Agronomy Dep.

Gainesville, FL, United States

Agronomy Dep.

Gainesville, FL, United States
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Berger S.T.,Agronomy Dep. | Ferrell J.A.,Agronomy Dep. | Dittmar P.J.,University of Florida | Leon R.,University of West Florida
Crop, Forage and Turfgrass Management | Year: 2015

Herbicide-resistant Palmer amaranth (Amaranthus palmeri S. Wats.) is the most troublesome weed in Florida cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production. In 2012, Palmer amaranth populations were surveyed to document the extent and level of resistance to glyphosate and imazapic. Mature seedheads were sampled at 31 locations in the northwest region of Florida where cotton and peanut are predominantly produced, and in the north-central region of Florida that mainly consists of peanut production. Palmer amaranth plants were grown from field-collected seed in the greenhouse and treated with glyphosate and imazapic to establish a dose response for each population. Glyphosate-resistant Palmer amaranth was found in 11 populations that were located primarily in the northwest region, with some populations having up to 30-fold resistance. Imazapic resistance was much more widespread, being found in 29 of the 30 populations tested. Since peanut production in Florida has historically relied on successive imazapic applications, it is not surprising that widespread resistance to imazapic has developed. Resistance to both herbicides was found in 10 populations. Results from this survey reveal the magnitude of herbicide resistance in Florida and the need for growers to diversify management strategies in the future. © 2015 American Society of Agronomy and Crop Science Society of America.


Aina O.,Agronomy Dep. | Quesenberry K.,Agronomy Dep. | Gallo M.,Agronomy Dep.
Crop Science | Year: 2012

Arachis paraguariensis Chodat & Hassl. is a potential source of novel genes for the genetic improvement of cultivated peanut (Arachis hypogaea L.) because some of its accessions show high levels of resistance to early leaf spot caused by Cercospora arachidicola Hori. In this study, induction of high frequency shoot regeneration from quartered-seed explants was accomplished for six plant introductions of A. paraguariensis under continuous light on Murashige and Skoog (MS) medium containing 4.4 mg L -1 thidiazuron (TDZ) in combination with 2.2 mg L -1 6-γ-γ-(dimethylallylamino)-purine (2ip). Recovery of a moderately high number of plantlets per quarter seed cultured was also achieved on medium containing 4.4 mg L -1 thidiazuron in combination with 1.1 to 4.4 mg L -1 6-benzylaminopurine (BAP) with bud formation occurring as early as 1 wk after culture initiation. There were no differences in seed production or in early leaf spot incidence between plants of two genotypes of A. paraguariensis derived from seeds vs. in vitro tissue culture derived plants; however, cultivated peanut cv. Florunner had a higher incidence of early leaf spot. © Crop Science Society of America.


Ramirez-Villegas J.,International Center for Tropical Agriculture | Ramirez-Villegas J.,CGIAR Research Program on Climate Change | Ramirez-Villegas J.,University of Leeds | Boote K.J.,Agronomy Dep. | And 2 more authors.
Agricultural and Forest Meteorology | Year: 2016

Common bean production in Goiás, Brazil is concentrated in the same geographic area, but spread across three distinct growing seasons, namely, wet, dry and winter. In the wet and dry seasons, common beans are grown under rainfed conditions, whereas the winter sowing is fully irrigated. The conventional breeding program performs all varietal selection stages solely in the winter season, with rainfed environments being incorporated in the breeding scheme only through the multi environment trials (METs) where basically only yield is recorded. As yield is the result of many interacting processes, it is challenging to determine the events (abiotic or biotic) associated with yield reduction in the rainfed environments (wet and dry seasons). To improve our understanding of rainfed dry bean production so as to produce information that can assist breeders in their efforts to develop stress-tolerant, high-yielding germplasm, we characterized environments by integrating weather, soil, crop and management factors using crop simulation models. Crop simulations based on two commonly grown cultivars (Pérola and BRS Radiante) and statistical analyses of simulated yield suggest that both rainfed seasons, wet and dry, can be divided in two groups of environments: highly favorable environment and favorable environment. For the wet and dry seasons, the highly favorable environment represents 44% and 58% of production area, respectively. Across all rainfed environment groups, terminal and/or reproductive drought stress occurs in roughly one fourth of the seasons (23.9% for Pérola and 24.7% for Radiante), with drought being most limiting in the favorable environment group in the dry TPE. Based on our results, we argue that even though drought-tailoring might not be warranted, the common bean breeding program should adapt their selection practices to the range of stresses occurring in the rainfed TPEs to select genotypes more suitable for these environments. © 2016 Elsevier B.V.

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