新农村建设视阈下大学生创业教育的路径选择

分析了新农村建设与大学生创业教育的关系,指出新农村建设对大学生创业素质提出新要求,即必须要有过硬的政治素质、强烈的创业意识、完整的知识结构和良好的心理素质。提出了在社会主义新农村建设背景下,大学生创业教育应采取的对策,包括要转变观念,培育师资,完善课程,校企合作,政府、企业、高校角色合理定位等,努力探寻大学生创业教育的新路径。     

中国水仙品种选育的初步研究

调查研究表明,平潭水仙具有生长健壮、花葶数多等特点.进行了优良多花株系选种,以鳞茎叶片生长量为依据,在试验统计的基础上提出翅仔钻仔的选留种指标。     

Selection for increased forage yield in alfalfa at different NaCl levels

Summary Alfalfa (Medicago sativa L.) forage yield may be reduced by moderate levels of salinity. Increasing forage yield in saline environments through plant breeding could partially ameliorate this problem. However, prior indirect selection either in cell culture, at germination, or during seedling growth has not resulted in agronomically relevant levels of salt tolerance. This study was conducted to determine whether mean forage yield of alfalfa grown in saline environments could be increased. To reduce the number of possible selection schemes, forage yield data for five harvests from Sonora and its parental cultivar African grown in a greenhouse and irrigated with 0, 30, 60, or 80 mM NaCl were used to simulate one cycle of selection at each NaCl environment. Greatest gains in forage yield were expected under non-saline conditions with decreased gains under saline conditions. Selection based on yield in regrowth harvests was also predicted to be more efficient than that based on seedling harvest. Experimental populations were developed from Sonora and African at each NaCl level using phenotypic selection for increased mean forage yield for harvests 3 to 5. After each of two cycles of selection, forage yield from selected, control (plants selected randomly under non-saline conditions), and parental populations was evaluated at 0, 30, 60, and 80 mM NaCl. Gains in forage yield were observed in African when the selection and evaluation environments were the same, but in Sonora this was observed only at 0 NaCl. Selection at 0 NaCl did not increase forage yield at 60 or 80 mM NaCl in either germplasm source. This suggests that selection for increased forage yield may be successful at low to moderate NaCl levels in germplasm with ample variation for yield when grown in saline environments, while selection for increased forage yield in non-saline conditions may be ineffective.     

A factor analysis of plant variables associated with architecture and seed size in dry bean

Summary A knowledge of the biological and functional relationships among traits would be of benefit to plant breeders in the choice of traits to use for increasing efficiency of selection in a breeding program. Principal factor analysis was used to identify biological and functional relationships among dry bean (Phaseolus vulgaris L.) traits in segregating populations of a phenotypic recurrent selection program designed to introduce upright architecture into medium-sized dry bean.Two biological interpretations were assigned to factors extracted in the analysis of four seed/pod traits. The first was a size factor, loaded with seed weight and pod width, and the second a number factor, which was loaded with number of seeds per pod and pod length. Similarly, three factors were extracted from the analysis of fifteen architectural traits. The first factor was interpreted as an elongation factor, and was loaded with internode length measurements, while the second factor was interpreted as a structural factor, and was further divided into two subclasses namely, sturdiness factor and profile factor. The sturdiness factor comprised hypocotyl diameter and hypocotyl length, while the profile factor comprised branch angle and number of basal branches. The third factor which was called a reproductive factor was loaded with pod distribution traits and the number and location of nodes on which pods were borne.     

Analysis of durable resistance to stem rust in barley

Summary Since the mid-1940's, barley cultivars grown in the northern Great Plains of the USA and Canada have been resistant to stem rust caused byPuccinia graminis f. sp.tritici. This durable resistance is largely conferred by a single gene,Rpg1, derived from a single plant selection of the cultivar Wisconsin 37 and an unimproved Swiss cultivar. At the seedling stage, barley genotypes withRpg1 generally exhibit low mesothetic reactions at 16–20° C and slightly higher mesothetic reactions at 24–28° C to many stem rust pathotypes. This resistance is manifested by a low level of rust infection and mostly incompatible type uredia on adult plants.Rpg1 reacts in a pathotype-specific manner since some genotypes ofP. g. f. sp.tritici are virulent on cultivars carrying this gene in the field. Several factors may have contributed to the longevity of stem rust resistance in barley, a) since barley is planted early and matures early, it can sometimes escape damage from stem rust inoculum carried from the south; b) one or more minor genes may augment the level of resistance already provided byRpg1; c) the cultivation of resistant wheat cultivars and eradication of barberry have reduced the effective population size and number of potential new pathotypes ofP. g. f. sp.tritici, respectively; and d) virulent pathotypes ofP. g. f. sp.tritici andP. g. f. sp.secalis have not become established. This situation changed in 1989 when a virulent pathotype (Pgt-QCC) ofP. g. f. sp.tritici became widely distributed over the Great Plains. However,Rpg1 may still confer some degree of resistance to pathotype QCC because stem rust severities have been low to moderate and yield losses light on barley cultivars carrying the gene during the last four seasons (1989–1992). Several sources of incomplete resistance to pathotype QCC have been identified in barley. To facilitate the transfer of resistance genes from these sources into advanced breeding lines, molecular marker assisted selection is being employed.     

Correlated Responses in Two Traits when Selection is Practised on their Ratio

In many fields of application in plant breeding and crop science, ratios of two component traits X and Y are of interest (harvest index in cereals, leaf-to-stem ratio in forage legumes, height-to-diameter ratio in forest trees etc.). When selection is practised on the ratio X/Y of two traits X and Y, the experimenter may be interested in the resulting changes of both trait means. Based on improved approximations for the covariances between X and X/Y and between Y and X/Y and for the variance of X/Y the changes in the means of X and Y can be predicted by applying the regression approach from conventional selection theory. Explicit expressions for these correlated responses in X and Y when selection is practised on their ratio X/Y are derived and discussed. The different outcomes (decrease, zero change or increase) for the selection pressures on X and Y are characterized by phenotypic coefficients of variation of X and Y, phenotypic and genotypic correlations between X and Y and heritabilities of X and Y.     

Location-Specific and Across-Location Selections for Seed Yield in Populations of Common Bean, Phaseolus vulgaris L.

Two populations of common bean, Phaseolus vulgaris L., were used to make three independent location-specific selections at Palmira, Quilichao, and Popayán, Colombia. Also, three across-location selections were made by alternating generations between Palmira and Popayan, between Quilichao and Popayán, and among Palmira, Quilichao, and Popayán. The seven highest yielding lines selected from each environment and population along with 14 parents and two checks were evaluated for seed yield, seed weight, maturity, and reaction to an-thracnose, angular leaf spot, and common bacterial blight. Mean squares due to evaluation and selection environments, selected lines, and their interactions were significant for all traits. Mean yields of selected lines were higher than the mean of parents in both populations. Among location-specific selections, lines yielded higher at their respective selection site. Moreover, selections made at Popayán were higher yielding than those made at Quilichao or Palmira when tested across locations and years. Use of Popayán, a relatively wetter and cooler site, either alone or in combination with other locations resulted in higher yield, higher seed weight, and higher resistance to anthracnose. On the average, location-specific selections were lower yielding than the across-location selections. Among across-location selections, those selected between Palmira and Popayán were the highest yielding in both populations. Selections at Palmira and across all three locations resulted in greater stability.     

Agronomic and Bioenergetic Consequences of Selection for High Groat-Oil Content and High Protein Yield in Oat*

Few studies have examined the effects of selection for high oil or protein content on the chemical composition of cereal seeds. This study was conducted to examine agronomic and bioenergetic consequences that result with changes in the chemical composition of groats of oat (Avena sativa L.). Oat lines with low and high groat-oil content (GO) and with low and high groat-protein content (GP) were chosen from each of five cycles of a recurrent selection program for increasing GO and from each of four cycles of a recurrent selection program for increasing protein yield via elevating GP, respectively. These lines were evaluated at three Iowa locations in 1988. The results indicated that GP was not significantly affected by selection for high GO and that GO significantly increased during selection for high protein yield via elevating GP. Both selection procedures resulted in oat lines with higher groat-energy contents. A bioenergetic cost analysis showed that for GO in the oil population and GP in the protein population to be increased, additional photosynthate needed to be available.     

杂草的形成

杂草的形成是自然选择和人工选择共同作用的结果,其形成机制与杂交,特别是渗入杂交(inerogressire hybridization)有着极为密切的关系。无融合生殖(apomixis)、染色体加倍或减少也都是杂草形成的重要方式。 本文还从自然和人工选择讨论了杂草不同生活习性的形成,并分析了一年生、二年生和多年生杂草对环境的适应和环境对杂草的选择;自花传粉对杂草后代生存和繁衍的重要性;杂草中种子大小的选择意义化及人工选择所产生的拟态种(mimicus)对环境适应的特点。 最后,还讨论了受人工干扰生境的变化和杂草在这变化环境中的变异情况。     

我国家禽产业化育种及制种的研究

探索家禽良种的社会经济的地位、属性、发展历史和现状。提出21世纪家禽育种、制种的发展方向和方法,建议采用生态优选育种方案与双选育种法及核心群选育法培养优质家禽良种,同时用生物技术进行辅助选择。用科学发展观构建我国家禽育种制种基地。