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The Department of Plant and Soil Science at Texas Tech University has developed on-line master's of science nonthesis and master's of agriculture nonthesis degree programs in response to the perceived needs of mature place bound students. Initial enrollments have been successful. The development of these types of programs requires time, funding and technically capable personnel. In addition, there are administrative, curricular and personnel issues involved with the implementation of such a project. These issues and the solutions we have employed will be discussed.
Abstract
Breeding programs depend upon genetic variation. Visual plant markers traditionally have been used in crop improvement. However, molecular markers provide additional selection criteria. Of the molecular markers available, isozymes are preferred by many researchers because they are expressed in young tissue as codominants and are easily extracted and detected. Mature plants may bias estimation of hybrid purity, whereas estimations of hybrid purity can be obtained at an early stage by enzyme analysis (1, 2, 4).
The trailing blackberries (Rubus sp. L.), particularly `Marion', are the primary blackberries grown for the processing market and they are largely machine harvested. While `Marion' is well known for its processed fruit quality, particularly flavor, aroma, and perception of low seediness, it has spines (thorns) that can be dislodged when machine harvested and end up in the product. A primary goal of the USDA–ARS blackberry breeding program in Corvallis is the development of cultivars that are comparable to `Marion' in fruit quality but are spineless (thornless). Nine thornless selections were compared with four standard cultivars as individually quick-frozen (IQF) and puree products in a blind evaluation. Each sample was scored panelists from the blackberry industry and research program. IQF samples were scored for appearance, color, seediness, flavor, and overall quality by 21 panelists and purees were scored for color, flavor, aroma, and overall quality by 25 panelists. Both panels used a 9 point hedonic scale (1 = dislike extremely, 5 = neither like nor dislike, 9 = like extremely). With the exception of color, there were significant differences among all genotypes for all traits evaluated in the IQF and pureed products. ORUS 1380-1 was ranked similar to `Marion' and significantly better than `Waldo', in overall quality of the IQF product. In puree form, ORUS 1843-1 and ORUS 1843-3 had the highest ranking in overall quality, but were only both statistically different from ORUS 1489-2. For pureed product flavor, ORUS 1843-1 was the highest rated selection but was not statistically different from `Marion'. While ORUS 1843-1 and ORUS 1843-3 hold great promise, they are from a cross between wild collected Rubus ursinus Cham. & Schlt. and `Waldo' and as a result have some negative characteristics of the native species, particularly small fruit size. The puree quality of NZ 9128R-1, NZ 9351-4 and ORUS 1380-1 was similar to `Marion' and these genotypes offer promise as thornless replacements for `Marion'.
Photosynthetically active radiation (PAR) was measured at two times of day (8:00 am and noon Central Standard Time) in a 915 × 915-cm area of a 1006 × 915-cm gable roof greenhouse. PAR measurements were taken across a grid at 40-cm intervals, a total of 529 data points. Spatial variation of PAR in the greenhouse was evaluated through contour plots and the geostatistical technique of semivariogram construction. Semivariograms provide a visual guide to the degree of spatial correlation of a variable, allowing a quantification of the distance at which variables cease to be spatially correlated (the range) Measured PAR contained distinct zones of lowered values, a function of overhead greenhouse structures, wall-hung electrical boxes, and tall plants in adjacent greenhouses. Although the amount of PAR changed over time, zones of high and low PAR remained relatively constant, except at the sides of the greenhouse. Constructed semivariograms revealed that PAR contained strong spatial correlation (up to a 350-cm separation) as measured in the north-south direction, moving parallel to greenhouse bench placement. When PAR measurements perpendicular to benches (east-west) were used in directional semivariograms PAR was found to be completely random, plotting as a horizontal line called a nugget effect. Thus, plants placed perpendicular to the greenhouse benches (east-west) would not be affected by the spatial correlation of PAR.
The horticulture faculty at Texas Tech Univ. has developed an introductory horticulture laboratory course offered asynchronously through several media. A print version has been developed as a traditional correspondence course. Students can also choose to access the course over the World Wide Web with laboratory instruction provided from an accompanying CD-ROM. The course is based on an introductory horticulture textbook and is supplemented by additional information. Students conduct the laboratory exercises at a location of their choice and return photographs or video tapes of their results along with a formal lab report. Self-help exercises, worksheets, and proctored exams are submitted by correspondence or electronically via the World Wide Web. The most challenging aspect of this project was the development of laboratory exercises that ensured adequate experiential learning. This was accomplished by using easily accessible materials for laboratories that would allow students to apply the scientific method. A CD-ROM version of the lab includes compressed video segments used to demonstrate laboratory techniques. Details of these laboratory components and samples of student work will be presented.
Abstract
Induced resistance to verticillium wilt occurs in fusarium-resistant tomato cultivars from dip inoculation with mixed cultures of Race 1 of Fusarium oxysporum f. lycopersici (F) and Verticillium albo-atrum (V). This induced resistance decreases as F level in mixed inoculi is reduced. Simultaneous screening for resistance to V and F can be achieved by inoculation with V and reinoculating 48 to 72 hours later with F.
Abstract
Interspecific hybridization is a technique commonly used by plant breeders to transfer genes from one species to another. Interspecific hybrids are usually obtained with greater difficulty than intraspecific hybrids because genetic barriers to hybridization usually increase with an increase in genetic unrelatedness (6, 11, 18, 41). Breeders resort to interspecific hybridization only when the characters are absent or inadequately expressed at the intraspecific level. Stone-fruit breeders have made much use of interspecific hybridization in the improvement of Prunus cultivars and rootstocks (3, 5, 6, 8, 12, 14, 15, 18, 19, 28, 34, 36, 37, 41, 42, 43) particularly in the subgenus Prunophora (plums), because plum species tend to intercross more freely than do members of other subgenera (41, 42). This paper will review the problems that have been encountered in making interspecific Prunus hybrids and the techniques that have been used to overcome them. In addition, techniques are presented that have been employed successfully with other interspecific hybridizations which may have application for Prunus.
Abstract
The net present value (NPV) criterion was selected for comparing the monthly net cash flows over a 3-year period resulting from replacing matted row (MR) with annual hill (AH) strawberry (Fragaria × ananassa) production. In the base analysis, AH culture was found to be a profitable alternative to the MR system. The time pattern of the yield response to AH culture (annual cropping) vs. MR (harvesting limited to years 2 and 3 only) is the major economic advantage of the AH system. Discounting at the end of yearly planning periods instead of on a monthly basis overstated the NPV of the AH system.
Abstract
Temperatures for several post-bloom periods were correlated with days from full bloom to ‘Bartlett’ pear maturity. Date of maturity based on pressure test showed a high negative correlation (r = -.88) with mean temp above 40°F for the 36 days following bloom. The peak thermal period occurred 26-30 days after bloom, with the highest correlation on the 28th day. Days to maturity had a higher correlation with accumulated mean temp above 45°F than with degree hr above 45°F for the same periods. Base temp of 38.5°F to 50°F gave r values greater than -.85 in this prediction method. Mean temp between 41.5°F and 68.5°F on the 28th day had a linear correlation r of -.71 with days to maturity. Equal temp increments were more effective at min levels than at max levels for accelerating maturity. The post-bloom thermal period affecting maturation coincides with the stage of cell division and most effective time for application of chemical thinning sprays.
A recycling nutriculture system was redesigned to improve growth and flowering of Tagetes erecta L., cv., Inca Yellow in four media; loose rockwool (RW), coal bottom ash (CBA), pinewood peelings (PWP) and CBA:PWP (1:1, v/v). Three nutricycle frequencies of 12, 6 and 4 per 12 hour light period were set with a nutricycle duration of 5 minutes. Volume, height and fresh and dry weights of marigolds in CBA, PWP and CBA: PWP were comparable to that of marigolds in RW. Flower diameters of plants in CBA, PWP and CBA:PWP were increased and days to harvest decreased compared to plants in RW. Plants in CBA: PWP increased in fresh weight compared to CBA or PWP plants. No interaction occurred between media and nutricycle frequency at 12 or 4 cycles per 12 hours; however a malfunctioning timer caused prolonged flooding of plant root zones at the 6 cycle setting. This resulted in decreased plant volume and fresh and dry weights at this frequency. These results show that growth and flowering of marigolds in CBA and PWP comparable with that in RW can be achieved with more than 1 nutricycle frequency.