Optimizing nutrient use efficiency, productivity, energetics, and economics of red cabbage following mineral fertilization and biopriming with compatible rhizosphere microbes.

Conventional agricultural practices and rising energy crisis create a question about the sustainability of the present-day food production system. Nutrient exhaustive crops can have a severe impact on native soil fertility by causing nutrient mining. In this backdrop, we conducted a comprehensive assessment of bio-priming intervention in red cabbage production considering nutrient uptake, the annual change in soil fertility, nutrient use efficiency, energy budgeting, and economic benefits for its sustainable intensification, among resource-poor farmers of Middle Gangetic Plains. The compatible microbial agents used in the study include Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis. Field assays (2016-2017 and 2017-2018) of the present study revealed supplementing 75% of recommended NPK fertilizer with dual inoculation of T. harzianum and P. fluorescens increased macronutrient uptake (N, P, and K), root length, heading percentage, head diameter, head weight, and the total weight of red cabbage along with a positive annual change in soil organic carbon. Maximum positive annual change in available N and available P was recorded under 75% RDF + P. fluorescens + B. subtilis and 75% RDF + T. harzianum + B. subtilis, respectively. Bio-primed plants were also higher in terms of growth and nutrient use efficiency (agronomic efficiency, physiological efficiency, apparent recovery efficiency, partial factor productivity). Energy output (26,370 and 26,630 MJ ha-1), energy balance (13,643 and 13,903 MJ ha-1), maximum gross return (US $ 16,030 and 13,877 ha-1), and net return (US $ 15,966 and 13,813 ha-1) were considerably higher in T. harzianum, and P. fluorescens treated plants. The results suggest the significance of the bio-priming approach under existing integrated nutrient management strategies and the role of dual inoculations in producing synergistic effects on plant growth and maintaining the soil, food, and energy nexus.

Doubled Haploid Broccoli (Brassica olearacea var. italica) Plants from Anther Culture.

Broccoli (Brassica olearecea var. italica) is a cole crop grown for its floral heads and stalks. It is rich in bioactive chemicals good for human health. Broccoli has been consumed as a vegetable since Roman times, but its production and consumption have increased significantly over the past few decades. Breeders try to develop new broccoli varieties with high yield, improved quality, and resistance to biotic and abiotic stresses. Almost all new broccoli varieties are F1 hybrids. Development of inbred broccoli lines that can be used as parents in hybrid production is a time-consuming and difficult process. Haploidization techniques can be utilized as a valuable support in broccoli breeding programs to speed up the production of genetically pure genotypes. Haploid plants of broccoli can be produced from immature male gametophytes via anther and microspore cultures with similar success rates. The most important parameters affecting the success of haploidization in broccoli are the genetic background (genotype) and the developmental stage of the microspores. Broccoli genotypes differ in their responses to androgenesis induction. The highest androgenesis response could be induced from microspores in late uninucleate and early binucleate stages. Recovery of diploid broccoli plants from haploids is possible via spontaneous and induced doubling. Doubled haploid (DH) broccoli lines are considered to be fully homozygous. Therefore, the production of DH lines is an alternative way to obtain pure inbred lines that can be utilized as parents in the development of new F1 hybrid varieties showing high levels of heterosis, high-quality heads, and uniform harvestable crop. We are using an anther culture-based haploid plant production system to develop DH broccoli lines in our broccoli breeding program. DH broccoli lines are produced from different genetic backgrounds within a year and handed to broccoli breeders.

Jasmonic acid-mediated enhanced regulation of oxidative, glyoxalase defense system and reduced chromium uptake contributes to alleviation of chromium (VI) toxicity in choysum (Brassica parachinensis L.).

The cultivation of leafy vegetables on metal contaminated soil embodies a serious threat to yield and quality. In the present study, the potential role of exogenous jasmonic acid (JA; 0, 5, 10, and 20 µM) on mitigating chromium toxicity (Cr; 0, 150, and 300 µM) was investigated in choysum (Brassica parachinensis L.). With exposure to increasing Cr stress levels, a dose-dependent decline in growth, photosynthesis, and physio-biochemical attributes of choysum plants was observed. An increase in Cr levels also resulted in oxidative stress closely associated with higher lipoxygenase activity (LOX), hydrogen peroxide (H2O2) generation, lipid peroxidation (MDA), and methylglyoxal (MG) levels. Exogenous application of JA alleviated the Cr-induced phytotoxic effects on photosynthetic pigments, gas exchange parameters, and restored growth of choysum plants. While exposed to Cr stress, JA supplementation induced plant defense system via enhanced regulation of antioxidant enzymes, ascorbate and glutathione pool, and the glyoxalase system enzymes. The coordinated regulation of antioxidant and glyoxalase systems expressively suppressed the oxidative and carbonyl stress at both Cr stress levels. More importantly, JA restored the mineral nutrient contents, restricted Cr uptake, and accumulation in roots and shoots of choysum plants when compared to the only Cr-stressed plants. Overall, the application of JA2 treatment (10 µM JA) was more effective and counteracted the detrimental effects of 150 µM Cr stress by restoring the growth and physio-biochemical attributes to the level of control plants, while partially mitigated the detrimental effects of 300 µM Cr stress. Hence, JA application might be considered as an effective approach for minimizing Cr uptake and its detrimental effects in choysum plants grown on contaminated soils.

Overexpression of Two CCCH-type Zinc-Finger Protein Genes Leads to Pollen Abortion in Brassica campestris ssp. chinensis.

The pollen grains produced by flowering plants are vital for sexual reproduction. Previous studies have shown that two CCCH-type zinc-finger protein genes in Brassica campestris, BcMF30a and BcMF30c, are involved in pollen development. Due to their possible functional redundancy, gain-of-function analysis is helpful to reveal their respective biological functions. Here, we found that the phenotypes of BcMF30a and BcMF30c overexpression transgenic plants driven by their native promoters were similar, suggesting their functional redundancy. The results showed that the vegetative growth was not affected in both transgenic plants, but male fertility was reduced. Further analysis found that the abortion of transgenic pollen was caused by the degradation of pollen contents from the late uninucleate microspore stage. Subcellular localization analysis demonstrated that BcMF30a and BcMF30c could localize in cytoplasmic foci. Combined with the studies of other CCCH-type genes, we speculated that the overexpression of these genes can induce the continuous assembly of abnormal cytoplasmic foci, thus resulting in defective plant growth and development, which, in this study, led to pollen abortion. Both the overexpression and knockout of BcMF30a and BcMF30c lead to abnormal pollen development, indicating that the appropriate expression levels of these two genes are critical for the maintenance of normal pollen development.

Jasmonic acid and methyl jasmonate modulate growth, photosynthetic activity and expression of photosystem II subunit genes in Brassica oleracea L.

The effects of jasmonic acid (JA) and methyl jasmonate (Me-JA) on photosynthetic efficiency and expression of some photosystem (PSII) related in different cultivars of Brassica oleracea L. (var. italica, capitata, and botrytis) were investigated. Plants raised from seeds subjected to a pre-sowing soaking treatment of varying concentrations of JA and Me-JA showed enhanced photosynthetic efficiency in terms of qP and chlorophyll fluorescence. Maximum quantum efficiency of PSII (Fv/Fm) was increased over that in the control seedlings. This enhancement was more pronounced in the Me-JA-treated seedlings compared to that in JA-treated ones. The expression of PSII genes was differentially regulated among the three varieties of B. oleracea. The gene PsbI up-upregulated in var. botrytis after treatment of JA and Me-JA, whereas PsbL up-regulated in capitata and botrytis after supplementation of JA. The gene PsbM showed many fold enhancements in these expressions in italica and botrytis after treatment with JA. However, the expression of the gene PsbM increased by both JA and Me-JA treatments. PsbTc(p) and PsbTc(n) were also found to be differentially expressed which revealed specificity with the variety chosen as well as JA or Me-JA treatments. The RuBP carboxylase activity remained unaffected by either JA or Me-JA supplementation in all three varieties of B. oleracea L. The data suggest that exogenous application of JA and Me-JA to seeds before germination could influence the assembly, stability, and repair of PS II in the three varieties of B. oleracea examined. Furthermore, this improvement in the PS II machinery enhanced the photosynthetic efficiency of the system and improved the photosynthetic productivity in terms of saccharides accumulation.

The role of selenium on mitigating arsenic accumulation, enhancing growth and antioxidant responses in metallicolous and non-metallicolous population of Isatis cappadocica Desv. and Brassica oleracea L.

A hydroponic experiment was conducted to explore the interactive effects of selenium (Se) supplementation (0, 5, and 10 µM) and arsenic (As) toxicity (0, 200, and 400 µM) on the growth, accumulation, and oxidative damage along with defense mechanisms of metallicolous (MP) and non-metallicolous population (NMP) of Isatis cappadocica, an As-hyperaccumulator, and Brassica oleracea as reference brassica. The results revealed that As stress significantly hampered plant growth particularly in B. oleracea. It reduced plant growth due to enhanced oxidative load of As-stressed plants. Between the two Isatis populations, metallicolous plants accumulated significantly higher As, however with considerably low growth defects. Furthermore, Se supplementation counteracted the adverse effects of stress on growth and physiological performance of all studied plants. Addition of Se, particularly at higher dose (10 µM), significantly suppressed root As uptake and slightly its accumulation in shoots of B. oleracea plants treated with 400 µM As, and thus improved growth characteristics of stressed plants. Under As stress, Se supplementation increased the activities of enzymatic (peroxidase (POD) and glutathione reductase (GR)) and non-enzymatic (anthocyanins and total flavonoids) antioxidants, thereby suggesting relieved As stress by reduced oxidative damage. Taken together, these results support the beneficial role of Se in the regulation of As stress by improving growth, physiology, and antioxidant capacity, and highlight its significance for plants grown on such metal-contaminated soils.

Electrical signal transmission in the plant-wide web.

Plants can communicate with other plants using wireless pathways in the plant-wide web. Some examples of these communication pathways are: (1) volatile organic compounds' emission and sensing; (2) mycorrhizal networks in the soil; (3) the plants' rhizosphere; (4) naturally grafting of roots of the same species; (5) electrostatic or electromagnetic interactions; and (6) acoustic communication. There is an additional pathway for electrical signal transmission between plants - electrical signal transmission between roots through the soil. To avoid the possibility of communication between plants using mechanisms (1)-(6), soils in pots with plants were connected by Ag/AgCl or platinum wires. Electrostimulation of Aloe vera, tomato, or cabbage plants induces electrotonic potentials transmission in the electro-stimulated plants as well as the plants located in different pots regardless if plants are the same or different types. The amplitude and sign of electrotonic potentials in electrostimulated and neighboring plants depend on the amplitude, rise, and fall of the applied voltage. Experimental results displayed cell-to-cell electrical coupling and the existence of electrical differentiators in plants. Electrostimulation by a sinusoidal wave induces an electrical response with a phase shift. Electrostimulation serves as an important tool for the evaluation of mechanisms of communication in the plant-wide web.

Microspore embryogenesis in Brassica: calcium signaling, epigenetic modification, and programmed cell death.

MAIN CONCLUSION: Stress induction followed by excessive calcium influx causes multiple changes in microspores resulting in chromatin remodeling, epigenetic modifications, and removal of unwanted gametophytic components via autophagy, switching microspores towards ME. In Brassica, isolated microspores that are placed under specific external stresses can switch their default developmental pathway towards an embryogenic state. Microspore embryogenesis is a unique system that speeds up breeding programs and, in the context of developmental biology, provides an excellent tool for embryogenesis to be investigated in greater detail. The last few years have provided ample evidence that has allowed Brassica researchers to markedly increase their understanding of the molecular and sub-cellular changes underlying this process. We review recent advances in this field, focusing mainly on the perception to inductive stresses, signal transduction, molecular and structural alterations, and the involvement of programmed cell death at the onset of embryogenic induction.

A quartet pollen phenotype identified in a population of Brassica interspecific hybrids shows incomplete penetrance and variable response to temperature.

Quartet pollen, where pollen grains remain attached to each other post-meiosis, is useful for tetrad analysis, crossover assessment and centromere mapping. We observed the quartet pollen phenotype for the first time in the agriculturally significant Brassica genus, in an experimental population of allohexaploid Brassica hybrids derived from the cross (Brassica napus × B. carinata) × B. juncea followed by two self-pollination generations. Quartet pollen production was assessed in 144 genotypes under glasshouse conditions, following which a set of 16 genotypes were selected to further investigate the effect of environment (warm: 25 °C and cold: 10 °C temperatures) on quartet pollen production in growth cabinets. Under glasshouse phenotyping conditions, only 92 out of 144 genotypes produced enough pollen to score: of these, 30 did not produce any observable quartet pollen, while 62 genotypes produced quartet pollen at varying frequencies. Quartet pollen production appeared quantitative and did not clearly fall into phenotypic or qualitative categories indicative of major gene expression. No consistent effect of temperature on quartet pollen production was identified, with some genotypes producing more and some producing less quartet pollen under different temperature treatments. The genetic heterogeneity and frequent pollen infertility of this population prevents strong conclusions being made. However, it is clear that the quartet phenotype in this Brassica population does not show complete penetrance and shows variable (likely genotype-specific) response to temperature stress. In future, identification of quartet phenotypes in Brassica would perhaps best be carried out via screening of diploid (e.g. B. rapa) TILLING populations.

Recessive male sterility in cabbage (Brassica oleracea var. capitata) caused by loss of function of BoCYP704B1 due to the insertion of a LTR-retrotransposon.

KEY MESSAGE: The LTR-retrotransposon insertion in BoCYP704B1 is proved to be the primary cause of the male sterility in cabbage. Effective allele-specific markers were developed for marker-assisted selection of male sterile gene. 83121A is a spontaneous male sterile mutant identified from cabbage. Genetic analysis indicated that male sterility is controlled by a single recessive gene. Pollen wall formation in the 83121A mutant was severely defective, with a lack of sporopollenin or exine. To understand the mechanisms of male sterility in 83121A, transcription analysis using RNA-Seq was carried out in the buds of the male sterile line 83121A and the male fertile line 83121B, which are near-isogenic lines differing only in the fertility trait. Via expression analysis of differentially expressed genes involved in pollen exine development before the bicellular pollen stage, BoCYP704B1 was identified as a candidate gene, which was approximately downregulated 30-fold in 83121A. BoCYP704B1 is a member of the evolutionarily conserved CYP704B family, which is essential for sporopollenin formation. The BoCYP704B1 transcript is specifically detected in the developing anthers of wild-type cabbage. Further sequence analysis revealed that a 5424-bp long terminal repeat-retrotransposon (LTR-RT) was inserted into the first exon of BoCYP704B1 in 83121A, which is not found in wild-type plants. The insertion of LTR-RT not only reduced the expression of BoCYP704B1 but also altered structure of protein encoded by BoCYP704B1. Moreover, linkage analysis showed that the homozygotic mutational BoCYP704B1 always cosegregated with male sterility. These data suggest that the LTR-RT insertion in BoCYP704B1 hinders sporopollenin formation in 83121A leading to male sterility. The allele-specific markers developed in this study were effective for marker-assisted selection of the male sterile gene.

Phytotoxic, antibacterial, and antioxidant activities of mycotoxins and other metabolites from Trichoderma sp.

A new natural mycotoxin was isolated from the fermentation broth of Trichoderma sp. Jing-8 and the structure was determined as alternariol 1'-hydroxy-9-methyl ether (1), together with twelve known compounds. The structures were elucidated on the basis of their 1D, 2D NMR spectra and mass spectrometric data. Compounds 1, 8 and 9 indicated inhibitions against germination of the seeds of cabbage with MICs < 3 µg/mL. The compound 1 showed the antibacterial activity against Bacillus subtilis and Staphylococcus aureus with MICs at 64 µg/mL. Compound 1 and 3 showed significant DPPH radical-scavenging activities with IC50 at 12 µg/mL, respectively. The OH at C-1' in compound 1 decreased the cytotoxicity of these mycotoxins. A primary structure-activity relationship about the alternariol derivatives was discussed. Compounds 2-7 and 8 were the first time to be isolated from the Trichoderma.

Knockdown of a cellulose synthase gene BoiCesA affects the leaf anatomy, cellulose content and salt tolerance in broccoli.

Cellulose is the major component of cell wall materials. A 300 bp specific fragment from the cDNA fragment was chosen to insert into vector pFGC1008 at forward and reverse orientations to construct the recombinant RNAi vector. Knockdown of BoiCesA caused "dwarf" phenotype with smaller leaves and a loss of the content of cellulose. Moreover, RT-PCR analysis confirmed that the expression of the RNAi apparatus could repress expression of the CesA gene. Meanwhile, examination of the leaves from the T3 of RNAi transformants indicated reduction of cell expansion in vascular bundles, particularly on their abaxial surface. The proline and soluble sugar content increased contrarily. Under the salt stress, the T3 of RNAi plants showed significant higher resistance. The expression levels of some salt tolerance related genes (BoiProH, BoiPIP2;2, BoiPIP2;3) were significantly changed in T3 of RNAi plants. The results showed that the hairpin structure of CesA specific fragment inhibited the endogenous gene expression and it was proved that the cDNA fragment was relevant to the cellulose biosynthesis. Moreover, modulation cellulose synthesis probably was an important influencing factor in polysaccharide metabolism and adaptations of plants to stresses. This will provide technological possibilities for the further study of modulation of the cellulose content of crops.

Segregation for fertility and meiotic stability in novel Brassica allohexaploids.

KEY MESSAGE: Allohexaploid Brassica populations reveal ongoing segregation for fertility, while genotype influences fertility and meiotic stability. Creation of a new Brassica allohexaploid species is of interest for the development of a crop type with increased heterosis and adaptability. At present, no naturally occurring, meiotically stable Brassica allohexaploid exists, with little data available on chromosome behaviour and meiotic control in allohexaploid germplasm. In this study, 100 plants from the cross B. carinata × B. rapa (A2 allohexaploid population) and 69 plants from the cross (B. napus × B. carinata) × B. juncea (H2 allohexaploid population) were assessed for fertility and meiotic behaviour. Estimated pollen viability, self-pollinated seed set, number of seeds on the main shoot, number of pods on the main shoot, seeds per ten pods and plant height were measured for both the A2 and H2 populations and for a set of reference control cultivars. The H2 population had high segregation for pollen viability and meiotic stability, while the A2 population was characterised by low pollen fertility and a high level of chromosome loss. Both populations were taller, but had lower average fertility trait values than the control cultivar samples. The study also characterises fertility and meiotic chromosome behaviour in genotypes and progeny sets in heterozygous allotetraploid Brassica derived lines, and indicates that genotypes of the parents and H1 hybrids are affecting chromosome pairing and fertility phenotypes in the H2 population. The identification and characterisation of factors influencing stability in novel allohexaploid Brassica populations will assist in the development of this as a new crop species for food and agricultural benefit.

Growing larger with domestication: a matter of physiology, morphology or allocation?

Domestication might affect plant size. We investigated whether herbaceous crops are larger than their wild progenitors, and the traits that influence size variation. We grew six crop plants and their wild progenitors under common garden conditions. We measured the aboveground biomass gain by individual plants during the vegetative stage. We then tested whether photosynthesis rate, biomass allocation to leaves, leaf size and specific leaf area (SLA) accounted for variations in whole-plant photosynthesis, and ultimately in aboveground biomass. Despite variations among crops, domestication generally increased the aboveground biomass (average effect +1.38, Cohen's d effect size). Domesticated plants invested less in leaves and more in stems than their wild progenitors. Photosynthesis rates remained similar after domestication. Variations in whole-plant C gains could not be explained by changes in leaf photosynthesis. Leaves were larger after domestication, which provided the main contribution to increases in leaf area per plant and plant-level C gain, and ultimately to larger aboveground biomass. In general, cultivated plants have become larger since domestication. In our six crops, this occurred despite lower investment in leaves, comparable leaf-level photosynthesis and similar biomass costs of leaf area (i.e. SLA) than their wild progenitors. Increased leaf size was the main driver of increases in aboveground size. Thus, we suggest that large seeds, which are also typical of crops, might produce individuals with larger organs (i.e. leaves) via cascading effects throughout ontogeny. Larger leaves would then scale into larger whole plants, which might partly explain the increases in size that accompanied domestication.

Difference in root K+ retention ability and reduced sensitivity of K+-permeable channels to reactive oxygen species confer differential salt tolerance in three Brassica species.

Brassica species are known to possess significant inter and intraspecies variability in salinity stress tolerance, but the cell-specific mechanisms conferring this difference remain elusive. In this work, the role and relative contribution of several key plasma membrane transporters to salinity stress tolerance were evaluated in three Brassica species (B. napus, B. juncea, and B. oleracea) using a range of electrophysiological assays. Initial root growth assay and viability staining revealed that B. napus was most tolerant amongst the three species, followed by B. juncea and B. oleracea At the mechanistic level, this difference was conferred by at least three complementary physiological mechanisms: (i) higher Na(+) extrusion ability from roots resulting from increased expression and activity of plasma membrane SOS1-like Na(+)/H(+) exchangers; (ii) better root K(+) retention ability resulting from stress-inducible activation of H(+)-ATPase and ability to maintain more negative membrane potential under saline conditions; and (iii) reduced sensitivity of B. napus root K(+)-permeable channels to reactive oxygen species (ROS). The last two mechanisms played the dominant role and conferred most of the differential salt sensitivity between species. Brassica napus plants were also more efficient in preventing the stress-induced increase in GORK transcript levels and up-regulation of expression of AKT1, HAK5, and HKT1 transporter genes. Taken together, our data provide the mechanistic explanation for differential salt stress sensitivity amongst these species and shed light on transcriptional and post-translational regulation of key ion transport systems involved in the maintenance of the root plasma membrane potential and cytosolic K/Na ratio as a key attribute for salt tolerance in Brassica species.

Bidirectional but asymmetrical sexual hybridization between Brassica carinata and Sinapis arvensis (Brassicaceae).

With transgenic crop development it is important to evaluate the potential for transgenes to escape into populations of wild, weedy relatives. Ethiopian mustard (Brassica carinata, BBCC) is easily transformed and is being investigated for uses from biodiesel fuels to biopharmaceuticals. However, little work has been done evaluating its ability to cross with relatives such as wild mustard (Sinapsis arvensis, SrSr), an abundant, cosmopolitan weedy relative. Here we conducted bidirectional crosses with Ethiopian mustard as a maternal parent in 997 crosses and paternal parent in 1,109 crosses. Hybrids were confirmed using flow cytometry and species-specific ITS molecular markers and indicate a high hybridization rate of 6.43 % between Ethiopian mustard (♀) and wild mustard (♂) and a lower, but not insignificant, hybridization rate of 0.01 % in the reverse direction. The majority of the hybrids were homoploid (BCSr) with less than 1 % of pollen production of their parents and low seed production (0.26 seeds/pollination) in crosses and backcrosses indicating a potential for advanced generation hybrids. The accession used had a significant effect on hybrid seed production with different accessions of Ethopian mustard varying in their production of hybrid offspring from 2.69 to 16.34 % and one accession of wild mustard siring almost twice as many hybrid offspring per flower as the other. One pentaploid (BBCCSr) and one hexaploid (BBCCSrSr) hybrid were produced and had higher pollen viability, though no and low seed production, respectively. As wild mustard is self-incompatible and the outcrossing rate of Ethiopian mustard has been estimated as 30 % potential for hybrid production in the wild appears to be high, though the hybridization rate found here represents a worst case scenario as it does not incorporate pre-pollination barriers. Hybridization in the wild needs to be directly evaluated as does the propensity of Ethiopian mustard to volunteer.

An RNA-seq transcriptome analysis of floral buds of an interspecific Brassica hybrid between B. carinata and B. napus.

Interspecific hybridizations promote gene transfer between species and play an important role in plant speciation and crop improvement. However, hybrid sterility that commonly found in the first generation of hybrids hinders the utilization of interspecific hybridization. The combination of divergent parental genomes can create extensive transcriptome variations, and to determine these gene expression alterations and their effects on hybrids, an interspecific Brassica hybrid of B. carinata × B. napus was generated. Scanning electron microscopy analysis indicated that some of the hybrid pollen grains were irregular in shape and exhibited abnormal exine patterns compared with those from the parents. Using the Illumina HiSeq 2000 platform, 39,598, 32,403 and 42,208 genes were identified in flower buds of B. carinata cv. W29, B. napus cv. Zhongshuang 11 and their hybrids, respectively. The differentially expressed genes were significantly enriched in pollen wall assembly, pollen exine formation, pollen development, pollen tube growth, pollination, gene transcription, macromolecule methylation and translation, which might be associated with impaired fertility in the F1 hybrid. These results will shed light on the mechanisms underlying the low fertility of the interspecific hybrids and expand our knowledge of interspecific hybridization.

Upregulation of the AT-hook DNA binding gene BoMF2 in OguCMS anthers of Brassica oleracea suggests that it encodes a transcriptional regulatory factor for anther development.

Ogura cytoplasmic male sterility (OguCMS) is the most important CMS system used for F1 hybrid cabbage production worldwide. The anther abortion and defective pollen development exhibited in OguCMS are coordinately regulated by the mitochondrial male sterile gene orf138 and many nuclear transcriptional regulatory factors. AT-hook DNA binding proteins regulate cell-specific gene expression. In this study, we cloned the gene encoding the AT-hook DNA binding protein BoMF2 using the cDNA-AFLP TDF sequence, which was upregulated in OguCMS cabbage flower buds, as a querying probe. BoMF2 contains a 783-nt continuous complete open reading frame encoding a 260 amino-acid polypeptide. In vivo transient expression assays using GFP fusions showed that BoMF2 protein was located in the nucleus. BoMF2 was preferentially expressed in cabbage stamens, with a short expression window at anther development stage 7-8. However, in OguCMS flowers, BoMF2 expression continued into the mature pollen stage and was concomitant with the continued proliferation of tapetum cells exhibited in this mutant. Arabidopsis plants overexpressing BoMF2 showed significantly shorter siliques than the wild type, as well as decrease of pollen viability. These results suggest that BoMF2, a transcriptional regulatory factor, might regulate tapetum proliferation during anther development.

Correlations between colonization of onion thrips and leaf reflectance measures across six cabbage varieties.

The main purpose of this study was to reveal if the UV-A, and visible light reflection of leaves of white cabbage varieties is correlated to resistance against onion thrips. The antixenotic resistance (AR) against onion thrips and thrips damage differed between varieties Balashi, Bloktor, Riana - considered resistant - and Green Gem, Hurricane, Quisor - considered susceptible. The solar UV-A (340-400 nm) and visible (401-650 nm) light reflection of white cabbage leaves were recorded. Correlation between AR against onion thrips and reflection of leaves in UV-A and visible range of the studied white cabbage varieties were computed. According to the AR evaluation onion thrips density was always higher on susceptible than on resistant varieties. The UV-A light reflection of head forming leaves and the contrast between head and exterior leaves (H/E) was negatively correlated with onion thrips host preference at an early stage of cabbage head formation. The visible light reflection of both head forming and exterior leaves was also negatively correlated with onion thrips host preference. Susceptible varieties had greater damage ratings at harvest than resistant ones and positive correlations were observed between AR and damage. AR against onion thrips may be affected by differences in reflection of cabbage leaves at an early growth stage. It is suggested that more intensive reflection of leaves and/or higher contrast values between the reflectance intensity of head versus outer leaves made the resistant varieties less attractive to onion thrips. Our results reported here provide the first evidence of negative correlation between UV-A and visible reflection of leaves and AR of white cabbage against a dangerous insect pest, opening new perspectives for understanding the role of reflection by plant leaves in pest management.

Consequences of gene flow between oilseed rape (Brassica napus) and its relatives.

Numerous studies have focused on the probability of occurrence of gene flow between transgenic crops and their wild relatives and the likelihood of transgene escape, which should be assessed before the commercial release of transgenic crops. This review paper focuses on this issue for oilseed rape, Brassica napus L., a species that produces huge numbers of pollen grains and seeds. We analyze separately the distinct steps of gene flow: (1) pollen and seeds as vectors of gene flow; (2) spontaneous hybridization; (3) hybrid behavior, fitness cost due to hybridization and mechanisms of introgression; (4) and fitness benefit due to transgenes (e.g. herbicide resistance and Bt toxin). Some physical, biological and molecular means of transgene containment are also described. Although hybrids and first generation progeny are difficult to identify in fields and non-crop habitats, the literature shows that transgenes could readily introgress into Brassica rapa, Brassica juncea and Brassica oleracea, while introgression is expected to be rare with Brassica nigra, Hirschfeldia incana and Raphanus raphanistrum. The hybrids grow well but produce less seed than their wild parent. The difference declines with increasing generations. However, there is large uncertainty about the evolution of chromosome numbers and recombination, and many parameters of life history traits of hybrids and progeny are not determined with satisfactory confidence to build generic models capable to really cover the wide diversity of situations. We show that more studies are needed to strengthen and organize biological knowledge, which is a necessary prerequisite for model simulations to assess the practical and evolutionary outputs of introgression, and to provide guidelines for gene flow management.