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MANAGEMENT OF PLANT-PARASITIC NEMATODES AND SOIL HEALTH USING OIL RADISH (RAPHANUS SATIVUS) AND BROWN MUSTARD (BRASSICA JUNCEA) COVER CROPS
|Title:||MANAGEMENT OF PLANT-PARASITIC NEMATODES AND SOIL HEALTH USING OIL RADISH (RAPHANUS SATIVUS) AND BROWN MUSTARD (BRASSICA JUNCEA) COVER CROPS|
|Contributors:||Wang, Koon-Hui (advisor)|
Tropical Plant Pathology (department)
show 4 moreMyrosianse activity
|Publisher:||University of Hawai'i at Manoa|
|Abstract:||This dissertation is composed of five chapters. Chapter one reviews factors that affect efficacy of biofumigation on management of plant-parasitic nematodes, focussing on Meloidogyne spp. in cropping systems and highlights two challenges. First, a number of literatures highlighted that susceptibility of biofumigant crops to target plant-parasitic nematodes could be an important management challenge and second, biofumigation being biocidal could have non-target impacts on free-living nematodes as bioindicators of soil health. Chapter two takes an alternative approach and elucidates the challenge of susceptibility as an opportunity to capitalize on as a trap crop arguing that using a good brassica host to a target nematode would be more effective as a conventional trap crop than using a poor host. When comparing trap cropping effects of ‘Sodbuster’ oil radish (OR; Raphanus sativus) as a poor host and ‘Caliente 199’ brown mustard (MS; Brassica juncea) as a good host against Meloidogyne spp. and R. Reniformis, MS showed potential as a trap crop depending on how long the trap crop was grown. MS suppressed soil population densities of Meloidogyne spp. in first and second trials by 60 and 50%, respectively where the cover crop was terminated within 42 days after planting (DAP; P ≤ 0.05) but not in third trial when terminated 49 DAP. However, population densities of R. reniformis were not suppressed by MS in the first two trials where it was terminated 42 DAP but were suppressed by 61% (P ≤ 0.05) in the third trial when the MS was terminated 49 DAP. Chapter three confirmed with previous studies that tissue maceration is necessary to activate myrosinase-glucosinolate system in brassica tissues to release bioactive isothiocyanates (ITC), soil tillage is required for the tissues to be in contact with the nematodes, and covering black plastic mulch is important to retain ITC from volatilization loss, together to maximize biofumigation effect on Meloidogyne spp. and R. reniformis. In three field trials conducted using OR and MS, soil populations of Meloidogyne spp. were suppressed by OR or MS if the biofumigant crops were macerated (M), tilled (T) into the soil and covered with black plastic (BP) in all the trials, and reduced zucchini root galls in Trials I and II. However, suppression of Meloidogyne spp. was stronger when using MS than OR in the MTBP treatment. Regardless, MTBP suppressed R. reniformis in Trial I but not in Trials II and III. None-the-less, the trend appeared that MTBP reduced R. reniformis by 33.9 and 54.9% in Trials II and III, respectively. MTBP also stimulated zucchini growth in Trials I and III, but not in II. Chapter four investigated whether biofumigation could have non-target impacts on free-living nematode as indicators of soil health. Both OR and MS did not compromise soil health but instead OR enhanced nutrient enrichment throughout zucchini growth while MS did transiently for up to 1 month after biofumigation. Terminating both OR and MS by MTBP enhanced soil health indicators but suppressive to plant-parasitic nematodes. As indicators of biofumigation, Myr activity (based on soil glucose analysis) and soil sulfate analysis were conducted to establish relationships with soil health indicators and other response variables. Myrosinase activity had a strong positive relationship with soil health indicators when toluene (methylbenzene) was added in soil samples to arrest microbial degradation of glucose. However, sulfate was stable in the soil without toluene and even had a stronger positive relationship with the soil health indicators, thus a good indicator of biofumigation in the field. Chapter five concludes the findings and provide recommendations and future directions to enhance biofumigation effects of brassicaceous cover crops against plant-parasitic nematodes.|
|Description:||Ph.D. Thesis. Ph.D. Thesis. University of Hawaiʻi at Mānoa 2019|
|Rights:||All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.|
|Appears in Collections:||
Ph.D. - Tropical Plant and Soil Sciences|
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