Studies of the effects of apple root distribution on the spread of Phymatotrichopsis omnivora within apple orchards /
Apple trees (Malus sylvestris var. domestica.) were studied in three orchards in Kerrville, Texas to determine root distribution within orchards using the soil core method. Root losses associated with washing and storing soil cores were identified and a data correction curve was developed to correct...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731681301&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Apple trees (Malus sylvestris var. domestica.) were studied in three orchards in Kerrville, Texas to determine root distribution within orchards using the soil core method. Root losses associated with washing and storing soil cores were identified and a data correction curve was developed to correct root length data. Root distributions for one-. Two- and three-year-old apple trees ('Fuji'/'Malling 26') revealed measurable differences in root length density (RLD) by tree age, soil depth, radial distance from the tree, and angular orientation within and across rows (P[]0.05). Mean RLD and percentages of samples with measurable roots declined for fine and coarse riots across all ages studied with increasing soil depth and radial distance from the trunk (P[]0.05). Greatest RLD for fine roots was found along rows for the youngest two orchards and along rows and under trellises for the oldest orchard (P[]0.05). For coarse roots, the greatest RLD was found in the along row direction for all orchards (P[]0.05). Movement of Phymatotrichopsis omnivore within two orchards of five-year-old, trellised apples on M.7a rootstocks in Kerrville, Texas was determined by visual observation of fungal strands on roots and by measuring infrared canopy temperatures. Pathogen movement (P[]0.01) occurred beyond symptomatic trees along and perpendicularly across rows. In both orchards, 80% to 100% of the first asymptomatic trees were infected along rows followed by 60% infection perpendicularly across rows. No movement was observed diagonally across rows in either orchard. Differences between canopy temperature and air temperature were significant for asymptomatic, infected trees in one orchard (P[]0.05). Infection, colonization, and movement of P. omnivore were evaluated in three-year-old trees ('Gala'/'M26') in 30-gallon containers. Infection was observed in the nursery after 12 weeks for trees inoculated in August 1997 and after 15 weeks for trees inoculated in February 1998. After 18 weeks, 100% and 80% of trees were infected after inoculation in August and February, respectively. A separate set of experiments, designed to study pathogen movement along live and dead apple roots and through bare soil, confirmed modality in cotton plants but visible colonization or movement of P. omnivore along apple roots was not detected. |
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| Item Description: | Vita. "Major Subject: Plant Pathology". |
| Physical Description: | xiii, 117 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 107-116). |