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We investigated the inheritance of head formation in Brassica oleracea by using two crosses, cabbage × ornamental cabbage and cabbage × kale. The degree of head formation (DHF) was classified into nine grades ranging from non‐heading to full heading. DHF in the two F2 populations showed a continuous distribution. The variance of F3 offspring selected for full heading or non‐heading was large. The DHF distributions in the F3 offspring selected for moderate heading or randomly selected F3 populations were similar to those of the respective F2 populations, but had smaller average values and variance. However, the realized heritability in F3 offspring was similar in full‐heading and non‐heading selections. Our findings suggest that head formation is a quantitative trait controlled additively with low dominance effects. In comparisons of leaf developmental patterns among the parents, only cabbage showed a change in leaf shape becoming wider because of the shorter petiole length with increasing leaf position. These findings suggest that cabbage acquired the developmental changes in leaves required to form a head during the process of domestication. 相似文献
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Endosperm balance number (EBN) was used to predict the outcome of crosses among a series of complex polyploid interspecific hybrids between Trifolium repens and T. nigrescens. Normal endosperm development, and hence seed‐set, requires a 2 : 1 maternal : paternal EBN ratio in endosperm. Based on their crossability, T. repens (2n = 4x = 32) and T. nigrescens (2n = 2x = 16) were assigned the same EBN of 4. This number was used to predict the relative success of different backcrosses and intercrosses. The method was further developed to successfully predict which gametes would effect fertilization when complex polyploid hybrids with uneven genomic constitutions (5x, 7x) produced mixtures of euploid and aneuploid gametes. This was achieved by allocating EBNs to all potential gametes of complex polyploids. Allocation of gamete EBNs enabled not only prediction of the success or failure of a cross, but also which gametes would be filtered to effect fertilization in complex crosses. This enhanced ability to understand the potential outcomes of complex crosses will increase the efficiency of plant breeding programmes that integrate secondary gene‐pools into economic species by interspecific hybridization. 相似文献
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Anna Hutchens 《Asia Pacific viewpoint》2011,52(3):299-315
Fairtrade market growth is characterised by expansion and exclusion in terms of producer opportunity. This paper draws producers in the Pacific region into the debate, analysing the development context among these small‐island developing states and, specifically, the practices and principles of four ‘ethical’ enterprises. The analysis reveals that the unique and complex context in which these organisations operate is at odds with Fairtrade's requirements, standards and assumptions. The paper highlights the need for contextually relevant requirements and principles, and the likelihood of alternative governance arrangements and actors, for an inclusive Fairtrade system and market in the region. 相似文献
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S. Fischer J. Möhring C. C. Schön H.‐P. Piepho D. Klein W. Schipprack H. F. Utz A. E. Melchinger J. C. Reif 《Plant Breeding》2008,127(5):446-451
The ratio of variance due to specific vs. general combining ability (GCA) (σ2SCA:σ2GCA) is of central importance for predicting hybrid performance from GCA effects. The objectives of our study were to (1) analyse the changes in estimates of σ2GCA, σ2SCA and their ratio during 30 years of hybrid maize breeding and (2) compare the observed trends in genetic variances with those expected under a simple genetic model. We analysed multilocation yield trials based on the North Carolina Design II conducted in the maize breeding programme of the University of Hohenheim from 1975 to 2004 for grain yield (GY) and dry matter content (DMC). GY showed a significant (P < 0.05) annual increase of 0.17 Mg/ha, but no linear trend was found for DMC. Since the beginning of hybrid breeding at the University of Hohenheim, the sum of estimates of σ2GCA of the flint and dent heterotic groups were higher than the estimates of their σ2SCA. This predominance did not change with ongoing inter‐population improvement. Consequently, superior hybrids can be identified and selected mainly based on their prediction from GCA effects. 相似文献
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This article explores the relationship between I‐Kiribati communities and the broader ‘imagined’ Pasifika community in Aotearoa New Zealand. It looks at the way a group of I‐Kiribati tertiary students experience identity within this context. Through the use of semi‐structured interviews and a discourse analysis, the study draws three main conclusions. First, that I‐Kiribati navigate multiple identities and are constantly negotiating these within different spaces. Although this contributes to uncertainties around identity, I‐Kiribati students also strategically enact identity to suit various contexts. Second, that Pasifika as a term tends to infer ‘Polynesian’ which in turn may marginalise I‐Kiribati identities within certain spaces, particularly in education settings that intend to support all Pacific identities. Yet, given such a narrow understanding of Pasifika, these efforts may counter that intention for those on the margins of, or outside the common usage of, the term Pasifika. Last, community plays a significant role in the formation of identities within minority groups, which is important for countering aspects of marginalisation experienced within broader pan‐ethnic labels such as Pasifika. Consequently, we argue that Pasifika as a label needs to better reflect inter‐Pacific diversity as well as the identity negotiations that Aotearoa New Zealand‐born Pacific peoples navigate. 相似文献
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In this study, the effects of nitrogen (N) rate (60, 120, 180 and 240 kg N ha?1 applied in three equal dressings at seeding and after the first and second cuttings) and stubble height (7, 14 and 21 cm) on the dry matter (DM) yield, crude protein (CP) content, and CP yield of a sorghum–sudangrass hybrid [Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf., cv. Pioneer 988] in the three‐cut system was investigated. The N rate had no significant effect in the first and third cuttings, but in the second cutting DM yields increased significantly with increase in N rate. The highest yield of 9.1 t ha?1 was obtained with 80 kg N ha?1 for the average of 2 years at the second cutting, but no significant difference was found among the 40, 60 and 80 kg N ha?1 rates. CP content and yield were not significantly affected by N rate at the first and third cuttings, but CP content and yield were significantly affected by application of N at the second cutting. Stubble height had a significant effect on CP content at the third cutting. However, it had no significant effect on CP content at the first and second cuttings. Stubble height had a significant effect on the CP yield at the first cutting, but no significant effect on CP yield at the second and third cuttings. 相似文献
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Deployment of cold tolerance loci from Oryza sativa ssp. Japonica cv. ‘Nipponbare’ in a high‐yielding Indica rice cultivar ‘93‐11’ 
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下载免费PDF全文 Cold tolerance is a complex trait, and QTL pyramiding is required for rice breeding. In this study, a total of seven QTLs for cold tolerance in the Japonica rice variety ‘Nipponbare’ were identified in an F2:3 population. A stably inherited major QTL, called qCTS11, was detected in the region adjacent to the centromere of chromosome 11. In a near‐isogenic line population, the QTL was further dissected into two linked loci, qCTS11.1 and qCTS11.2. Both of the homozygous alleles of qCTS11.1 and qCTS11.2 from ‘Nipponbare’ showed major positive effects on cold tolerance. Through pyramiding the linked QTLs in the cold‐sensitive Indica rice cultivar ‘93‐11’, we have developed a new elite, high‐yielding Indica variety with cold tolerance. 相似文献
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By using data of Belgian trials for Value of Cultivation and Use (1963–2007) the change in agronomic performance of ryegrass varieties was quantified. Data included 144 Lolium perenne and 69 Lolium multiflorum candidate varieties, plus ‘Vigor’ and ‘Lemtal’, two varieties which were always included in the Value of Cultivation and Use (VCU) trials. As the genetics of ‘Vigor’ and ‘Lemtal’ have remained identical to those in 1963, these were used as constant standards to measure improvements of new varieties. Dry matter yield (DMY) of ‘Vigor’ and ‘Lemtal’ varied annually but did not show a progressive change, indicating that cultural changes in VCU trials of ryegrasses were small. By expressing DMY, persistency and rust resistance of the candidate varieties relative to Vigor and ‘Lemtal’, the change in agronomic performance due to breeding was determined. DMY increased with 0.3% of ‘Vigor’ and ‘Lemtal’ annually. Persistency showed an annual increase around 0.5% of the standard varieties. Before 1990, rust resistance of ryegrasses varied around 100% relative to ‘Vigor’ or ‘Lemtal’. After 1990, an annual increase of 3.6% against these standard varieties was found. 相似文献