Silencing of Mannitol Transporter Gene In Phelipanche Aegyptiaca Reduces The Parasite Development On The Host Root

Parasitic weed Phelipanche aegyptiaca, is an obligate plant parasite which causes severe damage to host crops. Agriculture crops mainly belong to Brassicaceae, Leguminosae, Cruciferae and Solanaceae plant families affected by this parasitic weed which leads to devastating loss to crops yield and economic growth. This root specific parasitic plant is not able to complete its life-cycle without a suitable host and is totally dependent on the host plant for organic nutrients. Therefore, flow of organic solute molecules towards parasites is essential for the survival of the parasitic weed and disturbance in this network modulated host-parasitic interaction, which induces resistance in host against these parasitic weeds. To develop host resistance to this parasitic weed, we silenced selected prominent genes associated with P. aegyptiaca using virus-induced gene silencing (VIGS) methods. Our results demonstrated that the total number of parasite tubercle attached to root of the host plant Nicotiana benthamiana significantly reduced upon silencing of P. aegyptiaca specific gene which encodes mannitol transporter, however silencing of other gene(s), have no significant effects. Thus, our study indicates that mannitol transport plays an important role in host-parasite interaction and silencing of this gene causes development of host resistance against this parasite.

A Personal History in Parasitic Weeds and Their Control

This invited paper summarises a career in which I became increasingly involved in research and related activities on Striga and other parasitic weeds. It also presents a personal view of the present status of parasitic weed problems and their control.

Field Evaluation of Arbuscular Mycorrhizal Fungi in the Management of Orobanche: A Parasitic Weed in Tobacco (Nicotiana tabacum L.)

An investigation was carried out to evaluate the methods of application of AMF cultures in the management of Orobanche viz., planting of pre colonized tobacco seedling; soil application and the combination of both. The experiment was carried out in Orobanche infested soils of tobacco growing areas of Belagavi district. The results of the present investigations have revealed that the treatment received STD AMF had reduced the emergence of Orobanche (1.33 plot-1) compared to UASDAMFT (1.67 plot-1) and UASDAMFS (2.89 plot-1). The results with respect to different methods of applications of AMF on Orobanche numbers revealed that planting of pre colonized tobacco seedling plus soil application at the time of planting suppressed the Orobanche emergence (0.00 plot-1) compared to planting of pre colonized seedlings (1.67 plot-1) and direct soil application of AMF cultures at the time of planting (4.22 plot-1).The results pertaining to the interactive effect between mycorrhizal cultures in conjunction with the methods of application of AMF cultures significantly reduced the population of Orobanche with the treatment received planting of pre colonized seedling along with soil application of UASDAMFT, UASDAMFS and STD AMF recorded zero emergences of Orobanche at 60 DAP. However, the highest numbers of weeds were recorded in uninoculated control (68.67plot-1). Furthermore, mycorrhizal parameters like spore count and percent of root colonization were found to be the highest in the plots received mycorrhization in the form of pre-colonization and soil application with STD AMF at the time of transplanting in the main field compared to uninoculated control.

GBS analysis of Orobanche crenata populations in Algeria supports local adaptation and host-specialization

Crenate broomrape (Orobanche crenata Forsk.) is a serious long-standing parasitic weed problem in Algeria, mainly affecting legumes but also vegetable crops. Unresolved questions for parasitic weeds revolve around the extent to which these plants undergo local adaptation, especially with respect to host specialization, which would be expected to be a strong selective factor for obligate parasitic plants. In the present study, the Genotyping-By-Sequencing (GBS) approach was used to analyze genetic diversity and population structure of 10 Algerian O. crenata populations with different geographical origins and host species (faba bean, pea, chickpea, carrot and tomato). In total, 8,004 high-quality single-nucleotide polymorphisms were obtained and used across the study. Genetic diversity and relationships of 95 individuals from 10 populations were studied using model-based ancestry analysis, principal components analysis, discriminant analysis of principal components, and phylogeny approaches. The genetic differentiation (FST) between pairs of populations was lower between adjacent populations and higher between geographically separated ones, but no support was found for isolation by distance. Further analyses identified four genetic clusters and revealed evidence of structuring among populations and hosts with more evident structuring among hosts than strictly along a geographic gradient. In the most striking example, O. crenata growing on pea had a distinct SNP profile from those growing on faba bean or other crops. These results illustrate the potential of GBS to reveal the dynamics of parasitic weed dispersal and adaptation.

The potential threat of branched broomrape for California processing tomato: A review

Branched broomrape (Phelipanche ramosa), a parasitic weed that was the focus of a $1.5 million eradication effort four decades ago in California, has recently re-emerged in tomato fields in several Central Valley counties. Processing tomatoes are important to the California agricultural economy; the state produced over 90% of the 12 million tons of tomatoes grown in the United States in 2018. Branched broomrape is listed as an “A” noxious weed by the California Department of Food and Agriculture (CDFA); discovery of broomrape in California tomato fields leads to quarantine and crop destruction without harvest, resulting in significant economic loss to growers. In countries where broomrape is common, yield reductions caused by this parasitic weed can range from moderate to 80%, depending upon the infestation level, host and environmental conditions. Developing a detailed understanding of the biology of this weed under local conditions is an important step towards developing effective management plans for California. In this review, we discuss branched broomrape in the context of California production systems, particularly of tomato. We also discuss the potential management practices that could help to prevent or reduce the impacts of branched broomrape in tomatoes and other host crops.

Localization of planteose hydrolysis during seed germination of Orobanche minor

Root parasitic weeds of the Orobanchaceae, such as witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.), cause serious losses in agriculture worldwide. No practical method to control these parasitic weeds has been developed to date. Understanding the characteristic physiological processes in the life cycles of root parasitic weeds is particularly important to identify specific targets for growth modulators. In our previous study, planteose metabolism was revealed to be activated soon after the perception of strigolactones in germinating seeds of O. minor. Nojirimycin inhibited planteose metabolism and impeded seed germination of O. minor, indicating that planteose metabolism is a possible target for root parasitic weed control. In the present study, we investigated the distribution of planteose in dry seeds of O. minor by matrix-assisted laser desorption/ionization—mass spectrometry imaging. Planteose was detected in tissues surrounding—but not within—the embryo, supporting its suggested role as a storage carbohydrate. Biochemical assays and molecular characterization of an α-galactosidase family member, OmAGAL2, indicated the enzyme is involved in planteose hydrolysis in the apoplast around the embryo after the perception of strigolactones to provide the embryo with essential hexoses for germination. These results indicated that OmAGAL2 is a potential molecular target for root parasitic weed control.

Cuscuta campestris (field dodder).

The parasitic weed C. campestris is native to North America but has been introduced around the world and become a weed in many countries. It is by far the most important of the dodders, perhaps because of its wide host range. This ensures that there is a wide range of crop seeds that may be contaminated, and in which it may be introduced to new areas over both short and long distances. Once introduced it is almost certain that there will be suitable host plants on which it can thrive and be damaging, whether they are crops or wild species. Vegetative spread can be very rapid - up to 5 m in 2 months. It also has a wide tolerance of climatic conditions from warm temperate to sub-tropical and tropical.

Alectra vogelii (yellow witchweed).

A. vogelii is an annual parasitic weed of legume crops, particularly cowpea and groundnut, in semi-arid areas of East, West, Central and Southern Africa. It is closely associated with cultivation, is occasionally found associated with weeds of fallows but rarely in natural vegetation. Copious seed production and a long-lived seed-bank allow the rapid build up of infestations when susceptible crop cultivars are planted. Tiny seeds are easily spread by wind, surface water flow or in crop seed. The genus Alectra is on the USDA Federal Noxious Weed list. Despite the similar life cycle to Striga species which are listed, and potential for crop damage, A. vogelii does not appear on Noxious weed lists in Australia. An assessment of its global invasive potential is given by Mohamed et al. (2006).