Half-sib family selection for forage yield in orchardgrass

Genetic variation for forage yield of orchardgrass is abundant, but there are few reports of progress from selection for increased forage yield. The objective of this study was to estimate direct effects of selection from one cycle of half‐sib family selection for forage yield in orchardgrass. Eleven selected populations were compared with their parent populations within three maturity groups. Populations were evaluated under hay management at three locations and management‐intensive rotational grazing at two locations. Nine of the 11 selected populations differed, by an average of 7.4%, from their parent population in forage yield. Nine of the selected populations also showed changes in Drechslera leafspot reaction, all indicating a negative genetic correlation with forage yield. Selection for high forage yield tended to result in greater ground cover and later relative maturity. However, changes in net herbage accumulation (NHA) under rotational grazing were generally not significant and were uncorrelated with changes in forage yield, indicating that forage yield of hay plots is not correlated with the NHA of grazed plots. Although genetic gains in forage yield measured under hay management were very favourable relative to other reports from the literature, the lack of correlated progress under grazing management indicates that directed selection for NHA of orchardgrass should be conducted under grazing management.     

Photosynthesis,leaf conductance,and water relations of cowpea under saline conditions

Summary Cowpea (Vigna unguiculata L.), grown widely under both irrigated and dryland conditions, is well adapted to drought and high temperature and is moderately salt tolerant. Data on photosynthetic response and regulation of water relations in cowpea under salinity stress is lacking. Therefore, in conjunction with a field plot experiment to establish the leaching requirement of cowpea, measurements were made of carbon dioxide assimilation rates (A) by ¹⁴CO₂ uptake, leaf conductances to H₂O (g₁) by tritum uptake, and to CO₂ (g), and leaf total water potential (_t ¹) and osmotic potential ( ¹).Cowpeas, grown in field plots containing Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeraff), were irrigated daily with saline water (1,350 mg 1^–1 total salt concentration) to achieve leaching fractions of 0.17, 0.13, 0.09, 0.07, and 0.02. Cowpea maintained high leaf water potentials, high rates of CO₂ assimilation and high leaf conductances under moderately saline conditions (high leaching). Values of _t ¹ and ¹ for high leaching were consistently 50 to 200 J kg^–1 higher than for low leaching throughout the day. Calculating ¹ at full leaf turgor eliminated diurnal variation in ¹. As leaching decreased, however, A, g₁, and g, decreased significantly. About 45% of the 1°C assimilated by the leaf was incorporated rapidly into ethanol insoluble compounds. The relationship between A and g₁ for cowpea was similar to that reported for other crops.Contribution from the US Salinity Laboratory, USDA-ARS, 4500 Glenwood Dr., Riverside, CA. 92501, USA     

Foliar and yield response of Santa rosa plum to saline water spray

Summary Canopies of 22-year-old Santa Rosa plum trees irrigated with mini-sprinklers below the canopy with nonsaline (0.3 dS/m) water were sprayed weekly during one irrigation season with water having six levels of salinity (0.3, 1.1, 2.1, 3.3, 4.5, and 6.8 dS/m) to evaluate the extent of leaf injury, foliar absorption of Cl and Na, and yield response. Recognizable leaf injury was caused by spray water containing 29 mol/m³ of chloride and 15 mol/m³ of sodium. Severe leaf damage occurred when the leaf chloride and sodium concentrations exceeded 300 and 125 mmol/kg (dry weight), respectively. These concentrations were higher than those causing foliar damage on other trees in the same orchard which had been irrigated below the canopy with water having the same salinity as that sprayed on the canopy. No residual foliar injury was observed during the irrigation season following the year when the spray treatments were applied. Fruit yield measured six weeks after treatments were initiated was unaffected. In the following 2 years, yield was reduced by the highest salinity levels, even though the salt spray treatments were not continued and no foliar injury was visible.     

Minimizing genetic adaptation in captive breeding programs: A review

Captive breeding for species of conservation concern is the act of bringing rare or endangered animals into captivity with the hope of rearing sustained captive populations for eventual reintroduction into the wild. Within captivity, genetic changes can occur that may reduce a species’ ability to persist once a population is reintroduced back into its natural habitat. We sought to determine the efficacy of recommendations made to minimize genetic adaptation to captivity by addressing the following questions: (i) Are these recommendations already being carried out in captive programs? (ii) How practical is each recommendation? and (iii) Which recommendations call for future investigation? We performed an extensive search of the published literature for studies of non-domestic, non-model, captive animals in which the investigators used and reported a strategy that can minimize genetic adaptation to the captive environment. We found different forms of each recommendation already being executed in captive programs to varying degrees. In all, we reviewed 90 articles covering four broad categories of strategies. We conclude that the best approach to minimize genetic adaptation is to reduce the number of generations that a species spends in captivity. If this is not possible, then we suggest attempting to minimize generations first by delaying reproduction and then by cryopreservation of germplasm. Other strategies are effective to varying degrees depending on the species’ natural history. A large gap in the current literature is the interactive effects of multiple strategies being implemented simultaneously, future research should focus on this issue.     

The Impact of Reproductive Technologies on Stallion Mitochondrial Function

The traditional assessment of stallion sperm comprises evaluation of sperm motility and membrane integrity and identification of abnormal morphology of the spermatozoa. More recently, the progressive introduction of flow cytometry is increasing the number of tests available. However, compared with other sperm structures and functions, the evaluation of mitochondria has received less attention in stallion andrology. Recent research indicates that sperm mitochondria are key structures in sperm function suffering major changes during biotechnological procedures such as cryopreservation. In this paper, mitochondrial structure and function will be reviewed in the stallion, when possible specific stallion studies will be discussed, and general findings on mammalian mitochondrial function will be argued when relevant. Especial emphasis will be put on their role as source of reactive oxygen species and in their role regulating sperm lifespan, a possible target to investigate with the aim to improve the quality of frozen–thawed stallion sperm. Later on, the impact of current sperm technologies, principally cryopreservation, on mitochondrial function will be discussed pointing out novel areas of research interest with high potential to improve current sperm technologies.