Search Results
Abstract
Rooted twig cuttings of ‘Jefferson’ peach [Prunus persica (L.) Batsch] infected or noninfected with phony peach disease were divided into nonphony, medium phony, and severe phony based on symptoms and on Fastidious, gram-negative, xylemlimited bacteria (PPXLB) counts. During the dormant season, the rooted plants were subjected to cold treatments of -11.7°, -14.4°, -17.9°, -20.0°, and -21.6°C in cold chambers. Plants with higher PPXLB counts exhibited more cold injury than plants with lower counts.
Abstract
Twenty-seven cultivars of peach [Prunus persica (L.) Batsch] and 4 seedling clones were evaluated over a 3 year period for susceptibility to gummosis disease caused by Botryosphaeria dothidea (Moug. ex Fr.) ces. & de Not. ‘Harbrite’ was highly resistant while ‘Pekin’, ‘Harmony’, ‘Redskin’, ‘Harken’ and ‘White English’, a seedling clone, exhibited some degree of resistance. All other cultivars were susceptible.
Abstract
A device was designed to permit accurate and rapid measurement of the abscission or removal force of peaches when used with a mechanical force gauge. To handle fruit of different sizes, small and large units were constructed. A detail drawing of the two units is shown. This instrument was used to study the physiology of abscission, chemicals for thinning, and chemicals for uniform ripening of peaches for mechanical harvesting as related to the removal force.
Abstract
Softwood cuttings taken from phony peach disease-infected and uninfected trees of ‘Jefferson’ peach [Prunus persica (L.) Batsch] produced 80% or more well-rooted cuttings with no significant difference (5% level) between phony and non-phony cuttings.
Abstract
Greenhouse-grown peach [Prunus persica (L.) Batsch] seedlings and cuttings were drought-stressed by reducing soil water potential (ψsoil) from field capacity (FC) to permanent wilting point, (PWP). Mean ψsoil and leaf water potential (ψleaf) were correlated with measurements of stomatal conductance (gs), net photosynthetic (Pn) rate, and vapor pressure deficit (VPD). Decreasing Pn and gs trends were noted as ψsoil decreased. Photosynthetic rate and gs were significantly reduced at ψleaf more negative than −1.5 MPa. Values of Pn and gs were more highly correlated to ψleaf than ψsoil. A midday depression in Pn rates began 2 hr earlier and peak rates were at least 50% lower when ψsoil was more negative than −0.05 MPa. The correlation coefficient (r) between ψleaf and ψsoil and between gs and Pn rate at different ψsoil was above 0.70. The r values decreased as soil and plant water potential became more negative. Stomatal conductance peaked at optimal ψsoil (FC) 2 hr following sunrise. Photosynthetic rate peaked at a ψsoil around −0.05 MPa 4 hr after sunrise.
Abstract
‘Woodroof’ pecan [Carya illinoensis (Wang) K. Koch] has been released to provide a disease-resistant, very good quality cultivar for home orchards in the southeastern United States where scab [Fusicladium effusum (Wint.)] is a major disease. Within the past 20 years, scab has greatly reduced pecan yields in home plantings in the southeast where the small number of trees does not justify expensive disease-control equipment (3, 5).
Abstract
A growth equation and a yield relationship were calculated to estimate space requirements and yields of two pecan cultivars (Carya illinoensis (Wangenh.) C. Koch]. The resulting estimates were used with pruning cost estimates in a simulation model to determine the orchard space management practice that maximizes income over time. The income maximizing spacings were 10.7 × 10.7 m and 13.7 × 13.7 m for the precocious ‘Desirable’ and the non-precocious ‘Stuart’, respectively. Annual pruning after the canopy closed produced the highest income for both cultivars.
Abstract
‘Spalding’ pear (Pyrus sp. Nak) has been released to provide a good quality pear cultivar for home planting in the Piedmont area of the southeast where fire blight is a major problem.
Abstract
Nondestructive studies of plant root systems are limited to hydroponic and glass-wall-type growing systems, which are expensive and limit the ways to observe and measure root structures. The following system was adapted from agronomic studies as a convenient, cost-efficient, and sensitive method of monitoring root growth of horticultural crops.
Abstract
Application of 960 ppm (2-chIoroethyl)methylbis(phenylmethoxy)silane (CGA-15281) substantially inhibited carbon transport into young fruit of peach [Prunus persica (L.) Batsch] 4 to 5 days before visual symptoms of senescence occurred. Carbon transport was unaffected 4.25 hours after treatment, but was greatly reduced after 24 hours. Reduced carbon transport continued through 144 hours following CGA-15281 application.