scholarly journals Occurrence of the White Rust Pathogen, Albugo tragopogonis, in Seed of Sunflower

Plant Disease ◽  
1999 ◽  
Vol 83 (1) ◽  
pp. 77-77 ◽  
Author(s):  
A. Viljoen ◽  
P. S. van Wyk ◽  
W. J. Jooste
Keyword(s):  
Helianthus Annuus ◽  
South African ◽  
Long Range ◽  
Seed Transmission ◽  
Field Trials ◽  
Seed Infection ◽  
Causal Organism ◽  
White Rust ◽  
Epidermal Tissue ◽  
Rust Pathogen

White rust of sunflower (Helianthus annuus L.), caused by Albugo tragopogonis (Pers.) S. F. Gray, appeared in South African fields not previously planted to sunflower. Spread to these fields from infested fields was unlikely, as some of the newly affected fields were planted out of season and were more than 300 km away from other sunflower production fields. Several reports of this nature led us to investigate the possibility of seed transmission of the causal organism. Extensive colonization of sunflower heads by A. tragopogonis was observed in field trials and breeding nurseries. Head infections consisted of two distinct lesion types. White rust pustules, typical of those formed on abaxial sides of leaves, were recognized on abaxial sides of involucral bracts. Grayish, localized lesions containing dark-colored oospores of the fungus, similar to those formed on stems and petioles (1), were produced in sub-epidermal tissue and extended 3 to 5 mm deep into receptacles. Colonization of seeds was found in only a few lines. Oospores were produced in the pericarps and testae of seeds. No oospores or hyphae, however, were observed in the embryo. This is the first report of A. tragopogonis being seed-borne. Since the incidence of seed infection is low, spread of disease to infested fields is expected to be insignificant. Of more concern, however, is the possible long-range dissemination of the fungus by means of infected seed into regions or countries where the disease has not been previously reported. Reference: (1) P. S. Van Wyk et al. Helia 18:83, 1995.

Septoria helianthi. [Descriptions of Fungi and Bacteria].

1970 ◽  
Author(s):  
P. Holliday
Keyword(s):  
Helianthus Annuus ◽  
Geographical Distribution ◽  
Leaf Spot ◽  
Seed Treatment ◽  
Seed Transmission ◽  
Adaxial Surface ◽  
Young Leaves

Abstract A description is provided for Septoria helianthi. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Helianthus annuus, Helianthus grosseserratus and Helianthus rigidus. DISEASE: Leaf spot of sunflower. Yellowish spots up to 1.5 cm develop over the whole lamina, gradually turning necrotic and becoming almost black. The numerous pycnidia are mostly on the adaxial surface. The lesions have a polygonal outline, being sharply delimited by the veins. Infection may begin on the cotyledons and young leaves, spreading to later developing leaves. Severe attacks lead to defoliation and loss in yield. GEOGRAPHICAL DISTRIBUTION: Fairly widespread in E. Europe and the U.S.S.R. in Asia, China, Japan, Australia (Qd.); E. and S. Africa, N. America (CMI Map 468, ed. 1, 1970). TRANSMISSION: Overwintering occurs in host debris. Seed treatment is recommended although seed transmission does not appear to have been demonstrated. Introduction of the fungus into Hungary may have been via seed (43, 2013).

Mechanism of Seed Transmission and Seed Infection in Major Agricultural Crops in India

2020 ◽  
pp. 749-791
Author(s):  
P. Nallathambi ◽  
C. Umamaheswari ◽  
Sandeep K. Lal ◽  
C. Manjunatha ◽  
J. Berliner
Keyword(s):  
Seed Transmission ◽  
Seed Infection ◽  
Agricultural Crops

Adaptation of an immunodot assay for multiple prey identification of squid paralarvae in field trials

2005 ◽  
Vol 85 (6) ◽  
pp. 1499-1501 ◽  
Author(s):  
H.J.T. Hoving ◽  
J.D. Venter ◽  
D.E. Worst ◽  
M.R. Lipinski
Keyword(s):  
South African ◽  
Polyclonal Antibodies ◽  
Detection Limits ◽  
Field Trials ◽  
Negative Control ◽  
Prey Detection ◽  
Cross Reactions ◽  
Prey Identification

An optimized method, using polyclonal antibodies in an immunoassay, for prey detection in the diet of paralarvae of South African Loligo reynaudii is described. The study has increased the specificity of the antisera by determining the optimum antiserum dilutions and the detection limits of the antisera. Unfed laboratory-hatched paralarvae (negative control) were exposed to antisera and showed cross-reactions with polychaete antiserum.

scholarly journals Control of Seed Transmission of Cylindrocladium parasiticum in Peanut with Seed Treatment Fungicides

2003 ◽  
Vol 30 (2) ◽  
pp. 128-133
Author(s):  
D. L. Glenn ◽  
P. M. Phipps ◽  
R. J. Stipes
Keyword(s):  
Seed Treatment ◽  
Standard Treatment ◽  
Seed Transmission ◽  
Field Trials ◽  
Selective Medium ◽  
Significant Suppression ◽  
Greenhouse Trial ◽  
Cylindrocladium Parasiticum ◽  
Untreated Check ◽  
Peanut Cultivars

Abstract Seeds of peanut cultivars VA 98R and NC-V11 with speckled testae were treated with fungicide and assayed on a selective medium to determine the viability of Cylindrocladium parasiticum. The fungus was isolated from 78 and 90% of the untreated speckled seed of the respective cultivars. Seed treatment with captan + pcnb + carboxin, fludioxonil, captan, and thiophanate methyl significantly reduced recovery of the pathogen in both cultivars. Speckled seed of VA 98R and NC-V11 were treated with fungicides and planted in greenhouse and/or field trials in Suffolk, VA. Plants became infected with C. parasiticum after treated and untreated speckled seed were planted in steam-treated soil in the greenhouse. In one trial, seed treatment with fludioxonil, tebuconazole, and LS 176 significantly reduced taproot colonization by C. parasiticum compared to the untreated check. In a second greenhouse trial, only fludioxonil provided significant suppression of disease. In the field, treatment with fludioxonil, thiram, and tebuconazole significantly lowered Cylindrocladium black rot (CBR) incidence compared to the untreated check. Thiram significantly reduced taproot colonization compared to all treatments except fludioxonil. Based on the present study, the addition of thiram and/or fludioxonil to the standard treatment of captan + pcnb + carboxin may offer the best protection against seed transmission of C. parasiticum.

scholarly journals White blister disease control in radish seed crops

2018 ◽  
Vol 71 ◽  
pp. 325-331
Author(s):  
Mark Braithwaite ◽  
Richard Chynoweth ◽  
Matilda Gunnarsson ◽  
Lewis Braithwaite ◽  
Ian Harvey ◽  
...  
Keyword(s):  
Yield Loss ◽  
Seed Transmission ◽  
Brassica Species ◽  
Field Trials ◽  
Disease Suppression ◽  
Pot Trials ◽  
White Blister ◽  
Seed Crops ◽  
And Control ◽  
Better Than

Albugo candida is a significant pathogen of many brassica species causing leaf spotting but, more importantly, hypertrophy of flowering stems (“stagheads”) resulting in yield loss. No chemicals are currently registered for white blister control in New Zealand. Little research has been carried out on white-blister management. The implications of seed transmission and subsequent disease expression in radish are not fully understood and control has relied on products containing metalaxyl-m+mancozeb. A range of fungicides were evaluated in two field trials and a pot trial for both efficacy against the disease and effect on radish yield. While metalaxyl-m+mancozeb improved yields in field trials and provided good disease suppression in pot trials, the fungicides azoxystrobin, boscalid+pyraclostrobin and cyazofamid were also equally effective or better than metalaxyl-m+mancozeb. Treatments were able to suppress leaf spotting by up to 90% and inflorescence infection by 50%. Seed yield increases of up to 67% were recorded. Potential new control options for white blister were identified providing alternatives to metalaxyl-m+mancozeb and thus contributing to an anti-resistance strategy.

scholarly journals Identification of Novel Sources of Resistance to Sclerotinia Basal Stalk Rot in South African Sunflower Germplasm

2017 ◽  
Vol 18 (2) ◽  
pp. 87-90 ◽  
Author(s):  
Gerald J. Seiler ◽  
Christopher G. Misar ◽  
Thomas J. Gulya ◽  
William R. Underwood ◽  
Bradley C. Flett ◽  
...  
Keyword(s):  
South African ◽  
Research Council ◽  
Agricultural Research ◽  
Disease Incidence ◽  
Field Trials ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Stalk Rot ◽  
Agricultural Research Council ◽  
Moderately Resistant

Sclerotinia basal stalk rot (BSR) is a serious fungal disease that reduces yield of global sunflower (Helianthus annuus L.) production. Because limited chemical and biological controls of BSR are available and the present-day hybrids lack sufficient resistance, identification of new sources of resistance is needed to manage the disease in the future. A total of 59 cultivated oilseed sunflower accessions from the Agricultural Research Council, Grain Crops Institute, Potchefstroom, South Africa sunflower collection were evaluated for resistance to BSR in artificially inoculated field trials. Nine accessions from the South African sunflower collection were identified with a disease incidence less than or equal to the moderately resistant sunflower oilseed hybrid. These lines can be used in breeding programs to introgress the genes for resistance to Sclerotinia BSR into other adapted lines, providing a more efficient, durable, and environmentally friendly host plant resistance.

The effect of benomyl on Gloeotinia temulenta under laboratory and field conditions

1971 ◽  
Vol 11 (53) ◽  
pp. 693 ◽  
Author(s):  
DC McGee
Keyword(s):  
Lolium Perenne ◽  
No Reduction ◽  
Field Studies ◽  
Field Conditions ◽  
Seed Infection ◽  
Laboratory Studies ◽  
Causal Organism ◽  
Infected Seed ◽  
Application Rates ◽  
Seed Crops

Laboratory studies confirmed that benomyl can completely suppress apothecial formation of Gloeotinia temulenta, the causal organism of blind seed disease in grasses. Field studies in Lolium perenne seed crops showed that benomyl, applied at 2.80 and 5.60 kg/hectare, reduced the numbers of apothecia formed by 80 and 90 per cent respectively, while no reduction was apparent at 0.56 kg/hectare. Better results were obtained when the compound was applied in November, just before flowering, than when applied in September or October. At the application rates used, benomyl did not protect plants against seed infection. However, the degree of suppression of apothecial formation possible with benomyl suggests that, in areas where reinfestation of fields with infected seed after harvest is light, the compound should control blind seed disease by limiting formation of apothecia, which are the source of ascospore inoculum, to insignificant proportions.

scholarly journals Seedborne Infection of Rice by Pyricularia oryzae and Its Transmission to Seedlings

Plant Disease ◽  
1998 ◽  
Vol 82 (10) ◽  
pp. 1093-1099 ◽  
Author(s):  
H. K. Manandhar ◽  
H. J. Lyngs Jorgensen ◽  
V. Smedegaard-Petersen ◽  
S. B. Mathur
Keyword(s):  
Low Temperature ◽  
Transmission Rate ◽  
Seed Transmission ◽  
Pyricularia Oryzae ◽  
Infection Frequency ◽  
Seed Infection ◽  
Percent Recovery ◽  
Unsterilized Soil ◽  
Lower Infection ◽  
Germinating Seeds

Seedborne infection of rice by Pyricularia oryzae and its transmission to seedlings were studied quantitatively with naturally infected seeds of three rice cultivars collected from three locations in Nepal. A linear relationship on a logistic scale was found between panicle symptoms and seed infection, i.e., the more symptoms the higher seed infection. However, healthy-looking panicles and branches of panicles could also yield infected seeds. Postharvest measures such as winnowing and sun-drying significantly reduced seed infection by P. oryzae and filled grains had a lower degree of infection than unfilled grains. Sporulation of P. oryzae was most often confined to the embryonal end of germinating seeds. In contrast, most of the nongerminating seeds had sporulation all over the seed surface. Transmission of P. oryzae from seeds to seedlings, studied under various seeding conditions, showed that the transmission rate was always low. Thus, a seed sample with 21% seed infection resulted in less than 4% seedlings with blast lesions. Seed transmission was found for light covering of the seeds with soil or for moist seeding without covering. Transmission was rarely found when seeds were completely covered, and never in seedlings raised under water seeding conditions. Lower infection frequency was observed in seedlings raised in unsterilized soil than in seedlings raised in sterilized soil. Also, percent recovery of P. oryzae from infected seeds was higher in sterilized soil than in unsterilized soil and declined with time. Seedlings grown under low temperature (15 to 20°C) conditions did not develop blast lesions but when the same plants were transferred to high temperature (25 to 30°C) conditions, blast lesions were detected. This confirmed the latent infection in seedlings by P. oryzae grown under low temperature conditions.

TOLERANCE LEVEL OF ALTERNARIA SESAMI AND THE EFFECT OF SEED INFECTION ON YIELD OF SESAME IN KENYA

2000 ◽  
Vol 36 (3) ◽  
pp. 335-342 ◽  
Author(s):  
P. S. OJIAMBO ◽  
P. O. AYIECHO ◽  
R. D. NARLA ◽  
R. K. MIBEY
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Seed Weight ◽  
Sesame Seed ◽  
Seed Transmission ◽  
Gompertz Model ◽  
Major Effect ◽  
Seed Infection ◽  
Tolerance Level ◽  
Seed Increase

Field plots of sesame (Sesamum indicum) with six different levels of seed infection with Alternaria sesami were monitored for Alternaria leaf spot severity at Kibwezi, eastern Kenya. The aim of the study was to determine the effect of seed transmission of the pathogen on yield and tolerance level of the fungus in sesame seed. Increase in percentage leaf area diseased and percentage defoliation fitted the Gompertz model more closely than the logistic model. Areas under disease progress curves (AUDPC), infection and defoliation rates varied among the six infection levels. Disease severity increased with increase in seed infection and was least and most severe in plots established with seeds with 0 and 8% infection levels respectively. Yields ranged from 234.9 to 300.1 kg ha−1 compared with 312.5 kg ha−1 for the control, and losses due to seed infection ranged from 4% to 25%. Disease severity was negatively correlated with seed yield, 1000-seed weight and seeds per capsule. Alternaria leaf spot severity had a major effect on the seed weight component of yield. Tolerance level of A. sesami in sesame seed was determined to be less than 2%.

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