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Small broomrape (Orobanche minor) is an obligate, chlorophyll-lacking parasite that parasitizes red clover (Trifolium pratense) roots. This study was conducted to develop and implement an integrated, biologically based control program for small broomrape by using wheat as a false host to reduce the soil seed bank. The relationship between temperature and small broomrape seed germination was investigated. Small broomrape seed germination increased as temperature increased from 5 to 20 C. The greatest germination was 75% with the 20 C treatment. For germination to occur, small broomrape must be stimulated by host or false plant exudates. The relationship between temperature and germination stimulant production by red clover and wheat was studied. There were differences in small broomrape germination when exudates from red clover grown for 8 wk were used. Small broomrape germination stimulated by exudates from wheat grown for 4 wk differed among germination temperatures
tested. The least small broomrape germination occurred with the 15 C treatment. The timing of small broomrape germination stimulant production by red clover and wheat relative to crop growth stage was studied. The maximum germination was 77% using exudates produced by red clover at the 3-trifoliolate stage. For wheat, the maximum germination was 25% using exudates produced by 1-leaf wheat. Germination stimulant produced after the tillering stage of wheat was minimal. Red clover produced germination stimulant at all growth stages, while wheat produced germination stimulant only at early stages of development. A study investigated the number of winter wheat rotation life cycles (WRC) that are required to reduce parasitism of subsequent red clover crops. The greatest number of small broomrape attachments and the greatest small broomrape biomass were observed with 0-wheat rotation cycles (0-WRC), and both were reduced if wheat was included in the rotation. Above ground red clover biomass was less with the 0-WRC treatment than any of the other treatments. Wheat in rotation with red clover has the potential to reduce small broomrape impact on red clover. |
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