Heritability of Variations in Oil Content of Individual Corn Kernels

Nuclear magnetic resonance spectroscopy was used to determine oil content of individual corn kernels in order to evaluate this technique as an aid in the development of strains having greater oil content. This method is rapid and does not impair viability. Individual kernels from a selfed single-cross ear ranged from 2.7 to 5.4 percent oil and were significantly correlated (r = +0.75) with the oil content of their progeny ears. This indicates that the single-kernel differences in oil content were heritable, and this method may greatly increase selection efficiency in breeding for higher oil content in corn.     

Effects of moist chilling and solid matrix priming on germination of loblolly pine (Pinus taeda L.) seeds

Loblolly pine (Pinus taeda L.) seeds from sources with a mild climate under maritime influence (North Carolina) required shorter moist chilling to achieve maximum germination vigor than seeds from sources with a harsher continental climate (Oklahoma). Solid matrix priming (SMP) for 6 d achieved as much as 60 d of moist chilling to improve rapidity, synchrony and completeness of germination for three of the four families studied. SMP after moist chilling increased the rapidity, synchrony and completeness of germination. The benefit of SMP was greatest for non-stratified seeds and the benefit decreased with length of moist chilling. In general, delaying planting for one week after SMP had minor effects on germination when seeds were kept in the SMP matrix at 4°C. Delayed planting after SMP can increase germination rapidity and synchrony of seeds that have received long moist chilling and reduce the benefit of SMP in non-moist-chilled seeds.     

Relationships between canopy size,light interception and productivity in conventional avocado planting systems

Avocado (Persea americana Mill.) is a relatively under-developed tree crop, grown commercially in climates ranging from tropical to temperate. Orchard productivity across a broad range of tree crops has been demonstrated to be related to total light interception. However, little information is currently available for avocado. Here we document the relationships between canopy volume per hectare, total orchard light interception and yield per ha for avocados of cultivar ‘Hass’ grown in low density planting systems. Total orchard light interception increased with canopy volume, with increases in light interception per unit canopy volume becoming smaller at the higher levels of canopy volume/ha. Yield/ha increased with light interception and canopy volume up to approximately 80–84% total light interception and 30,000–35,000 m³ canopy volume/ha. It is unclear whether the trend in yield/ ha at the very highest measured levels of orchard light interception and canopy volume should be described as plateauing or declining. Mean fruit weight decreased as light interception increased, although the relationship varied between seasons. For these conventional planting systems there is no yield benefit from increasing canopy light interception above 80–84%, and there may be yield decline at higher levels of orchard light interception.     

In vitro Maturation of Oocytes from Santa Ines Ewes Subjected to Consecutive Sessions of Follicular Aspiration by Laparoscopy

The success of embryo production in vitro depends upon the use of an efficient oocyte retrieval technique, and the best results have been obtained by laparoscopic aspiration. The aim of this study was to evaluate the effect of consecutive sessions of follicular aspiration on the quantity, quality and in vitro maturation competence of oocytes obtained from ewes subjected to hormonal stimulation. Six Santa Ines ewes underwent nine sessions of follicular aspiration by laparoscopy with a 7‐day interval between sessions, totalling 56 aspirations. After 24 h of culture, oocytes were stained and classified according to the stage of nuclear and cytoplasmic maturation. Oocyte retrieval rate was 61.4 ± 2%, resulting in a total of 249 oocytes. No significant variation was observed between sessions (p > 0.05). The average number of oocytes retrieved from each ewe was 6.4 ± 2 per session and 42 ± 4 in total. No significant difference was observed between the frequencies of the different stages of nuclear maturation: 32.72% mature, 40.74% immature and 26.54% degenerated/indeterminate oocytes; however, a significant difference was observed between the frequencies of the different stages of cytoplasmic maturation: 10.7% mature, 73.25% immature and 16.05% degenerated/indeterminate oocytes. No significant difference was observed in nuclear or cytoplasmic maturation between the weeks of procedure. We conclude that after nine consecutive sessions of follicular aspiration, the quantity and quality of retrieved oocytes remained unchanged as well as the levels of nuclear and cytoplasmic maturation obtained, demonstrating the viability of this technique for repetitive follicular aspirations on the same donor.