Comparison of structural damage caused by Russian wheat aphid (Diuraphis noxia Mordvilko) and Bird cherry-oat aphid (Rhopalosiphum padi L.) in a susceptible barley cultivar, Hordeum vulgare L. cv Clipper

The Russian wheat aphid (RWA, (Diuraphis noxia Mordvilko) and the Bird cherry-oat aphid (BCA, (Rhopalosiphum padi L.) cause severe damage to grain crops, including barley. An investigation of the effects of these aphids on a susceptible cultivar revealed that BCA-infested barley plants remained healthy-looking for two weeks after feeding commenced. In contrast, signs of stress and damage, including chlorosis and leaf necrosis were evident in RWA infested plants. Our study suggests that damage to the vascular tissue due to sustained feeding by BCA, was not as extensive as that caused by RWA. In addition, there is a marked difference in the salivary secretion pattern within xylem elements punctured by aphids tapping the xylem for water. RWA deposit electron-dense, amorphous to smooth saliva, which completely encases the inner walls of affected elements, and saliva encases pit membranes between xylem elements, and between xylem vessels and xylem parenchyma. Xylem tapped by BCA, contained more granular saliva, which apparently does not occlude vessel wall apertures or the pit membranes to the same extent as was observed with RWA. Damage to phloem tissue, including phloem parenchyma elements, sieve tube-companion cell (CC-ST) complexes as well as thick-walled sieve tubes, was extensive. Plasmodesmata between phloem parenchyma elements as well as pore-plasmodesmata between the CC-ST were occluded by callose. We conclude that severe, perhaps permanent damage to conducting elements in RWA infested leaves may be responsible for the detrimental chlorosis and necrosis symptoms. These symptoms are absent in BCA-infested plants

Russian wheat aphid causes greater reduction in phloem transport capacity of barley leaves than bird cherry-oat aphid

The effects of feeding by the Russian wheat aphid (RWA), Diuraphis noxia Mordvilko and the Bird cherry-oat aphid (BCA), Rhopalosiphum padi L on the transport capacity of barley Hordeum vulgare L leaves were investigated and compared with a view to relating these effects to the visible symptoms shown by the respective infested plants. RWAcauses extensive chlorosis and necrosis on an infested plant whereas BCA causes no observable symptoms. Our results using the xenobiotic, phloem mobile fluorophore, 5, 6 carboxyfluorescein diacetate (5, 6-CFDA) revealed striking differences in damage to the transport of assimilates through the phloem by these two aphids. The result clearly suggests that short-term feeding by RWA causes a reduction in transport of assimilates and a more severe reduction or perhaps even permanent cessation of transport during long-term feeding. In contrast, feeding by BCA does not lead to a marked decrease in transport during short-term feeding period, however, a reduction in the transport was recorded during long-term feeding activities. These results perhaps suggest that damage to transport capacities of the barley leaves appears to be partly responsible for the observed symptoms in RWA-infested plants and the lack of them during BCAinfestations, symptoms such as reduction or cessation in transport of assimilates to growing tissues may lead to such observable symptoms

Russian wheat aphid causes greater reduction in phloem transport capacity of barley leaves than bird cherry-oat aphid

The effects of feeding by the Russian wheat aphid (RWA), Diuraphis noxia Mordvilko and the Bird cherry-oat aphid (BCA), Rhopalosiphum padi L on the transport capacity of barley Hordeum vulgare L leaves were investigated and compared with a view to relating these effects to the visible symptoms shown by the respective infested plants. RWAcauses extensive chlorosis and necrosis on an infested plant whereas BCA causes no observable symptoms. Our results using the xenobiotic, phloem mobile fluorophore, 5, 6 carboxyfluorescein diacetate (5, 6-CFDA) revealed striking differences in damage to the transport of assimilates through the phloem by these two aphids. The result clearly suggests that short-term feeding by RWA causes a reduction in transport of assimilates and a more severe reduction or perhaps even permanent cessation of transport during long-term feeding. In contrast, feeding by BCA does not lead to a marked decrease in transport during short-term feeding period, however, a reduction in the transport was recorded during long-term feeding activities. These results perhaps suggest that damage to transport capacities of the barley leaves appears to be partly responsible for the observed symptoms in RWA-infested plants and the lack of them during BCAinfestations, symptoms such as reduction or cessation in transport of assimilates to growing tissues may lead to such observable symptoms

Seabed Mapping and Marine Spatial Planning: A Case Study from a Swedish Marine Protected Area

Physical chemistr

Chapter Seabed Mapping and Marine Spatial Planning: A Case Study from a Swedish Marine Protected Area

Physical chemistr

Overexpression and Down-Regulation of Barley Lipoxygenase<i> LOX2.2 </i>Affects Jasmonate-Regulated Genes and Aphid Fecundity

Aphids are pests on many crops and depend on plant phloem sap as their food source. In an attempt to find factors improving plant resistance against aphids, we studied the effects of overexpression and down-regulation of the lipoxygenase gene LOX2.2 in barley (Hordeum vulgare L.) on the performance of two aphid species. A specialist, bird cherry-oat aphid (Rhopalosiphum padi L.) and a generalist, green peach aphid (Myzus persicae Sulzer) were studied. LOX2.2 overexpressing lines showed up-regulation of some other jasmonic acid (JA)-regulated genes, and antisense lines showed down-regulation of such genes. Overexpression or suppression of LOX2.2 did not affect aphid settling or the life span on the plants, but in short term fecundity tests, overexpressing plants supported lower aphid numbers and antisense plants higher aphid numbers. The amounts and composition of released volatile organic compounds did not differ between control and LOX2.2 overexpressing lines. Up-regulation of genes was similar for both aphid species. The results suggest that LOX2.2 plays a role in the activation of JA-mediated responses and indicates the involvement of LOX2.2 in basic defense responses

Stronger induction of callose deposition in barley by Russian wheat aphid than bird cherry-oat aphid is not associated with differences in callose synthase or ≤-1,3-glucanase expression

The effects of infestation by the bird cherry-oat aphid (BCA), (Rhopalosiphum padi L) and the Russian wheat aphid (RWA) (Diuraphis noxia Mordvilko) on callose deposition and gene expression related to callose accumulation were investigated in barley (Hordeum vulgare L. cv. Clipper). The BCA, which gives no visible symptoms, induced very limited callose deposition, even after 14 days of infestation. In contrast, RWA, which causes chlorosis, white and yellow streaking and leaf rolling, induced callose accumulation already after 24h in longitudinal leaf veins. The deposition was pronounced after 72 h, progressing during 7 and 14 days of infestation. In RWA-infested source leaves, callose was also induced in longitudinal veins basipetal to the aphid-infested tissue, whereas in sink leaves, more callose deposition was found above the feeding sites. Nine putative callose synthase genes were identified in a data base search, of which eight were expressed in the leaves, but with similar level of expression in control and aphid-infested tissue. Four out of 12 examined β-1,3-glucanases were expressed in the leaves, and three of them were up-regulated in aphid-infested tissue. They were all more strongly induced by RWA than BCA. The results suggest that callose accumulation may be partly responsible for the symptoms resulting from RWA feeding and that a callose-inducing signal may be transported in the phloem. Furthermore it is concluded that the absence of callose deposition in BCA-infested leaves is not due to a stronger induction of callose-degrading β-1,3-glucanases in this tissue, as compared to RWA-infested leaves

Upstream sources of the Denmark Strait Overflow : observations from a high-resolution mooring array

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 112 (2016): 94-112, doi:10.1016/j.dsr.2016.02.007.We present the first results from a densely instrumented mooring array upstream of the Denmark Strait sill, extending from the Iceland shelfbreak to the Greenland shelf. The array was deployed from September 2011 to July 2012, and captured the vast majority of overflow water denser than 27.8 kgm-3 approaching the sill. The mean transport of overflow water over the length of the deployment was 3.54 ± 0.16 Sv. Of this, 0.58 Sv originated from below sill depth, revealing that aspiration takes place in Denmark Strait. We confirm the presence of two main sources of overflow water: one approaching the sill in the East Greenland Current and the other via the North Icelandic Jet. Using an objective technique based on the hydrographic properties of the water, the transports of these two sources are found to be 2.54 ± 0.17 Sv and 1.00 ± 0.17 Sv, respectively. We further partition the East Greenland Current source into that carried by the shelfbreak jet (1.50 ± 0.16 Sv) versus that transported by a separated branch of the current on the Iceland slope (1.04 ± 0.15 Sv). Over the course of the year the total overflow transport is more consistent than the transport in either branch; compensation takes place among the pathways that maintains a stable total overflow transport. This is especially true for the two East Greenland Current branches whose transports vary out of phase with each other on weekly and longer time scales. We argue that wind forcing plays a role in this partitioning.The mooring and analysis work was supported by NSF OCE research grants OCE-0959381 and OCE-1433958, by the European Union 7th Framework Programme (FP7 2007-2013) under grant agreement n. 308299 NACLIM, and and by the Research Council of Norway through the Fram Centre Flaggship project 6606-299.2017-03-2