DROUGHT CONDITIONS INDUCE MOTE FORMATION IN INTERSPECIFIC COTTON HYBRIDS

Motes rue cotton ovules that fail to ripen into mature seeds, developi ng instead into aborted structures which cause imperfections in ginned fibers and textile products from cotton. Interspecific hybrids (ISHs) of cotton (Gossypium hirsutum L. x G. barbadense L.) tend to produce a high number of motes. The term motes refers to various types and siz es of aborted structures which result from different disorders, may ha ve different effect on lint quality and may be affected differently by various factors. This research was aimed at studying the effect of ir rigation regime on the formation of mote of various sizes in ISHs. Fiv e ISHs were examined in 1993 and four ISHs and two control cultivars ( G. hirsutum L. and G. barbadense L.) were evaluated in 1994 in the fie ld under both dryland and irrigated treatments. Motes found in seed-co tton samples were sorted into small, medium, and large sizes, and coun ted. In 1994, flowers were tagged at several stages, and the formation of motes at different reproductive phases was examined. Between 21 an d 56 % of the total seed potential developed into motes in the ISHs vs , 11 to 28 % in the control cultivars. Moreover, when considering mote numbers per gram of fiber, which was previously found to be more clos ely related to nep (tangled fibers) number, total mote numbers were up sevenfold higher in the ISHs than in the control cultivars. Analyses of motes by size category revealed that numbers of small and medium mo tes in ISHs were higher than in controls, whereas numbers of large mot es were similar. The number of small and large motes from the dryland treatment was 2 to 5 times greater than from the irrigated treatment, whereas medium motes were unaffected by irrigation. The number of smal l and large motes also increased under dryland conditions as the repro ductive process progressed. It was concluded that drought conditions i nduce the formation of small and large motes, whereas medium motes res ult from embryo abortion due to genetic disorders. (C) 1998 Elsevier S cience B.V.