Challenges to the exploitation of host plant resistance for Striga management in cereals and legumes by farmers in sub-Saharan Africa: a review

Striga hermonthica, Striga asiatica and Striga gesneroides are obligate root parasites that cause severe yield losses in cereals and legumes in sub-Saharan Africa. Genetic control of Striga through resistance is widely considered to be the most practical and economically feasible method for long term control. The paper presents a comprehensive account of the Striga resistance mechanisms and environmental limitations to their usage in sub-Saharan Africa. Components of Striga resistance in cereals and legumes include low germination stimulant production, low haustorial initiation factor, mechanical barriers, incompatibility, antibiosis and Striga avoidance due to root growth habits. The successful exploitation of resistance has been limited by existence of specificity towards hosts, parasites that have evolved races specific host cultivars, Striga genetic variance which enables parasite to adapt to new resistance alleles and diverse hosts which support the parasite even in the absence of cereals together with low fertility due to nutrient mining in the smallholder sector. The results imply that different resistance mechanism may need to be present in genetically heterogeneous varieties or cereals with different resistance mechanisms may be rotated in the same field. Comprehensive Striga management systems should also address soil fertility in the small holder farmers of sub-Saharan Africa.     

Coenzyme Q10 and α‐Tocopherol Prevent the Lipid Peroxidation of Cooled Equine Semen

Biotechnology applied for equine semen increases the levels of reactive oxygen species and reduces the natural antioxidant defence, by both dilution and removal of seminal plasma. Therefore, the aims of this study were to evaluate the effect of adding coenzyme Q10 (CoQ10) and α‐tocopherol (α‐TOH) to the cooling extender, singly or in combination, on sperm parameters, and their effectiveness in preventing lipid peroxidation (LPO) of equine semen during cooling at 5°C for 72 h. Ten adult stallions of proven fertility were used, using two ejaculates each, subjecting them to the treatments with the following concentrations: α‐TOH: 2 mm ; CoQ10: 40 μg/ml; and CoQ10 + α‐TOH: 40 μg/ml + 2 mm for control (C) without the addition of antioxidants and for vehicle control (EtOH) with 100 μl ethanol. The CoQ10 group had a higher percentage of total motility (69.1 ± 16.2%) compared to control (62.1 ± 16.2%) and EtOH (58.1 ± 18.6%). CoQ10 + α‐TOH and α‐TOH groups were most effective in preventing LPO compared to controls (1765.9 ± 695.9, 1890.8 ± 749.5, 2506.2 ± 769.4 ng malondialdehyde/10⁸ sptz, respectively). In conclusion, CoQ10 and α‐TOH were effective during the cooling process of equine semen at 5°C for 72 h, providing increased levels of total motility, as well as lower LPO.     

The ginsberg experiment: modern and prehistoric evidence of a bone-flaking technology

The discovery of butchered and modified bones of extinct Pleistocene fauna from Old Crow Flats, Yukon Territory, and the Dutton and Selby sites, Colorado, provides some of the earliest evidence for man in the New World. However, the significance of these discoveries rests entirely on the ability to determine whether these remains were modified by man. The results of experiments of elephant butchering, bone fracturing, and bone tool manufacturing support the hypothesis that these modified bones can be used to identify the presence of cultural activities.     

Constructing ``quality': The political economy of standards in Mexico's avocado industry

As the world's leader inavocado production, Mexico produces anestimated 900,000 tons/year, of which the stateof Michoacán produces 83% of nationalproduction and 40% of world avocado productionwithin five regional districts. In 1914 theUnited States imposed a phytosanitary banagainst Mexican avocado exports to the USmarket, a non-tariff barrier that stood despiteNAFTA. This paper examines increasedstandardization of product quality in avocadoas a political process in Michoacán duringthe 1980s and 1990s, during which differentregional groups and firms struggled to imposetheir standards and defend their economicinterests in the market. In the 1990s, alliedwith the Mexican government, elite avocadogrowers mounted a phytosanitary campaign thatconvinced the USDA and US government to liftthe ban and allow Mexican avocado imports intothe US market in 1997. Since 1997 the Mexicangovernment has expanded Michoacán'sphytosanitary campaign, imposing internationalstandards on all avocado growers, even thoseproducing for the national market. By expandingthe campaign and institutionalizing newstandards of quality, industry experts nowconsciously link phytosanitary quality tocommercial quality. They propose atransformation of previously acceptedproduction and post-harvest practices.Theoretically, increased standards of quality,accompanied by systematic methods of evaluationand verification, should benefit all producers.However those growers producing for thenational market adhere to new rules designed toimprove product quality yet receive noimmediate, tangible economic benefits. Thiscase study demonstrates that theinstitutionalization of product standards iscarried out within an existing politicalsystem. Understanding whose standards countrequires careful analysis of how powerfulactors in specific agricultural industriesreshape and define standards of quality interms that benefit themselves.     

Composting as a Means of Disposal of Sheep Mortalities

Four studies explored the feasibility of year-round composting of lamb and mature sheep mortalities within the arid climate of the Canadian prairies. In all studies, a ratio of 2:1:1 (manure : mortalities : chopped straw) was maintained, although depth of the mortality layer within the bin, number of layers of mortalities per bin, age of animal (lamb or mature sheep) and time of year (summer or winter) were varied. Composting neonatal lambs in the spring/summer was successful whether a single layer (n=15 lambs, weight 99.7 kg) or two, separated layers of mortalities (n=41 lambs, weight 198 kg) were added to a 2.4 m³ open bin. Residual bone, wool and soft tissues were negligible after the lamb compost had completed one heating cycle. In contrast, composting mature sheep in the fall/winter was more difficult due to: (1) over wet manure (31% dry matter) resulting in continuous anaerobic decomposition of carcasses; (2) fat/grease accumulation when composting a layer of carcasses 71 cm in depth (weight of sheep 1020 kg). For mature sheep mortalities, 2 heating cycles were required to eliminate soft tissues and wool. As compost in all studies heated in excess of 60°C in the primary and/or secondary bin, bacterial isolates taken after the compost completed the secondary heating cycle were all innocuous species. Provided that compost is protected from excessive moisture and compost is aerated by turning into a secondary bin, a 2:1:1 (manure:mortalities:straw) ratio allowed for year-round composting of lamb and mature sheep mortalities.     

Population structure and partial anadromy in Oncorhynchus mykiss from Kamchatka: relevance for conservation strategies around the Pacific Rim

Abstract –  Conservation of life-history diversity found in Oncorhynchus mykiss requires knowledge of the underlying population structure and genetic basis of this variability. We analysed variation at 10 microsatellite loci from seven rivers across Kamchatka to identify population structure and to test for divergence between life-history forms. We found lower heterozygosity in Kamchatkan populations compared with North American populations, but population structure was substantial (region-wide F _ST = 0.11) and followed an isolation-by-distance pattern similar to that reported for older North American populations. We found no evidence for genetic divergence between resident and anadromous individuals in the Sopochnaya River or between typically anadromous individuals and 'half-pounders' in the Utkholok River. A review of other studies of reproductive isolation, in combination with our results, suggests: (1) that pristine populations of steelhead should be expected to exhibit partial anadromy; and (2) that managing anadromous and resident individuals separately without demonstrating reproductive isolation is biologically unsound.     

Behavior of feedlot cattle affects voluntary oral and physical interactions with manila ropes

Providing cattle with access to manila ropes has shown promise as a means of monitoring zoonotic bacteria in pens of feedlot cattle. Studies were conducted to determine the impacts of climate, animal age and BW, number of ropes, duration of placement, and previous rope access on efficacy of ropes as a sampling technique for feedlot cattle. Eight pens of commercial finishing cattle (average 196 +/- 19 animals per pen, 536.7 +/- 22.9 kg) were monitored for a total of 7 d in October of 2003 (commercial study). One rope was tied on the pen railing adjacent to the feed bunk in each pen, and the proportion of animals within the pen contacting the rope was recorded. In a second study, 80 cattle housed in 8 pens (each 270 m(2); 10 animals/pen) were monitored for 1 d/wk using video cameras (video study). Video images were collected for 8 consecutive weeks immediately after weaning (average BW = 252.7 +/- 30.6 kg) and for 6 wk at the end of the finishing period (average BW 541.2 +/- 42.8 kg). In the commercial study, the proportion of cattle contacting the rope per pen increased over the first 6 h to 70% (P < 0.05), although approximately 50% of the cattle contacted the rope within 2 h after placement. A 40 degrees C reduction in ambient temperature on d 6 caused cattle to cease contact with the ropes, although after 6 d of acclimation to reduced ambient temperature, interactions with ropes recovered to 47% of previous values. In the video study, weaned calves required 2 wk of acclimation to the feedlot environment before contact with the rope was maximized. Contact with the rope was most frequent 3 to 8 wk after entry into the feedlot and decreased (P < 0.05) as cattle approached slaughter weight. It is likely that ropes will be most effective at monitoring zoonotic bacteria in pens of cattle during the mid-feeding period where the pen environment is stable and cattle are inquisitive but not highly reactive.