., P. tenella Batsch, P. texana D. Dietr., P. tomentosa Thunb., and P. webbii (Spach) Vierh. Also, another 66 interspecific hybrids were tested. Although a few accessions seemed to exhibit an unstable form of resistance, it seems unlikely that Prunus selections that exhibit useful resistance to population increase by C. xenoplax will be found.
Abstract
An inexpensive chamber for controlled freezing of large container-grown plants up to 2 m in height was constructed using liquid nitrogen as a refrigerant. A microcomputer-based system was developed to control the cooling sequence and to collect data on tissue temperature, air temperature, and exotherms. Versatile software was written that allowed the programmed rate of temperature drop to be based on either tissue temperature or air temperature.
Long-term field trials of a wide range of peach [Prunus persica (L.) Batsch] germplasm on two peach tree short-life (PTSL) sites revealed marked differences in survival among lines. Generally, cuttings and seedlings of a given line performed similarly, as did ungrafted seedlings and their counterparts grafted to a commercial cultivar. No apparent relationship existed between a line's chilling requirement and survival. B594520-9 survived best in Georgia and South Carolina, providing significantly greater longevity than Lovell, the standard rootstock for use on PTSL sites. B594520-9 is derived from root-knot-nematode-resistant parentage, and progeny of surviving seedlings have demonstrated root-knot resistance similar to Nemaguard seedlings.