The aim of this study was to assess the effect of exogenous DNA and incubation time on the viability of bovine sperm. Sperm were incubated at a concentration of 5 × 106/ml with or without plasmid pEYFP–NUC. Fluorescent probes, propidium iodide/Hoechst 33342, FITC–PSA and JC-1, were used to assess plasma membrane integrity (PMI), acrosome membrane integrity (AMI) and mitochondrial membrane potential (MMP) respectively at 0, 1, 2, 3 and 4 h of incubation. Exogenous DNA addition did not affect sperm viability; however, incubation time was related to sperm deterioration. Simultaneous assessment of PMI, AMI and MMP showed a reduction in the number of sperm with higher viability (integrity of plasma and acrosome membranes and high mitochondrial membrane potential) from 58.7% at 0 h to 7.5% after 4 h of incubation. Lower viability sperm (damaged plasma and acrosome membranes and low mitochondrial membrane potential) increased from 4.6% at 0 h to 25.9% after 4 h of incubation. When PMI, AMI and MMP were assessed separately we noticed a reduction in plasma and acrosome membrane integrity and mitochondrial membrane potential throughout the incubation period. Therefore, exogenous DNA addition does not affect sperm viability, but the viability is reduced by incubation time.

Four variant lines, HB1, HB2, HB3 and HB4, were derived from progenies of upland cotton (Gossypium hirsutum) cultivar Yumian 17 that had been transformed with genomic DNA from sea island cotton, Gossypium barbadense, using the pollen tube pathway (PTP) method. They showed significant differences from the wild-type recipient in terms of fibre quality, lint percentage, boll weight and other agronomic traits. The four variant lines also differed from the wild-type recipient in the amplification products of two SSR loci, indicating that the DNA of G. barbadense had been introduced into the genome of the recipient and was inherited stably. On the other hand, the agronomic traits of another three lines (HB5, HB6 and HB7) derived from the same transformation experiment were identical to those of the wild-type recipient, indicating that G. barbadense DNA had not integrated into the genome of these lines. A combination of the analyses on agronomic traits and SSR markers indicated that transgenic upland cotton strains produced by the PTP method could become homozygous in only a few generations and the foreign DNA introduced during the transformation experiments could be inherited stably in the transgenic progenies.