Characterizations of male sterility in a glyphosate-tolerant upland cotton (Gossypium hirsutum L.) induced by glyphosate and its assessments on safety utilization

Abstract

Productivity of hybrid cottonseed by steady male sterile line is considered as an effective strategy in heterosis utilization. The male sterility was obtained by glyphosate application on transgenic glyphosate-tolerant (TGT) cotton line GRR, and its phenotypes were stable and apparent from previous primarily study. Systematic characterizations and safety assessments on the male sterility must accelerate its utilization and release in hybrid cottonseeds productions. In this study, featured characteristics in the male sterility were revealed from morphological phenotype, microsporogenesis, expressing pattern of exogenous G6-EPSPS mRNA, antioxidant enzymes response. Additionally, safety assessments on the male sterility obtained from GRR, based on outcrossing rate test, yield and fiber quality traits, in comparison with conventional manual emasculating, which were conducted for 3 seasons. The results indicated that the male sterile is stable with typical characteristics as following: (1) shorter and fusion filaments, larger distance between androecium and stigma, and anther indehiscence; (2) pre-degradation on tapetum and “cavitation” pollen during microsporogenesis; (3) Higher increasing expression efficiency of G6-EPSPS, as much as approximate 8 times, in pistil versus stamen in GRR-GT (GRR after glyphosate) was revealed, comparing with the control GRR (4) APX activity increased in stamens while decreased in other organs, in GRR-GT versus GRR. GRR-GT is safe as complete abortion and capable in cotton heterosis utilization, since there were no negative effects on F1 yield traits and significance in fiber quality parameters, in comparison with conventional manual emasculation. In details, the all fiber lint yields and Micronaire values ranged from 1536.80 ± 115.64 to 1883.90 ± 18.58 kg/ha and 4.60 ± 0.10 to 5.10 ± 0.79 respectively.