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.     

Cucumber mosaic virus infection of chickpea stands: temporal and spatial patterns of spread and yield‐limiting potential

Patterns of spread and yield losses were examined when migrant aphid vectors transmitted Cucumber mosaic virus (CMV) within chickpea (Cicer arietinum) plots. When numbers of chickpea plant infection foci were varied to provide initial infection incidences of 0·3–2%, rate of virus spread and its final incidence increased in proportion to initial virus incidence and pathogen progress curves reflected a polycyclic pattern of spread. Chickpea seed yields decreased by 44–45% when CMV incidence reached 61–74% at final assessment in plots with simulated 1–2% initial incidence. In chickpea plots with or without introduced lupin plant infection foci, cumulative spatial data for diseased plants were assessed using spatial analysis by distance indices (sadie ). When CMV spread within a plot, infection was concentrated in large patch clusters and was consistent with comprehensive localized spread around primary infection foci. When introduced infection foci were absent, there was more diffuse spread with many isolated clusters. In individual plants that developed CMV symptoms at different growth stages, shoot and pod dry weight were reduced by 60–65% and 77–79% (early infection) and 44 and 66% (late infection), respectively. Seed yield losses were 78–80% (early) and 65–67% (late), and reduction in 50‐seed weight was 20–25% regardless of time of infection, so seed number was reduced more by early than late infection. Infection also reduced seed quality as, in addition to smaller seed size, seed coats were discoloured and malformed: the proportions of malformed seeds were 9–11% (early), 3–6% (late) and 0·5% (healthy).     

Real‐time quantitative PCR assays for the rapid detection and quantification of Fusarium oxysporum f. sp. phaseoli in Phaseolus vulgaris (common bean) seeds

Fusarium oxysporum f. sp. phaseoli (Fop) is a devastating pathogen that can cause significant economic losses and can be introduced into fields through infested Phaseolus vulgaris (common bean) seeds. Efficient seed health testing methods can aid in preventing long‐distance dissemination of this pathogen by contaminated seeds. In order to improve detection of Fop in seed, a rapid, accurate and sensitive real‐time PCR assay (qPCR) protocol was developed for detection of Fop in common bean seeds. Seed lots of seven cultivars with infection incidence ranging from 0·25 to 20% were prepared by mixing known amounts of Fop‐infected seeds with Fop‐free seeds. Direct comparisons between SYBR Green and TaqMan qPCR methods were performed using primers based on the Fop virulence factor ftf1. The primers developed in this study produced a 63 bp product for highly virulent strains of Fop but did not produce an amplicon for nonpathogenic or weakly pathogenic isolates of F. oxysporum from P. vulgaris or other hosts. Under optimized conditions, both qPCR assays detected Fop infection at low levels (0·25%); however, the results suggest the TaqMan assay was more reliable at quantification than the SYBR Green assay. Linear regression models were fitted to the relationships between results of qPCR assays and infection incidence, but the models differed among cultivars. Fungal biomass per seed differed among cultivars and was related to seed size. The results indicate that the TaqMan assay developed in this study is a useful tool for the detection and quantification of Fop in bean seeds.     

不同耕作方式对北疆夏大豆荚粒空间分布及产量的影响

采用大区试验设计,研究滴灌条件下翻耕覆膜(TP)、翻耕(T)、旋耕(RT)、免耕(NT)四种耕作方式对北疆复播大豆的农艺性状、单株荚数、粒数的空间垂直分布、每荚粒数及产量的影响。结果表明,夏大豆的主要农艺性状基本表现为土壤实施耕作处理均优于免耕,其中以翻耕覆膜的效果最好,翻耕次之;单株荚数和粒数的空间垂直分布因耕作方式而异,翻耕覆膜、翻耕、旋耕的主要分布于主茎的中层和上层,免耕的主要分布于主茎中层和下层;不同荚粒的数量均与单株产量呈正相关,其中2粒荚和3粒荚的数量是构成不同耕作方式单株产量的主体,相关系数分别为r=0.99**和r=0.98**;各类荚的数量均以翻耕覆膜的最多,使得其单株荚数和单株粒数的数量均最多,与其它各处理均达极显著差异水平(P0.01),其产量分别比翻耕、旋耕、免耕的增产7.43%、10.85%和16.05%。     

Evaluation of oilseed rape seed yield losses caused by <Emphasis Type="Italic">Leptosphaeria biglobosa</Emphasis> in central China

Phoma stem canker of oilseed rape (Brassica napus), caused by Leptosphaeria maculans/L. biglobosa is a globally important disease. Severe phoma stem canker symptoms have been observed on winter oilseed rape in China but the seed yield loss caused by this disease remains unknown. In May 2012 and May 2013, 17 and 13 crops were surveyed, respectively, in seven counties of Hubei Province, central China. Stems with phoma stem canker disease symptoms were sampled for pathogen isolation and identification. Only L. biglobosa was identified by culture morphology and species-specific PCR; no L. maculans was found. To evaluate the yield losses, yield components (number of branches per plant, number of pods per plant, 1000-seed weight, number of seeds per pod) were assessed on healthy and diseased plants sampled from crops in four counties and on plants from inoculated pot experiments (plants of three cultivars were inoculated at the green bud stage by injecting L. biglobosa conidia into the stem between the first and second leaf scars). Results of the field surveys showed that diseased plants had 14–61% less branches and 32–83% less pods than healthy plants, respectively. The estimated seed yield loss varied from 10% to 21% and from 13% to 37% in 2012 and 2013, respectively. In the pot experiments, there were no differences in numbers of branches or pods but there were differences in number of seeds per pod between inoculated and control plants. For the three cultivars tested, the inoculated plants had yield losses of 29–56% compared with the control. This study indicates that L. biglobosa could cause substantial seed yield loss in China.     

Prediction of yield loss caused by Orobanche spp. in carrot and pea crops based on the soil seedbank

Root parasites of the genus Orobanche cause serious losses in many subtropical crops. Direct control options are very limited and crop yield loss can reach 100%. Prediction of potential damage in a crop before sowing or planting would support farmers in their choice of crop. This paper discusses the relationship between the number of Orobanche spp. seeds in the field and yield loss in peas (Pisum sativum L.) and carrots (Daucus carota L.) in Israel. Yield loss due to Orobanche crenata Forsk. in peas was 100% at high infestations, whereas in carrots when O. crenata and O. aegyptiaca were present it stabilized at about 50% for moderate infestations of 200 seeds per kg of soil. Statistical analyses related the yield loss from parasitism in peas and carrots to the numbers of Orobanche seeds remaining in the soil. A rectangular hyperbolic model, previously applied to competition data, fitted the data well. Confidence intervals for per cent yield loss were calculated using the bootstrap method. The practical applications of these models in predicting yield loss are discussed.     

The influence of formulation on Trichoderma biological activity and frosty pod rot management in Theobroma cacao

Frosty pod rot (FPR), caused by Moniliophthora roreri, is responsible for significant losses in Theobroma cacao. Due to limited options for FPR management, biological control methods using Trichoderma are being studied. Combinations of three formulations and two Trichoderma isolates were studied between May 2009 and April 2011. The formulations were 0·3 mL L^?1 of the surfactant BreakThru 100SL (BT), a mixture of 1% w/v Sure‐Jell (source of pectin) and 1% w/v potato dextrose broth (PDB) (PP), and an invert oil emulsion of 50% v/v corn oil/2·5% w/v lecithin/0·5% w/v PDB (COP). Water and fungicide, copper oxychloride, were included as controls. Humidity chamber studies indicated that Trichoderma conidia germinated in all formulations if free water was maintained, while only the COP formulation supported germination under drying conditions. In the field, Trichoderma ovalisporum DIS‐70a and Trichoderma harzianum DIS‐219f were applied monthly in each of the three formulations at a rate of 180 mL per tree, 2·46 × 10⁷ conidia per mL. The COP/DIS‐70a formulation provided the largest yield increase compared to all other treatments, including the fungicide control. Averaged over the 2 years, the COP formulation increased yield to 30·7% healthy pods compared to 9·7% healthy pods in the water control. Although the formulation/isolate combinations did not consistently increase endophytic colonization, the PP/DIS‐219f, COP/DIS‐219f and COP/DIS‐70a combinations increased total endophytic/epiphytic colonization by Trichoderma. The invert corn oil formulation of DIS‐70a significantly enhanced yield of healthy cacao pods over 2 years providing a promising model for optimizing Trichoderma‐based biocontrol strategies.     

Phenology and growth of Orobanche crenata Forsk (broomrape) in four legume crops

Studies were conducted in the field in 2 years comparing the phenology and growth of Orobanche crenata (Forsk) (crenate broomrape) in lentils (Lens esculenta L.) cv. Castellana, peas (Pisum sativum L.) cv. Orix, vetch (Vicia sativa L.) cv. comun and broadbean (Vicia faba L. cv. Alameda. First attachment of O. crenata to these crops took place 9–14 weeks after mid-November planting and earlier after later plantings, Differences in the first O. crenata attachment dates and in the duration of the underground growth period of O. crenata were much greater between years for any given crop than between crops in a given year: both attributes were apparently affected more by seasonal climatic conditions than by crop species, Furthermore, there was no consistent relationship found between crop growth stages and time after first attachment of the parante. This occurred in lentils and vetch while they were vegetative, in peas at late vegetative-early flowering stages, and at widely varying growth stages in broadbean, depending on planting dates and years. The maximum number of O. crenata plants successfully attached to each individual crop plant decreased in the order: peas > broadbean > lentil > vetch, with 21, 14, 10 and 8 per plant, respectively, averaged over the two seasons. Similarly, plant parasites: host dry weight ratio were 1.0, 0.7, 0.3 and 0.2 For each of these crops, respectively.     

Broomrape control in faba bean (Vicia faba L.) with glyphosate and imazaquin

Field studies were carried out to evaluate the efficacy of imazaquin and glyphosate in controlling broomrape (Orobanche crenata Forsk. and O. aegyptiaca Pers.) in faba bean (Vicia faba L.) in Northern Syria. Several rates and times of application of the herbicides were tested. Nearly complete control of broomrape was achieved with both the herbicides when they were sprayed twice (when the broomrape attachments to the faba bean roots were at tubercle stage of develoment and 15 days later) at a rate of application of 80 g a.i. ha^?1 for glyphosate and 10 g a.i. ha^?1 for imazaquin. However, the yield of faba bean did not increase with these treatments, suggesting that the herbicides at these rates were still causing some physiological disorder in the plant that counteracted the beneficial effect of broomrape control on the performance of faba bean plants.     

Ameliorative Effects of Brassinosteroids on Growth and Productivity of Snap Beans Grown Under High Temperature

The effect of brassinosteroids (BRs) was tested, in order to assess the possibility of alleviation of the adverse effects of high temperature stress on snap bean plants during delayed summer cultivation. Therefore, two field experiments were carried out in successive seasons, 2010 and 2011, with two bean cultivars ‘Paulesta’ and ‘Oxzira’, spraying with BRs of the following concentrations 0 (control), 25, 50 and 100 ppm. Plant growth, yield and pods quality of beans were studied. Spraying bean plants with BRs at a concentration of 25 and 50 ppm increased vegetative growth, total yield and quality of pods with no significant difference between both treatments. Using BRs at 25 ppm increased the total free amino acids (FAA) in leaves and total phenolic acids in the pod in comparison to control-treatment. ‘Oxzira’ cultivar resulted in the highest number of leaves, number of branches, dry weight of whole plant, total yield, total FAA in leaves and total phenolic acids in pod. Whereas, ‘Paulesta’ cultivar had the highest of plant length and total FAA in pods.     

4个PGPR菌株拌种对干旱条件下蚕豆生长及产量的影响

于播种前,以5×108 CFU/mL浓度的PGPR菌株B9601 Y2, FZB42, B2 和 B9拌种蚕豆,在全生育期土壤重度干旱条件下,与清水拌种相比,它们均能提早出苗,促进幼苗生长,增加植株地上和地下重量与荚果数,B9601 Y2,FZB42,B2和B9菌株分别增加蚕豆株荚数0.65个、0.50个、0.05个和0.33个,有效荚数0.68个、0.53个、0.08个、0.28个,果荚重4.56 g、3.36 g、2.13 g、0.36 g,株粒数1.18粒、1.55粒、0.80粒、0.15粒,百粒重5.28 g,5.75 g,3.72 g,2.50 g,豆粒产量14.49%,12.04%,6.28%,2.21%。     

Allelopathic effect of Pluchea lanceolata on growth and yield components of mustard (Brassica juncea) and its influence on selected soil properties†

Pluchea lanceolata (DC.) C.B. Clarke (Asteraceae) is a rapidly spreading perennial weed in semiarid areas of north‐west India. While preparing fields for cultivation, farmers incorporate Pluchea plant debris into the soil. In the present study, mustard grown in plots with soil‐incorporated Pluchea had significantly reduced shoot height (61 ± 8.8 cm), number of pods per plant (7 ± 3.2), number of seeds per pod (4.1 ± 3.9) and weight per seed (0.08 ± 0.03 g) of mustard compared to mustard growing in Pluchea‐free soils. Pluchea‐infested and Pluchea‐free soils were analyzed for pH, electrical conductivity, organic matter, soluble chloride, exchangeable phosphate, copper, zinc, sodium, potassium, magnesium, calcium and water‐soluble phenolics. Pluchea‐infested soils had different values for electrical conductivity, Cl, K and total phenolics when compared to Pluchea‐free soils. Data on yield reduction of mustard due to soil‐incorporated Pluchea leaves have been reported for the first time. The reduced mustard growth and yield is proposed to be partly due to water‐soluble phenolic compounds contributed by Pluchea leaves into soil.     

Efficacy of Different Control Methods Applied Separately and in Combination in Managing Root-knot Nematodes (Meloidogyne spp.) in Common Beans

Investigations on the efficacy of various methods of managing root-knot nematodes in microplots and under field conditions revealed that soil solarization, Furadan 5G and Tagetes erecta applied separately or in combination with other control methods, were the most effective in reducing the numbers of three root-knot nematodes, and root gall and egg mass indices. These management methods also resulted in significant increases (P0.05) in number of pods per plant, number of seeds per pod and 100-seed weight, and increased seed yield by up to 96.7 percent. Farmyard manure and Crotalaria ochroleuca were the least effective treatments. The use of T. erecta was the most economical root-knot nematode control method.     

Root rot pathogens in field soil,roots and seeds in relation to common bean (Phaseolus vulgaris), disease and seed production

The interrelationships among bean productivity, prevalence of pathogens in roots, seeds and soil, and root rot disease were described at the pod maturity stage in 13 commercial fields. The soil population and frequency of pathogens isolated from seeds varied by pathogen species and field location. Fusarium solani was the most prevalent fungus isolated from bean seeds and field soil compared to Rhizoctonia solani, Macrophomina phaseolina and F. oxysporum. Principal component analysis revealed that the first component explaining 32% of the total variance was correlated with the root rot index. PC1 was more strongly linked to root and seed infections in comparison with soil populations of pathogens. Based on a correlation between PC2 (accounting for 23% of the total variance) and the number of seeds per bean plant, charcoal, Fusarium and Rhizoctonia root rots were recognized as more important determinants of seed losses to root rot disease. There were correlations among the major pathogens infecting either roots or seeds of beans. These findings provide useful information for future experimental plans to optimize management strategies for bean root rots.     

Spatial characteristics of white mould epidemics and the development of sequential sampling plans in Australian bean fields

To improve sampling efficiency and precision in the assessment of white mould (caused by Sclerotinia sclerotiorum) disease incidence on bean (Phaseolus vulgaris), the spatial characteristics of epidemics were characterized in 54 linear transects in 18 bean fields during 2008–2010 in northern Tasmania, Australia. The incidence of diseased pods and plants was assessed prior to harvest. Distributional and correlation‐based analyses indicated the incidence of diseased pods was characterized by a largely random pattern at the individual plant scale, with some patches of similar disease levels on pods occurring at a scale of 1·5 m or greater. Collectively, these results suggested epidemics may be dominated by localized sources of inoculum. Sequential sampling approaches were developed to estimate or classify disease incidence above or below provisional thresholds of 3, 5 and 15% incidence on pods near harvest. Achieving prespecified levels of precision by sequential estimation was possible only when disease incidence on pods was greater than approximately 4% and sampling was relatively intense (i.e. 10 pods evaluated on each of at least 64 plants). Using sequential classification, correct decisions on disease status were made in at least 95% of independent validation datasets after assessment of only 10·1–15 plants, depending on classification threshold and error rates. Outcomes of this research provide the basis for implementing more efficient sampling and management strategies for this disease in Australian fields.     

Fenugreek root exudates show species-specific stimulation of Orobanche seed germination

Various Orobanche species are weedy and cause severe reduction in the yields of many important crops. The seeds of these parasitic weeds may remain dormant in the soil for many years until germination is stimulated by the release of a chemical signal from a host plant. In order to determine the effects of fenugreek root exudate on the induction of Orobanche crenata, Orobanche ramosa and Orobanche foetida seed germination, root exudate was collected from hydroponically grown fenugreek seedlings. Fractionation patterns obtained from column and thin layer chromatography of the fenugreek root exudate showed a set of metabolites differing in their polarity with stimulatory activity on Orobanche seed germination. The crude root exudate stimulated both O. ramosa and O. crenata seed germination to the same level caused by the synthetic germination stimulant GR24 at 10 mg L^?1. It also stimulated O. foetida seed germination which did not respond to GR24. Active fractions of root exudate stimulated the germination of Orobanche species differentially.     

Variation in resistance to Orobanche crenata in species of Cicer

Crenate broomrape (Orobanche crenata) is a major constraint for legume cultivation in Mediterranean agriculture. Field trials, pot and in vitro experiments demonstrated that resistance to O. crenata is present in chickpea and wild species of Cicer. The resistance is the result of the combination of several mechanisms, including low induction of parasite seed germination and in some accessions, either a darkening at the infection site on the host root that prevents establishment, or a reduced development of established parasite tubercles.     

Quantitative aspects of Orobanche crenata infestation in faba beans as affected by abiotic factors and parasite soil seedbank

The interactions between the root parasitic weed Orobanche crenata Forsk. and its host plant faba bean ( Vicia faba L.) were quantified under controlled and field conditions at ICARDA's Tel Hadya research station. In the field experiments conducted in 1993–94 and 1994–95 faba beans were sown on two dates, in plots with 0, 50, 200 and 600 O. crenata seeds kg^–1 soil, under both limited and sufficient moisture supply. The effects of temperature on the duration of the early developmental stages of O. crenata were investigated in a growth chamber. The extent of O. crenata infestation was closely related to the number of parasite seeds in the soil. The seed-density treatment with 600 seeds kg^–1 soil resulted in complete crop failure. Furthermore, O. crenata infestation was higher under sufficient than under limiting water supply conditions, irrespective of sowing date. Only in the moderately infested plots, did shifting of the planting time of faba bean result in a significant decrease in parasite dry weight and an increase in crop seed yield. The timing of germination, attachment and further developmental stages of O. crenata was not related to faba bean growth stage and was affected primarily by soil temperature. The duration of O. crenata developmental stages was estimated using the thermal time concept. The relationship between total number of parasite attachments at the harvest of the faba bean crop and O. crenata seed density was dependent on maximum faba bean root-length density measured by the start of pod-filling in each treatment combination of sowing date and moisture supply. The results are discussed with reference to implications for the development of a dynamic simulation model for the prediction of faba bean yield losses caused by O. crenata .     

Erodium cicutarium density and duration of interference effects on yield of wheat,oilseed rape,pea and dry bean

Field studies were conducted to determine the effect of various densities and duration of interference of Erodium cicutarium (L.) L'Her. ex Ait. on the yield of wheat, oilseed rape, pea and dry bean. The magnitude of yield reductions caused by E. cicutarium differed among the crops. Results indicate that the ranking of crop tolerance to E. cicutarium, when established at their recommended planting densities, was wheat > oilseed rape > pea ? dry bean. Maximum yield reduction occurred at E. cicutarium densities of 100–200 plants m^?2 and were 36% for wheat, 37% for oilseed rape, 82% for dry bean and 92% for pea. Crop yield progressively decreased as the duration of E. cicutarium interference increased. Three weeks of E. cicutarium interference after emergence was sufficient to reduce the yield of all crops, indicating the importance of controlling this weed early in the growing season. The mean yield reduction for each week of E. cicutarium interference was 1·6%, 2·7%, 3·6% and 6·3% for wheat, oilseed rape, pea and dry bean respectively. E. cicutarium is therefore a weed that warrants consideration for control in annual cropping systems.     

Fourth International Conference on Spices

Abstract

The present article suggests a simple procedure for estimating yield and production losses in a given crop and region. The utility of the procedure is illustrated by an empirical application to bean production in Cauca Valley, Colombia. Using data obtained from direct field observations on a panel of farms, a production function approach is used to estimate yield and production losses caused by each of the yield constraints identified. It is expected that such estimates will be useful for establishing agricultural research priorities. In an empirical analysis of bean production in Cauca Valley, six important yield limiting factors were identified. Unfavourable rainfall conditions caused a yield loss of about 32% and a total production loss of about US $1.2 million for the region during one growing season. The production losses caused by rust and bacterial blight were slightly smaller. Other important yield constraints were Empoasca kraemeri, angular leaf spot and the use of noncertified seed. Small production increases could be obtained by increasing input use and plant population.