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  • Author or Editor: D. J. Weaver x
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Abstract

Visual rating scales were developed for evaluating tissue injury in peach trees [Prunus persica (L.) Batsch] in the orchard due to cold/winter temperatures and bacterial canker (Pseudomonas syringae van Hall) development. The numerical ratings on a scale of 1 to 9 separately describe key stages of damage and its severity due to cold and bacterial canker and are portrayed pictorially for clarity. Accurate estimation of tree status at very early stages of injury and good correlation with ultimate tree survival have been possible through the use of these rating scales. This information has been incoporated in the data collection for a regional research project dealing with the development and evaluation of rootstocks for peach in the southern United States and also is under consideration for use in another regional project involving peach in addition to apple, pear, and cherry.

Open Access

Abstract

During winter months, concentrations of K, Ca, Al, Sr, B and Zn were significantly greater in twigs of apparently healthy, dormant peach (Prunus persica (L.) Batsch) trees grown on old peach orchard sites than in twigs of apparently healthy trees on adjacent new sites in Georgia. Later in the spring, tree mortality and injury from cold and bacterial canker caused by Pseudomonas syringae Van Hall were also much greater on the old sites than the new sites. Differences in elemental concentrations in roots and 2-year-old shoots were not significant when trees on old and new orchard sites were compared. In a short life site in South Carolina, pruning trees in November greatly increased tree mortality compared to fumigated or nonfumigated trees pruned in February. Concentrations of K, Mg, Fe, and Al were also significantly greater in the November-pruned trees than in the February-pruned trees. Accumulation during dormancy of certain elements in peach twigs may be an indicator that the trees have been predisposed to short life.

Open Access

Abstract

The reliability, capability to predict survival, and convenience of 5 cold hardiness tests — triphenyl tetrazolium chloride reduction (TTC), electrolytic conductance (EC), ninhydrin-reactive compounds (NRC), trunk cambial browning (TCB), and bacterial canker development (BCD) — were evaluated using previous season's twigs of ‘Redhaven’ peach (Prunus persica (L.) Batsch) during the 1976-77 dormancy season. TTC, NRC, and EC were all significantly correlated with TCB as well as percent tree survival (PTS) in the field, and thus proved to be quantitative, reliable and capable of predicting survival at a later date. No statistical correlation was found between BCD and other hardiness tests.

Open Access

Linkage relationships among eight isozyme genes (Acp-3, Est-1, Est-5, Prx-1, Prx-2, Prx-3, Me, and Adh) and two morphological markers (Inh and Twh) were investigated in one F2 and two BC1 families of interspecific crosses between the American chestnut (Castanea dentata Borkh.) and the Chinese chestnut (C. mollissima Blume). Inh was consistently linked with Prx-1 and Est-5 in all families. In addition, four other gene pairs, Acp-3Inh, Acp-3Prx-1, Me–Inh, and Twh–Inh, were linked in one of the three families investigated. The two isozyme genes and two morphological marker genes were tentatively integrated into one linkage group with the gene order TwhInhPrx-1Est-5.

Free access

Abstract

Viability of pollen grains of isogenic sibling bean (Phaseolus vulgaris L.) selections of known tolerance of sensitivity to high temperatures (HT), as previously determined by pod retention and seed yield, was compared to that of a common parent bean selection and a cowpea [Vigna unguiculata (L.) Walp.] cultivar. Exposure of newly opened flowers to temperatures of 35° or 41°C reduced the viability of pollen grains in all bean selections. Pollen of all sibling selections was less affected by HT than pollen of their common parent suggesting transgressive segregation of factors for HT tolerance. At 41°, most pollen grains were destroyed in the parent bean selection and the 2 HT-sensitive siblings, whereas 44% to 55% of the pollen grains appeared to be viable in the 2 HT-tolerant siblings. Pollen viability of the HT-tolerant cowpea cultivar was not reduced by temperatures to 41°. Pollen staining indicated an interrelationship between pollen viability and tolerance to HT stress among the bean selections. The technique described has the potential for rapid selection of HT-tolerant genotypes in hybrid populations.

Open Access

Abstract

Two bean cultivars and one breeding selection with different pod-retention characteristics were grown at mean soil moisture tension (MSMT) of 0.05 and 0.1 MPa in 2 separate plantings. In the 5 May planting, flower buds developed during the 1st 3½ weeks of flowering, were dated and counted, and those developing mature pods were identified. Sixty-five percent to 90% of all pods that reached full maturity were from floral buds that reached anthesis during the 1st 2 weeks of flowering. The percentage of pods reaching maturity varied among cultivars. About 40% of the floral buds that developed on the determinate bean selection were retained to full pod maturity. Only 20% to 25% of the floral buds developed on each of the indeterminate cultivars were retained to full pod maturity. An increase in the MSMT from 0.05 to 0.1 MPa in the 23 June planting reduced the number of pods and seeds/plant and total seed weight/plant by 20% to 40%, but the number of seeds/pod and weight/seed was not influenced by MSMT or by number of pods produced on either of the dry bean cultivars or the breeding selection.

Open Access

Abstract

Chemicals often associated with pollen function in vitro were applied under field conditions to foliage of determinate, semi-determinate, and indeterminate beans (Phaseolus vulgaris L.) to evaluate pod and seed yield response. Sprays of calcium nitrate, boric acid, ethylenediaminotetraacetic acid, detergent “Micro”, and different sugars altered pod retention and seed yield, but response varied with bean source.

Open Access