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Abstract
A simple-leaved pecan [Carya illinoensis (Wang.) K. Koch] seedling was found in a Riverside seedling nursery by Larry Womack of Womack Nurseries, DeLeon, Texas. This uncommon specimen was preserved by grafting it to a normal pecan seedling rootstock sometime in the early 1960’s. Wood from the variant was grafted on orchard seedlings at the U. S. Pecan Field Station, Brownwood, Texas, in April 1973 and on 1-year-old greenhouse-grown Riverside seedlings in Feb. 1974. This paper reports observations of the growth and gross morphology of this unusual variant.
Abstract
Suitable parents for the production of F1 hybrid seed between almond and root-knot nematode resistant peach were selected. Three of 13 almond selections were found which, when pollinated by ‘Nemaguard’ pollen, produced good sets of seed. When germinated, their seedlings showed good root-knot nematode resistance, hybrid vigor, and exceptional compatibility with almond tops.
The self-incompatibility of almond was used to permit natural pollination between selection CP5-33 and a selected seedling of ‘Nemaguard’, 3-28. The F1 hybrids proved to be very compatible as rootstocks with almond and peach tops and imparted increased vigor to them.
Both ‘Nemaguard’ and a selected seedlings of ‘Nemaguard’ served as good pollen parents. ‘Okinawa’ peach, another rootknot nematode resistant peach type rootstock, was a less satisfactory pollen parent.
Abstract
The effects of plant nutrients on citrus fruit quality cannot be considered independently of their effects on yield. In some cases quality can be improved by sacrificing some yield;however, from the overall economic point of view, it is usually advantageous to sustain maximum fruit yield even though there may be some sacrifice in fruit quality. This report emphasizes the nutrient effects on quality in the ranges in which we expect maximum yield to be sustained. If the deficient ranges for yield are included, the degree of effects on quality is greater. The nutrient ranges and effects discussed are primarily those encountered by the authors under California conditions.
Phytophthora capsici is responsible for multiple disease syndromes of Capsicum annuum but the resistance mechanism is still unknown. Evaluating gene expression during foliar blight can be used to identify expression patterns associated with resistance in Capsicum species. This study reports a direct comparison of gene expression changes during the foliar blight syndrome using two different races of P. capsici on C. annuum host plants with resistant and susceptible phenotypes to those races. Four genes were evaluated for differential expression following leaf inoculation with P. capsici. RNA isolated from leaves at three time points was used to quantify gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Of four genes tested, two had differential expression in response to P. capsici at 72 hours postinoculation, a xyloglucan-specific endo-β-1,4-glucanase inhibitor protein (XEGIP2) in susceptible cultivar New Mexico Heritage 6-4 (NMH6-4), and a C. annuum cell wall protein (CWP) in resistant Criollo de Morelos 334 (CM334). Both genes had a 5-fold increase in transcription in leaves over the control. These results suggest that both genes are playing a role in disease resistance to foliar blight.
The pawpaw [Asimina triloba (L.) Dunal] is a native plant found mainly in the southeastern and eastern United States, and its fruit has great potential as a new high-value crop in these regions. Although there are ≈45 named pawpaw cultivars, breeding for improvement of specific traits, such as fruit size and quality, is desirable. Our long-term goal is to utilize molecular marker systems to identify markers that can be used for germplasm diversity analyses and for the construction of a molecular genetic map, where markers are correlated with desirable pawpaw traits. The objective of this study was to identify random amplified polymorphic DNA (RAPD) markers that segregate in a simple Mendelian fashion in a controlled A. triloba cross. DNA was extracted from young leaves collected from field-planted parents and 20 progeny of the cross 1-7 × 2-54. The DNA extraction method used gave acceptable yields of ≈7 μg·g-1 of leaf tissue. Additionally, sample 260/280 ratios were ≈1.4, which indicated that the DNA was of high enough purity to be subjected to the RAPD methodology. Screening of 10-base oligonucleotide RAPD primers with template DNA from the parents and progeny of the cross has begun. We have identified two markers using Operon primer B-07 at 1.1 and 0.9 kb that segregate in a simple Mendelian fashion in progeny of the 1-7 × 2-54 cross. Other primers and controlled crosses will also be screened.