刺槐心材腐朽病初报

辽宁大连和北京地区刺槐(Robinia pseudoacacia)心材腐朽病的病原菌为槐生多年卧孔菌(Perenniporia robiniophila(Murrill)Ryvarden)。根据野外调查对此新病害的症状和危害进行了报道,并根据采集的病原标本材料对该病原菌进行了详细描述。该菌主要危害30年生以上的活立木,造成心材白色腐朽,最终导致受害树木枯死或风折后死亡。     

稻草还田对免耕水稻根系生长及空间分布的影响

研究了稻草还田对免耕抛秧水稻立苗期根系生长及成熟期根系空间分布的影响。结果表明,稻草还田显著或极显著提高了立苗期免耕水稻根冠比、单株根生物量、总根数、白根数、单条根长、根毛区长、一次分枝、二次分枝根数量、根系活力和超氧化物歧化酶(SOD)活性,对根系的伸长、生长起到明显的促进作用。稻草还田明显提高了水稻产量及免耕抛秧水稻0~10cm土层根系干重和根系体积,6t/hm²稻草还田量比对照0~10cm土层根系干重和根系体积分别高29.85%、41.62%,产量提高11.18%,差异均达显著水平。     

饼肥与无机氮肥配施对水稻根系形态生理和产量的影响

以扬稻6号(籼稻)和扬辐粳8号(粳稻)为材料,设置4个处理:(T1)不施氮肥;(T2)施用无机氮;(T3)施用饼肥;(T4)饼肥与无机氮肥配施.研究饼肥与无机氮肥配施对水稻根系形态生理和产量形成的影响.结果表明:各处理的产量表现为饼肥与无机氮肥配施(T4)＞施用无机氮(T2)＞施用饼肥(T3)＞不施氮肥(T1),4个处理间差异显著.饼肥与无机氮肥配施(T4)显著增加了穗数、结实率、千粒重和收获指数.饼肥与无机氮肥配施(T4)显著提高了抽穗期有效叶面积和高效叶面积、灌浆期叶片叶绿素含量和光合速率以及各主要生育时期的根干重、根长、根系氧化力、根系伤流量、根系总吸收表面积和活跃吸收表面积.表明饼肥与无机氮肥配施可以促进根部生长,进而促进地上部生长并提高产量.     

三江平原主栽大豆品种对大豆根腐病尖孢镰孢菌的抗性分析

明确三江平原地区主栽大豆品种对主要大豆根腐病致病菌尖孢镰孢菌的抗性。收集了该地区主栽大豆品种13 个,对其同时进行盆栽接种和大田接种尖孢镰孢菌的抗性分析试验,大田接种试验设不接种对照。‘垦丰16’和‘合丰55’的抗性最好,盆栽试验中均表现为抗病,平均病情指数分别为15.33%和20.67%,大田接种试验中表现为抗病,病情指数分别为25.55%和22.89%,与未接种对照相比,减产率最低,分别为3.55%和3.77%,差异达到显著水平。‘垦丰16’和‘合丰55’是适宜三江平原地区种植的抗尖孢镰孢菌根腐病的抗病品种。     

Root-released organic acids and phosphorus uptake of two barley cultivars in laboratory and field experiments

A major portion of phosphorus (P) applied as fertilizers is bound in soils as P compounds of variable adsorption strength, reducing the effectiveness of P fertilization. Plant genotypes equipped with mechanisms for utilizing the adsorbed P more efficiently can, therefore, enhance the effectiveness of P fertilization. Such genotypes will also enrich plant gene pools for further analysis and upgrading of P efficiency by selection and breeding. We studied the variation and the mechanisms of P uptake of two winter barley (Hordeum vulgare L.) cultivars Marinka and Sonate (parents of existing 200 haploid progeny lines), by laboratory and field experiments. After cultivation in nutrient solution for 21 days, Marinka produced more roots than Sonate, but similar amounts of dry shoots of lower P content (Marinka 3.4±0.4 mg g⁻¹, Sonate 4.9±0.6 mg g⁻¹). The total P uptake per plant did not differ between the cultivars. Marinka retained more P in roots as indicated by the higher concentration of P in the roots (Marinka 3.9±0.3 mg g⁻¹ and Sonate 3.0±0.4 mg g⁻¹). In sterile nutrient solution culture, the cultivars differed mainly in release of organic acids from the roots, with Marinka releasing three times more citric acid and nearly two times more acetic acid than Sonate. The cultivars had similar root hair lengths and they did not differ (P>0.05) in depletion of available soil P fraction (extracted with 0.5 M NaHCO₃) in the rhizosphere. Marinka absorbed nearly twice as much P from the strongly adsorbed soil P fraction (extracted with 0.1M NaOH). Also under field conditions, Marinka absorbed more P and produced more shoot dry matter. The higher P uptake by Marinka than Sonate can be attributed to its ability to acquire P from strongly adsorbed soil P by releasing more organic acids, especially citric acid, from its roots.     

Resistance to septoria nodorum blotch in the Aegilops tauschii accession RL5271 is controlled by a single gene

Septoria nodorum blotch is the most important leaf disease of wheat in Western Australia. A potentially useful source of resistance has been identified in an accession of Aegilops tauschii. To study the genetics of resistance of this source a cross was made between the resistant Ae. tauschii accession, RL5271, and a susceptible accession, CPI110889. The resistant parent took significantly longer to develop symptoms, developed significantly fewer lesions and expressed significantly lower levels of disease than the susceptible parent. The F1 mean response for disease severity indicated there was no complete dominance. The F3 families were classified using three approaches. In the first approach the individual F3 plant response was used to classify the F3 families. In the second approach the F3 family means and standard errors were used to classify the F3 families. In the final approach Best Linear Unbiased Predictors of disease score and standard error for each F3 family derived from a REML analysis were used to classify the F3 families. The genotypic ratios generated by each of the approaches suggested that resistance is controlled by a single gene. The effectiveness of the resistance and its simple genetic control in the Ae. tauschii, accession RL5271 may be a useful resistance source for use in a bread wheat breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chromosomal location of Fusarium head blight resistance genes and analysis of the relationship between resistance to head blight and brown foot rot

In order to identify chromosomes involved in resistance to Fusarium head blight, a set of 21 substitution lines of Triticum macha (resistant) chromosomes into ‘Hobbit’'sib’(susceptible) were evaluated in trials over 2 years. For the first year's trial, all plants were inoculated on the same day with a conidial suspension of F. culmorum. For the second trial, individual plants were inoculated precisely at mid anthesis of each plant over a period of 2 weeks. The disease level was assessed by visual scoring, relative ear weight and F. culmorumn‐specfic quantitative polymerase chain reaction. The results showed that T. macha chromosomes 1B, 4A and 7A conferred good overall resistance, suggesting that they carry important genes for resistance. In two additional trials, T. macha and ‘Hobbit’'sib’ were evaluated for resistance to brown foot rot. The results showed that T. macha was more susceptible than ‘Hobbit’‘sib’, indicating that stem base disease response is not correlated with head blight resistance in these cultivars.     

Leaf stomatal conductance and stomatal morphology of Musa germplasm

Drought tolerance combined with resistance to black sigatoka (BS) disease are two desirable traits for plantains in some parts of the tropics. Field evaluation of leaf stomatal conductance, single leaf transpiration rate, photochemical efficiency, and role of stomata in BS resistance, was done for 18 genotypes of Musa spp., which included diploid and triploid banana and plantains and tetraploid plantain hybrids, at a sub-humid and a humid site. Conductances were significantly (P ≤ 0.01) higher for leaf abaxial than adaxial surfaces (S), while clonal (C) differences were significant (P ≤ 0.05). Interactions between sampling period (T: morning vs afternoon) and location (L), and clone and location (C × L) were significant for both conductance and transpiration; (C × T × L) interaction was significant for conductance. Significant interactions for (C × L) and (C × T) suggested that conductance and transpiration of a specific clone need to be considered for a given environment. Total variation in conductance was explained by the following variables: S, C, (C × L), (C × T), and (C × L × T). In general, ABB cooking banana had higher conductances than other Musa taxonomic groups (AAB, AA, AAA, and AAAB). Evaluation of morphological and physiological traits of leaf stomata indicated that the resistance to BS disease is due to non-stomatal mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breeding wheat and rye for resistance to Fusarium diseases

Fusarium culmorum and F. graminearum Groups 1 and 2 cause seedling blight, crown rot, foot rot and head blight in wheat and rye that may affect grain yield and quality for baking and feeding. This review starts with an analysis of Fusarium populations with regard to their genetic variation for aggressiveness, mycotoxin production, and isolate-by-host genotype interaction. To assess resistance in the different host growth stages, quantitative inoculation and disease assessment techniques are necessary. Based on estimated population parameters, breeding strategies are reviewed to improve Fusarium resistance in wheat and rye. Epidemiological and toxicological aspects of Fusarium resistance that are important for resistance breeding are discussed. F. culmorum and F. graminearum display large genetic variation for aggressiveness in isolate collections and in naturally occurring populations. The production of mycotoxins, especially deoxynivalenol and its derivatives, is a common trait in these populations. Significant isolate-by-host genotype interactions were not found across environments in wheat and rye. Artificial infections in the field are indispensable for improving Fusarium crown rot, foot rot and head blight resistance in wheat and rye. For a reliable disease assessment of large populations, disease severity ratings were found to be the most convenient. The differentiation of host resistance is greatly influenced by an array of nongenetic factors (macro-environment, microclimate, host growth stage, host organ) that show significant interactions with host genotype. Selection for environmentally stable resistance has to be performed in several environments under a maximum array of different infection levels. Selection in early growth stages or on one plant organ does not in most cases allow prediction of resistance in adult-plant stages or another plant organ. Significant genetic variation for resistance exists for all Fusarium-incited diseases in breeding populations of wheat and rye. The patho-systems studied displayed a prevalence of additive gene action with no consistent specific combining ability effects and thus rapid progress can be expected from recurrent selection. In wheat, intensive testing of parental genotypes allows good prediction of the mean head blight resistance after crossing. Subsequent selection during selfing generations enables the use of transgression towards resistance. In hybrid breeding of winter rye, the close correlation between foot rot resistance of inbred lines and their GCA effects implies that selection based on the lines per se should be highly effective. This is not valid for F. culmorum head blight of winter rye caused by a greater susceptibility of the inbred lines compared to their crosses. For both foot rot and head blight resistance, a high correlation between the resistance to F. graminearum and F. culmorum was found in wheat and rye. Mycotoxin accumulation occurs to a great extent in naturally and artificially infected plant stands. The correlation between resistance traits and mycotoxin contents are medium and highly dependent on the environment. Further experiments are needed to clarify whether greater resistance will lead to a correlated reduction of the mycotoxin content of the grains under natural infection.     

Potential use of doubled haploid lines for the screening of resistance to yellow rust (Puccinia striiformis) in hexaploid wheat

Doubled haploid lines derived from anther culture of two Iranian spring wheat genotypes‘Ghods’susceptible and‘9106’resistant to yellow rust in Iranian field conditions, and their F₁ hybrids were used in this study. Seedlings of 36 doubled haploid lines, selected out of 96 according to their agronomic traits and the two parental genotypes were inoculated with eight races of yellow rust. The parental genotypes (‘Ghods’and‘9106’) were segregating for some of the races but their doubled haploid lines were either resistant or susceptible to them.‘Ghods’was susceptible to three of the races studied but three doubled haploid lines derived from it were resistant to them. Five selected doubled haploids from the‘9106’genotype and six from F₁ hybrid plants were resistant to all eight races tested. After further investigations in Iranian field conditions it was found that some of these lines can be used as donor genotypes for resistance to yellow rust in wheat breeding programmes. Use of these genotypes should be possible if the French yellow rust races used for selection also represent the dominant races in Iran. It can be concluded that anther culture provides an efficient method for fixing genes of resistance to yellow rust and desirable doubled haploids from F₁ plants can be derived.