Climatology of Acacia mearnsii. 1. Characteristics of natural sites and exotic plantations

Climatic variation in the natural distribution of Acacia mearnsii in Australia was analysed. Data from sites where the species has been successfully grown in plantations and trials in Africa, Asia and South America were used to determine the species' climatic adaptability. Annual mean temperatures at these plantations and trial sites ranged from 13.9 to 23.9°C, whilst annual mean precipitation ranged from 693 to 2263 mm. The coldest month minimum temperature at these sites was –0.6°C. This information, along with other details of climatic requirements presented in the paper, will assist in selecting sites for future trials at new locations.     

From alley cropping to rotational fallow: Farmers' involvement in the development of fallow management techniques in the humid forest zone of Cameroon

Alley cropping was introduced in the humid forest zone of Cameroon to increase soil fertility in 1987, but until 1992 the adoption rate had remained low. To better understand the reasons behind this, three types of on farm trials were established from fully researcher controlled to fully farmer controlled. During the evaluation of the technology with farmers a number of modifications were registered (1) Pruning height and frequency: Because of the difficulties to consistently cut back at 30 cm, farmers decided to slash at ground level as they normally do while slashing the natural fallow vegetation. This equally allowed for more flexibility in time of pruning. (2) Cropping intensity and pattern: Initially, alleys were cropped each year. This however had several shortcomings. Having observed the positive impact of incidental fallow period in a farmer's field, it was decided to introduce a fallow phase of at least one year. During the fallow period the plot can be used for fodder production, bee farming and production of stakes. (3) Residue management: Fire went incidentally in a farmer's tree plot after slashing, and the trees were not affected. This gave farmers an alternative way to manage the residue, by controlling the fire, before bringing in other crops such as groundnut and cassava. (4) Agroforestry species: Because Leucaena leucocephala, in spite of it soil fertility restoration potential, rapidly became a noxious weed, farmers have asked for a less invasive species. Calliandra calothyrsus was introduced for this purpose and became a good bee forage. With these modifications, the original alley cropping system has evolved into a rotational tree fallow with higher adoption potential. From about 15 farmers who were testing the technology in 1992, the number increased to 52 in 1996, 120 in 1997 and 236 in 1998. This revised version was published online in June 2006 with corrections to the Cover Date.     

2009—2019 年广东省甜玉米区试品种主要性状选育进展

[目的]了解近年广东省甜玉米区域试验品种的变化规律,探索甜玉米的育种进展,进一步提高我国甜玉米育种的水平.[方法]根据2009—2019年广东省甜玉米区试品种多点试验数据,分析参试品种的农艺性状、经济性状、抗病性及综合品质等主要性状表现.[结果]11年间参试品种株高平均增加15 cm左右,穗位高总体稳定在68 cm左右,平均茎粗趋向稳定接近2.0 cm;穗长也有一定程度的增加,平均增幅为1.5 cm,穗粗增加趋势较为明显,表明注重大穗型品种的选育;区试品种产量在波动中呈现较快的上升趋势,育成品种中高产品种占据较大比例;抗小斑病育种取得较好的成果,多数品种对小斑病的抗性级别达中抗以上,但近3年来对纹枯病的抗性一般,部分品种感病,抗性级别降低;优质品种占参试品种的比例达30％以上,对品质的选育也在加强.[结论]连续11年广东省甜玉米区域试验表明,甜玉米主要性状的改良取得一定成效,相关农艺性状在不断探索协调产量构成各因素之间的关系,促使产量逐步提高,优质抗病品种比例有所提升,当今甜玉米育种在朝高产、优质、抗病抗倒、适应性强等复合性目标迈进,注重品种转化及推广应用,促进了我国甜玉米产业的快速发展.     

Analysis of series of variety trials with perennial crops

Field trials with perennial crops give rise to repeated measurements taken on the same plot on several occasions. It is important to account for serial correlation among repeated measurements in such trials. This study illustrates the use of mixed models for this purpose. We consider the analysis of trials conducted at several locations and the combination of trials with different starting years. A key issue in the analysis is the distinction between effects of calendar years, which are associated with external environmental variation, and harvest years, which represent internal yield formation processes of the perennial crop. Two methods of two‐stage analysis are compared with single‐stage analysis. It is shown that results of two‐stage analysis are very similar to those of single‐stage analysis, if serial correlation is properly taken into account. Program code for the MIXED procedure of the SAS system is given in an Appendix S1 for all considered cases.     

美国转基因作物田间试验频次分析

本研究通过对美国转基因作物田间试验频次分析揭示转基因作物研发的概貌和规律.采用EXCEL"数据透视表与数据透视图"软件,对美国转基因作物田间试验数据库和世界经济合作组织转基因作物田间试验数据库近20年数据进行统计分析.结果表明,至2008年9月止,美国转基因作物田间试验累计达13782次,涉及158种作物,10大类性状和98家公司或研究机构.1987-2008年间,审批的田间试验次数先呈直线上升,其后稳定在每年1000次左右.试验物种以玉米、大豆、棉花为主,分别占45.8%、9.7%和6.4%.涉及的主要性状有抗除草剂、抗虫和品质性状.62.7%的转基因作物田间试验由孟山都和国际先锋等五家私人公司完成.分析认为,只有经济价值高、安全性好、技术成熟、消费者容易接受的转基因作物才拥有更广阔的发展前景.建议我国加强非粮食作物转基因技术的研究.     

Estimates of stability for comparing varieties

Summary For purposes of comparison of analytical methods the yield data on pearl millet hybrids and varieties for five years from locations in India and Pakistan have been analysed using a regression analysis and a meanstandard deviation analysis. The results of the mean-standard deviation analysis and the regression analysis were similar whether carried out on all environments, or on the highest- and lowest-yielding sets of environments. This was substantiated by the remarkable correlation between the slopes from the regression analysis and the standard deviations whatever environmental set was considered. The validity of using a single year's across location data with the mean-standard deviation analysis, if choice-theoretic criteria are used, was examined. It is concluded that, although further confirmation is required, single-year data seem to suffice. The relative merits of the mean-standard deviation analysis and a regression analysis are discussed; the choice-theoretic framework of the mean-standard deviation analysis is advantageous and complementary to the regression analysis.     

Performance and prediction of potato genotypes tested in international trials

Summary A series of international trials with the potato crop was conducted in eight countries representing widely differing environments. The purpose of the experiments was: (1) to develop a method for obtaining environmental indexes which measure productivity of diverse potato-growing areas, and (2) to construct performance models for individual genotypes based on the environmental indexes. Yield data of 32 genotypes obtained from a series of 13 experiments conducted in the eight countries in 1983 and 1984 were used in the study. The response pattern of the genotypes was studied by a multivariate analysis. Five genotypes were chosen as representatives for different response patterns to the environments and their data were used for calculating a series of independent indexes for each of the experimental sites based on principal component analysis. Performance models for each of the genotypes were constructed by stepwise regression analysis of yields of a genotype on the environmental indexes based on 1983 data. Yield data of 1984 experiments were used to verify the models. Satisfactory correspondence between observed and predicted yields was obtained for most of the genotypes.     

Cooperative breeding for the northern marginal areas

Summary A joint breeding project for the northern areas of Scandinavia and Iceland was initiated in 1981 under the auspices of the Nordic Council of Ministers. Initially, efforts concentrated on cooperative trials in which both early and more advanced breeding material was tested at a number of experimental stations in the northern regions. This was followed by a joint breeding programme for timothy with the primary aim of developing varieties that possess broad adaptation to a range of Nordic climates and managements and can be grown throughout the northernmost part of Scandinavia. Each of the five national breeding stations originally provided 12 timothy genotypes for the project giving a total of 60 genotypes. The parental genotypes were compared as spaced plants at all five stations and their polycross progeny were grown under sward conditions at the same sites. On the basis of results obtained from these field trials parent clones have been selected and intercrossed to form synthetic populations.     

Trial heterogeneity and variance models in the genetic evaluation of potato tuber yield

Genetic evaluation aims to identify genotypes with high empirical breeding values (EBVs) for selection as parents. In this study, 2157 potato genotypes were evaluated for tuber yield using 8 years of early‐stage trial data collected from a potato breeding programme. Using linear mixed models, spatial parameters to target greater control of localised spatial heterogeneity within trials were estimated and variance models to account for across‐trial genetic heterogeneity were tested. When spatial components improved model fit, correlations of errors were mostly small and negative for marketable tuber yield (MTY) and total tuber yield (TTY), suggesting the presence of interplot competition in some years. For the analysis of multi‐environment trials, a variance model with a simple correlation structure (with heterogeneous variances) was the most favourable variance structure fitted for TTY and PTY (per cent marketable yield). There was very little difference in model fit when comparing a factor analytic structure of order 2 (FA2) with either FA1 or simple correlation structures for MTY, indicating that simple variance models may be preferable for early‐stage genetic evaluation of potato yield.     

Inter-site transferability of crop varieties: another approach for analyzing multi-locational variety trials

Summary Improved crop varieties developed at experimental stations are intended for release for production in farmers' fields which are not necessarily the test sites. Therefore, it is important to measure the inter-site transferability of the crop variety. This study was undertaken to establish a statistical measure of inter-site transferability of a variety. Data on grain yield from two sets of multi-locational trials on barley and four sets of the wheat trials conducted by the Cereal Program, International Center for Agricultural Research in the Dry Areas, Syria, were analyzed to evaluate the inter-site transferability of the varieties. Genotype × environment interaction was significant and experimental errors were heterogeneous in each set of trials. Correlations between the slope (of linear regression of variety mean on location mean) and variety mean were significant (P < 0.01) in all trials. Correlations between the developed inter-site transferability statistic and the variety mean were significant (P < 0.05) in only two trials. Correlations between mean yield and probability of the inter-site transferability statistic were insignificant in all trials. The inter-site transferability statistic and the associated probability of the transferability may be used to select varieties which are high yielding as well as transferable to a new environment. The strong association of slope with mean yield restricted the scope of varietal selection but the introduced statistic did not suffer from this drawback.