Photoperiodic sensitivity of the cotyledon and first true leaf of Xanthium1

1974 ◽  
Keyword(s):  
Photoperiodic Sensitivity ◽  
True Leaf

scholarly journals Response of Palmer amaranth (Amaranthus palmeri S. Watson) and sugarbeet to desmedipham and phenmedipham

2021 ◽  
pp. 1-9
Author(s):  
Clint W. Beiermann ◽  
Cody F. Creech ◽  
Stevan Z. Knezevic ◽  
Amit J. Jhala ◽  
Robert Harveson ◽  
...  
Keyword(s):  
Mortality Rates ◽  
Selectivity Index ◽  
Palmer Amaranth ◽  
Greenhouse Experiment ◽  
Amaranthus Palmeri ◽  
True Leaf ◽  
Cotyledon Stage ◽  
Equivalent Rate ◽  
Herbicide Treatments ◽  
High Level

Abstract A prepackaged mixture of desmedipham + phenmedipham was previously labeled for control of Amaranthus spp. in sugarbeet. Currently, there are no effective POST herbicide options to control glyphosate-resistant Palmer amaranth in sugarbeet. Sugarbeet growers are interested in using desmedipham + phenmedipham to control escaped Palmer amaranth. In 2019, a greenhouse experiment was initiated near Scottsbluff, NE, to determine the selectivity of desmedipham and phenmedipham between Palmer amaranth and sugarbeet. Three populations of Palmer amaranth and four sugarbeet hybrids were evaluated. Herbicide treatments consisted of desmedipham and phenmedipham applied singly or as mixtures at an equivalent rate. Herbicides were applied when Palmer amaranth and sugarbeet were at the cotyledon stage, or two true-leaf sugarbeet stage and when Palmer amaranth was 7 cm tall. The selectivity indices for desmedipham, phenmedipham, and desmedipham + phenmedipham were 1.61, 2.47, and 3.05, respectively, at the cotyledon stage. At the two true-leaf application stage, the highest rates of desmedipham and phenmedipham were associated with low mortality rates in sugarbeet, resulting in a failed response of death. The highest rates of desmedipham + phenmedipham caused a death response of sugarbeet; the selectivity index was 2.15. Desmedipham treatments resulted in lower LD50 estimates for Palmer amaranth compared to phenmedipham, indicating that desmedipham can provide greater levels of control for Palmer amaranth. However, desmedipham also caused greater injury in sugarbeet, producing lower LD50 estimates compared to phenmedipham. Desmedipham + phenmedipham provided 90% or greater control of cotyledon-size Palmer amaranth at a labeled rate but also caused high levels of sugarbeet injury. Neither desmedipham, phenmedipham, nor desmedipham + phenmedipham was able to control 7-cm tall Palmer amaranth at previously labeled rates. Results indicate that desmedipham + phenmedipham can only control Palmer amaranth if applied at the cotyledon stage and a high level of sugarbeet injury is acceptable.

scholarly journals Integration of early disease-resistance phenotyping, histological characterization, and transcriptome sequencing reveals insights into downy mildew resistance in impatiens

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Ze Peng ◽  
Yanhong He ◽  
Saroj Parajuli ◽  
Qian You ◽  
Weining Wang ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Downy Mildew ◽  
Transcriptome Sequencing ◽  
Early Stage ◽  
Economic Losses ◽  
Potential Candidate ◽  
Early Disease ◽  
True Leaf ◽  
Cotyledon Stage ◽  
Wide Range

AbstractDowny mildew (DM), caused by obligate parasitic oomycetes, is a destructive disease for a wide range of crops worldwide. Recent outbreaks of impatiens downy mildew (IDM) in many countries have caused huge economic losses. A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired. In this study, we established an early and rapid system to achieve these goals using impatiens as a model. Thirty-two cultivars of Impatiens walleriana and I. hawkeri were evaluated for their responses to IDM at cotyledon, first/second pair of true leaf, and mature plant stages. All I. walleriana cultivars were highly susceptible to IDM. While all I. hawkeri cultivars were resistant to IDM starting at the first true leaf stage, many (14/16) were susceptible to IDM at the cotyledon stage. Two cultivars showed resistance even at the cotyledon stage. Histological characterization showed that the resistance mechanism of the I. hawkeri cultivars resembles that in grapevine and type II resistance in sunflower. By integrating full-length transcriptome sequencing (Iso-Seq) and RNA-Seq, we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp. Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance, including three resistance genes orthologous to the sunflower gene RGC203, a potential candidate associated with DM resistance. Our approach of integrating early disease-resistance phenotyping, histological characterization, and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.

Reassessing the estimation of leaf area in oil palm (Elaeis guineensis Jacq.) by linear regression equation

2020 ◽  
Vol 56 (6) ◽  
pp. 815-824
Author(s):  
Cornelis Jan Breure ◽  
M. Mustiqa Siregar
Keyword(s):  
Leaf Area ◽  
Oil Palm ◽  
Elaeis Guineensis ◽  
Video Camera ◽  
Regression Equation ◽  
Regression Coefficients ◽  
Linear Regression Equation ◽  
True Leaf ◽  
The Common ◽  
Conventional Regression

AbstractThe area of individual leaves in oil palm has been conventionally estimated from a regression equation that is based on the size and number of leaflets. The aim of the present study is to verify the accuracy of this equation, which became standard in oil palm research. Therefore, true leaf area, measured with a video camera, was estimated from the product of number of leaflets per leaf (n) with mean length (l) times mid-width (w) of six of the longest leaflets (nlw). The database was assembled, annually for the first 4 years after planting, from 2961 leaves of dura × pisifera testcrosses descending from six distinct pisifera origins. The regression coefficients of the regression lines of nlw plotted against true area did not show a trend with age of the palms or a difference among pisifera origins. The common regression equation fitted through all data of this study accurately estimated true leaf area of the testcrosses and also the areas of 2- to 3.5-year-old dura palms of three distinct origins as well as 18-year-old tenera palms. These outcomes are at odds with the conventional regression equation that overestimates the true leaf areas by about 24%. A more recently-developed variant underestimates true area of the young tenera and dura palms by 28%, while overestimating true area of old tenera palms by 19%. Possible causes for these deviations from true area are discussed. The paper argues that parameters depending on leaf area of previous physiological studies need to be reassessed.

THE "LEAF GAP" IN EQUISETUM

1941 ◽  
Vol 19c (3) ◽  
pp. 80-84 ◽  
Author(s):  
Ruth Moore
Keyword(s):  
Vascular Plants ◽  
True Leaf

A previously undescribed feature of the structure of the stem in Equisetum has been found. This conforms more nearly with a true leaf gap than any other feature of Equisetum hitherto so considered. Its interpretation and bearing on the classification of the vascular plants into Lycopsida and Pteropsida are discussed.

scholarly journals Inheritance of True Leaf Stage Downy Mildew Resistance in Broccoli

2001 ◽  
Vol 126 (6) ◽  
pp. 727-729 ◽  
Author(s):  
Min Wang ◽  
Mark W. Farnham ◽  
Claude E. Thomas
Keyword(s):  
Downy Mildew ◽  
Control Method ◽  
Recurrent Parent ◽  
Downy Mildew Resistance ◽  
Resistant Parent ◽  
Dh Population ◽  
Mildew Resistance ◽  
Leaf Stage ◽  
True Leaf ◽  
High Level

Downy mildew, incited by the biotrophic fungal parasite, Peronospora parasitica (Pers. Fr.) Fr., is one of the most destructive diseases of broccoli (Brassica oleracea L., Italica Group) and other related crop species throughout the world. Cultivation of resistant cultivars is the most desirable control method because it provides a practical, long-term, and environmentally benign means of limiting damage from this disease. The commercial hybrid cultivar, Everest, has been shown previously to contain a high level of downy mildew resistance. Doubled-haploid (DH) lines developed from that hybrid were also shown to exhibit a similar, high level of resistance at the three- to four-leaf stage. To determine the mode of inheritance of this true leaf resistance, the resistant DH line was crossed to a susceptible line (derived from `Marathon') to produce an F1 hybrid. Subsequently, F2 and backcross (BC) populations were developed from the hybrid. In addition, a DH population of ≈100 lines was developed from the same F1 used to create the F2 and BC. All populations were evaluated for response to artificial inoculation with P. parasitica at the three- to four-leaf stage. F1 plants were resistant like the resistant parent and F2 populations segregated approximately nine resistant to seven susceptible. Using the resistant parent as recurrent parent, BC populations contained all resistant plants, while the BC to the susceptible parent fit a 1 resistant: 3 susceptible segregation ratio. These results can be explained by a model with two complementary dominant genes. This model was confirmed by the DH population that segregated ≈1:3, resistant to susceptible. Due to the dominant nature of this resistance, controlling genes should be easily incorporated into F1 hybrids and used commercially to prevent downy mildew.

THE INFLUENCE OF VARIOUS TEMPERATURES AND (2-CHLOROETHYL) TRIMETHYLAMMONIUM CHLORIDE AND (ALLYL) TRIMETHYLAMMONIUM BROMIDE ON PEPPERS AND TOMATOES

1962 ◽  
Vol 42 (1) ◽  
pp. 142-149 ◽  
Author(s):  
H. Tiessen
Keyword(s):  
Total Yield ◽  
Temperature Treatment ◽  
Seedling Stage ◽  
Trimethylammonium Chloride ◽  
Green Plants ◽  
True Leaf ◽  
Different Temperatures ◽  
Lower Temperature ◽  
Field Setting ◽  
Pepper Plants

Fireball tomato and Calwonder pepper plants were subjected, in the seedling stage, to different temperatures and to both drench and foliar applications of (2-chloroethyl) trimethylammonium chloride (CCC) and (allyl) trimethylammonium bromide (AMAB).Seedlings were exposed to minimum night temperatures of 54° to 56°F. and of 64° to 68°F. from the appearance of the first true leaf for 3 weeks for peppers and until field setting (6 weeks) for tomatoes. For both crops the lower temperature treatment gave an increase in early fruit number and yield.Drench applications of 100 milliliters per band to tomatoes and 900 milliliters per square foot to peppers of 10−3 and 10−4 M solutions of CCC or of AMAB produced shorter, stockier, darker-green plants with reduced foliage spread. Growth was further reduced by the lower temperature treatments. Both drenches reduced total yields in both tomatoes and peppers.Foliar treatments of CCC and of AMAB increased the total yield of peppers started at the warmer temperature. At the cooler temperature, however, yield was not affected by the CCC treatment but was reduced by the AMAB treatment. Foliar treatments with either chemical did not affect the total yield of tomatoes after seedling treatment at either temperature.

Degree-day models to predict carrot weevil (Coleoptera: Curculionidae) emergence and oviposition in Nova Scotia, Canada

2020 ◽  
Vol 152 (3) ◽  
pp. 374-388
Author(s):  
Suzanne Blatt ◽  
Deney Augustine Joseph ◽  
G. Christopher Cutler ◽  
A. Randall Olson ◽  
Scott White
Keyword(s):  
Nova Scotia ◽  
Adult Emergence ◽  
Hill Equation ◽  
Base Temperature ◽  
Degree Days ◽  
Eastern Canada ◽  
Leaf Stage ◽  
True Leaf ◽  
Listronotus Oregonensis ◽  
Carrot Weevil

AbstractCarrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae), is a pest of carrot (Daucus carota var. sativus Hoffmann; Apiaceae) throughout eastern Canada. Carrot weevil emergence and oviposition were monitored in commercial carrot fields in Nova Scotia. Cumulative degree days were calculated using a base temperature of 7 °C (DD7), and models were developed to predict cumulative emergence and oviposition using nonlinear regression. Cumulative emergence and oviposition were adequately explained as functions of DD7 by a three-parameter sigmoidal Hill equation. Our emergence model predicted initial and peak adult emergence at 35 and 387 DD7, respectively, with oviposition on carrot baits occurring as early as 42 DD7. Models were then validated to evaluate how well they performed. Oviposition on carrot plants began at the fourth true-leaf stage (342 DD7) and continued until eleventh true-leaf stage. Growers using these models can identify their window of opportunity to manage their carrot weevil populations targeting the majority of emerged adults before oviposition begins in the field.

scholarly journals Laboratory Evaluation of a Neem Product Against DBM Larvae, 1995

1997 ◽  
Vol 22 (1) ◽  
pp. 409-409
Author(s):  
R.F.L. Mau ◽  
L. R. Gusukuma-Minuto
Keyword(s):  
Petri Dish ◽  
Seedling Stage ◽  
Laboratory Evaluation ◽  
Complete Coverage ◽  
Plastic Petri Dish ◽  
True Leaf ◽  
Laboratory Colony ◽  
Treated Plant ◽  
Head Cabbage

Abstract Treatments were evaluated using the leaf dip method. Head cabbage was seeded in community pots. Each pot containing approximately 10 cabbage plants in the 5 true leaf seedling stage was inverted and dipped in a test insecticide mix for about 30 sees for complete coverage. The dipped plants were allowed to air dry. For each dip, 1 liter insecticide mix was prepared based on field rate concentrations of 100 gal/acre. Leaves from treated plants were detached and placed in a ventilated plastic petri dish. DBM larvae from a laboratory colony that originated from individuals collected from a cabbage field at Kula, Hawaii and Kamuela, Hawaii were used. Ten late 2nd instars were placed on each leaf. Fresh leaves from the original treated plant were added every two days. The number of dead larvae was counted at 24-hour intervals. Larvae were recorded as dead when there was no movement when probed.

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