Analysing agricultural users’ patterns of behaviour: The case of OPTIRas™, a decision support system for starch crop selection

Redesigning IT systems for specific user groups encompasses a lot of effort with respect to analysing and understanding user behaviour. The goal of this paper is to provide insights into patterns of behaviour of agricultural users, during the usage of a decision support system called OPTIRas™. This system aids agricultural users in their cultivar selection activities. We analyse logs resulting from OPTIRas™, and we get insights into user’s navigational patterns. We claim that the results of our analysis can be used to support the redesign of decision support systems in order to address specific agricultural users’ characteristics.     

中国北方棉区转基因抗虫棉对棉苗蚜及其两种天敌的影响（英）

2001年田间小区试验研究了转Bt基因棉和转双价基因(Bt+CpTI)棉对棉苗蚜及其天敌种群动态的影响;室内研究了转基因抗虫棉对两种棉蚜天敌的生物学影响.结果表明,转基因抗虫棉对棉蚜种群数量的影响不明显,未达显著水平.单作转基因棉田棉蚜发生期比麦套棉田提前5天左右,发生数量是麦套棉田的1.6倍,表明麦棉套作可有效的控制苗蚜的为害.室内研究表明,异色瓢虫对用Bt棉处理的的棉蚜的捕食量比对照增加22.0%,棉蚜茧蜂对用Bt棉处理的棉蚜的寄主率降低23.5%.     

Identifying nitrogen-efficient potato cultivars for organic farming

In organic farming, nitrogen efficiency of potato might vary among cultivars, even within the same maturity type. We therefore analysed in depth the response to nitrogen of a diverse set of cultivars, grown at different locations (differing in soil type and management) and in four years (differing in temperature and rainfall patterns). Yield increased with an increase in nitrogen supply and with growing later cultivars if the crop cycle lasted long enough. When crops had to be flamed to prevent spread of late blight, late cultivars yielded less than early cultivars, especially under high nitrogen. By measuring the fraction of soil covered by green leaves throughout the growing season and using a model, we analysed canopy development in detail and related nitrogen and genotype sensitive model parameters to tuber yield. In one year with early, temporary drought, model prediction was poor. We observed that cultivars that rapidly established a high maximum soil cover, maintained that maximum for long and senesced slowly, could sustain high yields. When late-blight infection was late, these (mid)-late cultivars showed high agronomic nitrogen use efficiency, but were not (always) high in nitrogen uptake efficiency, accumulation of nitrogen in the tubers or nitrogen utilisation efficiency. When late-blight infection started early, early or mid-late cultivars that rapidly established a high maximum soil cover under low nitrogen availability gave best performance. In most years, early canopy development is responsive to nitrogen, shows genetic variation, and is significantly related to early tuber yield. Nitrogen-efficient cultivars suitable for organic production should have rapid early canopy development, a high agronomic nitrogen use efficiency and nitrogen utilisation efficiency, but a low nitrogen concentration in the tubers.     

A historical analysis of diversity trends in French and Dutch lettuce cultivars

Using historical seed catalogues in combination with molecular fingerprinting data, diversity trends of lettuce, representing an important vegetable with active breeding programmes, were studied. Seed catalogues originating from France and the Netherlands from five different decades, the earliest dating from the 1840s, were checked for the occurence of lettuce cultivars. A total of 225 catalogues, with 7,311 records of lettuce, representing 878 different cultivars were found. The number of unique cultivars on offer by French and Dutch companies showed a small continuous increase until the 1960s, after which the number of cultivars on offer more than doubled to a total of 534 in the 1990s. Only a relatively small overlap between France and the Netherlands in the range of cultivars offered was observed. The 1960s appeared to be a period with many changes: the lowest genetic diversity in lettuce cultivars was found for this decade, whereas after the 1960s the number of companies supplying lettuce seeds reduced dramatically. The percentage of companies in a decade offering an identical cultivar decreased over time, and in the 1990s almost all cultivars were unique to only a single company. The possible relations of the observed trends with the developments in plant variety protection and in the plant breeding industry are discussed.     

Association mapping and marker development of the candidate genes (1 → 3),(1 → 4)-β-d-Glucan-4-glucanohydrolase and (1 → 4)-β-Xylan-endohydrolase 1 for malting quality in barley

Cell wall degradation is a crucial process within the malting process of barley. Therefore, the haplotype diversity of genes for two cell wall degrading enzymes, (1 → 3),(1 → 4)-β-d-Glucan-4-glucanohydrolase and (1 → 4)-β-Xylan-endohydrolase 1, was investigated and associations to malting quality parameters were performed. The (1 → 3),(1 → 4)-β-d-Glucan-4-glucanohydrolase gene glb2 had two major haplotypes defined by three SNPs and one INDEL, which explained 8.9 and 9.5% of the total variation of malt extract content and viscosity in the spring barley gene pool, respectively. The most significant associations of (1 → 4)-β-Xylan-endohydrolase 1 gene X-1 were found for diastatic power, saccharification VZ45 and soluble nitrogen with 18, 12 and 8% of the total variation explained by SNP3 in the spring barleys. High-throughput markers were developed for both genes which can be used for marker assisted selection.     

Postharvest water relations in cut rose cultivars with contrasting sensitivity to high relative air humidity during growth

A constant high relative air humidity (RH) during cultivation can strongly reduce the vase life in some cut rose cultivars. We studied three contrasting cultivars in their tolerance to high RH in order to analyse in detail the water relations during postharvest and better understand this genotypic variation. Plants were grown at moderate (60%) and high (95%) RH, and cut flowers were placed in water immediately after cutting. Flowers of cv. Pink Prophyta grown at high RH did not open throughout vase life, while flower opening of cvs. Frisco and Dream was not affected by preharvest RH. Cultivation at high RH resulted in about 80% shorter vase life in Pink Prophyta, whereas in Dream and Frisco the negative effect was considerably smaller (15 and 9% shorter vase life, respectively). The shorter vase life and reduced flower opening of cut roses grown at high RH was due to a higher rate of transpiration both in the light and dark periods. It was found that the leaves of Pink Prophyta grown at high RH could partly close their stomata upon lowering of the water potential or when flower stalks were fed with abscisic acid, but stomata remained far more open than in leaves grown at moderate RH. The RH during cultivation did not affect stem hydraulic conductivity and its recovery after air emboli induction. Preventing vascular occlusion largely alleviated the high-cultivation-RH effect on vase life and flower opening, showing that the effect of high-cultivation-RH becomes only important if water uptake is limited.     

Mapping antixenosis genes on chromosome 6A of wheat to greenbug and to a new biotype of Russian wheat aphid

Greenbug and Russian wheat aphid (RWA) are two devastating pests of wheat. The first has a long history of new biotype emergence and recently. RWA resistance has just started to break down. Thus, it is necessary to find new sources of resistance that will broaden the genetic base against these pests in wheat. Seventy‐five doubled haploid recombinant (DHR) lines for chromosome 6A from the F₁ of the cross between “Chinese Spring’ and the “Chinese Spring (Synthetic 6A) (Triticum dicoccoides × Aegilops tauschii)” substitution line were used as a mapping population for testing resistance to greenbug biotype C and to a new strain of RWA that appeared in Argentina in 2003. A quantitative trait locus (QTL) (br antixenosis to greenbug was significantly associated with the marker loci Xgwm1009 and Xgwm1185 located in the centromere region of chromosome 6A. Another QTL which accounted for most of the antixenosis against RWA was associated with the marker loci Xgwm1291 and Xiinni1150. both located on the long arm of chromosome 6A. This is the first report of greenbug and RWA resistance genes located on chromosome 6A. It is also the first report of antixenosis against the new strain of RWA. As most of the RWA resistance genes present in released cultivars have been located in [he D‐ genome, it is highly desirable to find new sources in other genomes to combine the existing resistance genes with new sources.     

Molecular mapping of powdery mildew resistance genes in wheat: A review

Powdery mildew, caused by Blumeria graminis f. sp. tritici (syn. Erysiphe graminis f. sp. tritici), is one of the most important diseases of common wheat (Triticum aestivum L.) worldwide. Molecular mapping and cloning of genes for resistance to powdery mildew in hexaploid wheat will facilitate the study of molecular mechanisms underlying resistance to powdery mildew diseases and help understand the structure and function of powdery mildew resistance genes, and permit marker-assisted selection in breeding programs. So far, 48 genes/alleles for resistance to powdery mildew at 32 loci have been identified and located on 16 different chromosomes, of which 21 resistance genes/alleles have been tagged by restriction fragment length polymorphisms (RFLPs), random-amplified polymorphic DNAs (RAPDs), amplified fragment length polymorphisms (AFLPs), sequence characterized amplified regions (SCARs), sequence-tagged sites (STS) or simple sequence repeats (SSRs). Several quantitative trait loci (QTLs) for adult plant resistance (APR) to powdery mildew have been associated with molecular markers. The detailed information on chromosomal location and molecular mapping of these genes has been reviewed. Isolation of powdery mildew resistance genes and development of valid molecular markers for pyramiding resistance genes in breeding programs is also discussed.     

Genetic analysis and genotype × environment (G × E) for grey leaf spot disease resistance in elite African maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) germplasm

Maize grey leaf spot (GLS) disease remains an important foliar disease in sub-Saharan Africa accounting for more than 25% yield losses in maize. Information on inheritance of GLS resistance of germplasm adapted to African environments is required in new sources being identified. Therefore, hybrids generated from a 10 × 10 half-diallel mating of tropical advanced maize inbred lines were evaluated in six environments to determine combining ability, genotype × environment interaction (G × E) and the impact of GLS disease on grain yield. General combining ability effects were highly significant and accounted for 72 and 68% of the variation for GLS resistance and grain yield, respectively. Significant specific combining ability effects associated with reduced disease levels were observed in some hybrids when one parent was resistant, and these may be exploited in developing single cross maize hybrids. Regression analysis showed a 260–320 kg ha^?1 decrease in maize grain yield per each increase in GLS disease severity score, and significant associations (r = ?0.31 to ?0.60) were observed between grain yield and GLS severity scores. This showed the potential of GLS disease to reduce yield in susceptible varieties grown under favourable disease conditions, without control measures. Genotype and genotype × environment biplots and correlation analysis indicated that the significant G × E observed was not due to changes in hybrid ranking, implying absence of a significant crossover interaction. Therefore, predominance of additive gene effects imply that breeding progress for GLS disease resistance would be made through selection and this could be achieved at a few hot-spot sites, such as Baynesfield and Cedara locations in South Africa, and still deploy the resistant germplasm to other environments in which they are adapted.