Crossing Success in Cotton in Arizona as Affected by Irrigation, Number of Flowers Pollinated, and Time of Emasculation1

Abstract

AbstractRetention of crossed bolls is low in plants of cotton (Gossypium hirsutumL.) that are exposed to the high temperatures and water deficits encountered commonly in irrigated desert regions. One purpose of this study was to determine the relationship of the retention of crossed bolls with number of days after irrigation and with the number of pistillate flowers pollinated with one staminate flower. Another purpose was to determine the feasibility of emasculating cotton flowers in the morning of the day of pollination rather than at the traditional time of the afternoon before pollination. For three seasons, flower buds of ‘Deltapine 61’ were hand‐emasculated from 0200 to 0600 h for 10 to 12 days through an irrigation cycle at Phoenix, Ariz. Soil type was Avondale clay loam (a fine, loamy, mixed, hyperthermic Torrifluventic Haplostolls). Groups of pistillate flowers‐10, 15, 20, 25, and 30‐were each pollinated with a single staminate flower from a breeding stock homozygous for R1, red plant color. After each daily session of crossing, 100 open–pollinated flowers were tagged to serve as controls. From this study, we observed 1) a progressive decrease over days in boll set, followed by an increase just before the next irrigation, which illustrates the transitory influence of water stress; 2) that crosses made the 1st week after an irrigation yielded almost as much total hybrid seed as those made for the entire 14‐day period between irrigations; 3) that seed yield loss would not have been severe even if limited amounts of pollen had forced us to pollinate 30 pistillate flowers per staminate flower; and 4) that emasculating flowers even as early as 0200 h on the day of pollination led to some self‐contamination.