| The winter wheat can stimulate Orobanche seed germination to be as one ‘trap crop’ forcontrolling the weeds of Orobanchaceae. Based on this, we studied the method of breakingdormancy, the best pre-conditioning time and observation time of Orobanche seeds. Throughthe hydroponic method, winter wheat root exudates were collected, and then purified andidentified by LC-MS/MS. Rhizosphere soils, roots and shoots at different growth stages ofwinter wheat were collected, and these samples were extracted by distilled water or methanoland then diluted to four concentration. The extracts (distilled water and methanol) were testedto stimulate O. cumana and O. aegyptiaca seeds germination. According to the twoOrobanche seeds germination rates, the stimulation effect among different organs of winterwheat were compared and the better solvent would be identified; the winter wheat whichperformed better at different growth stages could also be screened out to control Orobancheweeds; it could also reflect the allelopathy potential of different winter wheat genotypes.Through winter wheat/sunflower rotation, the O. cumana parasitic quantity were investigatedand the diameter at breast height (DBH), plant height and biomass of sunflower were alsotested. Through these indexes, we could found if different winter wheat genotypes can be as‘trap crops’ for O. cumana and increase sunflower production.The main conclusions of this study are as follows:1. Pre-conditioning O. cumana and O. aegyptiaca seeds by distilled water could breaktheir dormancy. They should be pre-conditioned at least for3days, and the germination ratetended to be stable after pre-conditioning for1-2weeks.2. After extracting for three times, ethyl acetate could extract the germination stimulantfrom the root exudates into ethyl acetate phase. The root exudates at the differentconcentration stimulated O. cumana and O. aegyptiaca seed germination followed the role of100mg/L>10mg/L>1mg/L. At the three concentration, the germination rate of O. cumanaand O. aegyptiaca increased as the ploidy of wheat genotypes doubled, and there weresignificant differences (P <0.05) among the different varieties. LC-MS/MS mass spectrometrymultiple reactions monitoring technology was used to analyze the germination stimulant inwheat samples and its structure were different with the14known strigolactones. Maybe the germination stimulant in wheat was not any one of the14substances. The structure needs tobe further isolated and identified by new methods.3. At seedling stage, the rhizosphere soil of different winter wheat genotypes coulddirectly stimulate O. cumana and O. aegyptiaca seed germination. It was shown that thegermination stimulant secreted from winter wheat at natural state could stimulate Orobancheseed germination at certain concentration.At jointing stage, the rhizosphere soil and its extracts of different winter wheat genotypescould stimulate the two Orobanche seed germination. The germination rate increased as theploidy of winter wheat genotypes doubled, and the hexaploid winter wheat stimulated thehighest germination rate. The germination stimulant was synthesized in the roots of winterwheat. There were positive correlations between Orobanche seed germination induced by rootand shoot extracts of winter wheat.At heading stage, the roots of Shaan253stimulated the highest germination rate of O.cumana seed (32.4%), while the O. aegyptiaca seed germination rate was between20%to30%. O. aegyptiaca seed germination rate induced by the stem methanol extracts of hexaploidgenotypes of Shaan139and Shaan253were up to49%and51.1%. Among O. cumana seedgermination induced by distilled water extracts of different organs of winter wheat, the leaveswas the highest, roots, stems and ears were similar. There were positive correlations betweenthe roots and stems, leaves and ears according to the germination rate. It showed that thegermination stimulant was synthesized in the wheat root and transported to the shoot.At maturity stage, O. cumana and O. aegyptiaca seed germination directly induced bythe rhizosphere soil of different winter wheat genotypes decreased gradually, while thegermination rate induced by aboveground extracts increased. The stem distilled water extractsof Shaan139stimulated the highest germination of O. cumana (28.1%), and methanolextracts stimulated the germination rate more than30%. The germination rate stimulated bythe stem extracts of Shaan253were up to27.7%(distilled water) and23.7%(methanol). O.cumana seed germination rate induced by the leaf methanol extracts of T. monococcum L. wasup to45.9%. O. aegyptiaca seed germination rate induced by the leaf extracts of hexaploidwinter wheat of Shaan253were up to24%(distilled water) and29%(methanol). O. cumanaseed germination rate induced by the glume extracts of Shan253were up to26.8%(distilledwater) and37.6%(methanol), and O. aegyptiaca seed germination rate was up to33.2%induced by its methanol extracts. Among O. cumana seed germination stimulated by theextracts of different organs of the winter wheat, there were positive correlations between theroots and stems, roots and grains. According to O. aegyptiaca seed germination rate, itshowed positive correlations among the roots, stems, leaves, grains and glumes. The germination stimulant was accumulated aboveground. Maybe the stalk could further releasethese substances to stimulate Orobanche seed germination, and this requires experimentalverification in future.4. The extracts (distilled water and methanol) of different organs of winter wheatstimulated O. cumana and O. aegyptiaca seed germination at seedling, jointing, heading andmaturity stages, and the germination rate increased gradually as the ploidy of winter wheatgenotype doubled.5. Planting the winter wheat of Shaan253and Shaan139in front stubble of sunflower,the parasitic number of O. cumana were3.2and4.6on per sunflower, which was1/6and1/4compared to the control. It could significantly reduce the parasitic rate of O. cumana. TheDBH of sunflower was0.2mm more than the control. The average plant height of sunflowerwas10cm more than the control. The fresh and dry weights of parasitized sunflower wereonly46%and37%of unparasitized sunflower. So planting winter wheat in front stubble ofsunflower could significantly increase the DBH, plant height, biomass of sunflower anddecrease the parasitic number of O. cumana, and improved the yield of sunflower indirectly. |
PDF Full Text Request