Differentiation of the high molecular weight glutenin subunit D t x 2.1 of Aegilops tauschii indicated by partial sequences of its encoding gene and SSR markers

The devastating late blight pathogen Phytophthora infestans infects foliage as well as tubers of potato. To date, resistance breeding has often focused on foliage blight resistance, but tuber blight resistance is becoming more and more important in cultivated potatoes. In this study, a reliable tuber assay for resistance assessment was developed and foliage and tuber blight resistance (R) was compared in four mapping populations. In the RH4X-103 population, tuber blight resistance inherited independently from foliage blight resistance. Three specific R genes against P. infestans were segregating. The Rpi-abpt and R3a genes function as foliage-specific R genes, whereas the R1 gene acts on both foliage and tuber. In the segregating populations SHRH and RH94-076, tuber and foliage blight resistance correlated significantly, which suggests that resistance in foliage and tuber is conferred by the same gene (could be R3b) and quantitative trait loci (QTL), respectively. In the CE population neither tuber nor foliage resistance was observed.     

Quantitative trait loci for adventitious and lateral roots in rice

The mass of a root is determined by two underlying morphogenetic factors: (1) the length of the main root axis (root axis length: RAL), and (2) the amount of lateral root development generated by a unit length of the axis (branching index: BI). The mass of a rice adventitious root was partitioned into these two factors at the quantitative trait locus (QTL) level, using ‘Akihikari’ (a lowland cultivar as a recurrent parent) × ‘IRAT 109’ (an upland cultivar) backcross inbred lines. Four QTLs were detected for the dry weight of individual adventitious roots (root dry weight: RDW), which were associated with a QTL for RAL (chromosomes 1 and 9) or a QTL for BI (chromosomes 6 and 11). For BI, an additional QTL was detected on chromosome 1. The absence of co‐located QTLs suggested that RAL and BI are under separate genetic control. Despite its small population size and few replications, this study suggests that the partitioning of root mass into these underlying components could be useful for understanding the complexity involved in the genetic control of root growth.     

Significance of host complexity and diversity for race-specific leaf-rust resistance in self-fertile synthetic rye populations

Leaf rust (Puccinia recondita Rob. ex. Des.) is the most frequently occurring leaf disease in German winter rye (Secale cereale L.). To test the usefulness of race‐specific resistance genes, the effects of increased host diversity and complexity by producing two‐ and four‐line synthetics from inbred lines carrying different resistance genes were analysed. Thirty‐three synthetics along with two full‐sib families and one hybrid variety were tested in 17 environments in Germany under natural infections. For comparison, the parent lines of the synthetics were evaluated in 11 environments. Only two synthetics and the full‐sib families were resistant across all environments. Observed resistance levels of the synthetics were highly correlated (r = 0.83, P = 0.01) with those predicted from the parental values. Host complexity had a minor effect in two‐line synthetics only. In conclusion, the effectiveness of race‐specific leaf‐rust resistances among environments, and increasing the host complexity and diversity does not lead to a higher resistance level than that expected from the resistances of the parents.     

Molecular diversity in Indian sugarcane cultivars as revealed by randomly amplified DNA polymorphisms

Genetic diversity in 28 prominent Indian sugarcane varieties cultivated under a wide range of agroclimatic conditions, was studied using 25 RAPD markers. The mean genetic distance among the 28 varieties was only 29.31%, implying that a large part of the genome is similar among the varieties. This probably arises from the lack of parental diversity, with few clones which are themselves related, contributing to the parentage of these varieties. The parentage of the varieties did not contribute significantly to the clustering pattern. Varieties belonging to the same parentage were grouped under different clusters while varieties from different parentages were grouped under the same cluster. The tropical and subtropical identities of the varieties also did not contribute to the clustering pattern as individual clusters included varieties from both tropics and subtropics. This shows that genetically similar varieties are present in both the regions. Among the varieties, Co 7717 was found to be totally distinct and divergent from rest of the varieties. The study reveals the limited genetic base of the current Indian commercial varieties and the need to diversify the genetic base by using new sources from the germplasm. This revised version was published online in August 2006 with corrections to the Cover Date.     

以热量指数表示北疆棉区棉花延迟型冷害指标的研究

应用乌兰乌苏农业气象试验站棉花试验的生育期、产量及旬气温资料,计算出棉花不同播期和不同生长阶段的热量指数,研究分析不同播期棉花产量、霜前花率与棉花不同生长阶段的热量指数之间的关系发现:1)随播种期推后,棉花生长前期热量指数明显增加,而棉花生长后期的热量指数则呈现出明显的下降趋势。2)现蕾—开花阶段的热量满足状况很好,热量指数稳定。3)分期播种的单产与棉花生长后期的热量指数具有很好的线性关系,霜前花率也与棉花生长后期的热量指数关系密切,生长后期的热量指数变化对棉花品质的影响较产量更加敏感。4)以减产幅度为标准,在棉花开花期以前热量充足的情况下,后期生长热量指数低于64为一般延迟型冷害年指标,低于61.8为严重延迟型冷害年指标。5)以霜前花率为标准,在棉花开花期以前热量充足的情况下,后期生长热量指数低于 70.9 会出现一般冷害年,低于63.2,会出现严重冷害年。     

Fertility Improvement in Autotetraploids of Pea — Selection for Seed-Set and Disjunction Index

Four seed-set groups of plants, viz. unselected ‘general’ and selected ‘high’, ‘medium’ and ‘low’ were constituted in C₁ generation from randomly selected autotetraploids of two pea cultivars, T 163 and 5064-S. In C₂ generation, ten plants were selected at random in each of the four groups. Two seeds each from selected autotetraploids were drawn and bulked to make 20 seeds in each of the four groups to raise C₃ generation. Selection resulted in a gradual shift in seed-set, though the magnitude and nature varied with the group and generation. Improvement in the seed-set from C₁ to C₃ generation was associated with the increase in bivalents per cell, disjunction index and total chiasmata. Increase in total chiasmata was mostly due to an increase in proximal ones. Increase in seed-set was reflected in improvement of grain yield per plant.     

Comparison of some selection procedures and objectives in faba beans (Vicia faba L.). I. direct and index selection for seed yield

Summary Starting with two heterogeneous F₂ populations, each based on 20 cross combinations, different selection procedures were applied for four consecutive selection cycles. Three of the selection procedures involved seed yield per plant (SYP): (i) direct selection for SYP (DSY); (ii) indexselection for SYP (ISY) with plant length, the ratio of the vegetative top to plant length, end of grain filling and duration of the generative stage as auxiliary characters and finally; (iii) independent culling levels selection (ICL) for the index described above and crude protein content. For ICL-selection the attention is focussed on SYP in this paper.For all three selection procedures, predicted and realized responses were calculated and expressed as percentage of a corresponding non-selected population. The intensities of selection differed over selection methods and generations, mostly due to practical constraints.As far as predicted responses are concerned, ISY-selection seemed to be slightly superior to DSY-selection and DSY-selection to ICL-selection. This order may partly be due to differences in selection intensity. However, none of the predictions was very accurate, but the predictions of ICL-selection seemed to be the most accurate. This has been ascribed also to the relative mild selection intensity applied in ICL-selection. It is concluded that a decision in favour of a complicated selection procedure like index selection based on predicted responses only cannot be defended. As far as realized responses are concerned, DSY-selection seems to be slightly superior to the other two selection procedures, as it is the only procedure that resulted in a more or less stable positive response to selection.The auxiliary characters, especially plant length, showed a marked correlated response to all three selection procedures. In case of direct selection for SYP this seemed paradoxical with the inefficiency of index selection, but, it may reflect the differences in the genuine genotypic correlations and the estimated genotypic correlations.     

Use of PCR-based methodologies for the determination of DNA diversity between Saccharum varieties

Summary In this study, two PCR-based methodologies were evaluated for potential use in the determination of DNA diversity between 20 commercial sugarcane hybrids and 6 outgroup varieties of S. spontaneum, S. officinarum and hybrids from early in the genealogy. The first method involved PCR amplification of sugarcane DNA in the presence of random, decamer primers (RAPDs), while the second protocol utilized specific microsatellite and telomere sequences as primers. A total of 41 RAPD primers (356 loci) were screened across the varieties of which 15 (160 loci) were used in the calculation of DNA diversity (expressed% similarity). This varied from 61 to 95%, with most of the commercial varieties showing more than 80% similarity in their DNA. The RAPD data indicated that there had been a gradual decline in DNA diversity (84% reduction) from the early inter-specific crosses to the commercial hybrids, probably as a result of backcrossing and in-breeding strategies used in the previous 5 to 6 generations of sugarcane breeding. The microsatellite and telomere data produced a much greater range in DNA similarity values (25–91%), probably due to the fact that these primers detect highly variable regions of the genome. It is suggested that these specific primers would not be suitable for determination of DNA diversity, but could be used more effectively in the development of a methodology for routine, rapid identification of sugarcane varieties.     

利用DNA分子标志鉴别台湾茶树品种及评估种原之遗传歧异性

为评估台湾茶树种原之遗传歧异性。本研究由100条ISSR引子申筛选出12条可产生多型性条带明显的引子．这些引子共可产生67个的多型性条带。依据每一种原之分子标志数据进行UPGMA法分群分析结果。可将台湾133个茶树种原区分成六大群，包括油茶群、赤芽山茶群、野生茶树群、大叶变种与小叶变种混合群、大叶、小叶及大叶、小叶杂交种混合群及小叶变种群。而主成分向量分析的结果与利用群聚分析得到的亲缘关系树形固结果相符合。台湾茶树种原高比例的遗传歧异度是由台湾的野生茶树所贡献．部分重要栽培种间的相似性仍极高。为了探讨制茶过程封分子级品种鉴定之影响及DNA分子标志应用于咸茶品种鉴定之可行性，本研究分析不同发酵程度的茶类。在制茶过程申封DNA质量之影响。试验结果显示高温杀菁过程严重造成咸茶DNA的降解。利用各种类别咸茶与新鲜茶叶（封照）所抽取之DNA样品进行PCR扩增反应．结果发现分子量小于1,000bp的ISSR DNA条带表现较稳定。     

系祖轮配对维持并提高豫州褐壳蛋鸡Ⅲ系生产性能的研究

对豫州褐壳蛋鸡Ⅲ系采用系祖间轮配的选配方法，经过连续3个世代的选育，开产日龄推迟5．72d，开产平均蛋重减少0．87g，72周龄平均蛋重增加2．82g、蛋数增加8．62枚，蛋品质维持在较高水平，蛋壳颜色变深。说明对已育成的纯系采用系祖间轮配的选配方法，可以维持并提高其生产性能。