Susceptibility of oat cultivars to groat discoloration: causes and remedies

Fungal isolations and fungicide efficacy trials were carried out to determine the possible causes of discoloration in oat groats and potential control measures. Alternaria species and Microdochium nivale were isolated from field samples, and Fusarium poae was found in glasshouse tests. Symptoms could be induced reliably in the field through the use of a mist irrigation system. The cultivar ‘Gerald’ was most resistant followed by ‘Jalna’. Cultivar ‘Image’ was most severely affected by discoloration and ‘Millennium’ was of intermediate susceptibility. None of the 28 fungicide‐timing combinations used in the field trials affected the occurrence of discoloured groats. It was concluded that the best strategy for minimizing risk of discoloured groats would be screening new cultivars or breeding material in mist‐irrigated field trials for genetically based resistance.     

RAPD analysis of interspecific relationships in presumably apomictic Cotoneaster species

A few of the approximately 300 Cotoneaster species described are diploid but the majority appear to be polyploid. The occurrence of apomixis inpolyploid Cotoneaster species has been reported but never proven with genetic markers. We have used 76 polymorphic RAPD markers to investigate the breeding system and phenetic grouping of some critical taxa, including a total of 19 plant accessions representing 13 mostly European species in the series Cotoneaster. Three to four individual plants, raised from seed from the same original plant, were analyzed for each of three accessions to investigate the possible occurrence of apomictic seed set. Absolutely congruent RAPD profiles were encountered among seedlings from one accession, whereas we found one or two marker differences among seedlings from the other two accessions. Genetic similarities among the different accessions were analyzed with a UPGMA-derived dendrogram. The most deviant taxon was the Chinese C. albokermesinus. A group withC. soczavianus and C. tomentosus was rather isolated from the remainder, as was also C. kullensis. Among the remaining taxa, two well supported clusters were found: (1) C. antoninae and C. uralensis, and (2) C. integerrimus and C. raboutensis, whereas the other five species (C. canescens, C. niger, C. scandinavicus, C. juranus, C. cambricus) formed a poorly supported cluster with no clear substructuring. A principal coordinate analysis yielded results that were in good correspondence with the dendrogram. Again C. albokermesinus appears to be totally isolated from the other species. In addition, two well-defined and rather isolated groups were found: (1) C. tomentosus and C. soczavianus, and (2) C. antoninae and C. uralensis, with the remainder comprising a loosely defined group. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.     

应用半矮生基因sd－1选育矮秆大库容量水稻新品系研究

用大穗高秆品种Ａｋｅｎｏｈｏｓｈｉ与半矮生粳型系统ＳＣ－ＴＮ１杂交后代Ｆ５的６个品系及其亲本为材料，比较分析了品系与亲本遗传性状的表现及其联系。结果表明，通过改善ｓｄ－１基因的遗传背景，使半矮生性及优良株型的特性与大库容量相结合是可能的，能够从中培育出有更高产量潜力的新品系     

哈密瓜嫁接栽培的防病增产效果研究

以黑籽南瓜为砧木，哈密甜瓜为接穗，采用不同的嫁接方法和育苗方法，研究了嫁接对哈密甜瓜幼苗和植株生物学特性及对枯萎病抗性、产量、品质的影响。结果表明，4种嫁接方法都有较强的亲和性，在无土育苗条件下，嫁接苗成活率均在95%以上，田间防效达到95.4%以上，无土育苗嫁接比有土育苗嫁接效果好。嫁接哈密瓜比自根哈密瓜增产75.9%-112.3%，增产效果主要表现在后期产量上。     

冬小麦育种目标十五年来的回顾和展望

本文总结了十五年来冬小麦育种工作的经验,结果表明,制定正确的育种目标是育种成败的关键.育种目标要适应生产的发展,要纠正脱离实际的过高的产量指标,在高产的基础上逐步改善品质.为了满足本地区不同条件下种植的小麦与其前后茬粮食作物,实现全年各茬均衡增产及连年持续丰产的要求,必须培育一整套品种,尤其要重视早熟品种的选育.还应要求冬小麦良种的性状在确保稳产的基础上去求高产;强调具备越冬抗寒性,抗多种病害,高抗倒伏,并能保持较大的生物学产量.文内设计及评价了产量构成因素不同组配的四种类型:多穗型、中间型、大穗(或穗重)型和耐晚播早熟型.     

北方粳稻分子育种研究进展

本文介绍了北方粳稻分子育种课题的研究情况和所取得的研究成果。目前主要进行两方面的研究，一方面为特异基因型的鉴定：主要有筛选鉴定出抗旱性材料86份，苗期抗寒性材料40份，后期抗寒性材料629份，抗稻瘟病材料28份，对筛选出的抗旱性材料进行了第二轮聚合杂交，共配组合171个。另一方面是关于遗传与生理基础研究，对穗部性状、粒形、产量和品质以及它们之间的关系进行了深入的研究。另外本文对北方粳稻分子育种材料构建过程中存在的问题进行了综合讨论，并讨论北方粳稻分子育种今后的发展方向。     

Sclerotinia resistance in sunflower: I. Genotypic variations of hybrids in three environments of Argentina

Sclerotinia sclerotiorum infections on sunflower capitula produce white rot, one of the most dangerous diseases sunflower bears in all humid areas. Therefore, disease quantification on developed genetic materials is a very important action in sunflower breeding. Given the horizontal type of resistance these evaluations should be made in different environments. Several hybrids obtained after crossing seven female × seven male sunflower inbred lines in a factorial mating design were evaluated for resistance to white rot in two locations in the southeast of the province of Buenos Aires, Argentina. Disease incidence and the symptom appearance index indicated significant genotypic effects and genotype × environment (G × E) interactions. Genotypic effects were a greater source of variance than the G × E interaction effects. The G × E interactions only represented changes in magnitude. These results were used to identify the best genotypes for both resistance factors. Four hybrids showed low disease incidence values under both artificial and natural infections, of which only two had high values of the symptom appearance index at both locations. These hybrids are considered to have adequate resistance attributes for the ascosporic penetration and the mycelium extension in the capitulum tissue and could therefore be sown in the province of Buenos Aires without increasing risks of S. sclerotiorum attacks.     

Assessment of genetic diversity in selected breeding lines and cultivars of canola quality Brassica juncea and their implications for canola breeding

AFLP markers were used to assess the genetic diversity of 77 breeding lines from three of the world's major canola qualityBrassica juncea breeding programs from Canada (Agriculture and Agri-Food Canada and Saskatchewan Wheat Pool) and Australia (Agriculture Victoria). The objectives of the paper were to assess the genetic diversity within and between these three breeding programs and to assess genetic diversity of the canola quality germplasm as compared to mustard quality B. juncea. Fifteen lines of mustard quality B. juncea from India, China, Russia and Australia were also included in the investigation. Ten EcoR1/Mse1 based primer pairs generated 751 scorable fragments with an average of 26 polymorphic bands per primer pair (35%). Similarity coefficients were calculated using the Simple Matching coefficient and adendrogram was developed using the UPGMA procedure, resulting in germplasm being partitioned into five main groups. Line specific markers were discovered that have potential in enhancing the efficiency of individual breeding programs using breeding techniques like accelerated backcrossing. Further understanding the genetic diversity within and between programs has implications for future breeding and collaboration within and between the three programs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Malting quality as affected by barley breeding (1944–1998) in Argentina

Eight malting cultivars of barley released from 1944 to 1998 in Argentina were sown in two growing seasons to evaluate the effect of breeding on malting quality. An adequate grain weight and screening percentage as in the older varieties were maintained in the recent releases. The grain protein concentration decreased in the modern cultivars together with a decreased in C-and an increased in B-hordein. These results were achieved without a clear trend through the time. Malt extract was increased by 0.054% per year in the period analysed and the most important contribution in the quality improvement was the introduction of Beka (known as a high quality cultivar released in Europe) in1966. There was not a clear trend in the breeding process to obtain more stability between years in the quality attributes, at least, in the characteristics analysed in the present study. Conversely, malt extract was less variable and this tendency was observed through the years of release of the cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.