利用ISSR标记对12种五针松亲缘关系的研究

采用ISSR 标记技术,对12 种五针松的亲缘关系进行分析。利用筛选出的12 个ISSR 引物共检测到117 个位点,多态条带比率(PPB)在9.40%～33.33 %之间,遗传分化最高的是偃松,最低的是柔枝松。12 种五针松的基因多样性(Ht)为26.21%,其中种内基因多样性(Hs)为7.66%,种间基因多样性(Dst)为18.55%,五针松种间变异占总变异的70.78%。遗传距离聚类,将12 种五针松分为2 个类群,第一类群包括乔松、华山松、海南五针松、华南五针松、北美乔松、山白松和云南五针松;第二类群包括美国白皮松、偃松、、柔枝松、西伯利亚红松和红松。图1 表3 参6。     

Erysiphe australiana: the cause of powdery mildew on Lagerstroemia speciosa in Brazil

Powdery mildew symptoms and signs were observed on seedlings of Lagerstroemia speciosa within an ornamental plant nursery in Viçosa, State of Minas Gerais, Brazil. Signs were most prominent as intense mycelial growth and sporulation on the shoots, new branches and leaves, which led to tissue necrosis. Based on morphological characteristics and phylogenetic analyses of ITS and 28S rDNA sequences, the powdery mildew pathogen of L. speciosa was identified as Erysiphe australiana, a well‐known powdery mildew pathogen infecting Lagerstroemia spp. worldwide. To our knowledge, this is the first report of E. australiana causing powdery mildew on L. speciosa in Brazil.     

Screening brassicaceous plants as biofumigants for management of Phytophthora cinnamomi oak disease

Brassicaceous plants rich in glucosinolates have been used as biofumigants for the management of soilborne pathogens. Efficacy of Brassica plant tissue has mainly been attributed to toxic isothiocyanates released upon the hydrolysis of glucosinolates. Management of Phytophthora cinnamomi, the causal agent of oak root rot in rangeland ecosystems using biofumigation, is promising, but requires further validation. The biofumigation activity of 14 brassicaceous plants was evaluated under experimental conditions. All evaluated plants rich in sinigrin suppressed (100%) the mycelial growth of P. cinnamomi, while plants rich in aromatic or other aliphatic glucosinolates had little or no suppressive effect. Simulating soil amendment in field conditions, the effects on natural soil artificially infested with P. cinnamomi chlamydospores were examined with Brassica juncea, Eruca vesicaria and Lepidium sativum, three species with different glucosinolate profiles. Only B. juncea decreased the viability of chlamydospores significantly in comparison with untreated soil only 1 day after biofumigation, whereas E. vesicaria needed 8 days to reach significance and L. sativum had no effect at all. Despite the decreases in soil inoculum, biofumigation with B. juncea did not prevent the root infections in a highly susceptible host (Lupinus luteus). However, biofumigation with plants rich in sinigrin, such as B. juncea, decreased P. cinnamomi soil inoculum under the experimental minimum threshold for oak disease expression. Although biofumigation should be considered as an effective measure to be incorporated in integrated control of the oak disease, biofumigation by itself would not be effective enough for the substantial suppression of P. cinnamomi inoculum.     

Taxonomic,geographic, and diversity trends for exotic plant pests in recent biosurveillance articles

Journal of Pest Science - Some plant protection organizations use biosurveillance to identify heightened risks from exotic plant pests or generally inform safeguarding. Biosurveillance programs...     

Estimating “autotrophic” belowground respiration in spruce and beech forests: decreases following girdling

Seasonal fluxes of CO₂ from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots. SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand. The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better understanding of tree level stresses that affect carbon allocation below ground.     

Determination of inter- and intra-species genetic relationships among six Eucalyptus species based on inter-simple sequence repeats (ISSR)

Eucalyptus is the most economically important hardwood plantation tree cultivated in tropical and subtropical countries. Inter-simple sequence repeat (ISSR) markers were used to evaluate genetic relationships within and between individuals of six Eucalyptus species. A total of 583 loci (265 to 1535 bp) were amplified from 149 individuals belonging to the six Eucalyptus species using seven ISSR primers (two to three nucleotide repeats anchored with one or two nucleotides at the 3' or 5' region). The ISSR fragments indicated significant polymorphism and genetic diversity among the individuals. Cluster analysis and principal component analysis revealed the occurrence of wide genetic diversity among populations of E. tereticornis Sm., E. camaldulensis Dehnh. and E. urophylla S.T. Blake and narrow genetic diversity among populations of E. citriodora Hook. and E. grandis W. Hill ex Maiden. Genetic diversity was high in E. tereticornis Sm. (47.27%) and low in E. citriodora (18.64%). Maximum Nei's genetic identity (0.897) was observed between E. camaldulensis and E. tereticornis species, whereas maximum genetic diversity (0.286) was found between individuals of E. citriodora and E. grandis.     

黄河下游灌区农田排水再利用效应模拟评价

在田间试验观测基础上,采用SWAP模型分析黄河下游簸箕李引黄灌区农田排水再利用下的土壤盐分季节性变化以及地下水位对土壤盐分剖面分布的影响,模拟农田排水补灌对作物产量的效应。研究结果表明,咸排水补灌引起的土壤盐分积聚主要在冬小麦生长期,夏玉米生长期内并不明显,有效地控制地下水位有助于减少土壤盐分累积量,维系作物根区的盐分平衡。利用含盐量为4mg/cm3以下的农田排水在冬小麦生长后期水分亏缺阶段进行补灌,可在基本不影响随后夏玉米产量的基础上,不同程度地改善冬小麦产量。对缺水严重的黄河下游引黄灌区,农田排水再利用是缓解水资源供需矛盾、改善作物产量的一种有效水管理措施。     

Lysimeter study on the use of biodrainage to control waterlogging and secondary salinization in (canal) irrigated arid/semi-arid environment

The study describes the capacity of trees to control the rise in water table and thus prevent the formation of waterlogged soils and development of secondary salinization in canal irrigated areas. It was conducted in RCC lysimeters of 1.2 m dia. and 2.5 m depth filled with sandy loam alluvial soil (Typic Ustochrept), with provisions to maintain water table depth at 1, 1.5 and 2 m from the surface and groundwater salinity at 0.4, 3, 6, 9 and 12 dS m-1. The amount of water biodrained by eucalyptus (Eucalyptus tereticornis) and bamboo (Bambusa arundinacea) at the given water table depths and groundwater salinity levels was monitored over four years by daily measuring the water needed for maintaining the water table. The trees continued to absorb and transpire water throughout the year, the capacity being more in summer and rainy than that was in the winter season. The eucalyptus plant could biodrain 2880, 5499, 5518 and 5148 mm of water in the first, second, third and fourth year of study period, from non-saline groundwater and a water table depth of 1.5 m. The amount of water biodrained was more at 1.5 m as compared to 1 and 2 m water table depths. The biodrainage capacity of trees was significantly affected by the salinity of the groundwater. However, even at salinity of 12 dS m-1, the eucalyptus plant biodrained 53% of that under non-saline conditions. It was calculated that biodrainage could control water table rises upto 1.95, 3.48, 3.76 and 3.64 m in first, second, third and fourth year, respectively. The secondary salinity developed in the root zone, upto 45 cm depth, did not exceed 4 dS m-1 even at water table depth of 1 m with salinity of 12 dS m-1. The volume of water biodrained by bamboo increased with time and could control water table rises upto 1.09, 1.86, 2.46 and 2.96 m in first, second, third and fourth year of growth, respectively.This study indicates that due to high transpiration capacity and an ability to extract water from deeper layers containing saline groundwater, the trees can control the rise in water table in irrigation command areas and prevent the formation of waterlogged and eventually the saline wastelands.     

Measuring yield-reducing plant water potential depressions in wheat by infrared thermometry

Summary Measurements of foliage and air wet- and dry-bulb temperatures were made over six differentially irrigated plots of Produra wheat grown at Phoenix, Arizona, in the spring of 1976. These data were used to evaluate a newly developed plant water stress index each day from the initiation of heading to the commencement of senescence. Daily measurements on total plant water potential were also obtained over this period; and after demonstrating how the atmospheric-induced component can be removed from these data, the resultant soil-induced component was plotted as a function of the new water stress index. The result was a simple linear relationship, which was found to be identical to one previously derived for alfalfa. Finally, it was shown that grain yield was directly related to the mean plant water stress index over the reproductive growth period from heading to senescence.Contribution from Agricultural Research, Science and Education Administration, US Department of AgricultureResearch physicist, soil scientist, research physicist, and research entomologist, respectively     

Water balance and crop coefficients of summer-grown peanut (Arachis hypogaea L.) in a humid tropical region of India

A field experiment was conducted with a bunched variety of peanut (Arachis hypogaea L.) cv. JL-24 during the summer seasons (March–June) of 1992 and 1993 in the humid tropical canal command area at the University Experimental Farm, Memari (23°1 N, 88°5 E and 21.34 m a.s.l) in West Bengal of eastern India. The soil at the site is of sandy loam (Typic Fluvaquent) texture and the area has a shallow water table. Weekly and seasonal field water balance components of actual evapotranspiration (ETa) including the capillary contribution into root zone were determined. Peanut yield and water productivity were determined for three ratios of irrigation water and cumulative pan evaporation (CPE) of 0.9, 0.7 and 0.5. Mean crop coefficients were determined for each 7-day period of growth and were related to leaf area index and growing degree-days. Average seasonal values of ETa of peanut were 434, 391 and 356 mm for the three treatments, respectively, for 115 days of growth. The total pod yield and WP were significantly higher in 0.9 IW:CPE treatment in the 1992 season. On an average, 0.9 IW:CPE treatment had 7 and 11% higher yields in 1992 and 1993, respectively, over treatments 0.7 and 0.5 IW:CPE. The maximum average Kc of 1.19 occurred about 9 weeks after sowing relative to grass reference ET (ETo).