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1.
In vitro experiments were carried out to test the efficacy of plant activator Acibenzolar-S-methyl (ASM, a benzothiadiazole derivative; trade name Bion 50WG) against rhizome rot disease of turmeric (Curcuma longa L.) caused by Pythium aphanidermatum. The plant activator was applied as a liquid rhizome pre-treatment followed by inoculation with P. aphanidermatum. Cell death, activities of pathogenesis related (PR) proteins such as cysteine protease (EC 3.4.22), peroxidases (EC 1.11.1.7) both soluble and ionically bound (IB), trypsin inhibitor (EC 3.4.21.1) and chymotrypsin inhibitor (EC 3.4.21.4) were monitored. Rhizome pre-treatment was effective in controlling P. aphanidermatum infection. Anatomical observation of turmeric rhizomes indicated the presence of calcium oxalate deposits in infected tissue and an accumulation of starch grains in response to infection by P. aphanidermatum. Pathogen infection also induced new basic polypeptides corresponding to 18.0 and 41.0 kDa. Induction of protease, protease inhibitors, soluble and ionically bound peroxidase activity was observed after ASM pre-treatment and P. aphanidermatum infection. ASM treatment also enhanced activities of proteases and peroxidase in rhizomes already infected with P. aphanidermatum. Increases in enzyme activities and protease inhibitors occurred much more rapidly and were enhanced in P. aphanidermatum infected rhizomes that were previously treated with ASM suggesting that increased activities of peroxidases and protease inhibitors may play a key role in restricting the development of disease symptoms on the rhizomes infected with P. aphanidermatum as evidenced by a reduction in cell death. Hence, pretreatment with ASM suppress the P. aphanidermatum induced oxidative damage through higher accumulation of peroxidases and induced defense through activities of protease inhibitors thereby, protected turmeric rhizomes from rhizome rot disease.  相似文献   

2.
The fungitoxic effects of 66 medicinal plants belonging to different families were evaluated in vitro on Pythium aphanidermatum, the causal agent of chilli damping-off. Of these, Zimmu leaf extract (Allium sativum L. × Allium cepa L.) showed the highest inhibition of mycelial growth of P. aphanidermatum (13.7 mm). The antimicrobial compounds were isolated from Zimmu leaf extract and 22 compounds were identified through gas chromatography mass spectroscopy (GC–MS). Biocontrol agents Trichoderma viride and Pseudomonas fluorescens and Zimmu extract were also tested alone and together in vitro and in vivo experiments for control of P. aphanidermatum. The in vitro studies revealed that combination of T. viride + P. fluorescens + Zimmu leaf extract showed the highest mycelial growth inhibition over the control. Both antagonists were compatible with each other and with Zimmu leaf extract. The pot culture studies revealed that seed treatment with combined application of T. viride + P. fluorescens + Zimmu leaf extract was superior in reducing the pre and post-emergence damping-off incidence (8.3 and 17.0%, respectively), and increased the plant growth and yield (shoot length and root length of 13.7 and 6.3 cm, 146 g/plant, respectively) of chilli when compared to control.  相似文献   

3.
The effects of water stress on Fusarium foot and root rot in durum wheat were investigated in growth chamber, greenhouse and field tests in Tunisia. In the seedling stage, emergence of six durum wheat cultivars in the growth chamber was significantly reduced by inoculation with Fusarium culmorum and water stress (P<0.0001), with more disease under drier conditions. Additionally, the tiller number per mature plant, the 1000 grain weight and disease severity in mature stage were reduced by inoculation in greenhouse studies. In a field test, inoculation with F. culmorum significantly reduced the yield (P<0.001), by more than 17% for Om Rabiaa and 38% for Karim, the two cultivars tested. Yield was also significantly affected by precipitation and irrigation levels. The severity of the disease, estimated by the percentage of white heads, was separately affected by the cultivar (P<0.001) and inoculation (P = 0.0004). Percentage of white heads was 1.5 and 2 × higher in inoculated plants than non-inoculated for Om Rabiaa and Karim cultivars, respectively. Disease severity was highest in treatments with the greatest water stress. This is the first detailed study of water stress and F. culmorum on durum wheat in Tunisia, and indicates that cultivar resistance and irrigation management may be important in the management of Fusarium foot rot.  相似文献   

4.
Summary The susceptibility of 21 potato cultivars to leak (watery wound rot) caused byPythium aphanidermatum was compared. Whole tubers were inoculated after wounding by dipping into a water suspension of 103 oospores/ml and incubated for 3 days at 25°C. The mean penetration of tissue calculated from the recording of lesion width and depth and the qualitative assessment of rot extension were highly correlated. For 10 of 12 cultivars tested at least twice, consistent reactions were obtained: cvs Korrigane. Superstar, Safrane and Yesmina were moderately susceptible, whereas Atlas, Diamant, Mondial, Obélix, Spunta and Timate were susceptible to highly susceptible. Tubers originated from two locations and/or two cropping seasons: thus, the performance of these cultivars under different production conditions reveals a satisfactory level of agreement with the test. Moreover, ratings assigned are supported by field or store observations.  相似文献   

5.
Several broomrape species including Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca are reported to infect various grain and forage legumes in the Mediterranean and West Asia. Pea (Pisum sativum) is severely damaged by O. crenata, but there are no reports on O. foetida or P. aegyptiaca infection. We report here that pea can induce high germination of seeds of O. crenata, O. foetida and P. aegyptiaca but only O. crenata success infecting pea roots and developing further. Some differences in levels of infection by O. crenata were observed among pea accessions what can be exploited in pea resistance breeding programmes. On the contrary, all pea accessions studied were highly resistant to infection by both O. foetida and P. aegyptiaca, preventing any tubercle attachment and development. This makes pea a promising candidate as trap crop for O. foetida and P. aegyptiaca seed bank demise in infested soils.  相似文献   

6.
Basal stem rot of oil palm (OP) by Ganoderma boninense is of major economic concern and it is the predominant disease of OP in SE Asia. Also, other plantation crops are affected by Ganoderma. The early detection of symptoms is crucial for control, although effective methods remain elusive. Ergosterol is the principal sterol of fungi and plays an essential role in the cell membrane and other cellular constituents. The analysis of ergosterol is useful for fungal detection in solid plant substrates. The present report compares ergosterol concentration in sound and decayed OP seedlings and mature plants using HPLC with diode array detection. The disease of OP requires to be considered as a white rot process where fungal biomass will increase from a low to high level as the infection progresses. G. boninense biomass was correlated with ergosterol concentration in vitro. Furthermore, the sterol was correlated with internal colonization (a) of inoculated seedlings, (b) of felled and standing OP and (c) to external symptoms of the disease. The compound was not detected in healthy samples. Disease treatments may be made more effective as the amounts of fungal biomass can be estimated and early detection is possible. Ergosterol quantification is a provisional diagnostic method for detection for G. boninense infection in OP which can be employed with other methods, enabling early remedial action to be taken. The method is recommended for further research involving basal stem rot of OP.  相似文献   

7.
Sclerotinia rot caused by the fungus Sclerotinia sclerotiorum is one of the most serious and damaging diseases of oilseed rape and there is keen worldwide interest to identify Brassica genotypes with resistance to this pathogen. Complete resistance against this pathogen has not been reported in the field, with only partial resistance being observed in some Brassica genotypes. Introgression lines were developed following hybridization of three wild crucifers (viz. Erucastrum cardaminoides, Diplotaxis tenuisiliqua and E. abyssinicum) with B. napus or B. juncea. Their resistance responses were characterized by using a stem inoculation test. Seed of 54 lines of B. napus and B. juncea obtained from Australia, India and China through an Australian Centre for International Agricultural Research (ACIAR) collaboration programme were used as susceptible check comparisons. Introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum had much higher levels (P < 0.001) of resistance compared with the ACIAR germplasm. Median values of stem lesion length of introgression lines derived from the wild species were 1.2, 1.7 and 2.0 cm, respectively, as compared with the ACIAR germplasm where the median value for stem lesion length was 8.7 cm. This is the first report of high levels of resistance against S. sclerotiorum in introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum. The novel sources of resistance identified in this study are a highly valuable resource that can be used in oilseed Brassica breeding programmes to enhance resistance in future B. napus and B. juncea cultivars against Sclerotinia stem rot.  相似文献   

8.
Summary TwoPythium spp. were isolated from diseased tubers exhibiting rots at harvest, in summer stores and also in refrigerated storage. Symptoms shared features described for both pink rot caused byPhytophthora erythroseptica and leak caused byPythium spp. The causal agents were identified asPythium aphanidermatum andP. ultimum by morphological and physiological observations and by fingerprinting using oomycete specific primers to amplify the internal transcribed spacer (ITS1) within ribosomal DNAs. The optimum temperatures for infection were 30°C forP. aphanidermatum and 25°C forP. ultimum, corresponding to the optimum temperatures for growth in vitro. The optimum concentration for infection of tubers inoculated by dipping in a suspension of oospores or hyphal swellings after wounding was found to be 103 reproductive organs/ml, whereas the infection threshold was 10 reproductive organs/ml.  相似文献   

9.
Southern stem rot, caused by Sclerotium rolfsii Sacc., is a destructive soil fungal disease of peanut in China and other countries. To evaluate resistant germplasm, a total of 256 peanut accessions were investigated on their resistance to southern stem rot in 3 environments by artificial inoculation. Variance analysis indicated that disease index was significantly influenced by environment, genotype and genotype ​× ​environment interactions. Peanut accessions of var. vulgaris type exhibited higher resistance to southern stem rot. Disease index was significantly negatively correlated with linoleic acid content, while positively correlated with oleic acid content. Six resistant accessions were identified, including Hua 28, Shandongzai, ICG 6326, Quanhua 7, Quanhua 9 and Guihua 836, with their disease indexes under 40 and mortality were less than 30% in the three environments. The identified resistant accessions showed the great potential to be applied in resistant peanut breeding, and would be good genetic resources for enhancing the resistance to southern stem rot.  相似文献   

10.
《Field Crops Research》2005,91(2-3):125-130
Stem rot, a fungal disease caused by Sclerotinia trifoliorum Eriks., is often a serious problem in many important forage legumes including faba beans (Vicia faba L.). Understanding the inheritance of resistance to the disease is essential for effective breeding of resistant cultivars. Experiments were conducted to study the inheritance of resistance to stem rot of faba beans. The F1, F2, and the backcross generations of five crosses between four resistant and four susceptible populations (Alto × Polycarpe, A-90 × Polycarpe, ILB-1814 × A-247, A-90 × A-244, VT × Tanagra) were used. The eight populations were crossed properly in the field, and progenies of F1 and F2, as well as backcross progenies of F1 with each of their parents, were evaluated for resistance to stem rot disease under controlled conditions after artificial inoculation of the plants with carrot root pieces colonized by the fungus. On the assumption that inheritance of stem rot resistance is governed by a single dominant gene, no significant differences were found between the observed and the expected frequencies of resistance for progenies, except for one cross. As the expression of resistance to the disease fits the expected ratios for a single dominant gene model, it is concluded that the inheritance of resistance to sclerotinia stem rot in the evaluated faba bean populations is controlled by a single dominant gene.  相似文献   

11.
Tomato spotted wilt virus causes tomato spotted wilt (TSW), a disease that results in economic losses on several crops including tobacco in the southeastern United States. The effect of imidacloprid (IMD) applied as a pre-transplant soil drench alone, in combination with acibenzolar-S-methyl (ASM), or followed by a foliar application of ASM immediately after transplanting on TSW incidence and severity on tobacco was quantified in studies conducted in North Carolina from 2006 to 2008. Pre-transplant IMD application in combination with ASM provided the greatest reduction in TSW incidence and severity; however other treatments provided economically efficacious controls when TSW incidence was <30% in a field. From these results, TSW incidence was classified as Low (<10%), Moderate (11-20%), High (21-30%), or Very High (>30%), classes corresponding to different control recommendations, and subsequently used for modeling temporal TSW progress in a field. The temporal progress of TSW was modeled with data collected from 23 tobacco fields in North Carolina from 2006 to 2008. Cumulative degree-days (DD) and the average class of TSW incidence observed in a field for 5 seasons before the one that data were collected were significant variables (P < 0.05) for explaining the temporal progress of TSW incidence. DD based on four temperature thresholds (10.5, 18.0, 20.0, and 26.0 °C) were investigated, resulting in four models. Models were validated with data collected in 2009 and the model in which DD were calculated based on the threshold of 10.5 °C had a higher predictability (R2 = 0.70) than the other three models. The 26 °C DD model had the poorest predictability (R2 = 0.33). These models are currently being validated in North Carolina and the other flue-cured production states of the southeast United States as a tool for implementing disease control recommendations.  相似文献   

12.
Peanut fields are monitored for pod rot, which is typically caused by Pythium spp. and Rhizoctonia solani, in order to determine need, and the type and timing of fungicide applications. Pod rot can lead to damaged peanut kernels and when damage exceeds 2.49%, substantial price reductions occur. Nine fields or tests were sampled weekly for pod rot during the 2009 through 2012 growing seasons. The sampling was conducted on fields treated uniformly with fungicides for pod rot or within large research plots with various fungicide treatments. Pythium myriotylum was the most frequently identified pathogen species, although Rhizoctonia spp. were also recovered from diseased pods at all sites. Pod rot incidence was related to percent damaged kernels at harvest in 3 of 5 sites. Collection of 304 samples (sample unit = 46 cm of row) in a field was required to estimate 1% pod rot accurately (CV = 20%). There was a linear relationship between average % pod rot in a field, and the percentage of sampling units (absence/presence) with pod rot at low disease incidences. Scouting for pod rot of peanuts to make in-season fungicide applications will be hampered by high sample number, destructive sampling of plants, frequent sampling (due to rapid increase of disease), and the poor relationship between disease during the season and kernel damage at harvest. Making one preventative application at 60–70 days after planting may be a better practice than timing the initial fungicide application based on sampling for disease.  相似文献   

13.
Northeast regions of China (38–55°N latitude) play an important role in Japonica rice planting. Heading dates of 10 Japonica rice cultivars native to the Northeast of China were investigated and their sensitivities to photoperiod and temperature were analyzed. The results showed that these Japonica rice cultivars were insensitive to photoperiod but strongly sensitive to temperature, i.e. a high temperature can markedly shorten the heading date. Genetic analyses were conducted on these 10 cultivars using a set of heading date tester lines. All these Japonica cultivars carried a dominant early heading gene Ef-1, and most of these cultivars carried the photoperiod insensitivity allele e1, and two types of alleles were presented at the Se-1 locus, including recessive photoperiod insensitivity gene Se-1e and dominant strong photoperiod-sensitivity (PS) gene Se-1n. The PS of these cultivars carrying E1 or Se-1n can be repressed or weakened by Ef-1 and the recessive allele hd2 they carried. These results provided a reasonable explanation to the adaptability of Japonica rice to the high latitude environment of the Northeast China, and could be useful for breeding new cultivars well adapted to the high latitude regions and expanding the rice cultivation range.  相似文献   

14.
The effects of fungicides and biofungicides applied during the growing season in combination with storage applications to control potato storage diseases caused by oomycete pathogens were evaluated. The in-season treatments included in-furrow and foliar application of mefenoxam or phosphorous acid and foliar application of Bacillus subtilis. Storage treatments included phosphorous acid, B. subtilis and a 3-way mixture of azoxystrobin, fludioxonil and difenoconazole. These products were tested for control of tuber late blight, Pythium leak and pink rot at 10 °C (cv. FL1879) or 4 °C (cv. Goldrush). The combination of phosphorous acid in the field and during storage significantly reduced tuber blight development. Field treatment with B. subtilis, mefenoxam or phosphorous acid combined with the storage treatment of phosphorous acid significantly reduced Pythium leak development. Interaction of field treatments, mefenoxam or phosphorous acid, with storage treatments, phosphorous acid or the 3-way mixture of azoxystrobin, fludioxonil and difenoconazole significantly reduced pink rot incidence.  相似文献   

15.
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16.
Calli were obtained from leaf, cotyledon and internode explants of in vitro-grown plants of Indian cultivar of Withania somnifera in MS medium supplemented with 2, 4-D (2.0 mg l−1) and Kinetin (0.2 mg l−1). The brown, semi-friable callus (500 mg FW) derived from leaf explants produced higher number of primary adventitious roots (9 roots/callus) in half strength MS medium fortified with IBA (0.5 mg l−1) and NAA (0.1 mg l−1). The primary adventitious roots with an inoculum mass of 15 g FW were cultured for 6 weeks in the same medium for secondary adventitious root proliferation. Elicitation of abiotic elicitor, aluminium chloride at 10 mg l−1 at the end of 4 weeks culture with 4 h exposure time enhanced withanolides productivity. Under similar culture conditions, the biotic elicitor, chitosan at 100 mg l−1 stimulated higher production of all withanolides when compared to aluminium chloride treatment. This is the first report on the use of callus-derived adventitious root culture for the enhanced production of withanolides upon chitosan elicitation.  相似文献   

17.
Laboratory tests and field trials were conducted in 2010 and 2011 in Salerno province, Southern Italy, to determine the causal agent(s) of pink rot of roots and bulbs of onion and the effects of soil solarization combined with municipal food waste compost amendment in reducing their infections on bulbs of onion. Three fungi were mainly isolated: Fusarium proliferatum and Fusarium tricinctum on bulbs and roots and Pyrenochaeta terrestris exclusively on roots. P. terrestris produce symptoms on roots, but it was not able to cause damage on unwounded bulbs. F. proliferatum and F. tricinctum were able to induce symptoms when inoculated separately and showed no synergistic effects on severity of symptoms on bulbs. They induced symptoms on roots at a lesser extent. Combined inoculations of P. terrestris with both Fusarium species on roots have not increased symptoms severity of pink rot of onion. This is the first report of F. tricinctum as agent of pink rot of onion bulbs. Two years field trials have been carried out from 2009 to 2011 to evaluate the efficacy of soil solarization, applied alone or in combination with municipal food waste compost amendment, for controlling pink rot of onion bulb caused by F. proliferatum and F. tricinctum. For this purpose, soil solarization, alone and combined with compost amendment, were compared with metham sodium and an untreated control. The results of both trials demonstrated that, in presence of pink rot of onion bulbs, compost amendments, applied after solarization, strongly reduced the efficacy of soil solarization from 68.7% to 16.3% in 2010 and from 76.9% to 4.6% in 2011. Organic amendments applied before soil solarization significantly reduced the efficacy of this technique only in 2011. Significant yield increases were detected at the end of both trials in plots treated with solarization alone, metham sodium and compost applied after solarization. The highest incidence of unmarketable infected plants recorded in plots solarized and then amended with compost was compensated by the increase of bulb size and plant weight. These results demonstrated as the benefits achieved with compost amendments in controlling pink rot of onion are not easily predictable and applicable on large scale.  相似文献   

18.
Potato tuber blight caused by Phytophthora infestans accounts for significant losses of tubers in storage. Despite research on infection and management of tuber blight, there is paucity of information on the prediction of the occurrence tuber blight or modelling of tuber infection by P. infestans under field conditions. A tuber blight prediction model was developed in New York in experiments conducted using cultivars Allegany, NY101, and Katahdin in 1998 and 1999. This model was validated using data collected from the potato cultivar Snowden in field experiments in Laingsburg, Michigan from 2000 to 2009. In both New York and Michigan experiments, disease was initiated by artificial inoculation of cultivars with a US-8 isolate of P. infestans. Mean leaf area affected ranged from 0 to 94% at New York, and 0 to 93% at Michigan. At New York and Michigan, mean tuber blight incidences ranged from 1 to 40% and 0 to 15%, respectively. In the validation of the model using data collected at Laingsburg, Michigan, the model correctly predicted tuber blight incidence in 7 out of 9 years. Comparison of observed with predicted values indicated that slopes of the regression line between observed and predicted germination and infection data were not significantly different (P > 0.3547). Correlation coefficient between observed and predicted values was high (r2 > 0.65) and the coefficient of variation of the residuals of error was about 12%. Although inoculum availability is assumed in the model, incorporation of relationships of inoculum density, propagule survival in soil, and tuber blight incidence would greatly improve the prediction of tuber blight under field conditions.  相似文献   

19.
Rhizobacteria and Trichoderma spp. that were antagonistic against Fusarium oxysporum f.sp. zingiberi and Pythium splendens inciting rhizome rot disease of ginger were identified. In vitro assays identified positive interactions for growth, antifungal and chitinase gene expression between antagonistic TEPF-Sungal (Burkholderia cepacia) and S2BC-1 (Bacillus subtilis) with S17TH (Trichoderma harzianum), and vice versa. In comparison with the other strains and strain mixtures, one strain mixture, TEPF-Sungal + S17TH, recorded a maximum rhizome production of 84% efficiency with less incidences of yellows and rhizome rot at an 84.2 and 79.7% reduction over the pathogen control, respectively, in a polyhouse with a challenge inoculation with the pathogens. Inoculation of the mixture of biocontrol agents was associated with an increase in known defence gene products such as chitinase etc., so we speculate that these are involved in the mechanism of disease suppression. In field experiments, the strain mixture reduced yellows and rhizome rot to 45.9 and 49.3% over the untreated control, respectively, which is comparatively better than that produced with fungicide (44.3 and 45.3%, respectively). The treatment also produced an increased rhizome yield with an average increase of 60.0% relative to the control.  相似文献   

20.
Wheat grain hardness is one of the most important phenotypes related to milling, baking and noodle making. Either a mutation of the Puroindoline-a (Pina) gene or Puroindoline-b (Pinb) gene results in hard grain texture. A deletion mutation of Pina (Pina-D1b) is widely distributed among common wheat cultivars. Although North/South American and Australian cultivars and their descendants have a 15-kbp deletion in common, two new types of deletion mutation were found among Asian wheat cultivars. A 4.4-kbp deletion was found in one Korean and two Chinese wheat cultivars beginning at position +371 within the Pina coding region. The other, a 10.4-kbp deletion, was found in three Chinese and nine Japanese wheat cultivars, including five Japanese landraces, beginning at position −5112. It caused the deletion of the full-length Pina gene. These findings suggest that Asian wheat cultivars are genetically distinct from those in other regions. The 4.4-kbp and 10.4-kbp deletion mutants were designated as Pina-D1r and Pina-D1s, respectively.  相似文献   

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