on the location, the time period, and how measurements are taken. In the 1950s comprehensive studies using vis-Many cotton (Gossypium hirsutum L.) pollination studies have ual phenotypic traits reported 10% outcrossing in Texas been performed in the southern USA, but no data exist for California. In this study, we measured pollen-mediated gene flow (PGF) in four to 47% in Tennessee (Simpson, 1954; Simpson and Dundirections over 2 yr from herbicide-resistant source plots in upland can, 1956). These studies reported 28% outcrossing in cotton in the California cotton growing region and in a region with Mississippi, but a mean of 2% outcrossing was reported high pollinator activity. In addition, samples were taken from fields in similar locations in Mississippi 20 yr later (Meredith of conventional varieties at varying distances from fields planted with and Bridge, 1973). The authors suggested the differherbicide-resistant varieties to assess PGF under commercial producences were due to a reduction in wooded areas and the tion conditions. A seedling herbicide bioassay confirmed by DNA tests heavy use of pesticides resulting in a decrease in bee was used to measure PGF. PGF was independent of direction from pollinators. Also in Mississippi, Umbeck et al. (1991) the source plot and declined exponentially with increasing distance measured pollen transfer to non-transgenic rows of cotfrom 7.65% at 0.3 m to less than 1% beyond 9 m when there was high ton planted up to 25 m from a 4 ha field of cotton carpollinator activity. In the absence of high pollinator (honeybee, Apis mellifera L.) populations, PGF was less than 1% beyond 1 m. Pollen rying the nptII gene. PGF dropped below 1% at disflow in commercial fields was consistent with the experimental plot tances beyond 7 m, but continued to be detectable at a data, with only 0.04% PGF detected at 1625 m (1 mile). This study distance of 25 m in solid-seeded cotton. Studies sumconfirms that PGF decreases exponentially with distance in cotton marizing data (Ͼ15 000 samples) in Arizona, Arkansas, grown under California conditions and is low in the absence of polli-Mississippi, and North Carolina showed that PGF denators, although sporadic occurrence of PGF can be detected up to creased exponentially with increasing distance from the 1625 m.Published in Crop Sci. 45:1565Sci. 45: -1570Sci. 45: (2005.

No abstract

Warm-season turfgrasses differ widely in their tolerance to low light. Shade conditions, as the result of shrub or tree presence, are greatly influenced depending on whether the tree or shrub is deciduous or evergreen in nature. The purpose of this study was to determine the influence of deciduous shade on the quality and yield of four major warm season lawngrasses. Zoysiagrass (Zoysia japonica (Stued.) X Z. tenuifolia (Willd.) 'Emerald'], St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze] 'Fioratam' and 'Floratine', and centipedegrass (Eremochloa ophiuroides (Munro.) (Hack.) 'Oklawn'] were sodded in outdoor plots on an Olivier silt loam (finesilty, mixed, thermic aquic, Fragiudalf) soil. All were exposed to unshaded and 47 and 63% shade regimes of green saran screening for 7 months each year to simulate Gulf South deciduous shade tree conditions. Determination of lawngrass quality and yield responses were made for 3 yr. Increased shade decreased air temperature at sod level. Mean air temperature at sod level was not correlated with quality of any lawngrass. Mean air temperature at sod level was significantly correlated only with clipping yields of Floratam St. Augustinegrass and Oklawn centipedegrass. Lawngrass quality generally decreased with increasing shade. Photon flux density was significantly correlated with quality of alllawngrasses except Oklawn. Quality ratings in 63% shade indicate that Floratam St. Augustinegrass quality was most intolerant, while Oklawn centipedegrass quality was most tolerant of reduced light conditions. Quality and yield were not significantly correlated in any lawngrass. Lawngrass yield generally decreased with increasing shade. Emerald Zoysiagrass mean clipping yields were least reduced, and Floratam St. Augustinegrass mean yields were most reduced in 63% shade treatments.Additional index words: Shade tolerance, Eremochloa ophiuroides (Munro.) (Hack.) Stenotaphrum secundatum (Walt.) Kuntze, Zoysia japonica (Stued.) X Z. tenuifolia (Willd.).

Identity preservation (IP) refers to a system of production, handling, and marketing practices that maintains the integrity and purity of agricultural commodities. In its simplest form, IP has been employed since the beginning of agriculture when the seeds and grain of different crops were first traded separately. As the seed and food industries developed, the purity and quality expectations of buyers and processors increased and standards were established. Seed certification programs such as that used by the Association of Official Seed Certifying Agencies (AOSCA) play a major role in maintaining seed purity standards at levels established by the industry for national and international trade. Similarly, commodity traders, marketing organizations, and food processors have established purity and quality tolerances for specific end-product uses. As crops and production systems have diversified to meet market demands, the need for segregation and identity preservation of agricultural commodities has increased.Crop varieties with unique product quality traits, such as high oleic sunflowers, low linolenic canola, or high oil corn, require IP programs to channel these commodities to specific markets to capture the added value. Similarly, organic commodities must be produced according to specific criteria and segregated in the marketplace in order to receive premium prices. The introduction of crops developed using biotechnology also requires new IP programs, as markets differ in their acceptance of these commodities. While some countries, such as the United States, Canada, Argentina, and China, have readily adopted crops enhanced through biotechnology, this has not been the case everywhere, particularly in the European Union (EU) and Japan. In addition, some countries are instituting labeling laws that require the segregation and identification of seed and food products developed using biotechnology. Thus, additional criteria for IP are based upon the method by which a variety was developed and whether it contains traits introduced via biotechnology (Suslow, Thomas, and Bradford 2002). Together, these factors are increasing the demand for IP programs that can certify the identity and composition of agricultural commodities. In many cases, changes in production and marketing procedures are required to meet these more stringent standards.This publication describes the essential features of IP programs, using seed certification as a model. Issues related to crops developed using biotechnology are addressed, and examples of specific commodity IP programs, including the California Rice Certification Act and the National Organic Act, are presented. Finally, economic issues associated with IP programs are discussed.

This study investigated the influence of plant size, as determined by plant density, and fruit load variation on the production and quality of bell pepper (Capsicum annuum L.) seeds. Six-week-old `Resistant Giant no. 4' bell pepper seedlings were transplanted 15, 30, 45, and 60 cm apart. Plants spaced 45 cm apart were not thinned or were thinned to one or three fruit per plant. Pepper plants grown at low plant densities produced larger fruit and seeds that germinated faster and at higher percentages than plants grown at higher densities. Assimilate export rate (AER) increased linearly with plant spacing. At harvest, C exchange rate (CER) and AER of plants with nonthinned fruit loads were ≈ 300% and 500% higher, respectively, than those of plants with one or three fruit. Fruit thinning decreased CER and AER; however, seeds produced by plants with one or three fruit had significantly higher germination percentages than plants with full fruit loads. These observations suggest that the high CERS of smaller plants with nonthinned fruit loads may have been insufficient to compensate completely for the higher sink demands. Therefore, crop cultural practices that increase the ratio of pepper plant size to total fruit count may increase the quality of seeds produced by those plants.