Accumulation of soluble phenolic compounds in sunflower capitula correlates with resistance to Sclerotinia sclerotiorum

Disease symptoms and total soluble phenolics content have been analysed in four sunflower (Helianthus annuus L.)lines with different resistance levels(from highly susceptible to resistant) to head rot caused by Sclerotinia sclerotiorum (Lib.) de Bary. At the beginning of the flowering stage, capitula were inoculated by spraying with a water suspension of ascospores, and disease symptoms were evaluated from day 6 to day14 after inoculation. The most susceptible genotypes showed all their ovaries to be necrosed and abundant lesions in corollas, bracts and receptacle. In the resistant line, the ovary and corolla were only partially necrosed with no symptoms in the bracts or the receptacle. Total soluble phenolics were extracted and quantified from different parts of the capitulum in both inoculated and non-inoculated plants. The amount of phenolic compounds depended on the sunflower line, the time after inoculation, and the tissue. Higher constitutive and induced phenolic content as well as phenylalanine ammonia-lyase activity were present in the most resistant line, these differences correlated with the absence/presence of disease symptoms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Introgression of low temperature tolerance and red rot resistance from Erianthus in sugarcane

Eighteen clones involving Erianthus, as one of the parents, were evaluated in a randomised block design under sub-tropical conditions of Karnal (Haryana, India). Fifteen characters, which contribute towards stalk yield and juice-quality, were studied. The growth of these clones was monitored during peak winter months of December and January. Significant variability existed among the clones for all the traits studied, except for pol % in juice at 10-month crop age, indicating potentiality of the clones to select desirable types. Nine clones showed significant increase in stalk length during winter months over the better standard Co 1148. Whereas 6 clones developed more number of leaves than Co 1148. Both these characters showed high genetic variability, high heritability and hence, high expected genetic gain. Path analysis revealed that these traits contributed about 16%, 5% and 4% to the total genetic variability in juice quality traits (pol % and CCS %), stalk yield and CCS yield, respectively. Growth in winter months has resulted in an increase in stalk yield and CCS yield. This may help in reducing the yield gap between tropical and sub-tropical regions. Majority of clones showed resistance to red rot disease (major disease of sugarcane in sub-tropical region). Hence, hybridization of Erianthus with sugarcane has resulted in introgression of genes for cold tolerance and red rot resistance. As Erianthus is known for its hardiness, resistance, of these clones, to other abiotic and biotic stresses is to be ascertained. This revised version was published online in August 2006 with corrections to the Cover Date.     

棉花烂铃病流行趋势超长期预报模型及其应用研究

本文对ＧＭ（１，１）模型参数估计方法进行了改进和简化，据此组建了苏北沿海棉区棉花烂铃病流行趋势超长期预报模型，经１９８０～１９８９年回报和１９９０～１９９５年预报，棉花烂铃病流行轻、重发生的符合率达１００％；１９９６～２０００年预报结果为１９９８年和２０００年为重发生，其余３ａ为轻发生。这将为棉花烂铃病的研究和防治规划提供科学决策依据，也为ＧＭ（１，１）模型能在基层病虫测报站推广应用创造了条件。     

黄瓜根腐病致病病原的鉴定

在天津市及周边地区采集病株进行组织分离，同时分离到两类病原菌，经初步的生物学特性鉴定表明，引起黄瓜根腐病的主要病原菌为甜瓜疫霉、尖孢镰刀菌和茄病镰刀菌。经接种试验，认为甜瓜疫霉为主要致病菌。     

Identification of levels of resistance to cassava root rot disease (<Emphasis Type="Italic">Botryodiplodia theobromae</Emphasis>) in African landraces and improved germplasm using <Emphasis Type="Italic">in vitro</Emphasis> inoculation method

Cassava root rot disease is an increasing problem in Africa where yield losses of about 80% have been recorded. We evaluated 290 African landraces and 306 improved genotypes from the germplasm collections of the International Institute of Tropical Agriculture (IITA), for sources of resistance using root slice laboratory assay. Disease severity was assessed quantitatively by direct percentage estimation (PS) and by use of a rating scale (RS). Both methods of assessment were compared for identification of variability in the germplasm, and genotypes were classified into response groups using an enlarged rank-sum method that combined the PS and RS assessments. The two scoring methods revealed continuous variation (P < 0.001) for resistance in the sets of germplasm. Disease assessments based on PS and RS were highly correlated in both the improved germplasm (r = 0.75) and the landraces (r = 0.72). Based on PS assessment, 50 improved genotypes (16.3%) and 53 landraces (18.3%) showed significantly lower disease scores than the resistant control. The rank-sum method separated each set of collections into highly resistant, resistant, moderately resistant, moderately susceptible, susceptible and highly susceptible groups. Fifty-nine improved genotypes (16.4%) and 61 African landraces (16.9%) were identified as either highly resistant or resistant. Generally, these genotypes exhibited resistance by limiting the growth of the pathogen (reduced amount of invaded surface area). This type of rate-reducing resistance is highly heritable and a quantitative trait which can be harnessed in breeding. Genotypes subsets were identified for further studies into the genetic basis of resistance to root rot disease.     

温度对白菜黑腐病侵染与发病影响的研究

白菜接种墨腐病后，置１５、２０、２５、３０℃的光照培养箱中保温４８ｈ。１１天后移在室温下，病均可以完成侵染。病害的进程随着环境环境的提高面表现出正相关。在上述温度梯度下，大白菜黑腐病病情指数达到５０的天数，分别为３５、３２、２７、８天。使其致死的时间分别为４１、３５、３２、３２天。因此，鉴定时提高环境的温度，有利缩短一病的时间，若接种的温度控制在２５℃或３０℃，则接种后的第１１或第８天即可进行病情     

栽培因子对棉花烂铃影响的数学模型研究

试验采用二次正交旋转组合设计，对安徽沿江棉区棉花的移栽密度、施氮量、施磷钾肥量、去早蕾数及喷缩节安量与棉花烂铃的关系进行了定性定量的研究，建立了棉花烂铃率和烂铃指数对５项栽培因子反应的数学模型，并对模型进行检验和解析。结果表明，模型极显著，并与实际相吻合，５项栽培因子对棉花烂铃存在显著或极显著的影响，同时因子间存在着互作效应。此模型可作为近似气候年份棉花烂铃的预测模式。     

Morphological variation within a sour cherry collection

Summary Morphological traits of 28 full-sib sour cherry (Prunus cerasus L.) families developed with pollen from European sour cherry selections were evaluated with principal component (PC) analysis. The traits which loaded on the first PC were size characters such as lateral length, leaf area, fruit weight, and trunk diameter increase. These character loading on the first PC could be interpreted as representing gradations between morphologies characteristic of the 2 presumed progenitor species, sweet cherry (P. avium L.) and ground cherry (P. fruticosa Pall.). Mean family differences in trunk diameter increase, lateral length, leaf area, and fruit weight varied approximately 12, 3.7, 2.5, and 2 fold, respectively. These results suggest that it may be possible to select sour cherry hybrids approaching the tree and fruit size of either progenitor species. The results are discussed in reference to germplasm collection and the potential of certain cultivars and hybrids as parents.     

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.     

Potential of Nicotiana glauca (Grah.) as a source of resistance to black root rot Thielaviopsis basicola (Berk. and Broome) Ferr. in tobacco improvement

Nicotiana glauca, a wild relative of Nicotiana tabacum, is an attractive potential source of black root rot (Thielaviopsis basicola)‐resistant germplasm. Moreover, it shows a resistance or tolerance to PVY, TEV, anthracnose and powdery mildew. In this study its potential as a source of resistance to black root rot caused by Th. basicola was investigated. Nicotiana glauca GG (2n = 2x = 24) was crossed as male with two N. tabacum TT (2n = 4x = 48) flue‐cured cultivars: ‘BY103’ and ‘K 326’, both of which are susceptible to black root rot. Amphihaploid F₁ TG (2n = 3x = 36), amphidiploid TTGG (2n = 6x = 72) and sesquidiploid TTG (2n = 5x = 60) hybrids were obtained. The resultant sesquidiploid hybrids were used as maternal components in backcrossing to N. tabacum and a segregating post‐sesquidiploid TTg (2n = 5x = 52–54) offspring was obtained. Amphihaploids exhibited a level of resistance to black root rot characteristic of N. glauca. The expression of resistance varied in the sesquidiploid generation, possibly reflecting cytological instabilities in that progeny. A wide variation in response to black root rot was found for post‐sesquidiploids a clear reflection of extensive chromosome segregation in that hybrid generation.