For about 30 years, the Univ. of California has used advanced laboratory techniques in addition to traditional methods to produce pathogen-free and true-to-type sweetpotato seedstock. The effort continues with the varieties important in the marketplace today. This program serves as a model for the use of meristem culture by foundation sweetpotato programs in other states.
A geographic information system (GIS) application was developed containing 18 layers of spatially explicit environmental data relevant to characterization of the eight officially recognized American Viticultural Areas (AVAs) for wine grape (Vitis vinifera) production in Texas. GIS climate variables included daily minimum temperature, daily maximum temperature, daily average temperature (TAVG), growing degree days (GDD), ripening period mean temperature (RPMT), annual precipitation, solar radiation, vapor pressure, and number of frost days. Soil attributes were texture, depth, available water capacity, pH, permeability, and bulk density. These data were used to develop interpretative descriptions of Texas AVAs published on the Winegrowing Regions of Texas web site, which also serves as the public portal to the interactive GIS (AVATXIS). Individuals can use AVATXIS to access data and visualize spatial variability on maps to characterize Texas AVAs for any or all of the environmental factors and to examine spatial relationships among factors.
Several microsprinkler treatments were tested on 5-year-old satsuma mandarin orange (Citrus unshiu Marc.) trees to compare survivability of trunks and scaffold limbs in severe freezes. Three damaging freeze events occurred during winter, with two in 1995-96 and one in 1996-97. Air temperature dropped to -9.4, -5.6, and -6.7 °C, respectively. Almost 90% of the foliage was dead on the control plants after the first freezing event and 98% after the second. A single microsprinkler 1.6 m high in the canopy delivering 90.8 L·h-1 reduced injury; only 54% of the canopy was dead after the first freeze and 71% after the second. There was slightly more shoot-tip dieback on the plants in the microsprinkler treatments than on the control plants after the first two freezes. The amount of limb breakage by ice was minor. The third freeze killed 34% of the canopy in the control plants, but only 26% in the plants in the microsprinkler treatments. Use of microsprinklers increased yield in 1996, but yield for all treatments was very low. Yield for all treatments fully recovered in 1997, averaging 153 kg/tree. Although no death of scaffold limbs or trunks occurred, these results demonstrate that microsprinkler irrigation reduces damage to foliage and increases yield somewhat in severe freezes.
Green roofs are becoming increasingly prevalent in the United States due to their economical and environmental benefits as compared with conventional roofs. Plant selection for green roofs in the variable climate of the southeastern United States has not been well evaluated. Shallow substrates on green roofs provide less moderation of temperature and soil moisture than deeper soils in traditional landscapes, necessitating empirical evaluation in green roof environments to make informed recommendations for green roof plant selection. Nineteen species and cultivars, including succulents, grasses, and forbs, were evaluated under seasonal irrigated and non-irrigated conditions in experimental green roofs. Plants were planted on 26 Oct. 2009 and each evaluated for survival and increase in two-dimensional coverage of the substrate during establishment, after overwintering, and after the first growing season. The winter 2009–10 was colder than normal, and some plants, such as ice plants (Delosperma spp.), considered to be cold-hardy in this climate did not survive through the winter. Irrigation influenced survival for the summer period and only succulent plants like stonecrops (Sedum spp.) survived without irrigation. Irrigated experimental green roofs had significantly lower summer substrate temperatures (up to 20 °F lower) and plants survived in irrigated conditions. Plants that survived both winter and summer under irrigated conditions include pussytoes (Antennaria plantaginifolia), mouse-ear tickseed (Coreopsis auriculata), eastern bottlebrush grass (Elymus hystrix), glade cleft phlox (Phlox bifida stellaria), and eggleston's violet (Viola egglestonii). Irrigation is recommended on extensive green roofs to increase the palette for plant selection by protecting against plant mortality due to drought and extreme soil temperatures.