Incidence of cabbage maggot (Diptera: Anthomyiidae) infestation and plant damage in seeded Brassica fields in California's central coast

The temporal incidence of cabbage maggot, Delia radicum L. was investigated using three exclusion cage experiments, one each during spring, summer and fall, in broccoli fields as well as two surveys, one each in three broccoli fields, and sixteen turnip plantings in central coast of California. In the cage experiments, sets of broccoli plants were exposed to natural populations of D. radicum flies for ∼14-d periods after plant emergence throughout the growing season. For the surveys, soil, root samples, and yellow sticky traps were collected every week from broccoli fields to determine number of eggs, maggots, feeding-injury and adults. Only roots were sampled from turnip plantings to determine feeding-injury. In all three cage experiments, feeding injury from D. radicum maggot was less during the first 14-d than ∼15–28 d after plant emergence (DAE). In the summer and fall, feeding injury by D. radicum was less during 29–42 and 43–56 DAE than it was 15–28 DAE. In the survey of broccoli fields, a greater number of D. radicum eggs were detected starting the fourth week after planting (WAP). Similarly, an increase in number of D. radicum maggots and feeding injury was observed at fifth and sixth WAP, respectively. However, adults were abundant throughout the growing period. In the turnip survey, increase in injury from D. radicum feeding did not appear until the fifth WAP. Overall, these studies indicate that increased incidence of D. radicum was delayed by about two to three weeks after plant emergence. The implications of these results for timing of insecticide application for D. radicum in the central coast of California are discussed.     

Uptake and Translocation of Copper in Brassicaceae

Abstract

Ten cvs. of four Brassicaceae species were tested to evaluate their copper (Cu) uptake and translocation. Germination and root length tests indicated that Brassica juncea cv. Aurea and Raphanus sativus cvs. Rimbo and Saxa were the species with the highest germinability and longest roots at Cu concentrations ranging from 25 up to 200 µM. Raphanus sativus cv. Rimbo grown in hydroponic culture at increasing Cu concentrations (from 0.12 up to 40 µM) for 10 days produced a relatively high biomass (17.2 mg plant^?1) at the highest concentration and had a more efficient Cu translocation (17.8%) in comparison with cvs. Aurea and Saxa. The potential of cv. Rimbo for Cu uptake was then followed for 28 days at 5, 10, and 15 µM Cu. In comparison with the control, after 28 days of growth the 15 µM Cu‐treated plants showed a reduction in the tolerance index (?40%) and in the above‐ground dry biomass (?19%). On the contrary, an increase in the below‐ground dry weight was observed (+35%). Copper accumulated during the growth period both in the below‐ and above‐ground parts (about 14 and 4 µg plant^?1 at 10 and 15 µM Cu, respectively), but the translocation decreased from 50 to 30% in the last week at all the concentrations used. In addition, cv. Rimbo grown in a multiple element [cadmium (Cd), chromium (Cr), Cu, lead (Pb), and zinc (Zn)] naturally‐contaminated site accumulated all elements in the above‐ground part in a range from 5 to 62 µg plant^?1.     

Inheritance of C3―C4 Intermediate Photosynthesis in Reciprocal Hybrids Between Moricandia Arvensis (C3―C4) and Brassica Oleracea (C3) That Differ in Their Genome Constitution

Abstract

To Elucidate The Genetic Mechanisms Underlying C₃―C₄ intermediate Photosynthesis, We investigated The Structural and Photosynthetic Characteristics of Leaves of Reciprocal Hybrids Between The C₃―C₄ intermediate Species Moricandia Arvensis (L.) Dc. (Mama) and The C₃ Species Brassica Oleracea L. (Cabbage; Cc), Which Differ in Genome Constitution. Moricandia Arvensis Bundle Sheath (Bs) Cells included Many Centripetally Located Chloroplasts and Mitochondria, Whereas Those of Cabbage Had Few Organelles. Hybrid Leaves Were Structurally intermediate Between Those of The Parents and Showed Stronger intermediate C₃―C₄ Features As The Proportion of The Ma Genome increased. The P-Protein of Glycine Decarboxylase (Gdc) Was Confined Mainly To Bs Mitochondria in M. Arvensis, But Accumulated More in The Mesophyll (M) of Cabbage. in The Hybrids, The Accumulation of Gdc in Bs Cells increased With An increasing Ma:C Ratio. Hybrids Exhibited Gradients in Structural and Biochemical Features, Even in Reciprocal Crosses. The Co₂ Compensation Point of Reciprocal Hybrids With High Ma:C Ratios Was Lower Than That of Cabbage But Higher Than That of M. Arvensis. Thus, The Structural and Biochemical Features in Hybrid Leaves Reduced Photorespiration. Moricandia Arvensis Had A Higher Photosynthetic Rate Than Cabbage, But The Photosynthetic Rates of Hybrids Were intermediate Between Those of The Parents Or Comparable To That of M. Arvensis. Our Results Demonstrate That The C₃―C₄ intermediate Characteristics Are inherited Based On The Ratio of The Parent Genomes, and That There Is No Evidence of Cytoplasmic inheritance in These Characteristics.     

What can we learn from clubroots: alterations in host roots and hormone homeostasis caused by <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

The clubroot disease of cruciferous crops is caused by an obligate biotrophic protist, Plasmodiophora brassicae. The disease is characterized by the development of large root galls accompanied by changes in source-sink relations and the hormonal balance within the plant. Since the disease is difficult to control, it is of high economic interest to understand the events leading to gall formation. In this review we will give an overview on the current knowledge of changes brought about in the host root by this obligate biotrophic pathogen. Emphasis will be on the regulation of changes in plant hormone homeostasis, mainly auxins and cytokinins; the possible role of secondary metabolites, especially indole glucosinolates, in gall formation and auxin homeostasis will be discussed. Also, results from mutant analysis and microarrays using the model plant Arabidopsis thaliana are presented.     

Suppression of the clubroot pathogen Plasmodiophora brassicae by plant growth promoting formulations in roots of two Brassica species

In this study, the ability of two organic plant growth stimulants, mainly based on algal extracts, amino acids and phosphonate, to reduce clubroot formation in the model plant Arabidopsis thaliana and two economically important Brassica species, Brassia rapa (Chinese cabbage) and Brassica napus (oilseed rape) was investigated. A commercial liquid (Frutogard^®) and a granulate (PlasmaSoil^®) formulation were used to find optimum conditions for both control of the pathogen and plant growth. Both formulations were able to significantly reduce gall formation after Plasmodiophora brassicae infection on Chinese cabbage, but PlasmaSoil^® gave better effects, possibly as a result of the continuous supply of the components to the soil. Individual components did not have the same effect. Clubroots on oilseed rape could also be reduced. In contrast, club formation was not reduced in the model plant Arabidopsis thaliana. This points to interesting differences in the induction of resistance in the different species. Cross‐sections of infected and treated roots stained for different macromolecules (callose, lignin, suberin) indicated differences in anatomy as a result of the two formulations. The results indicate an application for the granulate formulation PlasmaSoil^® in clubroot control.     

十字花科植物PIN3基因调控元件及表达分析

为探明十字花科不同物种PIN3基因的表达调控差异,从拟南芥(Arabidopsis thaliala)、红花荠菜(Capsella rubella)、白菜(Brassica rapa)、油菜(Brassica napus)和甘蓝(Brassica oleracea)等17个已完成基因组测序的十字花科物种基因组数据库中鉴定出18个PIN3同源基因。对这18个同源基因编码序列上游1 500bp启动子区域顺式作用元件进行预测及比对分析,结果发现,光响应、多种激素响应及胁迫响应等相关元件呈现出较大差异,其中生长素以及向地性响应相关元件具有较高的保守性。克隆普通荠菜PIN3同源基因(CbPIN3)并构建普通荠菜PIN3基因启动子的GUS报告系统CbPIN3pro::GUS转化拟南芥。与拟南芥基因表达数据库比较,荠菜启动子表达与拟南芥PIN3具有基本一致的组织表达模式,但也存在一定的组织差异,说明植株形态建成中生长素极性转运调控的差异。拟南芥和荠菜PIN3的表达差异是十字花科物种适应性进化模式的缩影。     

8种十字花科短命植物的物候及其对荒漠环境的适应

对8种广泛分布于新疆北部荒漠的十字花科早春短命植物物候特征及其对荒漠环境的适应进行了观测与分析。结果表明，8种植物的种子均在3月中、下旬萌发，5月下旬至6月上旬果实成熟，生活周期均在54～79d，其营养生长期约占整个生活周期的1／3，而生殖生长期约占2／3。植株的生长发育与温度及降水存在密切的联系，说明8种植物均属于典型的避旱型早春短命植物，其短的生活周期是逃避准噶尔荒漠夏季干热气候的一种适应对策。     

Sulfur-associated polioencephalomalacia in cattle grazing plants in the Family Brassicaceae

Polioencephalomalacia was diagnosed histologically in cattle from two herds on the Darling Downs, Queensland, during July–August 2007. In the first incident, 8 of 20 18-month-old Aberdeen Angus steers died while grazing pastures comprising 60% Sisymbrium irio (London rocket) and 40% Capsella bursapastoris (shepherd's purse). In the second incident, 2 of 150 mixed-breed adult cattle died, and another was successfully treated with thiamine, while grazing a pasture comprising almost 100% Raphanus raphanistrum (wild radish). Affected cattle were either found dead or comatose or were seen apparently blind and head-pressing in some cases. For both incidents, plant and water assays were used to calculate the total dietary sulfur content in dry matter as 0.62% and 1.01% respectively, both exceeding the recommended 0.5% for cattle eating more than 40% forage. Blood and tissue assays for lead were negative in both cases. No access to thiaminase, concentrated sodium ion or extrinsic hydrogen sulfide sources were identified in either incident. Below-median late summer and autumn rainfall followed by above-median unseasonal winter rainfall promoted weed growth at the expense of wholesome pasture species before these incidents.     

Sexual hybridization between Capsella bursa‐pastoris (L.) Medik (♀) and Camelina sativa (L.) Crantz (♂) (Brassicaceae)

The development of transgenic oilseed Camelina sativa (2n = 40) and the potential for hybridization with its weedy relative Capsella bursa‐pastoris (2n = 36) necessitates a careful evaluation of the reproductive compatibility between the species. Here, we conducted over 1800 crosses (emasculation and manual pollination) to examine the ability of 10 Canadian C. bursa‐pastoris (♀) accessions to hybridize with five accessions of C. sativa (♂). Seven hybrids were confirmed among 586 putative hybrids screened with species‐specific markers, indicating a hybridization rate of 1.5 hybrids per 10 000 ovules pollinated. All seven hybrids had intermediate DNA content compared to their parents, were morphologically distinct, had low (1.9%) pollen fertility and failed to produce selfed or backcrossed seed. Given the abundance of C. bursa‐pastoris along field margins, hybrids will likely be generated in the wild, but they will be unable to establish lineages unless fertility is restored. The large number of crosses and the diversity captured by the use of multiple accessions resulted in strong statistical power and a high degree of confidence in the estimated hybridization rate.     

Lignin is involved in the reduction of Verticillium dahliae var. longisporum inoculum in soil by crop residue incorporation

Verticillium wilt is an increasing problem in European cauliflower production. In this study, several crop residues were screened for their ability to reduce the viability of microsclerotia when incorporated into soil. In addition, the role of fungitoxic volatiles and lignin in the crop residue-mediated reduction in microsclerotia viability was studied.Broccoli (Brassica oleracea var. italica), cauliflower (B. oleracea var. botrytis), Indian mustard (Brassica juncea), ryegrass (Lolium perenne) and corn (Zea mays) were incorporated in naturally infested soil samples collected from two cauliflower fields in Belgium, labelled Is1 and S3. The effectiveness in reducing the viability of microsclerotia depended on the soil sample and on the type of residue. In the Is1 soil, broccoli, cauliflower and ryegrass incorporation significantly reduced the inoculum level by more than 90%, while Indian mustard significantly reduced numbers of viable microsclerotia by 50%. In the S3 soil, broccoli, cauliflower and Indian mustard were not effective, whereas ryegrass and corn incorporation reduced the microsclerotia level by 50% or more. In conclusion, incorporation of ryegrass and corn was more effective than incorporation of crucifer residues.In the conditions tested, fungicidal volatile compounds did not play an important role in Verticillium microsclerotia reduction in soil. Volatiles from broccoli and cauliflower did not affect microsclerotia viability in an in vitro bioassay, whereas the volatiles from Indian mustard killed the microsclerotia. Indian mustard incorporation in soil, however, only had a minor effect on microsclerotia viability.In the S3 soil, 1% (w/w) Kraft pine lignin, a waste product of the paper industry, had to be added to observe a significant reduction on the viability of microsclerotia, whereas in the Is1 soil, a significant effect was observed when 0.1% (w/w) Kraft pine lignin was added. Acid-insoluble lignin was extracted from all crop residues previously tested. Crop residues with high lignin content seemed to be more effective than crop residues with low lignin content. The reduction of Verticillium microsclerotia viability depended on lignin type and on crop structure, since lignin extracted from cauliflower leaves was more effective than lignin extracted from cauliflower stems and corn leaves were more effective than corn roots. Microsclerotia reduction was higher after fresh residue incorporation than after incorporation of their extracted acid-insoluble lignin, indicating that the effect of crop residue incorporation on microsclerotia viability cannot be explained solely by the effects of lignin.Incorporation of lignin-rich substrates in soil may open up new perspectives for integrated control of Verticillium.