Usefulness of subjective ovine milk scores: II. Genetic parameter estimates     

Snowder GD  Van Vleck LD  Knight AD  Kellom TR  Bromley CM 《Journal of animal science》2001,79(4):869-876

Genetic parameters for a subjective milk score given to ewes within 24 h of parturition were estimated to determine the usefulness of milk score as a selection trait to improve milk production, which influences total litter weight weaned. Heritability of milk score and the genetic correlation of milk score with litter weight weaned were estimated by REML separately for four sheep breeds, Rambouillet (n = 1,731), Targhee (n = 1,638), Columbia (n = 1,731), and Polypay (n = 1,129). Litter weight weaned was the total weight of lambs weaned at approximately 120 d of age under a western range production system. Observed heritability estimates for milk score at first parity were moderate and similar among breeds, ranging from 0.18 to 0.32. Heritability estimates adjusted for a binomial distribution of milk scores at first parity were high (Columbia, 0.43; Polypay, 0.35; Rambouillet, 0.50; Targhee, 0.84). Estimates of observed heritability for second-parity milk score were moderate to high, ranging from 0.23 to 0.46. Milk score at first or second parity was genetically correlated with milk score records at maturity (third parity and greater), with estimates ranging from 0.69 to 1.00. Milk score and litter weight weaned were genetically correlated at first or second parity in Rambouillet (r(g) = 1.00) and Targhee breeds (r(g) = 1.00 and 0.61, respectively), but not in the Columbia and Polypay breeds. Estimates of heritability for lifetime records for milk score ranged from 0.16 to 0.26 across breeds. Estimates of genetic correlations of annual lifetime milk score records with litter weight weaned were high (Columbia, 1.00; Polypay, 0.81; Rambouillet, 1.00; and Targhee, 0.77). Repeatability estimates for milk score were similar across breeds, 0.23 for Columbia, Rambouillet, and Targhee ewes and 0.28 for Polypay ewes. Milk score measured at first or second parity may be a good predictor of future potential milking ability. Further, milk score can be used as a selection trait to improve maternal ability for increasing litter weight weaned. The need for increasing ewe milking performance and lamb growth rate at first parity in commercial range sheep production systems may be addressed by selection for milk score at first parity.  相似文献   

Usefulness of subjective ovine milk scores: I. Associations with range ewe characteristics and lamb production     

Snowder GD  Knight AD  Van Vleck LD  Bromley CM  Kellom TR 《Journal of animal science》2001,79(4):811-818

Range ewes are commonly evaluated for milking ability by producers to determine the ewe's ability to rear lamb(s). The U.S. Sheep Experiment Station has subjectively scored (low, average, high) a ewe's milking ability within 24 h of lambing for many years. The relationship of subjective milk scores with lamb production was investigated using lambing records of Columbia (n = 1,731), Polypay (n = 1,129), Rambouillet (n = 1,704), and Targhee (n = 1,638) ewes. The incidence of high milk scores increased from less than 10% at first parity to 29 to 40% at second and greater parities. At maturity, Columbia ewes (38%) had the highest percentage of high milk scores. A positive association existed between ewe BW and her milk score at third and later parities. Ewes with high milk scores gave birth to heavier lambs (P < 0.05), whereas ewes with low milk scores were associated with lighter (P < 0.05) lambs at birth. Ewes with low milk scores weaned less (P < 0.05) total weight than ewes with better milk scores across all age groups for all breeds. Lighter weaned litter weights from ewes with low milk scores were linked to lighter birth weights and fewer weaned lambs. Differences for litter weight weaned between ewes with average and high milk scores were generally observed at 2 and 3 yr of age, when litter weights were heavier among ewes with high milk scores (P < 0.05) for all breeds. Between the ages of 1 and 3 yr, Columbia, Polypay, Rambouillet, and Targhee ewes with an average milk score weaned heavier (P < 0.05) litters (average differences of 10, 9, 13, and 12%, respectively) than ewes with low milk scores. For all breeds at all ages, individual lamb weaning weights were heavier (P < 0.05) when they were reared by ewes with high milk scores compared to lambs reared by ewes with low milk scores. Results suggest that milk score is an economically important trait in these four breeds and should be considered in management and breeding objectives; at a minimum, the incidence of low milk scores should be kept as small as possible.  相似文献   

A comment on the membrane filter technique for estimation of length of fungal hyphae in soil     

Veronica Sundman  Seppo Sivelä 《Soil biology & biochemistry》1978,10(5):399-401

A simple direct method is described to measure the length of fungal hyphae in soil. The accuracy of the method is discussed and comparison is made with other methods recommended for assaying fungal biomass in soil. Some results showing the seasonal fluctuation of mycelial length in soil are presented.  相似文献   

Diameter growth of Scots pine (Pinus sylvestris) trees grown at elevated temperature and carbon dioxide concentration under boreal conditions     

Peltola H  Kilpeläinen A  Kellomäki S 《Tree physiology》2002,22(14):963-972

We investigated the impacts of elevated temperature and carbon dioxide concentration ([CO2]) on diameter growth of Scots pine (Pinus sylvestris L.), aged about 20 years, grown with a low nitrogen supply in closed chambers at (i) ambient temperature and [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC), and (iv). elevated temperature and [CO2] (ET+EC). Each treatment was replicated four times. Diameter growth was monitored with a band dendrograph at 15-min intervals throughout the growing seasons of 1997, 1998 and 1999. Over the monitoring period, diameter growth began 2-3 weeks earlier in trees in the ET+EC and ET+AC chambers than in trees in the AT+AC and AT+EC chambers. However, the cessation of growth occurred about a week later in trees in the ET+EC, ET+AC and AT+EC chambers compared with the AT+AC chambers. The duration of the growing season was 115 and 108 days in the ET+EC and ET+AC chambers, respectively, and 95 and 84 days in the AT+EC and AT+AC chambers, respectively. The ET+AC and ET+EC treatments enhanced diameter growth most early in the growing season, whereas in trees in the AT+AC and AT+EC treatments diameter growth rate was highest in the middle of the growing season. Diameter growth rate leveled off more slowly in trees in the ET+EC and AT+EC treatments than in the other treatments. The growth response to elevated T, elevated [CO2] or both decreased with time and it was less than the maximum observed in other studies for small seedlings and under optimal growth conditions. Nevertheless, cumulative diameter growth for the 3-year period was 67% greater in trees in the ET+EC treatment, and 57 and 26% greater in trees in the AT+EC and ET+AC treatments, respectively, compared with trees in the AT+AC treatment. Over the 3 years, [CO2] had a statistically significant (P < 0.10) effect on both absolute and relative diameter growth, but the interaction between [CO2] and temperature was not significant.  相似文献   

Photosynthetic responses to needle water potentials in Scots pine after a four-year exposure to elevated CO(2) and temperature     

Kellomäki S  Wang KY 《Tree physiology》1996,16(9):765-772

Effects of needle water potential (Psi(l)) on gas exchange of Scots pine (Pinus sylvestris L.) grown for 4 years in open-top chambers with elevated temperature (ET), elevated CO(2) (EC) or a combination of elevated temperature and CO(2) (EC + ET) were examined at a high photon flux density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and optimal temperature (T). We used the Farquhar model of photosynthesis to estimate the separate effects of Psi(l) and the treatments on maximum carboxylation efficiency (V(c,max)), ribulose-1,5-bisphosphate regeneration capacity (J), rate of respiration in the light (R(d)), intercellular partial pressure of CO(2) (C(i)) and stomatal conductance (G(s)). Depression of CO(2) assimilation rate at low Psi(l) was the result of both stomatal and non-stomatal limitations on photosynthetic processes; however, stomatal limitations dominated during short-term water stress (Psi(l) < -1.2 MPa), whereas non-stomatal limitations dominated during severe water stress. Among the nonstomatal components, the decrease in J contributed more to the decline in photosynthesis than the decrease in V(c,max). Long-term elevation of CO(2) and temperature led to differences in the maximum values of the parameters, the threshold values of Psi(l) and the sensitivity of the parameters to decreasing Psi(l). The CO(2) treatment decreased the maximum values of V(c,max), J and R(d) but significantly increased the sensitivity of V(c,max), J and R(d) to decreasing Psi(l) (P < 0.05). The effects of the ET and EC + ET treatments on V(c,max), J and R(d) were opposite to the effects of the EC treatment on these parameters. The values of G(s), which were measured simultaneously with maximum net rate of assimilation (A(max)), declined in a curvilinear fashion as Psi(l) decreased. Both the EC + ET and ET treatments significantly decreased the sensitivity of G(s) to decreasing Psi(l). We conclude that, in the future, acclimation to increased atmospheric CO(2) and temperature could increase the tolerance of Scots pine to water stress.  相似文献   

Photosynthetic responses of Scots pine to elevated CO(2) and nitrogen supply: results of a branch-in-bag experiment     

Kellomäki S  Wang KY 《Tree physiology》1997,17(4):231-240

Naturally seeded Scots pine (Pinus sylvestris L.) trees, age 25-30 years, were subjected to two soil-nitrogen-supply regimes and to elevated atmospheric CO(2) concentrations by the branch-in-bag method from April 15 to September 15 for two or three years. Gas exchange in detached shoots was measured in a diffuse radiation field. Seven parameters associated with photosynthetic performance and two describing stomatal conductance were determined to assess the effects of treatments on photosynthetic components. An elevated concentration of CO(2) did not lead to a significant downward regulation in maximum carboxylation rate (V(cmax)) or maximum electron transport rate (J(max)), but it significantly decreased light-saturated stomatal conductance (g(sat)) and increased minimum stomatal conductance (g(min)). Light-saturated rates of CO(2) assimilation were higher (24-31%) in shoots grown and measured at elevated CO(2) concentration than in shoots grown and measured at ambient CO(2) concentration, regardless of treatment time or nitrogen-supply regime. High soil-nitrogen supply significantly increased photosynthetic capacity, corresponding to significant increases in V(cmax) and J(max). However, the combined elevated CO(2) + high nitrogen-supply treatment did not enhance the photosynthetic response above that observed in the elevated CO(2) treatment alone.  相似文献   

The role of competitors for <Emphasis Type="Italic">Chrysomela lapponica</Emphasis>, a north Eurasian willow pest,in pioneering a new host plant     

Jürgen Gross  Nina E. Fatouros  Seppo Neuvonen  Monika Hilker 《Journal of pest science》2007,80(3):139-143

The Palaearctic leaf beetle Chrysomela lapponica usually feeds upon willows in the northern region of its occurrence. However, in Central Europe, some populations are known that have specialised on birch. In this study, we investigated the significance of other herbivores occurring together on the same host plants as possible exploitative competitors of C. lapponica. Two populations were studied: a population from Finland specialised on the willow Salix borealis, and a population from the Czech Republic, specialised on the birch Betula pubescens. Abundances of folivorous and suctivorous insects on both host plants were recorded at both population sites. The willow leaf beetle Phratora vitellinae was the most abundant herbivorous insect at both study sites on willow. A field study was conducted to examine the effects of P. vitellinae on the performance of C. lapponica. The presence of P. vitellinae larvae on the same twig upon which C. lapponica larvae were feeding did not affect increase of body weight in C. lapponica larvae. Thus, the high resource availability of both willows and birches suggest that interspecific competition is unlikely to be a selection factor driving the evolution of host shift in C. lapponica.  相似文献   

Crystallinity of wood and the size of cellulose crystallites in Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis>)   总被引：5，自引：0，他引：5  

Seppo?Andersson  Ritva?SerimaaEmail author  Timo?Paakkari  Pekka?Saranp??  Erkki?Pesonen 《Journal of Wood Science》2003,49(6):531-537

X-ray diffraction was used to study variations in the crystallinity of wood and the average thickness and length of the crystallites of cellulose as a function of the number of the year ring in Norway spruce [Picea abies (L.) Karst.]. The crystallinity increased from ring 4 to ring 10 from the pith and was constant after ring 10. The crystallinity of mature wood was about 30% ± 5%. The average thickness and average length of the crystallites were 3.2 ± 0.1nm and 28 ± 2nm, respectively; and no systematic variation of these values with the number of the year ring was observed. The mean microfibril angle decreased near the pith but was constant in the mature wood.  相似文献   

Wood properties of Scots pines (Pinus sylvestris) grown at elevated temperature and carbon dioxide concentration     

Kilpeläinen A  Peltola H  Ryyppö A  Sauvala K  Laitinen K  Kellomäki S 《Tree physiology》2003,23(13):889-897

Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density.  相似文献   

Identification of somatic hybrids of dihaploid Solanum tuberosum lines and S. brevidens by species specific RAPD patterns and assessment of disease resistance of the hybrids     

Veli-Matti Rokka  Yong-Sheng Xu  Jyri Kankila  Anja Kuusela  Seppo Pulli  Eija Pehu 《Euphytica》1994,80(3):207-217

Summary Symmetric somatic hybrids were produced by electrofusion of protoplasts of two dihaploid tuber-bearing potato (Solanum tuberosum L.) lines and Solanum brevidens Phil., a diploid non-tuber-bearing wild potato species. A total of 985 plants was obtained. Verification of nuclear hybridity of putative hybrids was based on additive RAPD patterns, general morphological characteristics and chromosome counts. 53 (90%) calli regenerated into plants which were identified as somatic hybrids. Most of the hybrids were aneuploids at the tetraploid (4×) or hexaploid (6×) level. The 20 hybrids tested expressed a high level of resistance to potato virus Y (PVY ^N ) characteristic of the S. brevidens parent. Resistance to late blight (Phytophthora infestans (Mont.) de Bary) varied between hybrids, but was on average better than that of the fusion parents. Resistance of hybrids to bacterial stem rot (Erwinia carotovora subsp. atroseptica (van Hall) Dye) was not superior to that of commercial potato cultivars.  相似文献