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Responses of a Bt Cotton Cultivar (DP NuCOTN 33b) to Selected Levels of Boll Injury

J. Gore, B. R. Leonard, J. S. Russell, J. H. Fife, G. E. Church and J. J. Adamczyk


 
ABSTRACT

Plant maturity and yield responses of a transgenic Bacillus thuringiensis Berliner var. kurstaki (Bt) cotton cultivar (NuCOTN 33B) were measured after 7 levels (0, 2.5, 5, 10, 20, 40 and 80%) of mechanical boll injury were applied during each of the first 4 weeks of flowering during 1997 and 1998. Injury was produced by drilling a hole completely through bolls using a portable drill and bit (0.25 in. diameter) to simulate feeding by late instar Lepidopteran larvae. At the end of the season, crop maturity (percent open bolls) and seedcotton weights were recorded. No level of injury applied during the first 2 weeks of flowering significantly delayed crop maturity in 1997. Crop maturity was significantly delayed when boll injury was applied during weeks 3 and 4 of flowering in 1997. Percent open bolls ranged from 73-41% and 72-12% during weeks 3 and 4 of flowering, respectively, for 0-80% boll injury. Seedcotton weight was not significantly affected by boll injury when applied during the first 2 weeks of flowering in 1997. Boll injury applied during weeks 3 and 4 of flowering significantly reduced seedcotton yield by 5-16% and 0-32%, respectively, for 2.5-80% boll injury. Boll injury applied in 1998 produced results similar to those observed in 1997 for crop maturity. The only significant delays in crop maturity occurred during weeks 3 and 4 of flowering. Percent open bolls ranged from 81-47% and 87-26% during weeks 3 and 4 of flowering, respectively, for 0-80% boll injury. Seedcotton weight was not significantly affected by any level of boll injury applied during each of the first 4 weeks of flowering in 1998.



Reprinted from Proceedings of the 1999 Beltwide Cotton Conferences pp. 939 - 942
©National Cotton Council, Memphis TN

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Document last modified Monday, Jun 21 1999