تكامل جرعة منخفضة من مبيد الترفلان مع مخلفات زهرة الشمس في مكافحة الادغال وتحسين نمو محصول الماش لتقليل الاعتماد على المبيدات والحد من مخاطرها == Integration of Reduced Dose of Trifluralin Herbicide With Sunflower Residues For Weed Control In Mungbean Field
Author name:
اﺭﻭﻯ ﻋﺒﺪ ﺍﻟﻜﺮﻳﻢ ﺗﻮﻓﻴﻖ
Supervisor name:
اﺑﺮﺍﻫﻴﻢ ﺷﻌﺒﺎﻥ ﺍﻟﺴﻌﺪﺍﻭﻱ
General topic:
Biology
Specific topic:
Plant - Physiology
Degree:
Doctorate
University:
University of Baghdad
Language:
English
University location:
Baghdad
First pages:
24T2999 - p.pdf
Abstract:
Two field experiments, several greenhouse and laboratory experiments were conducted during the course of study to evaluate the allelopathic potential of two sunflower (Helianthus annuus L.) cultivars on companion weeds and weeds grown in mungbean (Vigna radiata L. R. Wilczek) field alone and in combination with reduced rate herbicide, and to determine the chemical and genetical bases of allelopathic traits in the test cultivars. The aim of the first experiment was to test whether the variation in weed growth between the sunflower cultivars (Shumoose and Sin Altheeb), which was observed in the field, was due to differences in their allelopathic potential. Results showed the ability of both cultivars to reduce weed population and biomass with the superiority of Shumoose cultivar in suppression of weed density at 60 and 120 days after sowing compared to Sin Altheeb. Weed biomass was significantly reduced up to 90 and 71% by Shumoose and Sin Altheeb cultivars, respectively. Stair case experiment indicated that root exudates of Shumoose cultivar showed more suppression to weeds than Sin Altheeb giving additional evidence for the superiority of Shumoose cultivar in its allelopathic weed suppression. Chemical analysis by High performance liquid chromatography indicated the presence of 9 compounds in root exudates of Sin Altheeb and 8 compounds in Shumoose, and all are Phenolic in nature. However, total of the isolated phenolics was doubled in Shumoose than in Sin Altheeb. Most of the isolated chemicals are reported to have inhibiting ability for germination and growth of plants, including weeds. Second field experiment was undertaken to explore the response of weeds and mungbean crop to soil incorporated with sunflower residues in combination with lower rate of a pre - plant herbicide (trifluralin). Sunflower residues of the two cultivars Shumoose and Sin Altheeb at 3.2 and 6.4 t ha - 1 were used either alone or in combination with trifluralin at 1.2 L ha - 1 (50% of label rate). Weedy check (control), trifluralin at full label rate (2.4 L ha - 1), and weed free treatments were also included for comparison. Plots treated with 50% of label rate of herbicide and amended with sunflower residues of cultivar Sin Altheeb recorded least weed density and dry biomass and this suppression was much greater than the residue treatments alone and more than cultivar Shumoose. Application of herbicide at 50% rate in plots amended with Sin Altheeb residue resulted yield 64 % more than with the label rate of herbicide treatment. Chromatographic analysis of sunflower amended field soil revealed the presence of several potent allelopathic compounds in the residues of both cultivars with greater quantity (355.5 µg/ml) in Sin Altheeb than in Shumoose (250.9 µg/ml). Dynamics of release, decomposition and degradation of allelochemicals into the soil showed that different compounds exhibited differential behavior for these processes. Overall quantity of allelochemicals started to increase after 2 weeks of decomposition and peaked at 4 week of decomposition (180.1 ppm) then declined sharply in their quantities thereafter. Periods indicating higher quantities of total phenolics as shown by chromatographic analysis was coincided with the periods in which higher suppressive activity against weeds grown under field conditions. Bioassay of sunflower residues decomposed in soil at different times on Echinochloa colonum L, one of the weeds dominated the mungbean field, revealed that residues of both cultivars suppressed growth of E. colonum weed. The phytotoxicity started after 2 weeks and persisted for 8 weeks. However, Sin Altheeb residues showed greater inhibition than Shumoose cultivar at the last three decomposition periods. Shumoose residues recorded appreciable reduction to the growth of test weed compared to Sin Altheeb. The effect of residues of both cultivars on chlorophyll content and ions uptake in Amaranthus retroflexus L. weed revealed that residues of both species reduced chlorophyll content of leaves and the reduction increased with the increased residue rate. Sin Altheeb cultivar residues were more inhibitory than Shumoose at the lower residue rate. In the same weed, ions uptake was significantly averted by the residues of both cultivars. P and K was significantly increased over control, while Ca, Mg an Fe were found to be decreased over control due to application of sunflower residues in soil at 8 g per kg soil. N was the only test element that did not significantly influence by the residue treatments. No significant differences were found in the test ion uptake between the test sunflower cultivars. Results of using RAPD technique on the sunflower genomic DNA revealed that all the 19 primers used in this study scored different amplification monomorphic and polymorphic bands in the tested genotypes with 12 primers generated polymorphic bands. These bands present in one cultivar and absent in another. They could be responsible for allelopathic trait or secondary compounds associated with this phenomenon. Further work is recommended to analyze the sequence of this band to find out whether it is related to allelopathic trait or not.
