Effect of Allelochemicals of Chinese-fir root extracted by supercritical CO_2 extraction on Chinese fir

Allelochemicals of Chinese-fir root was extracted by technology ofsupercritical CO_2 extraction under orthogonal experiment design, and it was used to analyzeallelopathic activity of Chinese-fir through bioassay of seed germination. The results showed thatas to the available rate of allelochemicals, the pressure and temperature of extraction were themost important factors. The allelochemicals of Chinese-fir root extracted by pure CO_2 and ethanolmixed with CO_2 have different allelopathic activities to seed germination, and the allelochemicalsextracted by ethanol mixed with CO_2 had stronger inhibitory effects on seed germination than thatextracted by pure CO_2.

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.

The basic helix-loop-helix transcription factor gene,OsbHLH38,plays a key role in controlling rice salt tolerance

The plant hormone abscisic acid(ABA)is crucial for plant seed germination and abiotic stress tolerance.However,the association between ABA sensitivity and plant abiotic stress tolerance remains largely unknown.In this study,436 rice accessions were assessed for their sensitivity to ABA during seed germination.The considerable diversity in ABA sensitivity among rice germplasm accessions was primarily reflected by the differentiation between the Xian(indica)and Geng(japonica)subspecies and between the upland-Geng and lowland-Geng ecotypes.The upland-Geng accessions were most sensitive to ABA.Genome-wide association analyses identified four major quantitative trait loci containing21 candidate genes associated with ABA sensitivity of which a basic helix-loop-helix transcription factor gene,OsbHLH38,was the most important for ABA sensitivity.Comprehensive functional analyses using knockout and overexpression transgenic lines revealed that OsbHLH38 expression was responsive to multiple abiotic stresses.Overexpression of OsbHLH38 increased seedling salt tolerance,while knockout of OsbHLH38 increased sensitivity to salt stress.A salt-responsive transcription factor,OsDREB2A,interacted with OsbHLH38 and was directly regulated by OsbHLH38.Moreover,OsbHLH38 affected rice abiotic stress tolerance by mediating the expression of a large set of transporter genes of phytohormones,transcription factor genes,and many downstream genes with diverse functions,including photosynthesis,redox homeostasis,and abiotic stress responsiveness.These results demonstrated that OsbHLH38 is a key regulator in plant abiotic stress tolerance.