Crop improvement in bahiagrass (Paspalum notatum Flüggé) is limited by apomixis in most natural tetraploids, however, diploid sexual types occur. Production of sexual tetraploids by chromosome doubling will allow hybridization with apomictic tetraploids. Diploid bahiagrass (Paspalum notatum Flüggé) embryogenic callus tissue was exposed to three concentrations of three antimitotic chemical agents, colchicine, oryzalin and trifluralin. Callus was generated to plants and ploidy was evaluated by stomata size, mitotic chromosome counts, and flow cytometry. A total of 310 plants were verified as tetraploid of 1,432 plants that reached transplanting size. All treatments yielded 4x plants. The mean percentage success over all treatments was 22%, with means of 31% for oryzalin, 24% for colchicine and 16% for trifluralin. The high rates of success indicate that all agents can be successfully used to double chromosome numbers in bahiagrass. The percentage of 4x plants ranged from 9% (20 μM trifluralin) to 43% (20 μM oryzalin). Several treatments adversely affected regeneration. Mitotic chromosome counts are difficult and labor intensive in bahiagrass. Therefore, leaf stomata measurements were used as a preliminary screen. Data gave a bimodal distribution with overlapping tails and based on chromosome counts would have given an error rate of 12%. Flow cytometry analysis of regenerated plants resulted in mean nucleus fluorescence distributions consistent with control diploid or tetraploid values. These values agreed with chromosome counts, and this method is recommended for determining bahiagrass ploidy level. Research goals and available resources should be taken into consideration when selecting a treatment for chromosome doubling in bahiagrass.

Abstract Background Developing monocots that accumulate more vegetative tissue protein is one strategy for improving nitrogen-sequestration and nutritive value of forage and silage crops. In soybeans (a dicotyledonous legume), the vspA and B genes encode subunits of a dimeric vegetative storage protein that plays an important role in nitrogen storage in vegetative tissues. Similar genes are found in monocots; however, they do not accumulate in leaves as storage proteins, and the ability of monocot leaves to support accumulation of an ectopically expressed soybean VSP is in question. To test this, transgenic maize (Zea Mays L. Hi-II hybrid) lines were created expressing soybean vspB from a maize ubiquitin Ubi-1 promoter. Results From 81 bombardments, 101 plants were regenerated, and plants from five independent lines produced vspB transcripts and VSPβ polypeptides. In leaves from seven-week-old plants (prior to flowering), VSPβ accumulated to 0.5% of the soluble leaf protein in primary transgenic plants (R0), but to only 0.03% in R1 plants. During seed-filling (silage-stage) in R1 plants, the VSPβ protein was no longer detected in leaves and stems despite continued presence of the vspB RNA. The RNA transcripts for this peptide either became less efficiently translated, or the VSPβ protein became unstable during seed-fill. Conclusion Developmental differences in the accumulation of soybean VSPβ when transgenically expressed in maize show that despite no changes in the vspB transcript level, VSPβ protein that is readily detected in leaves of preflowering plants, becomes undetectable as seeds begin to develop.

Lignin is a complex, aromatic polymer that limits plant cell wall degradation by ruminants and reduces the nutritional value of forages. Genetic engineering, using an antisense strategy, offers the potential to modulate enzymes in the lignin biosynthetic pathway as a way to reduce lignin, thereby improving forage quality and animal performance. We investigated the effectiveness of expressing antisense sorghum O ‐methyltransferase gene ( omt ) to downregulate maize OMT and reduce lignin. Constructs contained a sorghum omt coding region in the antisense orientation driven by the maize ubiquitin‐1 ( Ubi ) promoter (with the first intron and exon) along with bar , that confers glufosinate herbicide resistance, driven by the CaMV 35S promoter. Twenty‐eight T 0 plants regenerated from 17 herbicide‐resistant callus lines from 13 independent bombardments expressed the brown midrib phenotype. O ‐methyltransferase activity was significantly lower in T 1 transgenics compared with controls, with some plants showing a 60% reduction. Those T 1 transgenics with downregulated OMT averaged 20% less lignin in stems and 12% less lignin in leaves compared with controls. On a whole‐plant basis, lignin was reduced by an average of 17% with the greatest reduction being 31%. Digestibility was significantly improved in transgenic plants by 2% in leaves and 7% in stems. Mean whole‐plant digestibility increased from 72 to 76%. This research demonstrates that genetic engineering has the potential to improve forage grass digestibility. This could be important, especially in tropical forage species, which generally have lower quality than temperate species.

Bahiagrass (Paspalum notatum Flugge), a forage species widely used in the southeastern United States, and from Central Mexico to Argentina, was targeted for improvement through genetic engineering. Embryogenic callus, initiated from germinating seedlings, was bombarded with a vector containing the bar selectable marker/reporter gene that confers resistance to phosphinothricin (glufosinate) herbicide (trade names Liberty, Ignite and Finale). Thirty-two transgenic plants were recovered. These plants were identified by the polymerase chain reaction (PCR) and verified by Southern analysis. Transgenic plants with bar, as well as non-transgenic plants without bar, regenerated from bombarded callus and selected with glufosinate, developed strong and stable resistance to glufosinate during selection. This unusual resistance in non-transgenic plants has persisted for over a year and is passed on to new tillers. The development of resistance in non-transgenic cells reduced the herbicide selection efficiency and made it necessary to identify transgenic plants by PCR where the 32 transgenic plants were recovered from 674 glufosinate-resistant plants, giving a very low selection efficiency.

Experiments were performed to determine if RAPD profiles developed using total DNA isolated from soybean seed could be affected by the physiological state or the quality of the seed. RAPD profiles were developed using template DNA isolated from a single seed lot of soybean (Glycine max L. cv. Kirby). High quality seeds were used to produce four populations varying in either quality or physiological state: untreated control seed ambient temperature and humidity storage for 12 months, accelerated aging at 41 degrees C and 100% relative humidity for 48 h, and controlled hydration (seed priming). One hundred and eighty-eight primers were used to create separate RAPD profiles from total DNA isolated from each set of seed and from soybean leaf tissue. Sixteen polymorphisms from 14 primers were identified as a result of seed treatments. Six primers showed nine polymorphisms in RAPD profiles of ambient-stored seed DNA, while four and two primers produced polymorphisms in reactions using accelerated aged or primed-seed template DNA, respectively. Two primers showed a polymorphic fragment in vegetative DNA not observed in any of the seed DNA samples. Ten of the observed polymorphisms were due to the appearance of a DNA fragment in response to a specific seed treatment while six were the result of the treatment-induced loss of a DNA fragment. The six polymorphisms resulting from the loss of a major fragment were all due to ambient-temperature seed storage. Results were reproducibly obtained from multiple DNA isolations using three separate DNA isolation procedures involving either multiple seed or a single seed as the template source. Therefore, genetically identical seed can consistently display RAPD polymorphisms as a response to the environmental exposure.

Abstract Peanut (Arachis hypogaea L. subsp. fastigiata var. vulgaris) developing seed microsomal polypeptides of the high oleic acid variant (F435) and its presumed isogenic, normal line (78-1339) were compared using two-dimensional gel electrophoresis. A pair of 20 kDa polypeptides focusing at pH 6.8 and 7.3 was present in all of the polypeptide profiles from both isolines regardless of maturity or genotype except for (F435) at stage 1 maturity. The stage 1 (F435) profile contained, instead, an 18 kDa polypeptide pair focusing at about pH 9.3. Based on correlation evidence, we postulate that the 20 kDa polypeptides could be components of the $DT12-desaturase complex. The 18 kDa polypeptides appeared to be associated with lower desaturase activity, reduced linoleic acid and increased oleic acid seed content. Since the 18 kDa polypeptides focusing at pH 9.3 are not found at later stages, they are probably under developmental control. Changes in the developing seed polypeptides of the microsomal fraction over the four maturities are also reported.

Quality in wheat (Triticum aestivum L. em Thell.) is a very complex trait; however, the water insoluble gluten proteins are responsible for the elasticity and cohesiveness (strength) of dough and are important determinants of breadmaking quality. High molecular weight glutenin subunits encoded by genes on the long arms of Group 1 chromosomes have been associated with gluten strength, and a portion of the variability between cultivars can be attributed to glutenin subunit composition. Of the glutenins, Subunits 5 + 10 encoded by the D genome have been found to have the largest positive effect on dough strength, whereas the allelic Subunits 2 + 12 have a negative effect. Therefore, it has been important to incorporate the genes for the 5 + 10 subunits into bread wheats. There has been considerable interest in improving the dough strength and quality of soft wheats and triticale (X Triticosecale Whittm.) to use them in bread-like products. Glutenin subunit screening is accomplished using electrophoresis (SDS-PAGE). In this paper, we report the development of an alternative screening method based on the glutenin genes themselves, using the polymerase chain reaction (PCR). mimers designed from computer analyses were synthesized and tested on the cloned subunit 10 gene (Glu-D1-2b), 10 wheat cultivars of known subunit composition, and six triticales. Although the Glu-D1-2b (Dy10) and Glu-D1-2a (Dy12) genes have 98.9% DNA sequence similarity, marker fragments capable of consistently identifying those genotypes were amplified. Fragments correlating with glutenin subunit composition offering possibilities of extending the PCR screening system to other subunits were noted.

The objective of this research was to use new molecular techniques to improve efficiency of traditional breeding programs of Pennisetum for biomass and forage production. Restriction fragment length polymorphic (RFLP) and random amplified polymorphic DNA (RAPD) genetic markers were developed to characterize the Pennisetum purpureum genome and those markers were used to facilitate genetic study and breeding improvement. Standard RFLP and RAPD methodologies were adapted and/or modified to work well with Pennisetum and the DNA marker system was developed. This marker system was used to “fingerprint” the P. purpureum plant introduction collection, to determine the genetic diversity in that collection, to measure heterozygosity of selected lines and to measure hybridization/self fertilization rates using different crossing methods. Linkage relationships were studied between the DNA markers and quantitative trait loci (QTL), especially those loci associated with biomass/forage productivity, conversion to methane and rumen digestibility. Linkage analyses revealed 64 markers were linked to QTL of 26 plant traits. Those QTL-linked markers form the basis for genetic study of important biomasstforage productivity and quality traits. While the research was conducted with biomass for energy objectives, it is equally applicable to forage production and quality.

Crop ScienceVolume 30, Issue 6 cropsci1990.0011183X003000060065x p. 1368-1369 Registration of Cultivars Registration of ‘Transvala’ Digitgrass S. C. Schank, Corresponding Author S. C. Schank n/a@.dne Agronomy Dep.Corresponding author.Search for more papers by this authorF. T. Boyd, F. T. Boyd Agronomy Dep.Search for more papers by this authorRex L. Smith, Rex L. Smith Agronomy Dep.Search for more papers by this authorE. M. Hodges, E. M. Hodges Agronomy Dep.Search for more papers by this authorS. H. West, S. H. West Animal Science Dep., Univ. of Florida, Gainesville, 32611Search for more papers by this authorA. E. Kretschmer Jr., A. E. Kretschmer Jr. Agronomy Dep.Search for more papers by this authorJ. B. Brolmann, J. B. Brolmann Agronomy Dep.Search for more papers by this authorJ. E. Moore, J. E. Moore USDA-ARSSearch for more papers by this author S. C. Schank, Corresponding Author S. C. Schank n/a@.dne Agronomy Dep.Corresponding author.Search for more papers by this authorF. T. Boyd, F. T. Boyd Agronomy Dep.Search for more papers by this authorRex L. Smith, Rex L. Smith Agronomy Dep.Search for more papers by this authorE. M. Hodges, E. M. Hodges Agronomy Dep.Search for more papers by this authorS. H. West, S. H. West Animal Science Dep., Univ. of Florida, Gainesville, 32611Search for more papers by this authorA. E. Kretschmer Jr., A. E. Kretschmer Jr. Agronomy Dep.Search for more papers by this authorJ. B. Brolmann, J. B. Brolmann Agronomy Dep.Search for more papers by this authorJ. E. Moore, J. E. Moore USDA-ARSSearch for more papers by this author First published: 01 November 1990 https://doi.org/10.2135/cropsci1990.0011183X003000060065xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume30, Issue6November-December 1990Pages 1368-1369 RelatedInformation

Endonuclease restriction fragment patterns of Pennisetum americanum L. mitochondrial DNAs (mtDNAs) from a cytoplasmic male-sterile (CMS-A1), fertile revertants and a normal fertile cytoplasm were variable, while chloroplast DNA from those lines lacked variation. Comparisons between mtDNAs of CMS-A1 (parental) and fertile revertant lines revealed the presence of a unique 4.7 kbp PstI fragment in the sterile line that was not detected in any of the revertant lines. A 9.7 kbp PstI fragment was found in all of the revertants, but not in the CMS-A1. Neither of those fragments was found in the normal cytoplasm mtDNA. Hybridization studies revealed two sets of multiple homologies: 1) the 4.7 kbp fragment had homology with a 10.9 kbp and a 13.6 kbp fragment; and 2) the 9.7 kbp fragment was homologous with the 13.6 kbp fragment. The presence of those two repeated mitochondrial sequences on the altered fragments suggests that they may be involved in the recombinational associated events with reversion from CMS to fertility in P. americanum.

The effect of reduced solar radiation on associative N2-fixation and plant parameters was studied in three field experiments (1978–80). ‘Gahi-3’ pearl millet (Pennisetum americanum (L.) K. Monch.) field plots were shaded with saran shade cloth that reduced solar radiation by 50% and 75%. Acetylene reduction activity (ARA) was reduced by shading in one of the three experiments. The two non-responding experiments were conducted on a wall-drained, low-activity site (ARA means ranging 17–68 n moles ethylene core−1 h−1), the responding experiment was conducted on a poorly drained, high-ARA site.

Bacterial cells of Azospirillum brasilense (Tarrand) from their natural habitat were labeled with peroxidase-antiperoxidase (PAP), identified, and observed using the transmission electron microscope. Pure cultures of A. brasilense , axenically inoculated pearl millet root samples, and field-grown inoculated pearl millet root samples were embedded in Luffs araldite. Thin sections were treated using the immunological PAP method. Identification was possible because of the heavy outlining of the cells with a dense deposit of osmium. Pleomorphic forms of A. brasilense were observed in axenic pearl millet root cultures. Encapsulated forms were larger than vibrioid forms, and both types reacted with antiserum against the bacterial strain.

Seed production of guineagrass ( Panicum maximum Jacq.), an important pasture and forage crop in the tropics, is hindered by its heavy loss of seeds through spikelet abscission. A method whereby abscission could be delayed or arrested would be a great aid in seed harvest of this and other Panicum species. Auxin and gibberellin at three concentrations (10 ‐3 , 5✕10 ‐3 and 10 ‐2M ) were applied to the inflorescences of two experimental genotypes (PM285 and 68s‐5‐2) when the panicle was three‐fourths emerged from the flag leaf to inhibit spikelet abscission. Growth chamber and field experiments were conducted. Response was dependent on plant genotype and growth regulator concentration. In the growth chamber, panicle branch explants were inserted into semisolid agar solutions of growth regulators. The most responsive auxin treatment inhibited abscission by 32%. In the field, aqueous sprays of growth regulators were app.lied to entire inflorescences. The most responsive auxin treatment inhibited abscission by 40%, The two genotypes responded differently to IAA treatment with 68s‐5‐2 exhibiting significantly less abscission than PM285. Gibberellin treatments either stimulated abscission or had no influence under the conditions tested. Histological sections of pedicels of the genotype 68s‐5‐2 were made to follow the development of the abscission zone with and without applied auxin. The abscission zone exhibited no readily observable morphologlc or histologic response to auxin.

Plant yield and acetylene reduction were measured on six hybrids and 15 inbreds (including the hybrid parents) of pearl millet, Pennisetum americanum (L.) K. Shum., after field inoculation with Azospirillum brasilense, Sp 13t (reclassified from Spirillum lipoferum Beijerinck). During the first year of testing, inoculation responses were investigated among all plant genotypes by measuring plant dry weight, % N, total N, and acetylene reduction activity. A smaller population of genotypes were tested a second year for repeatability of inoculum response. The first year, one hybrid, Tift 23DA ✕ Tift 186 (‘Gahi 3’), gave significantly higher plant dry weight and total N in response to inoculation. Inoculated Gahi 3 produced 31.7% more dry weight and 37.4% more total plant N when compared to autoclaved inoculum controls. No inbred was found to respond. Acetylene reduction values were low among all genotypes (range 0.54 nmole/[g dry root ✕ hour] and did not support yield effects or confirm inoculum treatments. Inoculation responses were found to be repeatable for all genotypes tested during the second year (positive or negative) but not of a statistically significant magnitude. Of the genotypes tested both years, a combined analysis of the 2‐year yields revealed significant dry weight increases after inoculation of 19.2 and 14.0% with Gahi 3 and the inbred, Bil 3B, respectively. Again, acetylene reduction values did not explain any data. A N balance study was conducted in greenhouse containers on inoculated Gahi 3 plants in an attempt to repeat the yield differences observed in the field and to monitor inputs of N into the soil‐plant system. No significant yield increase of N into the soil‐plant system was found due to inoculation. Sampling error possibly negated an accurate measurement of all N.