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* Premise of the study: Gene flow from crops to wild relatives has received considerable attention since the advent genetically modified crops. Numerous researchers have found wild-crop hybrids to be nearly as fit as their wild parents, which suggests that crop genes may persist in wild populations. Components of the ecological fitness of cultivated sorghum, its wild relative, shattercane, and their hybrids have not been studied. * Methods: To assess the potential for gene introgression into shattercane, we crossed cultivated sorghum to a single inbred shattercane line to produce [F.sub.1] hybrids and measured growth and several components of ecological fitness in relation to both parents in Nebraska, USA. * Key results: Germination of [F.sub.1] seeds was similar to that of its shattercane parent except at high temperatures, where it was as sensitive as the sorghum parent. The [F.sub.1] grew taller and produced more biomass than either parent, but the [F.sub.1] leaf area index was intermediate. Fecundity of the [F.sub.1] plant was similar to that of shattercane and much greater than that of cultivated sorghum. * Conclusions: Considering all data, the ecological fitness of shattercane x cultivated sorghum [F.sub.1] hybrids may be equivalent to the wild shattercane parent, which suggests that crop genes that are either neutral or beneficial to shattercane would persist in populations within agroecosystems. Key words: fecundity; fitness; germination; introgression; phenology; wild-crop gene flow. doi: 10.3732/ajb.0900170

Few studies have examined grain quality of food-grade sorghum hybrids. The objective of this study was to determine the effects of environment and hybrid on grain quality of commercially available food-grade sorghums. A randomized complete block experiment with three replications was planted in 12 environments, which included the 2004 and 2005 growing seasons and irrigated and dryland water regimes in eastern, central, and west central Nebraska and a dryland low-N environment in eastern Nebraska. Environment accounted for 5 to 140 times greater variation in measured parameters than hybrid, and the hybrid x environment interaction accounted for less than 2% of the total variation. Grain yield and kernel mass varied, with low yields of 1.4 Mg [ha.sup.-1] and kernels weighing 9.5 g 1000 [kernels.sup.-1] in the low-N 2004 environment, high grain yields of 10.5 Mg [ha.sup.-1] under irrigated conditions in central Nebraska in 2005, and kernels weighing 27.8 g 1000 [kernels.sup.-1] in the eastern Nebraska dryland 2005 environment. Harder grain was produced in 2005 than in 2004, with the west central and central 2005 environments having the lowest tangential abrasive dehulling device (TADD) removals of 14%. Non-food-grade hybrids produced higher grain yields and kernel mass than food-grade hybrids. Grain hardness was greater for non-food-grade and medium maturity hybrids when environmental means were lower (i.e., softer) but showed little or no difference in hardness when environmental means were high. Nebraska production environments have the capability to produce high quality food-grade sorghums for specific food uses to benefit both the producer and the food processor. doi: 10.2135/cropsci2009.08.0463

Hyperosmotic stress induces cytoskeleton reorganization and a net increase in cellular F-actin, but the underlying mechanisms are incompletely understood. Whereas de novo F-actin polymerization likely contributes to the actin response, the role of F-actin severing is unknown. To address this problem, we investigated whether hyperosmolarity regulates cofilin, a key actin-severing protein, the activity of which is inhibited by phosphorylation. Since the small GTPases Rho and Rac are sensitive to cell volume changes and can regulate cofilin phosphorylation, we also asked whether they might link osmostress to cofilin. Here we show that hyperosmolarity induced rapid, sustained, and reversible phosphorylation of cofilin in kidney tubular (LLC-PK1 and Madin-Darby canine kidney) cells. Hyperosmolarity-provoked cofilin phosphorylation was mediated by the Rho/Rho kinase (ROCK)/LIM kinase (LIMK) but not the Rac/PAK/LIMK pathway, because 1) dominant negative (DN) Rho and DN-ROCK but not DN-Rac and DN-PAK inhibited cofilin phosphorylation; 2) constitutively active (CA) Rho and CA-ROCK but not CA-Rac and CA-PAK induced cofilin phosphorylation; 3) hyperosmolarity induced LIMK-2 phosphorylation, and 4) inhibition of ROCK by Y-27632 suppressed the hypertonicity-triggered LIMK-2 and cofilin phosphorylation. We thenexamined whether cofilin and its phosphorylation play a role in the hypertonicity-triggered F-actin changes. Downregulation of cofilin by small interfering RNA increased the resting F-actin level and eliminated any further rise upon hypertonic treatment. Inhibition of cofilin phosphorylation by Y-27632 prevented the hyperosmolarity-provoked F-actin increase. Taken together, cofilin is necessary for maintaining the osmotic responsiveness of the cytoskeleton in tubular cells, and the Rho/ROCK/LIMK-mediated cofilin phosphorylation is a key mechanism in the hyperosmotic stress-induced F-actin increase. cytoskeleton; hypertonicty; cell volume; small GTPases