Influence of plant density on yield of homozygous and heterozygous winter rapeseed (Brassica napus L.)

Summary Plot yields and both environmental correlations and variances of various morphological and yield characters were compared at different plant densities of lines and F1 hybrids in rapeseed over a two-year period. These variances and correlations were measured on single plant basis and are independent of the genotype: they may partly reflect physiological relations between characters.At intermediate or low density, results indicate no significant heterogeneity for behaviour of both homozygotes and heterozygotes, with some lower correlations at very low densities. At high density hybrid vigour is significantly higher than at low or intermediate density. In heterozygotes, it is associated with reinforced correlations between morphological and yield criteria. The results are discussed with regard to seed yield elaboration, to heterosis and possible homeostasis of hybrids.     

Correlations Between Soil Exchangeable Ca2+, Mg2+, K+ and Foliar Nutrient Concentrations in Mature Biological Olive Groves (Olea europaea L., cv. ‘Chondrolia Chalkidikis’)

Leaf and soil samples were taken and analyzed from two mature biological olive groves (Olea europaea L., cv. ‘Chondrolia Chalkidikis’), in Thessaloniki, Macedonia, Northern Greece, in order to determine the correlations between soil exchangeable cations and foliar calcium (Ca), magnesium (Mg) and potassium (K) concentrations, and the interrelations among leaf nutrients. Τhe nutritional requirements of trees for both biological groves were exclusively based on patent kali supply and nutrient recycling (via pruning material and weed cut recycling). Foliar K, Ca and Mg were positively correlated with soil exchangeable K, Ca and Mg, in the 40–60 cm layer, then in the 20–40 cm layer. Synergistic uptake mechanisms among Ca²⁺, Mg²⁺ and K⁺ probably exist. Leaf N was negatively correlated with foliar K, and positively with leaf Ca, Mg and manganese (Mn). Foliar P was negatively correlated with leaf Ca, Mg and Mn, while foliar Ca was positively correlated with leaf Mg and Mn. Foliar Mg was positively related with leaf Mn. High phosphorus (P) may decrease leaf Ca, Mg and Mn. Enhanced Ca may increase leaf Mg and Mn, while high Mg may also enhance foliar Mn. Finally, based on the determination of foliar nutrient concentrations, the nutritional requirements of olive trees in Ca, Mg, K, P, Fe, Zn were sufficiently (or over-sufficiently) satisfied. However, additional organic fertilization is needed, in order to achieve optimum levels of N, B and Mn (since their foliar concentrations were slightly insufficient). The correlations between leaf and soil exchangeable Ca, Mg and K, as well as among foliar nutrients should be taken into consideration, in order to achieve successful organic fertilization for mature biological olive groves, and to avoid nutritional imbalances and disorders.     

Genetic variation and inheritance in a 9 × 9 diallel in silver birch (Betula pendula)

A complete diallel cross was made among nine Betula pendula trees growing in a natural population and a trial was planted on agricultural soil at one site. This exceptional trial has provided estimates of genetic parameters that can only be estimated in complete diallels. Traits measured were height and diameter during a period of 37 years, and assessments were made of bud burst, leaf abscission and rust infection at the early ages. All traits showed genetic variation and the variance components of general combining ability (GCA) effects were dominating, with heritability estimates of 0.16 and 0.23 for height and diameter at age six years. The best-growing families could be identified at that age. At age 37 years, when the trial had been thinned twice, the offspring from the highest and lowest ranked parent for growth contributed with 19% and 6% of the total volume of the stand, respectively. The GCA effects were also highly significant for the assessment traits, but with an interaction with year for bud burst. High values of estimates of genetic correlations proved that bud burst, leaf abscission and rust infection are interrelated, and also to some extent with growth traits. Families with an early bud burst were tallest, were less affected by the rust fungus and kept their leaves later in the autumn.     

毛竹叶片的生理特性

对毛竹叶片的光合特性、叶绿素含量、游离氨基酸含量、β-胡萝卜素含量和硝酸还原酶活性等生理指标进行测定.结果表明:毛竹叶片光合速率日变化呈现双峰曲线,出现光合“午睡”现象,上午8∶00~9∶30,叶片光合速率随着光照强度的增加呈直线上升趋势,在9∶30出现全天第1个高峰值,16∶30出现第2个高峰值;叶绿素含量与硝酸还原酶活性、游离氨基酸含量呈显著性相关;β-胡萝卜素含量高、保护光合机构能力强、光合速率大、叶绿素含量高、净光合速率大,反映植物体内N代谢旺盛、N素利用水平高,利于植物的生长发育.     

白檀果实内含物与矿物质变化规律及相关性

为了探索白檀果实发育过程中主要内含物与矿物质积累规律和相关性,对不同发育阶段白檀果实进行内含物和矿物质相对含量测定分析。结果发现:白檀果实发育阶段大致可以根据含油率变化规律划分为3个阶段:油脂积累缓慢期、油脂积累快速期和油脂积累稳定期。不同果实发育时期中,油脂、糖类和蛋白质三大主要内含物的积累规律并非一致,油脂积累缓慢期主要合成糖类和蛋白质,但是在油脂积累快速期大量分解促进油脂合成,而蛋白质等储存物质最后在油脂积累稳定期积累。同时发现氮磷钾元素在油脂积累快速期大量富集,并且与果实内含物积累密切相关,其中钾元素与内含物合成代谢相关性显著。     

中国美利奴羊超细型羊毛理化性能研究及灰评估

测定中国美利奴羊超细型羊毛理化性能,并与主要经济性状进行相关性分析,运用灰色理论评估不同品系羊毛品质。研究结果表明,超细型羊羊毛纤维直径极显著低于其它品系（P<0.01）;弯曲数显著提高（P<0.05）;纤维直径与其它各性状间均不相关（P>0.05）;毛丛长度增加,净毛量随之增加（P<0.05）;弯曲数增加,抗压缩弹性增强（P<0.01）;净毛光泽度、白度、黄度间呈显著正相关（P<0.05）。超细型羊毛综合品质优良,在本品种内品质较高。     

Conservation of seed-dispersing migrant birds in Mediterranean habitats: Shedding light on patterns to preserve processes

Migratory frugivorous birds disperse the seeds of many plant species, forming mutualistic associations that render frugivores a priority for conservation in many habitats worldwide. We analysed the distribution of seed-dispersing frugivorous passerines in southern Spain, which is an important area for the conservation of European birds during winter. Frugivorous birds showed similar regional abundance and richness during four winters, although fruit availability changed among years. However, the spatial distribution of frugivorous birds in the area changed among years. These changes were principally determined by annual variation in the distribution of fruits in the area, revealing a clear ability of birds to track the distribution of fruits. The unpredictable distribution of fruits each year suggests that regional fruit crops, rather than selected habitat patches, need to be protected for the long-term conservation of frugivorous bird populations in wintering grounds. Remarkably, the distribution of frugivores was independent of forest development or general cover of shrubs, which helps to reconcile the protection of fruiting shrubs with forest cleaning, an usual management to prevent devastating summer fires that is destroying fleshy-fruited plant communities in many areas of southern Spain. Thus, leaving a part of the fruiting shrubs untouched when cleaning forest undergrowth will allow the settlement of frugivorous birds. Interestingly, both abundance and richness of frugivores decreased with elevation, probably as a consequence of impaired climatic conditions at high altitude, revealing the importance of lowland shrublands as wintering grounds for frugivorous birds. These habitats deserve special conservation efforts, as they are seriously threatened by the ongoing encroachment of agricultural and urban areas along the Mediterranean coasts.     

Genetic Variability, Genotypic and Phenotypic Correlations and Path-Coefficient Analysis in Egyptian Clover (Trifolium alexandrinum L.)

Fifty-six accessions of multi-cut Egyptian clover were compared at four experiments under different environmental conditions; i.e. location and season. Considerable variation existed for all the characters studied. The genetic variance exceeded the environmental variance for all the studied traits. Heritability was high for all characters studied. The expected genetic advance from selection of the superior 10.7% of the accessions as calculated from the combined data reached to 16.10, 17.50, 5.20, 20.60, 3.52 and 21.00 for mean plant height, seasonal fresh forage yield, mean dry matter percentage, seasonal dry forage yield, mean protein percentage, and seasonal protein yield, respectively. Both phenotypic and genotypic correlations among traits showed that mean plant height was positively correlated with each of seasonal fresh forage yield, seasonal dry forage yield, mean dry matter percentage and seasonal protein yield, but negatively correlated with mean protein percentage. Negative correlation were also found between mean protein percentage with seasonal fresh and dry forage yield.
Over all experiments, pat-coefficient analysis revealed that seasonal fresh forage yield had the highest positive direct effect on seasonal protein yield (0.841), followed by mean dry matter percentage (0.461). The mean protein percentage showed the minimum direct (0.172) and indirect influence on seasonal protein yield.     

Stability of performance of tetraploid wheat landraces in the Ethiopian highland

Plant breeding has always been concerned with genotype-environment interaction. Normally high and stable performance are desirable attributes of cultivars. However, this is practically difficult to achieve where environmental variations are high and unpredictable and significant genotype-environment interactions occur. Stability of performance of 13 landraces evaluated at 4 different locations for 3 years in the highlands of Ethiopia was investigated. The testing locations have different climatic and edaphic conditions providing the conditions necessary for the assessment of stability. Stability parameters like b, s²d, s², r² and cv which are in common use were employed. Grain yield and 1000-kernel weight were the agronomic traits considered for the stability analysis. There were differences in the ranks of genotypes across the locations. Significant main environmental as well as interaction effects were observed showing the importance of genotype-environment interaction in both traits. Many of the landraces evaluated are rated as stable for these traits within the environmental conditions prevailing in these highland locations. Genotypes with specific adaptation to poor and favourable conditions were also identified. Certain genotypes showed similar manners of adaptation and stability for both of the traits. Grain yield showed low correlations with the stability parameters showing the possibility of attaining high yield and stability. Correlations between the stability parameters were mainly positive and significant for grain yield. Only a few of these correlations were found to be significant for kernel weight. The good adaptability of landraces should be exploited in the improvement of their yield potential. This revised version was published online in July 2006 with corrections to the Cover Date.     

波尔山羊羔羊生长发育规律研究

根据1 067只波尔羔羊出生时的同胞数、体重、体尺和出生至周岁各月龄体重、体尺等21 000余个数据资料,分析不同性别和同胞数羔羊体重、体长、体高、胸围的生长曲线、遗传力及表型相关,旨在探讨波尔羔羊的生长发育规律。结果表明,羔羊在出生时,体重、体高、体长、胸围和管围的遗传力分别为0.276、0.354、0.280、0.256和0.365,同胞数与体重、体高、体长和胸围之间存在表型负相关(P<0.01),体重和体尺之间存在正相关(P<0.01)。应用SPSS和MATLAB方法对羔羊周岁内体重和体尺生长曲线进行拟合,发现公羔生长不受断奶的影响,体重均比同年龄母羔大,公羔在3月龄、母羔在7月龄时体重出现拐点;而体尺生长则相反,公羔至9月龄、母羔至7月龄出现拐点。无论公羔还是母羔,单羔生长始终最快,双羔和多羔则差异不明显,出现拐点的时期类似。