Responses to Nickel in the Proteome of the Hyperaccumulator Plant <Emphasis Type="BoldItalic">Alyssum lesbiacum</Emphasis>

A proteomic analysis of the Ni hyperaccumulator plant Alyssum lesbiacum was carried out to identify proteins that may play a role in the exceptional degree of Ni tolerance and accumulation characteristic of this metallophyte. Of the 816 polypeptides detected in root tissue by 2D SDS-PAGE, eleven increased and one decreased in abundance relative to total protein after 6-week-old plants were transferred from a standard nutrient solution containing trace concentrations of Ni to a moderately high Ni treatment (0.3 mM NiSO₄) for 48 h. These polypeptides were identified by tandem mass spectrometry and the majority were found to be involved in sulphur metabolism (consistent with a re-allocation of sulphur towards cysteine and glutathione), protection against reactive oxygen species, or heat-shock response. In contrast, very few polypeptides were found to change in abundance in root or shoot tissue after plants were exposed for 28 days to 0.03 mM NiSO₄, a concentration representing the optimum for growth of this species but sufficient to lead to hyperaccumulation of Ni in the shoot. Under these conditions, constitutively expressed genes in this highly Ni-tolerant species may be sufficient to allow for effective chelation and sequestration of Ni without the need for additional protein synthesis.     

Phytoextraction of Soil Cobalt Using Hyperaccumulator Plants

A greenhouse study was conducted on phytoextraction of cobalt by nickel hyperaccumulators Alyssum murale and Alyssum corsicum and by two varieties of cobalt accumulator Nyssa sylvatica compared with the nonmetal accumulator crop plant Brassica juncea. The plants were grown on Sassafras sandy loam soil (<2 mg Co and 5 mg Ni/kg dry soil), amended with 1 mmol Co/kg dry soil (58.9 mg/kg), and two Ni smelter-contaminated soils, Quarry muck with 24 mg Co and 1720 mg Ni/kg dry soil and Welland loam with 37 mg Co and 2570 mg Ni/kg dry soil. All soils were adjusted to pH 6.5 to prevent Ni phytotoxicity. Of the five plant entries tested in the study, the two Alyssum species demonstrated the most promising Co phytoextraction results. In Co-amended Sassafras soil, the maximum concentration accumulated by Alyssum murale was 1320 mg Co/kg dry weight, which was almost 60 times higher than accumulation by crop plant Brassica juncea. At a single harvest after 60 days of growth, A. murale was able to extract more than 3% of Co from Co-amended soil. As expected, both Alyssum species accumulated up to 1% Ni on dry weight basis when grown on Ni-contaminated soils.

Nyssa sylvatica showed considerable Co accumulation; foliar Co concentration in the second harvest was as high as 800 mg/kg dry weight. The first few leaves that emerged were chlorotic, both in the Co-amended soil and Ni-contaminated soils, but with growth the signs of toxicity disappeared. In the Co amended soil, Co concentration in Nyssa sylvatica leaves was 30% of that found in shoots of Alyssum species, but an order of magnitude higher than that of Brassica juncea. The leaves accumulated a higher concentration compared with the stems.

Both Alyssum species and Nyssa sylvatica offer promise for phytoextraction of Co and ⁶⁰Co from contaminated or mineralized soils.     

A new species of Bornmuellera Hausskn. (Brassicaceae) from south Anatolia, Turkey

A new species Bornmuellera kiyakii Aytac. & Aksoy (Brassicaceaei is described and illustrated. The species grows on serpentine rocks in south Anatolia. Turkey- Diagnostic morphological characters from closely similar taxa are discussed. A key of Turkish Bornmuellera species is presented.     

Flowering alyssum (Lobularia maritima) promote arthropod diversity and biological control of Myzus persicae

Radish, Raphanus sativus is an important vegetable crop worldwide. It is the second most important vegetable after cabbage and cauliflower in winter (January to March) in Nepal. This crop is damaged by various herbivores such as the green peach aphid, Myzus persicae, the soybean hairy caterpillar, Spilarctia casigneta and the flea beetle, Monolepta signata. Prophylactic pesticide use is a part of the common pest management practice in Nepal. The candidate floral plant, alyssum, Lobularia maritima, was deployed in a radish field to improve pest biological control. Beneficial arthropods trapped such as Syrphidae, Coccinellidae, Carabidae, Staphylinidae, Formicidae, Lycosidae, Apidae and Ichneumonidae were significantly more abundant in flowering alyssum plots than the control (non-flowering) plots. Flowering alyssum in radish fields significantly increases the population of observed syrphids (larva and adult). Similarly observed ladybirds was slightly higher in flowering plot compared with control plot however that was not significant. These beneficial predators potentially increase the biological control of M. persicae. These results provide evidence of the alyssum’s ability to increase the abundance of predators and support the suppression of M. persicae in radishes. This study is useful in developing an integrated pest management protocol by integrating flowering strips in radish fields. Habitat manipulation in radish fields by maintaining flower strips can improve pest biological control and support the provision of multiple ecosystem services that restore diminished ecosystem functions in agriculture.     

Evaluation of potential trap plant species for the wheat bug Nysius huttoni (Hemiptera: Lygaeidae) in forage brassicas

1. The wheat bug Nysius huttoni is a major pest of brassica seedlings. Management of this insect currently relies on seed treatment with neonicotinoids and spraying with chlorpyrifos and pyrethroid insecticides. These practices can generate severe external costs, including human health, the environment and biodiversity. Trap cropping is one alternative option to protect brassica seedlings from N. huttoni.
2. Trap crop species evaluated in field cage experiments were: alyssum (Lobularia maritima L. Desvauxcv. Benthamii White), wheat (Triticum aestivum L. cv. Morph), coriander (Coriandrum sativum L. cv. Santo) and clover (Trifolium repens L. cv. Nomad). These were compared with kale (Brassica oleracea L. cv. Kestrel). In open‐field experiments, alyssum (L maritima), wheat (T. aestivum) and a mixture of alyssum (L. maritima) and wheat (T. aestivum) were used. All of these were compared to kale (B. oleracea).
3. Alyssum and wheat were the most favoured potential trap plants for N. huttoni. Results indicated that two treatments: alyssum (used as a single trap crop) or ‘alyssum plus wheat’ (a multiple trap crop), may be useful in brassica fields to protect the seedlings from N. huttoni damage.
4. Such a trap cropping protocol potentially reduces pesticide use in forage brassicas and can also deliver multiple ecosystem services such as biological control of insect pests.

     

The Genetic Basis of Metal Hyperaccumulation in Plants

Referee: Professor Alan J.M. Baker, School of Botany, The University of Melbourne, VIC 3010, Australia A relatively small yet diverse group of plants are capable of sequestering metals in their shoot tissues at remarkably high concentrations that would be toxic to most organisms. This process, known as metal hyperaccumulation, is of interest for several reasons, including its relevance to the phytoremediation of metalpolluted soils. Most research on hyperaccumulators has focused on the physiological mechanisms of metal uptake, transport, and sequestration, but relatively little is known regarding the genetic basis of hyperaccumulation. There are no known cases of major genetic polymorphisms in which some members of a species are capable of hyperaccumulation and others are not. This is in contrast to the related phenomenon of metal tolerance, in which most species that possess any metal tolerance are polymorphic, evolving tolerance only in local populations on metalliferous soil. However, although some degree of hyperaccumulation occurs in all members of the species that can hyperaccumulate, there is evidence of quantitative genetic variation in ability to hyperaccumulate, both between and within populations. Such variation does not appear to correlate positively with either the metal concentration in the soil or the degree of metal tolerance in the plant. Studies using controlled crosses, interspecific hybrids, and molecular markers are beginning to shed light on the genetic control of this variation. As molecular physiology provides greater insights into the specific genes that control metal accumulation, we may learn more about the genetic and regulatory factors that influence variable expression of the hyperaccumulation phenotype.