The Genetics of Flowering Response in Cotton. IV. Quantitative Analysis of Photoperiodism of Texas 86, Gossypium Hirsutum Race Latifolium, in a Cross with an Inbred Line of Cultivated American Upland Cotton.

T H I S paper, the fourth in a series reporting the research on flowering response of cotton at College Station, Texas, presents the results of the quantitative analysis of an experimental strain of American Upland cotton, Gossypium hirsutum L. race latifolium, designated as Texas 86. Previous studies: In the first paper of this series, LEWIS and RICHMOND (1 957) reported observing three factors which were important in controlling the time of flowering in the cross involving G. hirsutum race marie-galante, a short-day photoperiodic perennial cotton. According to them the short-day photoperiodic response was under multigenic control, and, in addition to photoperiodic response, marie-galante carried factors for delayed flower initiation. Also pronounced facultative shedding of fruit forms occurred under field-grown conditions. In the second paper, (LEWIS and RICHMOND 1960), another allotetraploid species of cotton, G. barbizdense, was studied, and the photoperiodic response was found to be under monogenic control. The day-neutral response was recessive, and there was no pronounced shedding of fruit forms or a delayed flowering response. The third paper, (WADDLE, LEWIS, and RICHMOND 1961 ) , reported studies of two selections of the race latifolium. The Zatifolium cottons are classified as annuals, and in contrast to experience with perennial mrie-galante, no expression of lateness was found. At College Station, Texas they behaved similarly to marie-galante in that the photoperiodic response was under multigenic control and facultative shedding of fruit forms was pronounced. One of the latifolium parents was grown the same year at five widely separated stations in the U. S. Cotton Belt. Modification of the response to short-day photoperiod, by temperature and perhaps other factors, was demonstrated by the fact that: none of the Zatifolium parental plants flowered at College Station, Texas; all flowered at Shafter, California; and flowering at Lubbock, Texas, Sacaton, Arizona, and Brawley, California was late and sporadic.