Are Root Hydraulic Conductivity Responses to Salinity Controlled by Aquaporins in Broccoli Plants?

Broccoli (Brassica oleracea L. var. Italica) is a recognised health-promoting vegetable, which is moderately sensitive to salinity. In this study, the primary response of broccoli plants (cv. Marathon) to salinity has been characterised. For this, leaf water relations, nutrient composition, root hydraulic conductivity (L ₀) and the effect of mercury (an aquaporin blocker) on L ₀ were determined for plants grown with 0, 20, 40, 60, 80 or 100 mM NaCl for 2 weeks. During the 2 weeks of treatment, the plants showed a two-phase growth response to salinity. During the first phase (1 week), growth reduction was high, probably related to water stress as no osmotic adjustment occurred and reductions of L ₀, the mercury effect and Gs were observed. After 2 weeks, the growth reduction could have resulted from internal injury caused by Na⁺ or Cl⁻, since osmotic adjustment was achieved and water relations plus the mercury effect were re-established to a high degree, indicating high aquaporin functionality. The fact that aquaporin functionality fits well with the overall water relations response is very relevant, since the two-phase adaptation to salinity may imply two types of aquaporin regulation.     

Influence of water stress on the glucosinolate profile of Brassica oleracea var. italica and the performance of Brevicoryne brassicae and Myzus persicae

Drought stress alters the chemical composition of plants, which can influence their tolerance to insect herbivory. To evaluate plant chemical responses to drought stress, broccoli, Brassica oleracea L. var. italica Plenck (Brassicaceae), was grown under well‐watered, drought, and water‐logged conditions. The glucosinolate (GS) levels and the performance of two aphid species, the specialist Brevicoryne brassicae (L.) and the generalist Myzus persicae (Sulzer) (both Hemiptera: Aphididae), in relation to water stress conditions were studied. High Performance Liquid Chromatography analysis showed that water stress changed the levels of GS in broccoli plants. Plants grown for 2 weeks under drought stress were significantly smaller and showed decreased levels of total GS when compared with GS contents of well‐watered plants, whereas water‐logged conditions led to a slight increase in the GS contents. A substantial decrease in indolyl GS was detected in water‐deficient plants, whereas aliphatic GS decreased slightly. Analysis of sugar levels in phloem sap of broccoli plants revealed that plants under water‐logged conditions contained the highest amounts of sugars followed by drought‐stressed and well‐watered plants. The two aphid species responded differently to water stress‐induced changes in their host plants. Significantly larger populations of M. persicae were recorded on plants with a limited water supply than on plants grown under well‐watered or water‐logged conditions. Brevicoryne brassicae was less affected by water stress, and similar population sizes were found on plants that were subject to different treatments. Analysis of covariance showed a significant effect of the plants’ water condition but no significant effect of GS content on the performance of M. persicae. However, the specialist B. brassicae remained unaffected by changes induced under water stress conditions.     

应用正交设计建立青花菜植株的再生体系

通过L16(4 5)正交试验 ,研究最适合青花菜 2周龄下胚轴愈伤组织诱导和不定芽发生的植物生长调节物质的种类和浓度组合。结果发现在NAA、6 BA、TDZ和KT四种激素中 ,NAA对下胚轴愈伤组织发生指数、不定芽发生频率的影响作用最大 ,确定以MS +NAA 0 .2 5mg/L +6 BA 0 .2 5mg/L +TDZ 0 .0 1mg/L(琼脂 0 .8% ,蔗糖 3 % ,pH5 .8)作为单因子试验的培养基。NAA、6 BA和TDZ浓度的单因子试验结果表明最适合下胚轴的培养基配方为 :MS +NAA 0 .1mg/L +6 BA 1 .0mg/L +TDZ 0 .0 6mg/L(琼脂 0 .8% ,蔗糖 3 % ,pH5 .8)。     

Heat shock response during anther culture of broccoli (Brassica oleracea var italica)

Embryo formation from microspores of Brassica oleracea var Italica (Broccoli) and other Brassica species is greatly enhanced by an initial incubation at elevated temperatures (eg 35°C) followed by continued incubation of 25°C. In the present study we observed that a three hour high temperature treatment induced the formation of heat shock proteins in cultured anthers. These were identified in two dimensional gels by silver staining, and labelled heat shock proteins were synthesised in vitro from isolated anther RNA. The appearance of heat shock proteins in anthers followed a similar pattern and displayed similar characteristics to that from leaves. Comparison of the heat shock proteins induced in isolated cultured anthers of known highly embryogenic and less embryogenic plans did not reveal obvious qualitative differences.     

The influence of 6-benzylaminopurine on post-harvest senescence of floral tissues of broccoli (Brassica oleracea var Italica)

The pattern of post-harvest senescence of broccoli (Brassica oleracea) and the effect of the cytokinin 6-benzylaminopurine (6-BAP) were investigated. Chlorophyll degraded before ammonia production increased and this was earlier in florets at the edge of the head than those at the centre. Application of 6-BAP delayed the onset of both chlorophyll degradation and ammonia production. Pedicels contained low levels of chlorophyll which changed little over the duration of the experiment. Pedicels were unresponsive to 6-BAP treatment with no differences between chlorophyll degradation or ammonia accumulation between the treated and non-treated tissues.Application of 6-BAP to the carpel delayed chlorophyll degradation in the sepals, stimulated growth of the carpel and, when over-mature heads of broccoli were used, stimulated petal emergence.Treatment of florets with 1-aminocyclopropane carboxylic acid (ACC) and silver ions indicated that ethylene may be involved in the control of chlorophyll degradation. Cytokinin application negated the ACC-stimulated senescence.     

Transgenic broccoli with high levels of Bacillus thuringiensis Cry1C protein control diamondback moth larvae resistant to Cry1A or Cry1C

A synthetic Bacillus thuringiensis (Bt) cry1C gene was introduced into broccoli (Brassica oleracea ssp. italica) by Agrobacterium-mediated transformation. Twenty-one Cry1C transgenic plants were regenerated from 400 hypocotyl and petiole explants. Variable amounts of stable steady- state cry1C mRNA accumulated in different transgenic plants. Cry1C protein (up to 0.4% of total soluble protein) was produced in correlation with the cry1C mRNA levels. Leaf section and whole-plant bioassays were done using diamondback moth (DBM) larvae from lines susceptible to Bt or resistant to Cry1A or Cry1C proteins (Cry1AR or Cry1CR, respectively). Plants with high levels of Cry1C protein caused rapid and complete mortality of all three types of DBM larvae with no defoliation. Plants with lower levels of Cry1C protein showed an increasing differential between control of susceptible of Cry1AR DBM. This study demonstrated that high production of Cry1C protein can protect transgenic broccoli not only from susceptible or Cry1AR DBM larvae but also from DBM selected for moderate levels of resistance of Cry1C. The Cry1C- transgenic broccoli were also resistant to two other lepidopteran pests of crucifers (cabbage looper and imported cabbage worm). These plants will be useful in studies of resistance management strategies involving multiple transgenes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pathogenicity and life cycle of Meloidogyne javanica on broccoli

A pathogenicity trial conducted against root-knot nematode, Meloidogyne javanica on broccoli indicated that a gradual increase in the nematode inoculum from 500 to 8000 juveniles/kg soil was associated with a progressive decline in all the plant growth parameters and reproduction factor of the nematode. Although 8000 juveniles/kg soil showed maximum plant growth reduction and root knot index, statistical analysis of the data revealed that the population of 1000 juveniles/kg soil was associated with a significant decline in plant growth. Hence, this level was indicative of being the pathogenic level. The significant reduction in seedling emergence was recorded at and above 2000 juveniles/kg soil and it decreased further with increasing inoculum levels. Meloidogyne javanica required 27 days to complete the life cycle on broccoli at a temperature range of 28–35°C.     

Transgenic broccoli expressing aBacillus thuringiensis insecticidal crystal protein: Implications for pest resistance management strategies

We usedAgrobacterium tumefaciens to transform flowering stalk explants of five genotypes of broccoli with a construct containing the neomycin phosphotransferase gene and aBacillus thuringiensis (Bt) gene [CryIA(c) type] optimized for plant expression. Overall transformation efficiency was 6.4%; 181 kanamycin-resistant plants were recovered. Of the 162 kanamycin-resistant plants tested, 112 (69%) caused 100% morality of 1st-instar larvae of aBt-susceptible diamondback moth strain. Southern blots of some resistant transformants confirmed presence of theBt gene. Selected plants that gave 100% mortality of susceptible larvae allowed survival of a strain of diamondback moth that had evolved resistance toBt in the field. F₁ hybrids between resistant and susceptible insects did not survive. Analysis of progeny from 26 resistant transgenic lines showed 16 that gave segregation ratios consistent with a single T-DNA integration. Southern analysis was used to verify those plants possessing a single T-DNA integration. Because these transgenic plants kill susceptible larvae and F₁ larvae, but serve as a suitable host for resistant ones, they provide an excellent model for tests ofBt resistance management strategies.     

Assessment of three strategies for the management of Meloidogyne arenaria on carrot in Mexico using Pochonia chlamydosporia var. mexicana under greenhouse conditions

Three control strategies for management of Meloidogyne arenaria were evaluated on carrot under greenhouse conditions. The control strategies tested were: i) incorporation of fresh broccoli; ii) carbofuran (Furadan®); and iii) Pochonia chlamydosporia var. mexicana, isolate Pcp21. Each strategy was evaluated separately and in combination (16 treatment combinations), each with three replicates. The experiment was done between February and April 2014 and repeated over the same time period in 2015. Each replicate experimental unit consisted of a 1?kg pot filled with tyndallised soil, to which broccoli, fungus and carbofuran were added according to treatment. Carrot seeds were sown into each pot and inoculated with M. arenaria eggs according to treatment. Pots were then maintained in the glasshouse for 12 weeks at 25?±?5°C. After this time the fresh root weight, root length, percent reduction in root galling, P. chlamydosporia var. mexicana colony forming units (CFU)/g of soil, and CFU/g root were all measured. Results showed that isolate Pcp21 of P. chlamydosporia var. mexicana significantly reduced root galling percentage by 50 and 78% in 2014 and 2015, respectively. Application of the fungus in combination with broccoli or carbofuran also reduced root galling. The number of CFU/ g of soil or root remained the same over the 12 weeks of the experiment. This isolate of P. chlamydosporia significantly reduced damage caused by M. arenaria on carrot and is a promising agent for management of this nematode.