Effects of Pratylenchus brachyurus and P. coffeae on Seedlings of Coffea arabica

Two experiments were carried out to evaluate the effects of Pratylenchus brachyurus and P. coffeae on Coffea arabica. The first experiment was conducted in a greenhouse to determine the effects of Pratylenchus brachyurus and P. coffeae on seedlings of Coffea arabica cv. Mundo Novo. Both Pratylenchus spp. reduced the growth of coffee seedlings. Higher contents of soluble sugars were detected in the leaves of infected plants. The reproduction rate of P. brachyurus was very low on cv. Mundo Novo, indicating an intolerance to this nematode. In a second experiment, C. arabica cultivars Mundo Novo and Catuaf both were intolerant hosts of P. brachyurus.     

Comparison of Populations of Pratylenchus brachyurus Based on Isozyme Phenotypes

Enzymes from females of five Pratylenchus brachyurus populations and one P. scribneri population were analyzed by isoelectric focusing electrophoresis. Of the 18 enzyme systems investigated, only malate dehydrogenase (MDH), phosphoglucomutase (PGM), and phosphoglucose isomerase (PGI) were detected from all five P. brachyurus populations and P. scribneri. Faint bands were detected for isocitrate dehydrogenase and phosphogluconate dehydrogenase from one P. brachyurus population. Three distinct phenotypic groups were found in the MDH and PGM systems for P. brachyurus populations, but only a single electromorph was detected for PGI. Multiple electromorphs for MDH, PGM, and PGI were detected for P. scribneri; there was no similarity among these patterns with those from P. brachyurus. No phenotypic differences in PGI were observed between females and mixed juveniles of one population of P. brachyurus.     

Temperature Effects on Reproduction and Pathogenicity of Pratylenchus coffeae and P. brachyurus and Survival of P. coffeae in Roots of Citrus jambhiri

Optimum temperature for reproduction of Pratylenchus coffeae on Rough lemon, Citrus jambhiri Lush. was 29.5 C. Pratylenchus coffeae populations reached 7653 per g of root 2 months after initial inoculation with 140 nematodes. Maximum plant weight reduction was 38%; root weights were reduced by as much as 47%. Pratylenchus brachyurus significantly reduced plant and root weights but population sizes never approached those of P. coffeae. Pratylenchus coffeae survived in stored excised roots and were still infective after 4 months at temperatures ranging from 4.5 to 32 C.     

Morphological Variation in Pratylenchus penetrans

Variability of morphological characters used to separate Pratylenchus penetrans from other species of the genus was studied in a population originating from a single gravid female. Pronounced heteromorphism was observed and characterized. About 30% of females had a crenate-tail terminus. Several shapes of stylet knobs were characterized; 50% of them were anteriorly flattened to indented. The outer margin of the cephalic framework extended into the body from one-half to two annules. The shape of the spermatheca varied from round to oval. A fifth lateral line was observed in many specimens. Environmental factors, and particularly the host plant, influenced such morphometric characters as body length, width, esophagus length, stylet length, V value, a and b'' ratios, as well as qualitative characters such as tail terminus, growth of ovary, and shape of median bulb. Nematodes reared on pea and cabbage had a higher percentage of females with a crenate-tail terminus than those from tomato, rye, beet, and alfalfa callus culture. Nematodes from peas were longer and wider; they often had gonads that extended to esophagi, but they had shorter esophagi amt stylets than those from callus culture. Populations from different geographical locations also exhibited variahility in morphological characters, as did the Cornell population. The validity of many characters used in species identification is discussed, and the possibility that other related Pratylenchus species are conspecific with P. penetrans is suggested.     

Embryonic Ammonoid Shell Features: Intraspecific Variation Revisited

Two samples of ammonoids belonging to the Oppeliidae, Sublunuloceras virguloidesHecticoceras (Brightii) canaliculatum, are analyzed to estimate the intraspecific variability of embryonic shell features. The study of embryonic shell characters reveals two main shapes of protoconch, flattened and round. Prosiphons may be straight or slightly curved. New parameters for area are added to the linear parameters commonly found in the literature. Prosiphon length and caecum area vary greatly whereas protoconch and ammonitella diameter vary only slightly, and the ammonitella angle is almost constant. The protoconch-to-ammonitella size ratio behaves differently in each species, suggesting different patterns of embryonic growth. We compare our results with published data and discuss their significance for species determination and ontogenetic interpretation. The main finding is that intraspecific embryonic variation is greater than was previously believed.     

Intraspecific Variation in the Amino Acid Content of Floral Nectar

In order to evaluate the constancy of amino acid composition and concentration, several randomly collected samples of genuine floral nectar from different flowers of several plant species were analysed. Although there seems to exist a rough pattern of species-specific nectar amino acid composition, amino acid concentration varied strongly from sample to sample. Apart from the lack of constancy in concentration of floral amino acids, our samples do not show amino acid concentration values as assigned typical for the pertinent pollination mode by other workers.     

柠条锦鸡儿不同居群形态变异研究

结合数量统计方法对柠条锦鸡儿12个居群的12项形态特征进行了研究。结果表明：除小叶对数、叶形和荚果长外,其余形态性状在居群内或居群间都表现显著差异;以12个形态性状为基础的聚类分析将所研究的12个居群分为3类;主成分分析结果显示每荚种子、干粒重、托叶长和叶长等4个性状是造成柠条锦鸡儿表型差异的主要因素。     

Damage and Reproductive Potentials of Pratylenchus brachyurus and P. penetrans on soybean

Damage and reproductive potentials of Pratylenchus brachyurus and P. penetrans on soybean, Glycine max, cvs. Essex, Forrest, and Lee 68, were determined in microplot tests. Cultivar Essex was generally tolerant to P. brachyurus. Yield of Forrest was suppressed linearly with increasing P_i''s in the sandy soil (r = -0.92) and loamy sand soil (r = -0.99). Low to moderate P_i''s in the sandy clay loam gave an increase in yields as compared to plants without nematodes. Yield was not affected by this nematode in muck. Lee 68 was very sensitive to P. penetrans in microplots. Yield vs. P_i was fitted by a quadratic model (r = 0.82) with yield decreasing sharply as P_i''s were increased. The reproduction of both species decreased with increases in P_i. Lee 68 was a good host for P. penetrans, whereas Essex and Forrest were fair to poor hosts for P. brachyurus.     

Morphological Variation among 23 Xiphinema americanum Populations

Morphometrics of 23 United States populations of Xiphinema americanum sensu lato, sharing the characteristics of an offset lip region and conoid tail, were examined and analyzed statistically by canonical discriminant analysis (CDA). Specimens were collected from Arkansas, Georgia, Tennessee, Mississippi, Florida, Oklahoma, California, and North Dakota. Eleven measurements and body ratios obtained from female specimens were used in the analysis. Xiphinema americanum, X. bricolensis, X. californicum, X. citricolum, X, intermedium, X. tarjanense, and X. thornei, and one undescribed species were identified among the 23 populations. Three groups -- X. americanum-group, X. californicum-group, and X. intermedium-group (X. intermedium and X. tarjanense) -- were formed and four populations belonging to four different species were separated consistently from these groups in CDA scatterplots of the 23 populations. Composition of the groups was somewhat related to the geographical origins of the populations in the groups. A population from California had morphometrics intermediate between X. americanum and X. californicum. Separation between the X. americanum-group and X. californicum-group in the CDA scatterplots was not as distinct as that between them and the X. intermedium-group or between any of the three groups and the four single outlying populations.     

Interaction of Pratylenchus brachyurus and Gigaspora margarita on Cotton

An endomycorrhizal fungus, Gigaspora margarita, was more effective in stimulating the growth of cotton (Gossypium hirsutum) ''Coker 201'' at a low fertility level (1.77 gm 10-10-10 N-P-K/pot) than doubling the fertility rate for nonmycorrhizal plants. Gigaspora margarita alone stimulated shoot growth (height, weight, and flower production by 96%, 553%, and 760%, respectively) and root growth (385%) over that of nonmycorrhizal controls at low fertility. Plant development was also stimulated by G. margarita at the high fertility level (3.54 gm 10-10-10 N-P-K/pot), but the magnitude of the increase was not as great as that at the low fertility level. Although cotton was a suitable host for Pratylenchus brachyurus, plant development was not retarded by this nematode at either fertility level. In concomitant culture, mycorrhizal-induced plant growth, and sporulation of the endomycorrhizal fungus were not affected by P. brachyurus. Reproduction of P. brachyurus was similar on mycorrhizal and nonmycorrhizal cotton.     

Comparative Influence of Radopholus similis and Pratylenchus coffeae on Citrus

Pratylenchus coffeae was as pathogenic as Radopholus sirnilis to commercial citrus rootstocks. No rootstock resistant to R. similis was resistant to P. coffeae. Both nematodes stunted citrus in three soil types. Seedling damage by P. coffeae and R. similis was greatest in fine- and coarse-textured soils, respectively. Reproduction and survival on citrus were greater for P. coffeae than for R. similis. Mixed inoculations with R. similis and P. coffeae resulted in lower populations of each species than did separate inoculations.     

余甘子天然居群果实形态变异研究

为了从数量性状上分析余甘子天然居群果实表型性状在居群间和居群内的变异,在云南省选取了6个余甘子天然居群,分别测量了其8个果实表型性状并作比较分析。结果显示:(1)余甘子果实表型性状在居群间和居群内存在着较丰富的变异,8个果实性状在居群间的F值为20.17～35.21,部分差异达到显著水平;居群内的F值为1.27～3.07,差异均达到极显著水平。(2)余甘子居群内的平均表型变异接近90%,是余甘子果实表型遗传变异的主要来源。(3)余甘子表型性状的变化与生态和地理因子显著相关;主成分分析结果显示,单果重、果实横径、外果皮重、果核宽、果核重等5个表型性状指标是反映滇西北余甘子果实表型差异的主要因素。     

Anatomical Studies of Citrus jambhiri Lush. Roots Infected by Pratylenchus coffeae

All motile stages of Pratylenchus coffeae infected mature and immature tissues of Citrus jambhiri (rough lemon) seedling tap roots. The nematodes fed primarily in the cortex and colonized in pockets or cavities. Intra- and intercellular migration within the cortex occurred in either direction from the point of entry. When P. coffeae invaded a root tip the meristem often was destroyed and lateral root initiation usually occurred near the destroyed root tip. Males were essential for reproduction and survived at least 2 1/2 months within root tissues, but with males alone used as inoculum, no cortical pockets were formed. On infected trees in the field P. coffeae were most numerous in C. jambhiri feeder roots.     

西藏喜马拉雅紫茉莉野生居群果实形态变异

为了明确不同种源喜马拉雅紫茉莉野生种质资源的果实形态差异,在西藏选取了16个居群,测量了8个果实性状,分别进行了单因素方差分析、主成分分析、聚类分析和相关性分析,为喜马拉雅紫茉莉遗传多样性的评价和种质选育提供依据。结果显示：（1）8个果实性状的平均值在不同居群存在差异,八宿县怒江山居群（TNC2）的总苞筒长、总苞裂片长和宽、果长、果形、百粒重均最小,其他居群未表现出明显的规律性;9个居群均以果纹路的变异系数最大,多数居群以果宽或果长变异最小。（2）总体上看,8个性状的变异系数在8.58%~25.57%之间,其中总苞裂片宽变异最大（25.57%）,而果宽变异最小（8.58%）;各性状的F值在12.180~134.761之间,均表现为差异极显著,表明8个性状在不同居群间均存在明显差异。（3）主成分分析显示,果长和总苞裂片大小是造成各居群间果实表型差异的主要因素。（4）根据果实性状,16个居群分为两大支,聚类结果与各居群的地域分布并无关联。（5）除总苞裂片宽与经度呈显著负相关关系外,经度、纬度和海拔对8个果实性状不存在显著影响。     

Intraspecific variation in the direction and degree of sex-biased dispersal among sea-snake populations

Higher rates of dispersal in one sex than the other are widespread, and often attributed to the genetic advantages of reduced inbreeding. The direction of sex-biased dispersal shows strong phylogenetic conservatism (e.g. males disperse more than females in most mammals, but the reverse is true in most birds). By contrast, our genetic data reveal strong inter-population variation in the relative dispersal rates of two species of sea snakes (Laticauda saintgironsi and L. laticaudata) in the Noumea Lagoon of New Caledonia. Assignment methods using microsatellite data identified parallel variation in sex-specific dispersal in both species: dispersal was female-biased in the north-west of the sampling area (in islands far from the main island), but male-biased in the south-east (in islands closer to the main island). This flexibility may reflect sex differences in diets, with spatial variation in sex-specific resources generating spatial variation in sex-specific dispersal distances.     

The geographic structure of morphological variation in eight species of fiddler crabs (Ocypodidae: genus Uca) from the eastern United States and Mexico

Species with larger geographic distributions are more likely to encounter a greater variety of environmental conditions and barriers to gene flow than geographically‐restricted species. Thus, even closely‐related species with similar life‐history strategies might vary in degree and geographic structure of variation if they differ in geographic range size. In the present study, we investigated this using samples collected across the geographic ranges of eight species of fiddler crabs (Crustacea: Uca) from the Atlantic and Gulf coasts of North America. Morphological variation in the carapace was assessed using geometric morphometric analysis of 945 specimens. Although the eight Uca species exhibit different degrees of intraspecific variation, widespread species do not necessarily exhibit more intraspecific or geographic variation in carapace morphology. Instead, species with more intraspecific variation show stronger morphological divergence among populations. This morphological divergence is partly a result of allometric growth coupled with differences in maximum body size among populations. On average, 10% of total within‐species variation is attributable to allometry. Possible drivers of the remaining morphological differences among populations include gene flow mediated by ocean currents and plastic responses to various environmental stimuli, with isolation‐by‐distance playing a less important role. The results obtained indicate that morphological divergence among populations can occur over shorter distances than expected based on dispersal potential. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 248–270.     

不同居群五柱绞股蓝叶形变异及总黄酮含量分析

以不同生境的五柱绞股蓝为材料,对4个不同来源的五柱绞股蓝的叶片性状、裂叶数进行了统计,并以芦丁为对照品,采用分光光度法对4个居群五柱绞股蓝的总黄酮含量进行了测定。结果表明,五柱绞股蓝的叶型变异较大,其复叶具有3-9裂叶型类型,以7裂叶型和5裂叶型为主。相关性统计显示,野生型五柱绞股蓝黄酮含量高,与7裂叶型极显著相关,家种型五柱绞股蓝黄酮含量低,与叶型无关,环境因子可能是影响其黄酮含量的主要因子。在引种时,7裂叶型的五柱绞股蓝可作为优选资源引用。     

Control of Pratylenchus brachyurus in soybean with Trichoderma spp. and resistance inducers

Trichoderma spp. is a fungus with nematode control potential; however, its potential to control the root lesion nematode Pratylenchus brachyurus remains poorly studied. Thus, the aim of this study was to select Trichoderma spp. isolates and assess their ability to control P. brachyurus in soybean crops. Different experiments were conducted aiming at selecting isolates, assessing whether they were able to reduce nematode penetration in plants or cause mortality in vitro, and whether they were able to induce resistance in soybean, as well as at studying the possibility of using the selected isolates associated with resistance inducers (acibenzolar‐S‐methyl, Ecolife^? and AgroMos^?). The selection experiment found three isolates showing satisfactory results, namely GF422, GF425 and GF427; the GF362 isolate was assessed in the subsequent experiments. These four isolates reduced P. brachyurus penetration in soybean roots and promoted nematode mortality in vitro. Increased total protein and catalase activity were recorded, mainly in the 72‐hr assessments. Overall, the protein production was different between isolates. The best results were found in the combination between the GF362 isolate and the three resistance inducers, between GF427 and Ecolife^?, between GF427 and AgroMos^? and between GF422 and Ecolife^?.     

Inter- and Intraspecific Variation in Wild-type and Single Female-derived Populations of Xiphinema americanum-group Nematodes

Ten populations of Xiphinema americanum-group nematodes were reared from individual females to evaluate inter- and intraspecific variation under identical host and environmental conditions. Data indicated that morphometric variability of X. americanum was the result of genetic variation rather than phenotypic plasticity and that genetic heterogeneity was greater than previously thought. Morphometrics of single female derived (SFD) populations identified different genotypes present in the field populations. Stylet length was the least variable morphometric character of SFD populations, but collectively stylet measurements of all individuals formed an uninterrupted continuum ranging from 107-148 μm. Range and frequency of stylet measurements of field populations could be accounted for by the relative proportion of different genotypes in the population. Nine SFD populations were identified as X. americanum sensu stricto, and one SFD population was similar to X. californicum.