Sperm chromatin in beef bulls in tropical environments

Sperm chromatin status was assessed in 565 Zebu and Zebu crossbred beef bulls in extensive tropical environments using the sperm chromatin structure assay (SCSA). The SCSA involved exposure of sperm to acid hydrolysis for 0.5 or 5.0 minutes, followed by flow cytometry to ascertain relative amounts of double-stranded (normal) and single-stranded (denatured) DNA, which was used to generate a DNA fragmentation index (%DFI). With conventional SCSA (0.5-minute SCSA), 513 bulls (91%) had <15 %DFI, 24 bulls (4%) had 15 to 27 %DFI, and 28 bulls (5%) had >27 %DFI. In 5.0-minute SCSA, 432 bulls (76%) had <15 %DFI, 68 bulls (12%) had 15 to 27 %DFI and 65 bulls (12%) had >27 %DFI. For most bulls, the SCSA was repeatable on two to four occasions; however, because most bulls had <15 %DFI, repeatability of the SCSA will need to be determined in a larger number of bulls in the 15 to 27 %DFI and >27 %DFI categories. The %DFI was negatively correlated with several bull semen parameters and the strongest negative correlation was with normal sperm. There was a strong positive correlation between %DFI and sperm head abnormalities. Based on these findings, most Zebu beef bulls in extensive tropical environments had relatively stable sperm chromatin. Based on the apparent negative correlations with conventional semen parameters, we inferred that the SCSA measured a unique feature of sperm quality, which has also been suggested for other species. Further studies on the relationships between sperm chromatin stability and fertility are required in beef bulls before chromatin status can be used as an additional predictor of the siring capacity of individual bulls in extensive multiple-sire herds. (C) 2013 Elsevier Inc. All rights reserved.

Ginger (Zingiber officinale) autotetraploids with improved processing quality produced by an in vitro colchicine treatment

Ginger autotetraploids were produced by immersing shoot tips in a 0.5% w/v colchicine, 2% v/v dimethyl sulfoxide solution for 2 h. Stomatal measurements were used as an early indicator of ploidy differences in culture with mean stomata length of tetraploids (49.2 μm) being significantly larger than the diploid (38.8 µm). Of the 500 shoot tips treated, 2% were characterised as stable autotetraploid lines following field evaluation over several seasons. Results were confirmed with flow cytometry and, of the 7 lines evaluated for distinctness and uniformity, 6 were solid tetraploid mutants and 1 was a periclinal chimera. Significant differences were noted between individual tetraploid lines in terms of shoot length, leaf length, leaf width, size of rhizome sections (knob weight) and fibre content. The solid autotetraploid lines had significantly wider, greener leaves than the diploids, they had significantly fewer but thicker shoots and, although ‘Queensland’ (the diploid parent from which the tetraploids were derived) had a greater total rhizome mass at harvest, its knob size was significantly smaller. From the autotetraploid lines, one line was selected for commercial release as ‘Buderim Gold’. It compared the most favourably with ‘Queensland’ in terms of the aroma/flavour profile and fibre content at early harvest, and had consistently good rhizome yield. More importantly it produced large rhizome sections, resulting in a higher recovery of premium grade confectionery ginger and a more attractive fresh market product.