Studies on sunflower rust. XI. Effect of temperature and light on germination and infection of sunflowers by Puccinia helianthi

1972 ◽  
Vol 50 (9) ◽  
pp. 1879-1886 ◽  
Author(s):  
P. N. Sood ◽  
W. E. Sackston
Keyword(s):  
Light Intensity ◽  
Incubation Period ◽  
Dark Period ◽  
Effect Of Temperature ◽  
Appressorium Formation ◽  
Leaf Discs ◽  
Puccinia Helianthi ◽  
Race 2 ◽  
Race 4

Urediospores of four races of Puccinia helianthi incubated on water agar for 6 h or on sunflower leaf discs for 16 h germinated equally well from 10 to 25 °C, but significantly less at 30° and least at 5 °C. Appressorium formation was highest at 10 to 25 °C, lower at 30 °C, and lowest at 5 °C for races 1 and 3; none occurred at 30 and 5° in races 2 and 4. The optimum for penetration by races 1 and 3 was 20 °C, for race 2, 15° to 20 °C, and for race 4, 20° to 25 °C. Results were the same on susceptible and resistant hosts.Germination percentage on water agar was reduced with increasing light intensity from 2200 to 17 600 lx during incubation for 6 h. Germination on sunflower leaf discs was reduced with increasing light intensity during incubation for 16 h. Appressorium formation and penetration were adversely affected by increasing light intensity.Inhibition by light was overcome during a subsequent dark period when inoculated leaf discs were exposed to various cycles of light and dark during a 16-h incubation period.

scholarly journals The Effect of Temperature on Disease Severity and Growth of Fusarium oxysporum f. sp. apii Races 2 and 4 in Celery

2021 ◽  
Author(s):  
Sukhwinder Kaur ◽  
Radwan Barakat ◽  
Jaskirat Kaur ◽  
Lynn Epstein
Keyword(s):  
Fusarium Oxysporum ◽  
Species Complex ◽  
Effect Of Temperature ◽  
In Planta ◽  
Soil Temperatures ◽  
Logistic Regressions ◽  
Race 2 ◽  
Production Areas ◽  
Race 4 ◽  
Linear Regressions

Fusarium oxysporum f. sp. apii (Foa) race 4, which is in F. oxysporum species complex (FOSC) Clade 2, causes a new Fusarium wilt of celery. We compared Foa race 4 with race 2, which causes Fusarium yellows of celery and is in FOSC Clade 3. Optimal temperatures for celery yield are 16 to 18°C. Soil temperatures in California celery production areas can range up to 26°C, and the maximal rate of hyphal extension of Foa races 2 and 4 in culture are 25°C and 28°C, respectively. Here, we compared the effect of temperatures from 16 to 26°C on growth of Foa races 4 and 2 in two celery cultivars: Challenger, which is resistant to Foa race 2 and susceptible to race 4; and Sonora, which is susceptible to both Foa races 2 and 4. Based on linear regressions, as temperature increases, there is an increase in the log of Foa race 4 DNA concentration in celery crowns and in the reduction in plant height. Based on logistic regressions, as temperature increases, the incidence of vascular discoloration increases in celery with either Foa race 2 or 4 infection. In both cultivars, temperatures of 22°C and above resulted in a significantly (α=0.05) greater concentration of Foa race 4 than race 2 in planta. The concentration of Foa race 2 in crowns in Challenger is temperature-independent and comparatively low; consequently, Challenger is, at least partly, resistant rather than tolerant to Foa race 2.

Studies on sunflower rust. VII. Effect of light and temperature during spore formation on the germinability of fresh and stored urediospores of Puccinia helianthi

1971 ◽  
Vol 49 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Praim N. Sood ◽  
W. E. Sackston
Keyword(s):  
Adverse Effect ◽  
Light Intensity ◽  
Spore Formation ◽  
Effect Of Temperature ◽  
Consistent Effect ◽  
Puccinia Helianthi ◽  
Light Intensities ◽  
Race 1 ◽  
And Storage ◽  
Effect Of Light

Light intensity from 2200 to 43 000 lux during production of urediospores of Puccinia helianthi had little influence on germinability of fresh spores. The higher light intensities had an adverse effect on germinability of spores stored at −16 °C for 2 months. Daylength had little consistent effect on germinability of fresh or stored spores. Spores produced at day temperatures of 16, 21, and 27 °C showed no effect of temperature on germinability when fresh. After 2 months storage at −16 °C germination was highest for spores produced at 21°. Spores of races 1 and 3 germinated well after 1218 days of storage at −16°, and a small percentage germinated after storage at 4 °C. Races 2 and 4 germinated well after 1136 days storage at −16 and 4 °C. Races 2 and 4 survived longer than races 1 and 3 at 30° and at 23 °C, but not at 13 °C. Race 3 appeared more susceptible than race 1 to effects of light, temperature, and storage.

Studies on sunflower rust. X. Specialization of Puccinia helianthi on wild sunflowers in Texas

1972 ◽  
Vol 50 (9) ◽  
pp. 1871-1877 ◽  
Author(s):  
C. M. R. Hennessy ◽  
W. E. Sackston
Keyword(s):  
Helianthus Annuus ◽  
Host Species ◽  
Rust Resistance ◽  
Puccinia Helianthi ◽  
Race 1 ◽  
Race 2 ◽  
High Degree ◽  
Race 4 ◽  
Adaptive Variability

Sunflower rust (Puccinia helianthi) was collected in Texas on wild Helianthus spp. believed to be ancestors of the cultivated sunflower (Helianthus annuus). Race 1, the least pathogenic on the standard "Canadian" differentials, was the most common. Races 1 and 2 predominated on H. annuus and H. debilis, race 2 on H. praecox, and race 4 on H. petiolaris. Most host species proved to be heterozygous for rust resistance; cross-infectivity tests between them were inconclusive. Puccinia helianthi shows a high degree of adaptive variability, which suggests that local specialization may be relatively unimportant.

Effect of Temperature on ADP-Induced Platelet Aggregation

1973 ◽  
Vol 29 (01) ◽  
pp. 183-189
Author(s):  
C. A Praga ◽  
E. M Pogliani
Keyword(s):  
Platelet Aggregation ◽  
Incubation Period ◽  
Room Temperature ◽  
Important Variable ◽  
Practical Significance ◽  
Effect Of Temperature ◽  
Induce Platelet Aggregation ◽  
Cuvette Holder ◽  
Exact Temperature

SummaryTemperature represents a very important variable in ADP-induced platelet aggregation.When low doses of ADP ( < 1 (μM) are used to induce platelet aggregation, the length of the incubation period of PRP in the cuvette holder of the aggregometer, thermostatted at 37° C, is very critical. Samples of the same PRP previously kept at room temperature, were incubated for increasing periods of time in the cuvette of the aggregometer before adding ADP, and a significant decrease of aggregation, proportional to the length of incubation, was observed. Stirring of the PRP during the incubation period made these changes more evident.To measure the exact temperature of the PRP during incubation in the aggre- gometer, a thermocouple device was used. While the temperature of the cuvette holder was stable at 37° C, the PRP temperature itself increased exponentially, taking about ten minutes from the beginning of the incubation to reach the value of 37° C. The above results have a practical significance in the reproducibility of the platelet aggregation test in vitro and acquire particular value when the effect of inhibitors of ADP induced platelet aggregation is studied.Experiments carried out with three anti-aggregating agents (acetyl salicyclic acid, dipyridamole and metergoline) have shown that the incubation conditions which influence both the effect of the drugs on platelets and the ADP breakdown in plasma must be strictly controlled.

Effect of Temperature on Incubation Time for Spontaneous Morphology Change in Electrodeposited Copper Metallization

2005 ◽  
Vol 863 ◽  
Author(s):  
S. Ahmed ◽  
D.N. Buckley ◽  
S. Nakahara ◽  
Y. Kuo
Keyword(s):  
Incubation Period ◽  
Incubation Time ◽  
Annealing Time ◽  
Room Temperature ◽  
Diffusion Mechanism ◽  
Systematic Investigation ◽  
Effect Of Temperature ◽  
Copper Metallization ◽  
Morphology Change ◽  
A Value

AbstractA systematic investigation of the effect of annealing time and temperature on the incubation period for spontaneous morphology change (SMC) in electrodeposited copper metallization is reported. The incubation time is greatly reduced at higher temperatures. At each temperature, the remaining incubation time at room temperature was found to decrease approximately linearly with increasing annealing time. An Arhennius plot of the measured rates of decrease showed good linearity and yielded a value of 0.48 eV for the activation energy. This is consistent with a vacancy diffusion mechanism for the process occurring during the incubation period and supports our proposed mechanism for SMC.

Seed germination ecology of Sumatran fleabane (Conyza sumatrensis) in relations to various environmental parameters

Weed Science ◽  
2021 ◽  
pp. 1-26
Author(s):  
Gulshan Mahajan ◽  
Asheneel Prasad ◽  
Bhagirath Singh Chauhan
Keyword(s):  
Seed Germination ◽  
Light Intensity ◽  
Chloride Concentration ◽  
Soil Surface ◽  
Control Treatment ◽  
Effect Of Temperature ◽  
Burial Depth ◽  
Germination Ecology ◽  
Wide Range ◽  
Dark Conditions

Abstract Sumatran fleabane [Conyza sumatrensis (Retz.) Walker] is an emerging weed in the Australian cropping region. Populations resistant to glyphosate have evolved in Australia, creating the demand for information regarding the seed germination ecology of glyphosate-resistant (R) and glyphosate susceptible (S) populations of C. sumatrensis. A study was conducted to examine the effect of temperature, light intensity, salt stress, osmotic stress, and burial depth on the germination and emergence of two populations (R and S) of C. sumatrensis. Both populations were able to germinate over a wide range of alternating day/night temperatures (15/5 to 35/25 C). In light/dark conditions, the R population had higher germination than the S population at 20/10 and 35/25 C. In the dark, the R population had higher germination than the S population at 25/15 C. In the dark, germination was inhibited at 30/20 C and above. Averaged over populations, seed germination of C. sumatrensis was reduced by 97% at zero light intensity (completely dark conditions) compared with full light intensity. Seed germination of C. sumatrensis reduced by 17 and 85% at an osmotic potential of −0.4, and −0.8 MPa, respectively, compared with the control treatment. The R population had lower germination (57%) than the S population (72%) at a sodium chloride concentration of 80 mM. Seed germination was highest on the soil surface and emergence was reduced by 87 and 90% at burial depths of 0.5 and 1.0 cm, respectively. Knowledge gained from this study suggests that a shallow-tillage operation to bury weed seeds in conventional tillage systems, and retention of high residue cover in a zero-till system on the soil surface may inhibit the germination of C. sumatrensis. This study also warrants that the R population may have a greater risk of invasion over a greater part of a year due to germination over a broader temperature range.

scholarly journals Characterizing Virulence of the Pyrenophora tritici-repentis Isolates Lacking Both ToxA and ToxB Genes

Pathogens ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 74 ◽  
Author(s):  
Jingwei Guo ◽  
Gongjun Shi ◽  
Zhaohui Liu
Keyword(s):  
Triticum Aestivum L ◽  
Tan Spot ◽  
Pyrenophora Tritici Repentis ◽  
Tan Spot Disease ◽  
Hard Red Winter Wheat ◽  
Winter Wheat Cultivars ◽  
Race 2 ◽  
Genomic Regions ◽  
Race 4 ◽  
Necrotrophic Effectors

The fungus Pyrenophora tritici-repentis (Ptr) causes tan spot of wheat crops, which is an important disease worldwide. Based on the production of the three known necrotrophic effectors (NEs), the fungal isolates are classified into eight races with race 4 producing no known NEs. From a laboratory cross between 86–124 (race 2 carrying the ToxA gene for the production of Ptr ToxA) and DW5 (race 5 carrying the ToxB gene for the production of Ptr ToxB), we have obtained some Ptr isolates lacking both the ToxA and ToxB genes, which, by definition, should be classified as race 4. In this work, we characterized virulence of two of these isolates called B16 and B17 by inoculating them onto various common wheat (Triticum aestivum L.) and durum (T. turgidum L.) genotypes. It was found that the two isolates still caused disease on some genotypes of both common and durum wheat. Disease evaluations were also conducted in recombinant inbred line populations derived from two hard red winter wheat cultivars: Harry and Wesley. QTL mapping in this population revealed that three genomic regions were significantly associated with disease, which are different from the three known NE sensitivity loci. This result further indicates the existence of other NE-host sensitivity gene interactions in the wheat tan spot disease system.

Investigations into the increased rust (Puccinia helianthi) intensity on some hybrid sunflower cultivars grown in Queensland

1984 ◽  
Vol 35 (1) ◽  
pp. 99
Author(s):  
KC Goulter ◽  
JK Kochman ◽  
JF Brown
Keyword(s):  
Light Intensity ◽  
Leaf Area ◽  
Liquid Nitrogen ◽  
Low Light ◽  
Puccinia Helianthi ◽  
Low Light Intensity ◽  
Generation Times ◽  
Race 1 ◽  
Hybrid Sunflower

Sunflower rust intensity in crops of several hybrid cultivars in Queensland during the 1980, 1981 and 1982 seasons ranged from 30 to 60% of leaf area. In previous years, these cultivars had rust ratings of 2-5%. Rust was also found on some crops of usually immune hybrids grown during winter in central Queensland. A number of rust differential lines were inoculated with several isolates collected from throughout Queensland during 1981 and 1982, as well as with isolates stored in liquid nitrogen from the years 1976, 1978 and 1980. Because all isolates failed to infect the differentials possessing either the R1 or R2 genes for resistance, all collections were allocated to race 1. Comparisons of the temporal isolates revealed that no differences could be detected among the generation times, pustule number and pustule size produced by isolates on a range of sunflower rust differentials and hybrid cultivars. These data indicated that the composition of the pathogenic population had not altered. The application of higher inoculum densities shortened generation times and produced more pustules; both relationships were linear. The development of race 1 rust on seedlings of the immune hybrid Hysun 30 was induced by maintaining the plants under low light intensity or short photoperiods.

The effect of temperature and of cofactor concentrations on the conversion of 4-14C-progesterone to corticosterone by rat adrenal preparations

1970 ◽  
Vol 48 (7) ◽  
pp. 740-745 ◽  
Author(s):  
Charles P. W. Tsang ◽  
J. Stachenko
Keyword(s):  
Incubation Period ◽  
Significant Degree ◽  
Effect Of Temperature ◽  
Steroid Hydroxylase ◽  
Generating System

When a Krebs–Ringer bicarbonate medium in which adrenal quarters have been preincubated (hereafter called PIM), is reincubated for 3 h in the presence of 4-14C-progesterone and a NADPH-generating system, it possesses the capacity of hydroxylating the progesterone molecule (5). When the PIM is prepared at 0 °C, its subsequent incubation at 37 °C enhances the conversion of progesterone to 21-hydroxy- and 11β-hydroxy-steroids 30-fold and fivefold, respectively, above those observed upon incubation of PIM prepared at 37 °C. Similarly when dilute homogenates (0.6 mg tissue per milliliter) are preincubated for 1 h at 21 °C prior to a 3-h incubation period in the presence of 4-14C-progesterone and proper cofactors, 21- and 11β-hydroxylations of progesterone are, respectively, six times and twice greater than when the preincubation temperature is 37 °C.It is concluded that: (i) 21- and 11β-hydroxylating systems are inactivated to a significant degree at 37 °C and that under these conditions the 21-hydroxylase system is much more labile than the 11β-hydroxylase system; and (ii) this difference in the degree of denaturation of these two steroid hydroxylase systems explains in part the accumulation of 11β-hydroxyprogesterone in the PIM as well as in homogenates.

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