02506nam a2200253 a 450000100080000000500110000800800410001910000180006024501450007826000430022330000100026650000190027652018150029565000160211065000130212665000160213965000120215565000170216765000170218465000090220165000160221065300140222665300120224015575272007-04-19       1977    bl uuuu  m   00u1 u    #d1 aSPEHAR, C. R.  aScreening maturity groups "OO" and "O" of the U.S. world soybean collection for germination at 10 C, and field evaluation of selected lines.  aMadison: University of Wisconsinc1977  a93 p.  aTese Mestrado.  aThe culture of many tropical or subtropical crops has been expanded into the cooler climates or higher latitudes by developing cultivars that either tolerate cooler temperatures or avoid them by utilizing only a short, warm growing season. Soybeans are one crop wich originated in warm climates but have been adapted to grow in more temperatue regions. Because they are not very tolerant of cool temperatures, planting in the northern U. S. is customarily delayed until a soil temperature of 10C is reached. This delay in planting reduces the period of vegetative growth and, consequently, limits the ability of the plant to produce grain yield. The soybean plant is especially sensitive to daylenght so that cultivars are adapted to relatively narrow zones of latitude. In the U. S., these zones are refference to as maturity groupings, and ten of these maturity zones have been delimited. Group "00" is the classification for the zone in the northern U. S. which will have the shortest growing season but the longest daylenght during the season. Group VIII is the southernmost region of the northern groups will flower and mature too early is planted in the south, while southern cultivars planted in the north flower too late to produce a crop of grain before the freezing temperatures of fall. The specific objectives of this study were to: 1) screen the U. S. World Collection of Group "00" and Goup "0" maturity for their ability to germinate under the cool temperature of 10C; 2) evaluate the relative performance of lines which germinated most rapidly at 10C and those which germinated most slowly, by planting them in the field at early and normal dates, and 3) compare the tolerance to drought stress of fast germinating and slow germinating lines by using differential irrigation of a droughty soil.  agermination  asoybeans  atemperature  aCerrado  aGerminação  aMelhoramento  aSoja  aTemperatura  aAvaliacao  aColecao