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1.
The effect of soluble silicon (Si) on photosynthetic parameters and soluble sugar concentrations was determined in leaves of rice cv. Oochikara and mutant plants of Oochikara defective in active Si uptake [low silicon 1 (lsi1)]. Plants were grown in hydroponic culture amended with 0 (?Si) or 2 mm Si (+Si), under either low or high photon flux density (PFD) and with or without inoculation with Bipolaris oryzae, the causal agent of brown spot of rice. Leaf Si concentration increased by 141 and 435% in +Si cv. Oochikara and by 119 and 251% in +Si lsi1 mutant plants under high and low PFD, respectively, compared with ?Si plants. Plant biomass accumulation was improved by Si regardless of PFD, especially plants for cv. Oochikara. Brown spot severity was highest in ?Si plants for cv. Oochikara and lsi1 mutant plants under low PFD. In the presence of Si, disease severity in plants grown under both low and high PFD was reduced, except for lsi1 mutant plants under high PFD. Plant inoculation reduced the photosynthetic parameters measured regardless of plant material or Si supply. A decrease of net carbon assimilation rate (A) of inoculated plants under low PFD compared with non‐inoculated plants was associated with damage in the photosynthetic apparatus, except for +Si cv. Oochikara in which stomatal restriction [low water vapour conductance (gs)] contributed to A reduction. Under high PFD, damage to the photosynthetic apparatus of inoculated plants was the main reason for the reduction in A for +Si and ?Si lsi1 mutant plants. In addition, for ?Si cv. Oochikara, a reduction in gs contributed to reduced A. However, for +Si cv. Oochikara, gs was the limiting factor for A. Inoculated plants of +Si cv. Oochikara had higher A values than +Si lsi1 mutant plants, regardless of environmental conditions. Soluble sugars were not detected in leaf tissues of plants under low PFD. For high PFD, Si improved the hexose concentration in non‐inoculated plants at 144 h after inoculation (hai) for lsi1 mutant plants and from 96 hai onwards for cv. Oochikara compared with ?Si plants. However, plant inoculation reduced hexose concentration compared with non‐inoculated plants, mainly in +Si plants, regardless of plant material. Sucrose concentration increased in leaves of cv. Oochikara in the presence of Si whether inoculated or not. For +Si lsi1 mutant plants, sucrose concentration increased only at 48 hai compared with ?Si plants, whether inoculated or not. The results of this study show that a minimum Si concentration is needed in leaf tissues of rice plants to avoid the negative impact of B. oryzae infection on photosynthesis and sugar concentration. High leaf Si concentration resulted in an increased soluble sugar concentration and together, but in independent ways, soluble sugar and Si reduced brown spot severity of rice.  相似文献   

2.
Two experiments were carried out to assess the changes associated with photoassimilate production and partitioning in the source–sink relationship of flag leaves and spikes of wheat plants infected with Pyricularia oryzae, the causal agent of blast. Flag leaves and spikes were inoculated at 10 and 20 days after anthesis (daa) with a conidial suspension of P. oryzae. Analysis of chlorophyll a fluorescence using maximal photosystem II quantum efficiency (Fv?Fm), fraction of energy absorbed that is used in photochemistry (YII), quantum yield of non‐regulated energy dissipation (Y(NO)) and quantum yield of regulated energy dissipation (Y(NPQ)), showed an impairment of the photosynthetic performance in both infected flag leaves and spikes, coupled with reduced concentrations of chlorophyll a  + b and carotenoids. Compared to non‐inoculated controls, there was lower capacity for CO2 fixation by RuBisCO in the infected flag leaves. Similarly, in the infected flag leaves and grains (obtained from infected spikes), there were lower concentrations of soluble sugars, while the hexoses‐to‐sucrose ratio increased in infected flag leaves. Compared to non‐inoculated controls, infected flag leaves showed lower sucrose phosphate synthase (SPS) activity and lower expression of the sucrose synthesis (SuSy) gene, while higher expression and activity of acid invertases also occurred. At the advanced stages of fungal infection, the concentration of starch in grains decreased but remained high for the infected flag leaves. There were reductions in ADP‐glucose pyrophosphorylase activity and the expression of ADP‐glucose pyrophosphorylase genes and a down‐regulation of β‐ and α‐amylase expression at the advanced stages of fungal infection on flag leaves and spikes. In conclusion, the effect of blast on both grain quality and yield can be associated with alterations in both production and partitioning of carbohydrates during the grain filling process.  相似文献   

3.
Increased atmospheric carbon dioxide (CO2) and soil nitrogen (N) may confer competitive advantages to invasive species over native plant species. We conducted a two‐way factorial experiment, growing the model invasive plant Arundo donax in CO2 growth chambers to test how CO2 and N availability interact to affect plant growth and biomass allocation. CO2 was supplied at c. 400 mg L?1 and c. 750 mg L?1. N was supplied as ammonium nitrate at 640, 320 and 80 mg L?1. We hypothesised that the fertilisation effect of CO2 enrichment would offset limitations from N deficiency. The results indicated that A. donax plants grown with enriched CO2 and abundant N accumulated approximately 50–100% more biomass and allocated approximately 50% more biomass to rhizomes than plants grown under ambient CO2 conditions. Neither treatment affected the leaf area per unit mass (specific leaf area; SLA). Greater growth will likely increase A. donax's competitive potential, because increased rhizome biomass has been associated with increased stress tolerance and post‐disturbance resprouting capacity. The consistent SLA under all treatments suggests that A. donax has a morphological strategy that prioritises increasing leaf quantity over increasing individual leaves' photosynthetic potential. These results reveal the ecological strategies that contribute to the successful establishment, dominance and persistence of this invasive plant species.  相似文献   

4.
The development of plant diseases is associated with biophysical and biochemical changes in host plants. Various sensor methods have been used and assessed as alternative diagnostic tools under greenhouse conditions. Changes in photosynthetic activity, spectral reflectance and transpiration rate of diseased leaves, inoculated with Cucumber mosaic virus (CMV), Cucumber green mottle mosaic virus (CGMMV), and the powdery mildew fungus Sphaerotheca fuliginea were assessed by the use of non‐invasive sensors during disease development. Spatiotemporal changes in leaf temperature related to transpiration were visualized by digital infrared thermography. The maximum temperature difference within a leaf was an appropriate parameter to differentiate between healthy and diseased plants. The photosynthetic activity of healthy and diseased cucumber plants varied as measured by chlorophyll fluorescence and compared to the actual chlorophyll content. Hyperspectral imaging data were analysed using spectral vegetation indices. The results from this study confirm that each pathogen has a characteristic influence on the physiology and vitality of cucumber plants, which can be measured by a combination of non‐invasive sensors. Whereas thermography and chlorophyll fluorescence are unspecific indicators for plant diseases, hyperspectral imaging offers the potential for an identification of plant diseases. In a sensor data fusion approach, an early detection of each pathogen was possible by discriminant analysis. Although it still needs to be validated under real conditions, the combination of information from different sensors seems to be a promising tool.  相似文献   

5.
L Ziska 《Weed Research》2013,53(2):140-145
Soyabean (Glycine max) was grown at ambient and projected levels of atmospheric carbon dioxide (+250 μmol mol?1 above ambient) over two field seasons with and without the presence of a weed, Abutilon theophrasti, to quantify the potential effect of rising atmospheric carbon dioxide concentration on weed–crop interactions and potential yield loss in soyabean. Under weed‐free conditions, elevated CO2 resulted in stimulations in soyabean seed yield and associated components, including pod number. At an approximate density of 6 plants m?2, A. theophrasti competition resulted in a significant reduction (?40%) in soyabean seed yield. Although differences in seed yield reduction by A. theophrasti were observed as a function of year, the relative decrease in seed yield with A. theophrasti biomass did not differ in response to CO2. Although careful weed management will be necessary if CO2‐induced increases in seed yield for soyabean are to be achieved, these data suggest that soyabean seed yield may be more resilient in competition with A. theophrasti as a function of rising atmospheric levels of carbon dioxide.  相似文献   

6.
Fusarium head blight in wheat spikes is associated with production of mycotoxins by the fungi. Although flowering is recognized as the most favourable host stage for infection, a better understanding of infection timing on disease development and toxin accumulation is needed. This study monitored the development of eight characterized isolates of F. graminearum, F. culmorum and F. poae in a greenhouse experiment. The fungi were inoculated on winter wheat spikes before or at anther extrusion, or at 8, 18 and 28 days later. Disease levels were estimated by the AUDPC and thousand‐kernel weight (TKW). The fungal biomass (estimated by qPCR) and toxin concentration (deoxynivalenol and nivalenol, estimated by UPLC‐UV‐MS/MS) were measured in each inoculated spike, providing a robust estimation of these variables and allowing correlations based on single‐individual measurements to be established. The toxin content correlated well with fungal biomass in kernels, independently of inoculation date. The AUDPC was correlated with fungal DNA, but not for early and late infection dates. The highest disease and toxin levels were for inoculations around anthesis, but early or late infections led to detectable levels of fungus and toxin for the most aggressive isolates. Fungal development appeared higher in kernels than in the chaff for inoculations at anthesis, but the opposite was found for later inoculations. These results show that anthesis is the most susceptible stage for FHB, but also clearly shows that early and late infections can produce significant disease development and toxin accumulation with symptoms difficult to estimate visually.  相似文献   

7.
This study aimed to assess the extent and distribution of Fusarium graminearum species complex (FGSC) diversity in rice seeds produced in southern Brazil. Four species and two trichothecene genotypes were detected among 89 FGSC isolates, based on a multilocus genotyping assay: F. asiaticum (69·6%) with the nivalenol (NIV) genotype, F. graminearum (14·6%) with the 15‐acetyldeoxynivalenol (ADON) genotype, and F. cortaderiae (14·6%) and F. meridionale (1·1%), both with the NIV genotype. Seven selected F. asiaticum isolates from rice produced NIV in rice‐based substrate in vitro, at levels ranging from 4·7 to 84·1 μg g?1. Similarly, two F. graminearum isolates from rice produced mainly 15‐ADON (c. 15–41 μg g?1) and a smaller amount of 3‐ADON (c. 6–12 μg g?1). One F. meridionale and two F. cortaderiae isolates did not produce detectable levels of trichothecenes. Two F. asiaticum isolates from rice and two from wheat (from a previous study), and one F. graminearum isolate from wheat, were pathogenic to both crops at various levels of aggressiveness based on measures of disease severity in wheat spikes and rice kernel infection in a greenhouse assay. Fusarium asiaticum and the reference F. graminearum isolate from wheat produced NIV, and deoxynivalenol and acetylates, respectively, in the kernels of inoculated wheat heads. No trichothecene was produced in kernels from inoculated rice panicles by any of the isolates. These findings constitute the first report of FGSC composition in rice outside Asia, and confirm the dominance of F. asiaticum in rice agroecosystems.  相似文献   

8.
Mycosphaerella species that cause the ‘Sigatoka disease complex’ account for significant yield losses in banana and plantain worldwide. Disease surveys were conducted in the humid forest (HF) and derived savanna (DS) agroecological zones from 2004 to 2006 to determine the distribution of the disease and variation among Mycosphaerella species in Nigeria. Disease prevalence and severity were higher in the HF than in the DS zone, but significant (P < 0·001) differences between agroecological zones were only observed for disease severity. A total of 85 isolates of M. fijiensis and 11 isolates of M. eumusae were collected during the survey and used to characterize the pathogenic structure of Mycosphaerella spp. using a putative host differential cultivar set consisting of Calcutta‐4 (resistant), Valery (intermediate) and Agbagba (highly susceptible). Area under disease progress curve (AUDPC) was higher on all cultivars when inoculated with M. eumusae than with M. fijiensis, but significant (P < 0·05) differences between the two species were only observed on Valery. Based on the rank‐sum method, 8·3% of the isolates were classified as highly aggressive and 46·9% were classified as aggressive. About 11·5% of all the isolates were classified as least aggressive, and all of these were M. fijiensis. The majority of M. eumusae isolates (seven out of 11; 64%) were classified as aggressive. A total of nine pathotype clusters were identified using cluster analysis of AUDPC. At least one M. fijiensis isolate was present in all the nine pathotype clusters, while isolates of M. eumusae were present in six of the nine clusters. Isolates in pathotype clusters III and V were the most aggressive, while those in cluster VIII were the least aggressive. Shannon’s index (H) revealed a more diverse Mycosphaerella collection in the DS zone (H = 1·81) than in the HF (H = 1·50) zone, with M. fijiensis being more diverse than M. eumusae. These results describe the current pathotype structure of Mycosphaerella in Nigeria and provide a useful resource that will facilitate screening of newly developed Musa genotypes for resistance against two important leaf spot diseases of banana and plantain.  相似文献   

9.
BACKGROUND: Changes in chlorophyll fluorescence have often been advocated as a sensitive biomarker of plant stress, assuming that any kind of plant stress serious enough to affect plant growth will also affect photosynthesis. Glyphosate affects photosynthetic electron transport indirectly by inhibiting sink processes. The question is how fast this inhibition can be observed on CO2 assimilation and ultimately on chlorophyll fluorescence? RESULTS: Experiments measuring CO2 assimilation, conductance and chlorophyll fluorescence using four Kautsky curve parameters on barley (Hordeum vulgare L.) exposed to increasing doses of glyphosate showed a total cessation of CO2 fixation and conductance without significant changes in chlorophyll fluorescence. The decrease in CO2 fixation and conductance was significant 1 day after spraying and corresponded well to the decrease in biomass 5–7 days after spraying. CONCLUSION: A total cessation of CO2 assimilation can take place without affecting chlorophyll fluorescence. Hypotheses concerning what happens to the energy from the photosynthetic apparatus that is not used for CO2 assimilation are discussed. The results question the use of chlorophyll fluorescence as a universal indicator of stress on photosynthetic processes. Also, they demonstrate that changes in gas‐exchange parameters are more sensitive biomarkers for glyphosate toxicity compared with chlorophyll fluorescence. Copyright © 2010 Society of Chemical Industry  相似文献   

10.
In this study, we used Parthenium hysterophorus and one of its biological control agents, the winter rust (Puccinia abrupta var. partheniicola) as a model system to investigate how the weed may respond to infection under a climate change scenario involving an elevated atmospheric CO2 (550 μmol mol?1) concentration. Under such a scenario, P. hysterophorus plants grew significantly taller (52%) and produced more biomass (55%) than under the ambient atmospheric CO2 concentration (380 μmol mol?1). Following winter rust infection, biomass production was reduced by 17% under the ambient and by 30% under the elevated atmospheric CO2 concentration. The production of branches and leaf area was significantly increased by 62% and 120%, under the elevated as compared with ambient CO2 concentration, but unaffected by rust infection under either condition. The photosynthesis and water use efficiency (WUE) of P. hysterophorus plants were increased by 94% and 400%, under the elevated as compared with the ambient atmospheric CO2 concentration. However, in the rust‐infected plants, the photosynthesis and WUE decreased by 18% and 28%, respectively, under the elevated CO2 and were unaffected by the ambient atmospheric CO2 concentration. The results suggest that although P. hysterophorus will benefit from a future climate involving an elevation of the atmospheric CO2 concentration, it is also likely that the winter rust will perform more effectively as a biological control agent under these same conditions.  相似文献   

11.
The control of seedborne rice seedling diseases in the seed beds is important to avoid epidemics in rice nurseries and paddies, which may result in severe yield loss. Recently, irradiation with plasma containing electrons, creating positive or negative ions and neutral species, has been shown to have an antimicrobial effect, probably via generation of reactive oxygen species. This study examines whether two seedborne rice seedling diseases, bakanae disease caused by the fungal pathogen Fusarium fujikuroi, and bacterial seedling blight caused by Burkholderia plantarii, are suppressed by irradiation of infected rice seeds with atmospheric plasma. Seed germination and seedling growth were not inhibited in plasma‐treated healthy seeds. When F. fujikuroi‐infected rice seeds were irradiated with plasma after being immersed in sterile distilled water, bakanae disease severity index and the percentage of plants with symptoms were reduced to 18.1% and 7.8% of non‐irradiated control, respectively, depending on the duration of plasma irradiation. The bacterial seedling blight disease index was also reduced by plasma irradiation in vacuum‐inoculated seeds to 38.6% of the non‐irradiated control, and in infected seeds harvested from spray‐inoculated heads of rice plants to 40.1% of the control. Therefore, plasma irradiation seems to be effective in controlling two independent seedborne rice seedling diseases.  相似文献   

12.
Verticillium albo‐atrum is responsible for considerable yield losses in many economically important crops, among them alfalfa (Medicago sativa). Using Medicago truncatula as a model for studying resistance and susceptibility to V. albo‐atrum, previous work has identified genetic variability and major resistance quantitative trait loci (QTLs) to Verticillium. In order to study the genetic control of resistance to a non‐legume isolate of this pathogen, a population of recombinant inbred lines (RILs) from a cross between resistant line F83005.5 and susceptible line A17 was inoculated with a potato isolate of V. albo‐atrum, LPP0323. High genetic variability and transgressive segregation for resistance to LPP0323 were observed among RILs. Heritabilites were found to be 0·63 for area under the disease progress curve (AUDPC) and 0·93 for maximum symptom score (MSS). A set of four QTLs associated with resistance towards LPP0323 was detected for the parameters MSS and AUDPC. The phenotypic variance explained by each QTL (R2) was moderate, ranging from 4 to 21%. Additive gene effects showed that favourable alleles for resistance all came from the resistant parent. The four QTLs are distinct from those described for an alfalfa V. albo‐atrum isolate, confirming the existence of several resistance mechanisms in this species. None of the QTLs co‐localized with regions involved in resistance against other pathogens in M. truncatula.  相似文献   

13.
Barley (Hordeum vulgare) was grown in different climatic environments with elevated [CO2] (700 vs 385 ppm), [O3] (60/90 vs 20 ppb) and temperature (24/19 vs 19/12°C day/night) as single factors and in combinations, to evaluate the impact of these climatic factors on photosynthesis and susceptibility to powdery mildew and spot blotch disease. No significant increase in net CO2 assimilation rate was observed in barley grown under elevated [CO2] at ambient temperature. However, this rate was positively stimulated under elevated temperature together with a slightly higher potential quantum efficiency of PSII, both at ambient and elevated [CO2], suggesting that photosynthesis was not limited by [CO2] at ambient temperature. When growing under elevated temperature or [O3], infection by the biotrophic powdery mildew fungus decreased, whereas disease symptoms and growth of the toxin‐secreting hemibiotrophic spot blotch fungus increased compared to ambient conditions, implying that climate‐induced changes in disease severity could be linked to the trophic lifestyle of the pathogens. Elevated [CO2] decreased powdery mildew infection but had no effect on spot blotch disease compared to ambient condition. However, the effect of elevated [CO2], [O3] and temperature did not act in an additive manner when combined. This led to a surprising disease development in the combination treatments, where powdery mildew infection increased despite the individual reducing effect of the climatic factors, and spot blotch disease decreased despite the individual promoting effect of temperature and ozone, emphasizing the importance of conducting multifactorial experiments when evaluating the potential effects of climate change.  相似文献   

14.
The effects of root‐knot nematodes on black root rot of watermelon and bottle gourd were studied using field surveys and co‐inoculation tests with Meloidogyne incognita (southern root‐knot nematode) and Diaporthe sclerotioides. The results of the field survey suggested that root‐knot nematodes had little effect on either the severity of black root rot or infection with D. sclerotioides. None of the three fields showed a significant positive correlation between disease severity and nematode gall index, with low correlation coefficients. Co‐inoculation experiments under controlled conditions found no significant effect of root‐knot nematodes on black root rot of watermelon and bottle gourd based on area under disease progress curves (AUDPC). These results were supported by the quantities of DNA of the two agents in root tissues because no significant difference was found between dual‐ and single‐inoculation treatments with M. incognita and/or D. sclerotioides. These findings suggest that root‐knot nematodes probably do not affect the infection of watermelon or bottle gourd roots by D. sclerotioides or the incidence of black root rot in these crops caused by this fungus.  相似文献   

15.
The effect of Citrus tristeza virus (CTV) infection on photosynthetic activity and antioxidant metabolism was analysed in plants of the highly susceptible citrus genotype Mexican lime (Citrus aurantifolia). Two virus isolates differing in their virulence (the severe T318 and the mild T385) were used in the experiments. CTV infection caused a reduction in photosynthetic capacity in infected plants. This limitation was mainly due to a reduction in the carboxylative efficiency whereas the limitation of CO2 diffusion through the stoma had lower impact. The virus did not damage the antennae and did not reduce the efficiency of light harvesting complexes. Oxidative damage occurred in infected plants, as evidenced by the increase in malondialdehyde levels. Indeed, CTV infection caused an increase in ascorbate peroxidase activity in new shoots developed in infected plants during the 2 years of the experiment. Data suggest that the H2O2 removal machinery was not damaged as a result of stress but the defence mechanism was overwhelmed with time due to the continuing pressure of biotic stress.  相似文献   

16.
In response to the extensive development of upland rice on the hillsides of the Madagascan highlands, alternative cropping systems based on conservation agriculture have been recommended to halt declining soil fertility and to limit erosion. To assess the efficiency of these cropping systems in limiting rice blast disease and to measure their yield performance, an experiment was set up in 2003 at Andranomanelatra (1640 m a.s.l.) in the Madagascan highlands. The rice crop was planted every second year following oat (Avena sativa) after common bean (Phaseolus vulgaris), with both conventional tillage and no tillage. For each cropping system, two levels of fertilization were used: (i) organic and (ii) organic + mineral fertilization. The level of blast epidemic was measured on two different cultivars over a 5‐year period. Disease severity was significantly lower in the no‐tillage cropping system than in the conventional tillage system. Mineral fertilization increased the level of blast. A significant interaction between cropping system and fertilization indicated that the impact of fertilization differed with the cropping system. When the level of blast was low, yield was higher in the conventional cropping system but as soon as blast level increased, yield was better in the no‐tillage cropping system. Possible interactions between cropping system and blast epidemics are explained and the problem of high performance but risky cropping systems is discussed.  相似文献   

17.
T K Das  D K Das 《Weed Research》2018,58(3):188-199
Variable dormancies result in periodicity in the germination of weeds and make weed control a repetitive practice. Under some conditions, repeated applications of selective herbicides can lead to the dominance of perennial weeds like Cyperus rotundus . Our hypothesis was that applying a chemical dormancy breaker (DB ) plus herbicide mixture would better control a mixture of weed species. Three experiments were designed to develop a cost‐effective DB treatment and to evaluate its dose with herbicides tank‐mixtures for effective weed management. KNO 3 and gibberellic acid GA 3 as dormancy breakers offered comparable effects, but KNO 3 was more economical than GA 3. KNO 3 at a 6% concentration was more effective in promoting weed germination than a 3% concentration in soyabean. A combination of KNO 3 (6%) and pre‐emergence pendimethalin 0.75 kg a.i. ha?1 + imazethapyr 0.10 kg a.i. ha?1 controlled annual weeds by 99% and reduced C. rotundus growth by 83%. This treatment gave significantly higher soyabean yield and net returns. Similarly, a tank‐mixture comprising of clodinafop 0.06 kg a.i. ha?1 + metsulfuron 0.006 kga.i. ha?1 was more effective against weeds than pre‐emergence tank‐mix application of pendimethalin 0.75 kg a.i. ha?1 + carfentrazone‐ethyl 0.02 kg a.i. ha?1 and isoproturon 0.75 kg a.i. ha?1. The use of pre‐emergence tank‐mixture of pendimethalin 0.75 kg a.i. ha?1 + imazethapyr 0.10 kg a.i. ha?1 should exhaust seed/tuber bank if repeated and reduce the application cost of herbicides by 50% and the dose, residue and cost of pendimethalin by 25%.  相似文献   

18.
The effects of herbicide dose on rice‐weed competition were investigated to develop a combined model, which can be utilised to estimate an optimum herbicide dose for a given weed density in paddy rice cultivation. Field studies were conducted in Suwon for rice‐Echinochloa crus‐galli competition and Iksan for rice‐Eleocharis kuroguwai during 2007. The competitive effect of the weeds E. crus‐galli and E. kuroguwai decreased with increasing doses of flucetosulfuron and azimsulfuron, respectively, in the same manner as the standard dose–response curve. The combination of the rectangular hyperbolic model and the standard dose–response curve adequately described the complex effects of herbicide dose and weed competition on rice yield. Parameter estimates were used with the model to predict rice yield and estimate the doses of flucetosulfuron and azimsulfuron required to restrict rice yield loss caused by E. crus‐galli and E. kuroguwai, respectively, to an acceptable level. For a rice yield of 5.0 t ha?1, the model recommended flucetosulfuron doses of 8.7, 13.4 and 20.1 g a.i. ha?1 when infested with E. crus‐galli at 12, 24 and 48 plants m?2 respectively. For a rice yield of 5.2 t ha?1, the model recommended azimsulfuron doses of 3.9, 7.5 and 12.6 g a.i. ha?1 when infested with E. kuroguwai at 24, 48 and 96 plants m?2 respectively. The theoretical outputs of the combined model appear robust and indicate there are opportunities for reduced herbicide use in the field. These now require evaluation under field conditions.  相似文献   

19.
为研究枯萎病对马铃薯光合特性的影响,在幼苗期接种尖孢镰刀菌Fusarium oxysporum后,统计抗病品种陇薯10号和感病品种新大坪的病情指数,并测定叶绿素含量、光合及荧光参数。结果表明,尖孢镰刀菌侵染30 d后马铃薯表现出枯萎病症状,叶绿素含量显著降低,其中叶绿素a含量降幅最大,抗病品种陇薯10号比对照降低9.64%,感病品种新大坪比对照降低14.24%。尖孢镰刀菌侵染后马铃薯光合效率显著降低,侵染30 d后,抗病品种陇薯10号净光合速率比对照降低39.56%,感病品种新大坪比对照降低47.13%。病株的光响应曲线参数光补偿点、暗呼吸速率和表观量子效率都显著提高;而光饱和点和最大净光合速率都显著低于对照,表明尖孢镰刀菌侵染缩小了马铃薯对光能的利用有效范围。病株CO2响应曲线参数CO2饱和点、最大净光合速率和羧化效率分别显著低于对照;病株CO2补偿点和光呼吸速率反而升高,说明碳同化过程受到尖孢镰刀菌的限制。暗适应下的初始荧光、最小荧光、最大荧光、PSII最大光化学效率、光适应下PSII最大光化学效率及实际光化学效率、光化学猝灭系数、非光化学猝灭系数和光合电子传递速率均显著低于对照,...  相似文献   

20.
F. Liu  M. Wang  J. Wen  B. Yi  J. Shen  C. Ma  J. Tu  T. Fu 《Plant pathology》2015,64(6):1407-1416
Sclerotinia stem rot (SSR) is a severe disease of oilseed rape, which severely impacts the crop productivity worldwide. Sclerotinia sclerotiorum causes SSR, resulting in the secretion of oxalic acid (OA), which can be further degraded to carbon dioxide (CO2) and hydrogen peroxide (H2O2) by oxalate oxidase (OXO). In the present investigation, the barley oxalate oxidase (BOXO, Y14203) gene was introduced into oilseed rape by Agrobacterium‐mediated transformation to investigate the mechanism by which OXO promotes resistance to S. sclerotiorum. Compared to the control 72 h post‐inoculation, there were c. 15–61% fewer lesions on leaves of the transgenic oilseed rape, which thus exhibited a detectable level of partial resistance in leaf tissue to S. sclerotiorum. Transgenic oilseed rape also showed decreased oxalate and increased hydrogen peroxide levels compared to the control, and the expression of defence response genes involved in the hydrogen peroxide signalling pathway was also induced. Therefore, the improved resistance of oilseed rape could be attributed to the enhanced OA metabolism, production of hydrogen peroxide and the hydrogen peroxide‐mediated defence levels during infection.  相似文献   

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