Living with a giant, flowering parasite: metabolic differences between Tetrastigma loheri Gagnep. (Vitaceae) shoots uninfected and infected with Rafflesia (Rafflesiaceae) and potential applications for propagation

Main conclusion Metabolites in Rafflesia-infected and non-infected Tetrastigma were compared which may have applications in Rafflesia propagation. Benzylisoquinoline alkaloids, here reported for the first time in Vitaceae, were abundant in non-infected shoots and may be a form of defense. In Rafflesia-infected shoots, oxylipins, which mediate immune response, were elevated. Abstract Endemic to the forests of Southeast Asia, Rafflesia (Rafflesiaceae) is a genus of holoparasitic plants producing the largest flowers in the world, yet completely dependent on its host, the tropical grape vine, Tetrastigma. Rafflesia species are threatened with extinction, making them an iconic symbol of plant conservation. Thus far, propagation has proved challenging, greatly decreasing efficacy of conservation efforts. This study compared the metabolites in the shoots of Rafflesia-infected and non-infected Tetrastigma loheri to examine how Rafflesia infection affects host metabolomics and elucidate the Rafflesia infection process. Results from LC–MS-based untargeted metabolomics analysis showed benzylisoquinoline alkaloids were naturally more abundant in non-infected shoots and are here reported for the first time in the genus Tetrastigma, and in the grape family, Vitaceae. These metabolites have been implicated in plant defense mechanisms and may prevent a Rafflesia infection. In Rafflesia-infected shoots, oxygenated fatty acids, or oxylipins, and a flavonoid, previously shown involved in plant immune response, were significantly elevated. This study provides a preliminary assessment of metabolites that differ between Rafflesia-infected and non-infected Tetrastigma hosts and may have applications in Rafflesia propagation to meet conservation goals.

Efficacy of Fungicides against Soil Borne and Grapevine Pathogens under In vitro Conditions

In vitro bio-efficacy of the novel copper (NC101 and NCP102) and phosphonate (PN103 and PMN104) based fungicides against various soil borne and grape vine pathogens was evaluated at ICAR-National Research Centre for Grapes, Pune, Maharashtra, India during February - April 2021. The fungicides were screened against five bacterial pathogens viz. Xanthomonas campestris pv. citri, X. campestris pv. campestris, X. campestris pv. punicae, X. campestris pv. viticola and X. oryzae pv. oryzae and 10 fungal pathogens viz. Rhizoctonia bataticola, Sclerotium rolfsii, Cladosporium sp, Alternaria alternata, Colletotrichum gloeosporioides, Penicillium notatum, Magnaporthe oryzae, Fusarium oxysporium, Macrophomina phaseolina (Soyabean isolate) and Macrophomina phaseolina (Jute isolate) at different concentrations. Results indicated that among all the tested fungicides viz. NC101, NCP102, PN103 and PMN104, phosphonate based fungicides (PN103 and PMN104) were highly effective against bacterial isolates with zone of inhibition ranging between 8.75 - 31.12 mm in which X. campestris pv. viticola was found to express least inhibition zone. In case of pathogenic fungal isolates, similar trend was observed, most of the isolates showed cent percent inhibition at higher concentration of PN103 and PMN104. However Sclerotium rolfsii showed least or no inhibition when tested at different concentrations of fungicides. The chemicals exhibited wide range of inhibition and it was found to increase steadily with increase in concentrations of the test fungicides.

Cissus verticillata (possum grape vine).

Cissus verticillata is a large, climbing species cultivated as an ornamental and medicinal plant around the world. It is native to Mexico, Central America and the Caribbean. Once established, C. verticillata grows climbing over the top of the canopy and supporting itself by means of coiled tendrils, or scrambling over the ground. It is common to find this species engulfing entire trees. If the plant is cut, the remaining branches and stems can develop aerial roots that will find their way to the ground, regenerating new. C. verticillata is regarded as a weed in areas within and outside its native distribution range. It was reported in the Lower Rio Grande Valley in Texas in 2003 and may pose a potential weed problem in the citrus groves there and in Florida.

Design and evaluation of calibrated and seamless ensemble weather forecasts for crop protection applications

Agriculture is a highly weather-dependent activity, climatic conditions impact both directly crop growth and indirectly diseases and pests developments causing yield losses. Weather forecasts are now a major component of various decision-support systems that assist farmers to optimize the positioning of crop protection treatments. However, properly accounting for weather uncertainty in these systems still remains a challenge. In this paper, three global and regional ensemble prediction systems (EPSs), covering different spatio-temporal scales, are coupled to a temperature-driven developmental model for grape vine moth in order to provide probabilistic forecasts of treatment dates. It is first shown that a parametric post-processing of the EPSs significantly improves the prediction of treatment dates. Anticipating the need for phytosanitary treatments also requires seamless weather forecasts from the next hour to sub-seasonal time scales. An approach is presented to design seamless ensemble forecasts from the combination of the three EPSs used. The proposed method is able to leverage the increased performance of high-resolution EPS at short ranges, while ensuring a smooth transition toward larger-scale EPSs for longer ranges. The added value of this seamless integration on agronomic predictions is, however, difficult to assess with the current experimental setup. Additional simulations over a larger number of locations and years may be required.