Ambrosia grayi as a new alien causal species in Israel: plant biology and chemical management.

BACKGROUND: Ambrosia grayi is a perennial weed native to northern Mexico, which can also be found in the Great Plains of the US. Outside the Americas, A. grayi has only been documented in Israel, where it is currently categorized as a casual species at advanced eradication stages. Here, we studied the plant biology and chemical weed management options of A. grayi. RESULTS: Only large achenes of A. grayi (~5% of all achenes) contain seeds; moreover, the viability of seeds extracted from large achenes was ~25%. Examination of plant anatomy revealed that underground vegetative segments show an anatomical structure of stems (rhizomes) with anomalous secondary growth. The optimal (night/day) temperature for the emergence of A. grayi rhizomes was 20/30 °C, and the emergence rate increased under elevated temperatures. Emergence may occur at different soil moisture content (25-60%); rhizomes were able to emerge even after 1 month of drought conditions (20%, 25% and 30%). Herbicide combinations, such as fluroxypyr + glufosinate, fluroxypyr + glyphosate, and glyphosate + saflufenacil + surfactant, were tested under quarantine conditions and showed high efficacy for the control of A. grayi. However, the efficiency of these treatments was highly correlated with plant growth stage. CONCLUSION: In Israel, the spread of A. grayi occurs mainly via rhizomes that can emerge under a wide range of temperatures and soil moisture conditions. Data regarding herbicide efficacy will aid in improving the eradication efforts taken by Israel's Plant Protection and Inspection Services. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

"Hong Long" Lychee (Litchi chinensis Sonn.) Is the Optimal Pollinizer for the Main Lychee Cultivars in Israel.

The lychee fruit is in high demand worldwide. However, the yields of many cultivars are low, including the high-quality cultivars "Nuomici" (NMC) and "Fei Zi Xiao" (FZX), which are very tasty and produce large fruit with a small seed, but tend to shed their fruitlets. In a previous work, we found that cross-hand pollination of "Mauritius" (MA) with pollen of another cultivar increased fruit set and reduced fruit-drop in comparison to self-hand pollination. In the current research, we aimed to identify the optimal pollen donor for three of the main cultivars grown in Israel: MA, FZX, and "Tamuz" (TA). We compared the effect of different pollinizers and found that the Vietnamese cultivar "Hong Long" (HL), which is becoming an important cultivar in Israel, was the optimal pollinizer for the three cultivars. In addition, we found that FZX and TA were not self-fertile under the Israeli environmental conditions since they tend to shed fruitlets that originated from self-fertilization. In contrast, MA is able to fertilize itself, although cross-pollination greatly increased its fruit number and size. We also identified a new PCR marker for lychee, M3, that enabled us to distinguish between self- and cross-fertilized FZX fruits pollinated by HL. Our results indicate that cross-pollination, particularly by HL, has beneficial effects on the production of lychee and it is especially important for cultivars that generate small seeds and tend to shed their fruitlets.

Metamitron, a Photosynthetic Electron Transport Chain Inhibitor, Modulates the Photoprotective Mechanism of Apple Trees.

Chemical thinning of apple fruitlets is an important practice as it reduces the natural fruit load and, therefore, increases the size of the final fruit for commercial markets. In apples, one chemical thinner used is Metamitron, which is sold as the commercial product Brevis® (Adama, Ashdod, Israel). This thinner inhibits the electron transfer between Photosystem II and Quinone-b within light reactions of photosynthesis. In this study, we investigated the responses of two apple cultivars-Golden Delicious and Top Red-and photosynthetic light reactions after administration of Brevis®. The analysis revealed that the presence of the inhibitor affects both cultivars' energetic status. The kinetics of the photoprotective mechanism's sub-processes are attenuated in both cultivars, but this seems more severe in the Top Red cultivar. State transitions of the antenna and Photosystem II repair cycle are decreased substantially when the Metamitron concentration is above 0.6% in the Top Red cultivar but not in the Golden Delicious cultivar. These attenuations result from a biased absorbed energy distribution between photochemistry and photoprotection pathways in the two cultivars. We suggest that Metamitron inadvertently interacts with photoprotective mechanism-related enzymes in chloroplasts of apple tree leaves. Specifically, we hypothesize that it may interact with the kinases responsible for the induction of state transitions and the Photosystem II repair cycle.

Characterization of extracellular lytic enzymes produced by the yeast biocontrol agent Candida oleophila.

The yeast Candida oleophila, the base of the commercial product Aspire, is recommended for the control of postharvest decay of citrus and pome fruit. Competition for nutrients and space is believed to be the major mode of action. Involvement of fungal cell wall-degrading enzymes is also suggested to play a role in the mechanism of action of yeast antagonists. The present study showed that the yeast C. oleophila is capable of producing and secreting various cell wall-degrading enzymes, including exo-beta-1,3-glucanase, chitinase and protease. Exo-beta-1,3-glucanase and chitinase were produced and maximized in the early stages of growth, whereas protease reached a maximum level only after 6-8 days. Production of exo-beta-1,3-glucanase, chitinase and protease was stimulated by the presence of cell wall fragments of Penicillium digitatum in the growth medium, in addition to glucose. This study also provided evidence that C. oleophila is capable of secreting exo-beta-1,3-glucanase into the wounded surface of grapefruit. The role of exo-beta-1,3-glucanase ( CoEXG1) in the biocontrol activity of C. oleophila was tested using CoEXG1-knockouts and double- CoEXG1 over-producing transformants. In vitro bioassays showed that wild-type C. oleophila and exo-beta-1,3-glucanase over-expressing transformants had similar inhibitory effects on spore germination and germ-tube elongation; and both were more inhibitory to the fungus than the knockout transformant. In experiments conducted on fruit to test the biocontrol activity against infection by P. digitatum, no significant difference in inhibition was observed between transformants and untransformed C. oleophila cells at the high concentrations of cells used, whereas at a lower concentration of yeast cells the knockout transformants appeared to be less effective.

Development and large-scale use of recombinant VP2 vaccine for the prevention of infectious bursal disease of chickens.

Infectious bursal disease virus (IBDV) is the causative agent of Gumboro disease, an infectious disease of global economic importance in poultry. One of the most effective types of inactivated IBDV vaccine is produced by infecting young chickens with a virulent strain, sacrificing them and extracting the virus from the bursa of Fabricius. The goal of this study was to produce an effective subunit vaccine against IBDV thereby providing an effective means of combating the disease. In areas in which the bursa-derived vaccine is in use, this subunit vaccine would eliminate the use of live birds for the production of inactivated vaccines. The gene for viral protein 2 (VP2) of IBDV was cloned into a Pichia pastoris expression system. This efficient system allowed us to meet the need for inexpensive vaccines required by the poultry industry. Following expression and scale-up, the protein was used to vaccinate chickens, against either Gumboro disease alone or in combination with inactivated Newcastle disease virus (NDV). Full protection was conferred against IBDV following vaccination with the subunit recombinant vaccine. No untoward influence on the response to the NDV vaccine was recorded. Over 250 million birds have already been vaccinated with this vaccine. The advantages of a subunit vaccine over an inactivated one are discussed. This approach will enable rapid adjustment to new virulent strains if and when they appear.

The effect of under- and overexpressed CoEXG1-encoded exoglucanase secreted by Candida oleophila on the biocontrol of Penicillium digitatum.

The yeast, Candida oleophila, is acknowledged for its biocontrol activity against postharvest moulds. However, the mechanism of this activity is not fully understood. One of the conjectured modes of action is associated with extracellular lytic enzymes, such as beta-exoglucanase. The relationship of beta-exoglucanase in the biocontrol activity of C. oleophila was investigated by generating C. oleophila CoEXG1-knockouts and double-CoEXG1 transformants. The knockout transformants secreted 0-13% of the exoglucanase activity detected in the medium of the untransformed yeast (depending on the medium), indicating that CoEXG1 is the main gene responsible for the production of the secreted exoglucanase. Correspondingly, the double-CoEXG1 transformants secreted approximately twice as much 1,3-beta-exoglucanase as the untransformed C. oleophila. The biocontrol activity of the CoEXG1-knockout and the double-CoEXG1 transformants against Penicillium digitatum did not differ from that of the untransformed C. oleophila on kumquats. These results imply that the 1,3-beta-exoglucanase encoded by the gene CoEXG1 is not involved in the biocontrol activity of C. oleophila against P. digitatum under these experimental terms. However, these findings do not rule out the possibilities, that the participation of CoEXG1 in biocontrol is dependent on the activity of other gene products, or that its effect may be manifested under altered environmental conditions.

Cloning and analysis of CoEXG1, a secreted 1,3-beta-glucanase of the yeast biocontrol agent Candida oleophila.

Lytic enzymes may have a role in the biological control of fungi. The yeast biocontrol agent, Candida oleophila, is an excellent subject to research this matter. In the present study, CoEXG1, which encodes for a secreted 1,3-beta-glucanase, is the first gene to be cloned from C. oleophila. It was isolated from a partial genomic library and analysed. Its open reading frame and putative promoter were expressed in baker's yeast, Saccharomyces cerevisiae. The reading frame, expressed under the inducible GAL1 promoter, caused an increased secretion of beta-glucanase, and the putative promoter region activated the lacZ reporter gene, to which it was fused. Sequencing analysis revealed that CoEXG1 carries the signature pattern of the 5 glycohydrolases family and has a putative secretion leader, as well as a high degree of identity to yeast 1,3-beta-glucanases. The GenBank Accession No. of CoEXG1 is AF393806.