The Effect of Herbicides on the Egyptian Broomrape (<i>Orobanche aegyptiaca</i>) in Tomato Fields

The Egyptian broomrape (Orobanche aegyptiaca Pers.) is an obligate holoparasitic weed that causes severe damage to many important vegetable and field crops. In this investigation, three herbicides;chlorsulfuron, triasulfuron and imazaquin were tested to evaluate their efficiency in controlling the tomato broomrape. The herbicides significantly reduced the broomrape parasitizing tomato plants growing in pots, irrigated open field and under greenhouse conditions as foliar spray at the concentrations (0.5 - 10 μg·ml-1) without visible injury effect on the plants. In the pot experiments, triasulfuron increased the dead spikes from 77% to 84%;chlorsulfuron from 51% to 84% and imazaquin from 52% to 84% at the concentrations (0.5 - 5 μg·ml-1) compared with the control. In the irrigated open field experiment, the herbicides were less efficient in controlling the broomrape. The dead spikes increased from 10.5% to 29.1% at the concentrations (1 - 5 μg·ml-1) compared with the control. In the greenhouse experiment, the herbicides were more effective than open field and the dead spikes were increased from 30 to 68% at the concentrations 5 and 10 μg·ml-1. In conclusion, the foliar application of herbicides were able to increase the broomrape dead spikes attached to the tomato plants at the concentrations (3 - 5 μg·ml-1) without visible negative effect on tomato plants.

Identification of candidate gene for resistance to broomrape(Orobanche cumana) in sunflower by BSA-seq

Broomrape(Orobanche cumana)is one of the most important parasitic plants that drastically reduces sunflower yield.The majority of existing resistance varieties have become insufficient for crop protection.Breeding for broomrape resistance is regarded as the most effective and environmentally friendly control measure.In this paper,mapping of a resistance gene for broomrape races E was performed in a recombinant inbred line population by bulk segregate analyses(BSA)combined with genotyping by-sequencing technology.One QTL with resistance candidate genes was mapped on 5 kb interval location from 157,393,001 to 157,850,000 on chromosome 3,the other QTL was located at 5,000 bp interval location from 173,910,001 to 173,915,000 on chromosome 14.Genomic region on candidate interval of chromosome 3 revealed 6 genes with potential resistance for broomrape including transcription factor MYB1 R1,Phylloplanin,histone-lysine N-methyltransferase,methylglutaconyl-CoA hydratase,fasciclin-like arabinogalactan protein and fatty acid dehydrogenase.Two resistant genes on candidate interval of chromosome 14 were discovered with potential resistance for broomrape,which were ABC transporter C family member and Ethylene-responsive transcription factor.These precise locations would be valuable for selecting resistant genotypes in future.

Possibilities for Increasing Sunflower Resistance to Broomrape （ Orobanche cumana Wallr.）

Broomrape causes economic damage in sunflower production in many countries worldwide, but especially in Central and Eastern Europe, Spain, Turkey, Israel, Iran, Kazakhstan, and China. Sunflower selection for broomrape resistance uses different methods for testing breeding materials, looks for resistance sources in certain wild species of the genus Helianthus, and has so far produced significant results. Dominant genes for resistance to races A, B, C, D, E and F have been found and incorporated into cultivated sunflower genotypes. In the last two to three years, new broomrape populations have been discovered in several countries. None of the existing commercial hybrids resistant to races A, B, C, D, E and F have proven resistant to these new populations. Greenhouse testing conducted by the Fundulea Institute in Romania in 2009 has managed to identify two restorer lines that are resistant to all the new populations and can be used directly in developing hybrids. Sunflower breeders and geneticists have achieved significant results in the use of molecular markers for identifying new broomrape races. Marker-assisted selection should be used even more in the future search for Orobanche resistance. Broomrape can also be managed by the development of IMl-resistant hybrids or by using biological control.

Effectiveness of ten commercial maize cultivars in inducing Egyptian broomrape germination

Egyptian broomrape(EB),Phelipanche aegyptiaca,is a devastating root parasite,causing enormous crop losses around the world.Maize has the potential to influence the growth of other plants through releasing certain allelochemicals and is able to induce germination of at least three broomrape species.To determine whether maize could be used as a trap crop for EB,10 maize cultivars were tested for their ability to induce EB germination.The results showed that maize cultivars can induce EB germination,and that germination rates in a cut-root experiment and a hydroponic experiment were consistent.Maize cvs Changcheng 799 and Zhengdan 958 induced the highest EB germination rates,while cvs Luyu 13 and Zhengyu 203 were the least effective.These four maize cultivars were further studied in a pot experiment.Rhizosphere soil,rhizosphere soil extracts,root extracts and shoot extracts from these cultivars were all able to induce EB germination,with cv.Changcheng 799 inducing the highest germination rates.Root extracts generally induced higher germination rates than shoot extracts.It is suggested that Changcheng799 could be planted as a trap crop for control of EB.

Recent Achievements in the Bio-control of Orobanche Infesting Important Crops in the Mediterranean Basin

Orobanche spp. （broomrapes） are holoparasitic plants distributed predominantly in the Northern Hemisphere parasitizing the roots of a range of plant species mainly in wild ecosystems. Orobanche species cause severe yield reduction of many important crops. There are only very few herbicides which are able to selectively control broomrapes and different approaches have been put forward to develop natural product based pesticides to control Orobanche. Several phytopathogenic fungi were evaluated for their use as potential mycoherbicide and for ability to produce toxic metabolites which could be applied as herbicides. Using the alternative approach ＂suicidal germination＂, interesting results were obtained by testing two microbial metabolites （fusicoccins and ophiobolin A） especially with Orobanche species whose germination is not induced by the synthetic strigolactone GR24. From pea root exudates, peagol and peagoldione, close related to strigolactones, and three polyphenols, named peapolyphenols A-C, together with already well known polyphenol and a chalcone, were isolated. They showed a selective stimulation of Orobanche seed germination with the last two and peapolyphenol A showing a specific stimulatory activity on O. foetida. This review describes the most recent results achieved on Orobanche bio-control, mainly focusing on those regarding O. ramosa, O. crenata and O. foetida.

Parasitic Plants <i>Striga</i>and <i>Phelipanche</i>Dependent upon Exogenous Strigolactones for Germination Have Retained Genes for Strigolactone Biosynthesis

Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.