Effect of plant density on grain yield, root–length density and Orobanche crenata infestation in two faba bean genotypes

The effect of host plant cultivar and sowing density on Orobanche crenata Forsk. L. infestation in Vicia faba was studied in a field experiment in north–west Syria. Two faba bean genotypes. ILB 1814 (Syrian Local Large) and 402/29/84 (new breeding line from Egypt), were planted at four sowing densities. Whereas ILB 1814 was severely affected by O. crenata , 402/29/84 proved to be highly resistant. Sowing density did not have a significant effect on O. crenata dry weight in either genotype. However, the number of O. crenata attachments in ILB 1814 was positively correlated with plant density. The resistance of faba bean genotype 402/29/84 to O. crenata is due to: (a) less plant vigour and root–length density; (b) necrosis of host cells preventing O. crenata attack either before or just after penetration into the host root, or developing a barrier in the host root after the formation of a small tubercle: (c) early flowering and pod setting.     

Solarization; a physical control method for weeds and parasitic plants (Orobanche spp.) in Mediterranean agriculture

Summary. Experiments were conducted between 1985 and 1988 to evaluate the effect of duration and time of solarization on the control of two broom rapes ( Orobanche aegyptiaca Pers., O. crenata Forsk.) and other weeds common in the fields of faba bean ( Vicia faba L.) and lentil ( Lens culinaris Medik.) in West Asia. Solarization was performed by applying clear polyethylene sheet to the soil for 0, 10, 20, or 40 days in 1985/86, 0, 30, or 40 days in 1986/87 and 0, 20, 30, 40 or 50 days in 1987/88 during the hot season (July and August) and for 50 days immediately before sowing during milder weather (September and October) in 1986/87. Best control was obtained with solarization for 30–50 days in the hot season. Maximum soil temperature under polyethylene at 5 cm was 55°C in 1985, 48°C in 1986 and 57°C in 1987. Broomrape dry weight decreased in the first experiment by more than 90% in both faba bean and lentil fields. Solarization controlled broom-rape and other weeds in the following two seasons when the soil was left undisturbed during the season of the treatment.     

Effect of sowing date and host resistance on the establishment and development of Orobanche crenata in faba bean and common vetch

The effect of early and late sowing dates on the establishment of Orobanche crenata Forsk. (crenate broomrape) in resistant and susceptible cultivars of faba bean (Vicia faba L.) and vetch (Vicia sativa L.) were studied over four seasons in southern Spain. Differences in establishment, development and shoot emergence of the parasite were compared. With resistant faba bean and vetch cultivars, there was reduced attachment and shoot emergence of O. crenata with all sowing dates. Susceptible cultivars were more severely affected by the parasite with early sowing. Orobanche crenata development was also delayed in resistant cultivars. Crop yield, estimated by the number of pods per plant, decreased with late sowings. The combined use of resistant cultivars and early sowing is a useful tool as part of an integrated control strategy. Resistant cultivars allow early sowing (with low O. crenata attack), thus avoiding yield losses due to the short crop cycle with late sowing.     

Distribution of 14C-glyphosate in legumes parasitised by Orobanche crenata

Absorption and translocation of ¹⁴C-glyphosate was evaluated under controlled conditions in peas ( Pisum sativum L.) and broad beans ( Vicia faba L.) parasitised or not by crenate broomrape Orobanche crenata Forsk.). Absorption increased with time up to 12 days after treatment, and reached about 50% of the ¹⁴C-glyphosate applied. Three days after treatment 70–85% of the total herbicide absorbed had been translocated out of the treated leaflet. There was no consistent differ ence in absorption and translocation between infected and non-infected plants 12 days after treatment. The ¹⁴C-glyphosate concentration in the root system increased with time in broad beans. In peas it remained more or less constant from 3 days after treatment. Generally, pods were stronger sinks for glyphosate than other parts of the plant. Herbicide accumulation in broomrape increased with its growth stage, and the parasite was a much stronger sink for glyphosate than the legume root system.     

Uptake and translocation of imazethapyr in peas as affected by parasitism of Orobanche crenata and herbicide application methods

[¹⁴C]-Imazethapyr was applied as a seed treatment and at plant pre-emergence and post-emergence to peas ( Pisum sativum L.) parasitized by Orobanche crenata Forsk. Herbicide uptake increased with time regardless of the application method. Uptake reached about 98%, 89%, 81% and 94% of the total herbicide applied for the seed coating, seed soaking, pre-emergence and post-emergence treatments respectively. Herbicide translocation within the host plants consistently differed between O. crenata -infected and non-infected plants. High levels of ¹⁴C activity were accumulated by parasitic plants from the host. In non-infected pea plants, pods were stronger sinks for imazethapyr than the other parts of the plant, regardless of the application method. The herbicide distribution in the pea plant: O. crenata complex showed the same pattern regardless of the application methods. However, accumulation of radioactivity in the parasite was lower with pre-emergence and post-emergence application than with the seed treatments. In addition, radioactivity concentration in O. crenata plants was slightly higher when [¹⁴C]-imazethapyr was applied to pea seeds by coating than by soaking.     

Seed viability determination in parasitic broomrapes (Orobanche and Phelipanche) using fluorescein diacetate staining

Fluorescein diacetate (FDA) was investigated as a potential viability stain for seeds of holoparasitic broomrapes Orobanche and Phelipanche (Orobanchaceae), using four weedy and two non-weedy taxa. FDA viabilities were compared with the currently used 2,3,5-triphenyl tetrazolium chloride (TTC) test, and in vitro germination induced by the strigolactone analogue GR-24. Viable FDA-stained seeds were characterised by bright yellow–green fluorescence under 450–490 nm blue light. These viable seeds could be discriminated from non-viable seeds, in which low levels of fluorescence, similar to non-stained control seeds were observed. FDA viabilities were not significantly different from those obtained using the TTC stain; however, viability values for both stains were consistently higher than levels of artificially induced germination. Positive TTC-staining showed continuous variation that was difficult to interpret. Nevertheless, the TTC test does not involve grinding seeds, and therefore probably remains a practical alternative to FDA for screening soil samples contaminated with Orobanche and Phelipanche seeds, which indicates different applications for the two viability tests. Interestingly, the strigolactone analogue GR-24 only induced germination in O. crenata , P. ramosa and O. minor , suggesting a high specificity towards this germination inducer among the species investigated. We suggest that FDA-staining provides a potential alternative to the currently used TTC test for seed viability assays for Orobanche and Phelipanche , and other parasitic weeds which are an obstacle to crop cultivation.     

Gene expression profiling of Medicago truncatula roots in response to the parasitic plant Orobanche crenata

Orobanche crenata is a root parasitic weed that is a major constraint for grain and forage legume cultivation in Mediterranean and West Asia. Only moderate to low levels of incomplete resistance of complex inheritance has been identified so far in legume crops, which has hampered genetic and genomic analysis. In the present study, we provide a gene expression profile of roots of the model legume Medicago truncatula in response to infection by O. crenata . M. truncatula accessions SA27774 (complete resistance acting at early penetration stages) and SA4087 (incomplete late acting resistance mediated by necrosis of parasite tubercle) were inoculated with O. crenata seeds in a semi-sterile dish system. Roots were harvested at 15 (first contacts of the parasitism structures with the host roots), 21 (initial stage of parasite tubercle formation on SA4087) and 35 (prior necrosis of well-developed parasite tubercle of on SA4087) days post-inoculation. Array hybridisations revealed several hundred genes up-regulated in response to O. crenata infection. Gene expression patterns suggest that resistance mechanisms activated in both genotypes are temporally and spatially different and resemble those associated with plant resistance to microbial pathogens. Regulated genes identified here represent a comprehensive resource that can be used as a support to breeding strategies for resistance.     

旱作农业区全膜微垄沟播蚕豆留膜免耕穴播胡麻栽培技术研究

为探讨旱作农业区全膜微垄沟播蚕豆留膜免耕穴播胡麻种植技术的效应,于2014-2017年在甘肃省渭源县进行大田试验,设白膜全膜微垄沟播蚕豆留膜免耕穴播胡麻(T1)、黑膜全膜微垄沟播蚕豆留膜免耕穴播胡麻(T2)、白膜全膜双垄沟播蚕豆留膜免耕穴播胡麻(T3)、露地种植(T4) 4个处理,来研究蚕豆-胡麻轮作产量、土壤水热效应。结果表明,不同处理的蚕豆、胡麻增产顺序均为T1T2T3T4,0～25 cm土壤平均含水量为T1T2T3T4,0～25 cm平均地温为T1T3T2T4。T1蚕豆和胡麻降水利用率分别为19.9、16.9 kg·hm-2mm-1,分别较T2提高24.4%、15.0%,分别较T3提高55.5%、19.9%,分别较T4(CK)提高188.4%、156.1%; T1蚕豆、胡麻平均产量分别为2 454.5、1 875.6 kg·hm-2,蚕豆分别较T2、T3、T4(CK)增产23.8%、54.9%、186.2%,胡麻分别较T2、T3、T4(CK)增产14.9%、19.6%、154.3%。因此,白膜全膜微垄沟播蚕豆留膜免耕穴播胡麻种植技术是适合当地的蚕豆-胡麻轮作高效栽培技术。     

Mitigation of vanillic acid-promoted faba bean Fusarium wilt by faba bean–wheat intercropping

Long-term continuous monocropping of faba beans increases the incidence of faba bean wilt, while faba bean–wheat intercropping can effectively control it. This study aimed to understand the underlying mechanism of faba bean–wheat intercropping for the control of Fusarium oxysporum and vanillic acid (VA)-promoted occurrence of faba bean wilt. The occurrence of faba bean wilt was investigated among the monocropped and intercropped plants of faba beans in a field experiment. The contents and types of phenolic acids were examined in the rhizosphere soil. Monocropped and intercropped faba beans were examined under the dual stress of F. oxysporum and different concentrations of VA (0, 50, 100, 200 mg/L) to understand the alleviating mechanism of faba bean–wheat intercropping. Exogenous addition of high concentrations of VA significantly inhibited the growth and reproduction of F. oxysporum, but under the dual stress of F. oxysporum and different concentrations of VA, it significantly inhibited the defence enzymes of faba bean roots, stems, and leaves, and rhizosphere soil enzymes. Interestingly, faba bean–wheat intercropping alleviated VA stress and thereby the incidence and disease index of faba bean Fusarium wilt by improving plant resistance and soil enzyme activity. The dual stress of F. oxysporum and VA promotes the occurrence of Fusarium wilt by damaging the defence system of the faba bean root system and rhizosphere soil environment. However, faba bean–wheat intercropping effectively alleviates the autotoxicity of VA by improving the physiological and biochemical resistance of faba beans and soil enzyme activities, and thus controls the occurrence of Fusarium wilt.     

Detecting<Emphasis Type="Italic">Orobanche</Emphasis> species by using cpDNA diagnostic markers

Some species of the genusOrobanche are among the most devastating parasitic weeds, causing extensive damage in agricultural fields. Considering the difficult control due to seed longevity in the soil, small seed size, high fecundity and a subterranean phase that allows them to parasitize the host before they emerge and become evident, the development of diagnostic markers is highly recommended. In our study we identified potential molecular diagnostic markers from the plastid genome in order to distinguish among the most importantOrobanche species attacking crops in Andalusia, the southern region of the Iberian Peninsula. The study has consideredO. crenata, O ramosa andO. cumana causing serious losses in legumes, solanaceous crops and sunflower fields, respectively, andO. minor that, although abundant in Andalusia, has to our knowledge not yet been found parasitizing agricultural hosts. We amplified a non-coding region from the plastid genome, studied sequence differences among the amplified fragments and digested those of the same length with selected restriction enzymes. Here, we propose a molecular protocol to distinguish the main parasitic plants in crop fields of southern Spain. Different applications such as identification ofOrobanche seeds in soil or crop seed lots are discussed in order to offer right crop recommendations or to prevent new infestation of parasite-free fields. Recommendations for further development of these diagnostic markers are also considered. http://www.phytoparasitica.org posting Jan. 15, 2007.     

Degradation of chlorsulfuron and triasulfuron in alkaline soils under laboratory conditions

The degradation of chlorsulfuron and triasulfuron was investigated in alkaline soils (pH 7.1–9.4) spiked at 40 μg a.i. kg^–1 under laboratory conditions at 25 °C and a moisture content corresponding to 70% field capacity (–33 kPa), using high-performance liquid chromatography. Degradation data for the two herbicides did not follow first-order kinetics, and observed DT₅₀ values in surface soils ranged from 19 to 42 days and from 3 to 24 days for chlorsulfuron and triasulfuron respectively. Disappearance of both chlorsulfuron and triasulfuron was faster in non-sterile than in sterile soil, demonstrating the importance of microbes in the breakdown process. The persistence of chlorsulfuron increased with increasing depth, which can be attributed to the decline in the microbial populations down the profile. The DT₅₀ value for chlorsulfuron at 30–40 cm depth was nearly four times higher than that in the top-soil. The results obtained show that persistence of these herbicides in alkaline surface soils at 25 °C and at a moisture content of 70% field capacity is similar to those reported in other European and North American soils. The study shows that if these herbicides are contained in surface soil layers, the risk of residue carry-over under southern Australian conditions is small. However, the rate of their degradation in alkaline subsoils is very slow, and under conditions conducive to leaching their prolonged persistence in the soil profile is possible.     

Field and controlled conditions screenings of some faba bean (Vicia faba L.) genotypes for resistance to the parasitic plant Orobanche crenata Forsk. and investigation of involved resistance mechanisms

Journal of Plant Diseases and Protection - The parasitic weed Orobanche crenata is a serious constraint to legumes crops in Mediterranean area. In Morocco, heavy O. crenata infestation level was...     

Biological activity of dinitramine in soils

In pot studies with dinitramine the susceptibility of French bean (Pltaseolus vulgaris L.) seedlings to the herbicide was influenced by the depth of sowing the seed and the dose and depth of incorporation of the herbicide. Maximum phytotoxicity occurred when the seeds of French bean were sown into a zone in which dinitramine had been incorporated. Where the seeds were separated from the herbicidetreated zone by a layer of untreated soil, the susceptibility of the French bean seedlings increased with increasing depth of sowing. The greater the distance between the point of contact with the herbicide and the soil surface the greater was the injury. Dinitramine is active in the vapour phase, and volatilization and bioactivity were directly related to concentration and inversely related to depth of incorporation and of placement in the soil.     

Effects of soil moisture and sowing depth on the development of bean plants grown in sterile soil infested by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> and <Emphasis Type="Italic">Trichoderma harzianum</Emphasis>

The effects of soil moisture (varying from 15% to 42% (v/v)) and sowing depth (1.5–6.0 cm) on the development of bean plants grown in sterile soil infested by the pathogen Rhizoctonia solani and its antagonist Trichoderma harzianum were studied under greenhouse conditions. The four possible combinations of soil infestation with both fungi were tested. Disease severity, percentage of plants emerged, plant height and dry weight were evaluated 3 weeks after sowing. Emergence rate and growth of plants inoculated only with R. solani were not affected by soil moisture, but in the presence of both fungi, plant emergence, plant height and dry weight significantly decreased when soil moisture diminished. Deep sowing significantly reduced the emergence rate and growth of those plants that were inoculated with R. solani only. However, when the soil was infested with both fungi, the effect of sowing depth was not significant. At a sowing depth of 6.0 cm, the percentage of plants emerged was 50% in the presence of T. harzianum, but only 6.7% when the pathogen was inoculated alone. The antagonist protected bean seedlings from pre-emergence damping-off, reduced disease severity and increased plant growth in the presence of R. solani, especially in moist soil.     

Biology and management of Phalaris minor in wheat under a rice/wheat system

Summary Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 °C . Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38–60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2–5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively.     

土壤湿度对蚕豆根病及其生长的影响

 土壤湿度是影响蚕豆(Vicia faba L.)生长和根腐病发生的主要环境因素之一。本文以来源于蚕豆产区的田间土壤,分别以30%、50%和70%的土壤饱和持水量(WHC)处理进行盆栽试验,在室外自然条件下生长,测定了出苗率、出苗速度、株高、生长速度、叶面积、总叶绿素含量、净光合速率、结荚数、根瘤数、生物量干重、根腐病严重度及死亡率。结果表明50% WHC的土壤含水量为蚕豆生长的最佳土壤湿度,有利于蚕豆健康生长,减少根腐病的发生与危害。在30%、50%和70%WHC土壤湿度条件下,播后10周蚕豆生物量干重和植株的死亡率依次分别为1.53、3.16、2.68g和18.5%、4.8%、25.6%。     

Orobanche aegyptiaca control in tomato fields with sulfonylurea herbicides

Field experiments were conducted from 1994 to 1997 at two locations to study the effectiveness of chlorsulfuron and triasulfuron applied through different irrigation methods (chemigation) for control of Orobanche aegyptiaca Pers. in tomato ( Lycopersicon esculentum Mill). Three split applications of chlorsulfuron at 2.5 g a.i. ha⁻¹ and of triasulfuron at 7.5 g a.i. ha⁻¹, through conventional sprinkler irrigation systems, 10–14 days apart followed immediately by sprinkling with water, controlled O. aegyptiaca by about 90% and 80% and increased crop yield 25–47% and 30%, respectively, without any crop injury symptoms. Repeated applications of the same herbicides at half rates resulted in slightly higher O. aegyptiaca control and crop yield than only one herbicide application at double rate. Chemigation by the sprinkler systems (microsprinklers, 60 m³ ha⁻¹) slightly increased the herbicide efficiency as compared with the high volume spray (800 m³ ha⁻¹). O. aegyptiaca control from sulfonylureas applied by drip chemigation was poor, as this probably requires very accurate timing and the herbicide distribution in the soil was not uniform.     

Possible involvement of gibberellins and ethylene in Orobanche ramosa germination

Summary Six inhibitors acting at different stages of gibberellin biosynthesis, applied during conditioning of Orobanche ramosa seeds, reduced subsequent germination in the presence of GR₂₄ (a strigol analogue). Ethylene seems to be involved in the induction of germination of conditioned seeds by GR₂₄, as inhibitors of its synthesis or action, applied to conditioned seeds, also strongly reduced induction of germination by GR₂₄. Exogenous ethylene did not induce germination of conditioned seeds, but 2-chloroethylphosphonic acid was able to do so. When inhibitors of gibberellin biosynthesis were applied to conditioned seeds in the presence of GR₂₄, they inhibited germination. These same inhibitors also strongly inhibited germination of conditioned Striga hermonthica seeds in response to GR₂₄; this inhibitory effect was reversed by the addition of 2-chloroethylphosphonic acid. The effect of these inhibitors on S. hermonthica , in which ethylene is a necessary mediator of germination induction by GR₂₄, strongly suggests that ethylene synthesis is also required for the induction of O. ramosa seed germination by GR₂₄. These growth regulators, which inhibit the two steps of germination in O. ramosa , could be useful for the development of methods for early season control of this parasite.     

Distribution and incidence of faba bean necrotic yellows virus in Jordan

Faba bean necrotic yellows virus (FBNYV) was isolated from naturally infected faba bean plants in Jordan. The identification was based on host range, mode of transmission, symptomatology and serological properties. FBNYV occurred naturally in several leguminous crops including cultivated legumes and wild forage legumes, such as species of Medicago , Trifolium and Lathyrus . and infected other plant species belonging to the Malvaceae, such as Malva parviflora and Hibiscus esculentus . Such hosts may act as important natural reservoirs for both the virus and its aphid vectors. This is the first report of infection of M. parviflora and H. esculentus with FBNYV. The virus was not recovered from samples taken from some cultivated crops, including squash, cucumber, tomato, eggplant and pepper, growing near to faba bean fields. Also, it was not detected in commercial faba bean seeds collected from local companies or in seeds collected from infected faba bean plants. It was transmitted efficiently by Aphis craccivora . Serological testing of 1392 samples from faba beans showing virus-like symptoms and collected randomly from 16 locations (fields) in the Jordan Valley and Jarash areas showed that FBNYV occurred in 54.5% of the samples. These results indicate that FBNYV was an important pathogen of beans during the growing season of 1996 in Jordan.     

Successive legumes tested in a greenhouse crop rotation experiment modify the inoculum potential of soils naturally infested by Aphanomyces euteiches

The consequence of 10 successive monocultural cycles involving different legume species/cultivars on the inoculum potential (IP) of soils naturally infested by Aphanomyces euteiches was investigated under greenhouse conditions. The results showed that the IP of a soil naturally infested by A. euteiches can be significantly modified not only by the non‐host or host status of crop species but also by the level of resistance of the cultivar. Susceptible species/cultivars (pea, lentil and susceptible cultivars of vetch and faba bean) are very favourable to pathogen multiplication, and continuous cultivation of each of these increased the IP values of a soil with a moderate initial IP (from 1·9 to 3·5 after 10 cycles). Conversely, non‐host species and resistant cultivars of vetch or faba bean contributed to reducing the IP values of soils irrespective of the initial IP (from 1·9 to 0·5 and from 4 to 2, respectively, after 10 cycles). Aphanomyces root rot severity values on the resistant legume species/cultivars were not affected by the successive cultural cycles. This study, which showed that the IP of A. euteiches in soil can be reduced by planting appropriate legume species and cultivars in greenhouse conditions, will be useful for defining better crop successions for legumes.