Phylogenetic and morphological identification of Colletotrichum boninense: a novel causal agent of anthracnose in avocado

In recent years, anthracnose has become a significant disease affecting avocado fruit in the state of Michoacan, Mexico, where it significantly reduces fruit quality and commercial yield. Anthracnose has been assumed to involve Colletotrichum gloeosporioides and C. acutatum as causal agents. However, because of the increasing incidence of anthracnose, a more precise identification of the Colletotrichum spp. involved in this disease has become desirable. During the years 2004–2007, avocado fruits of different sizes exhibiting brown‐black and reddish spots on the pericarp and soft rot in the mesocarp, were gathered from orchards in nine counties. Fungal isolates were cultured on potato dextrose agar, and among these, 31 were selected for molecular, morphological and pathogenicity analyses. The molecular approaches used sequence typing of the internal transcribed spacer region and the partial nuclear large ribosomal subunit, allowing the unequivocal identification of C. gloeosporioides (71%), C. acutatum (16%) and C. boninense (13%). This last species has not been previously reported as being associated with anthracnose symptoms in avocado fruits anywhere in the world. Various morphological characteristics such as the size and shape of conidia were determined, as well as the conidial mass colour. Pathogenicity tests performed with all three species were conducted by inoculating healthy fruits. In each case, identical symptoms developed within 3 days of inoculation. Knowledge of the Colletotrichum populations in the Michoacan state, including the newly encountered avocado pathogen C. boninense, will facilitate further studies addressing the relationships between these Colletotrichum spp. and their avocado host.     

Influence of supraphysiological cortisol manipulation on predator avoidance behaviors and physiological responses to a predation threat in a wild marine teleost fish

The stress axis in teleost fish attempts to maintain internal homeostasis in the face of allostatic loading. However, stress axis induction has been associated with a higher predation rate in fish. To date, the physiological and behavioral factors associated with this outcome are poorly understood. The purpose of the present study was to investigate the impact of experimental cortisol elevation on anti‐predator behavior and physiological responses to predator presence. We hypothesized that semi‐chronic cortisol elevation would increase susceptibility to predation by increasing stress‐induced risk‐taking behaviors. To test this hypothesis, schoolmaster snapper were given cocoa butter implants without cortisol (sham) or with cortisol (50 mg/kg body weight) and tethered to cover. Fish were exposed to either a lemon shark or control conditions for 15‐min. Space use and activity were recorded throughout and fish were terminally sampled for blood. Cortisol implantation, relative to shams, resulted in higher blood glucose and plasma cortisol concentrations with a lower plasma lactate concentration. Shark exposure, relative to controls, elicited higher blood glucose and lactate concentrations but had no effect on plasma cortisol concentration. No interactions were detected between shark exposure and cortisol treatment for any physiological trait. Behavioral metrics, including shelter use and activity, were unaffected by either cortisol implantation or shark exposure. Physiological responses to cortisol implantation likely resulted from enhanced gluconeogenic activity, whereas alterations under predator exposure may have been the product of catecholamine mobilization. Further work should address context‐specific influences of stress in mediating behavioral responses to predation.     

地表蚂蚁群落对不同类型柠檬园的物种响应及生物指示——以云南省主要柠檬产区为例

通过陷阱法调查云南省主要柠檬产区9种类型柠檬园地表蚂蚁群落。采集地表蚂蚁52种2 641头,地表蚂蚁群落结构划分为5组。不同类型柠檬园地表蚂蚁特有种不同,柠檬园BC、BB及LE无特有种,柠檬园BA有1种,其余柠檬园有2~10种。6种以上柠檬园中均出现的物种在不同类型柠檬园中的多度变化明显。对群落结构相似性贡献率≥5%的特征物种分析显示,9种类型柠檬园间地表蚂蚁特征物种明显不同;柠檬园LE、BB及RI的指示物种各有1种,分别为宽结大头蚁Pheidole noda、黑头酸臭蚁Tapinoma melanocephalum及印度大头蚁P.indica。蚂蚁的生物学特性与样地特征相关联,地表蚂蚁通过物种组成及多度变化对不同类型柠檬园做出了响应。9种类型柠檬生产方式不利于地表蚂蚁群落的保护,建议柠檬生产中减少化学农药的使用,一定程度提高植被复杂程度,降低人为干扰,增加柠檬绿色生产技术的投入。     

Growth, reproduction and resource allocation of Tithonia diversifolia and Tithonia rotundifolia

Growth, reproduction and resource allocation of the polycarpic Tithonia diversifolia and the monocarpic Tithonia rotundifolia were studied in mixed and monoculture populations. The aim was to identify the characteristics contributing to the invasive habits of these species. Tithonia rotundifolia attained reproductive maturity at 2 months and T. diversifolia 4 months after planting. Tithonia rotundifolia completed its life cycle after 4 months, just as T. diversifolia was starting to flower. Both plant species produced a high number of seeds per capitulum (136–144 seeds in T. diversifolia; 113–120 in T. rotundifolia). Tithonia diversifolia reproduced asexually and sexually and produced many small light seeds. Tithonia rotundifolia produced large seeds, had early rapid growth, short life cycle and high reproductive effort. Growth in mixture did not significantly affect plant height, numbers of branches and leaves, or leaf size, but affected biomass allocation to reproductive and vegetative activities in the species. The attributes contributing to the invasiveness of these species are large seeds, early rapid growth, short life cycle and high reproductive effort in T. rotundifolia, with many small light seeds and asexual and sexual reproduction in T. diversifolia. For both species, control of recruitment would be a means of limiting their invasiveness.     

柠檬不同部位精油的成分分析及抑菌活性

采用水蒸气蒸馏法提取北京柠檬叶片、枝干和果皮的精油,并进行GC-MS分析,共鉴定出38种成分,其中叶片23种,枝干21种,果皮29种。3份精油主要挥发油成分均为D-柠檬烯,相对含量分别为52.85%、53.03%和51.23%;共有成分14种,特异性成分分别有4种、3种和14种。通过对3种食源性细菌的抑菌活性的测定,3份柠檬精油均有一定程度的抑菌作用,其中,叶片精油对大肠埃希氏菌和金黄色葡萄球菌抑菌效果最佳,且抑菌圈直径最大;果皮精油对伤寒沙门氏菌的抑菌效果最佳,抑菌圈最大。研究结果表明,柠檬不同部位精油活性成分含量差异较大,在对其开发利用时,可考虑各自优势,合理利用柠檬的叶片、枝干和果皮,为柠檬资源合理化和精细化的开发利用提供一定的科学依据。     

Richness, distribution and conservation status of cavity nesting birds in Mexico

A considerable number of bird species depend on tree cavities availability for nesting in temperate and tropical forests in Mexico. Tree cavity availability is reduced in heavily managed forests, making cavity nesting species particularly vulnerable to the high rates of forest loss and degradation that occur every day in the remaining wilderness areas of the country. We analyzed information about nesting behavior, distribution, and conservation status of resident landbird avifauna from 35 important and protected bird areas of Mexico. The main intention was to determine the proportion of resident bird species that nest in tree cavities and are more sensitive to intensive forest management practices. Our results revealed that 17% (112 species) of the resident landbird avifauna need tree cavities for nesting. Cavity nesters represented a higher proportion of endangered and threatened species than non-cavity nesters. The families Strigidae and Psittacidae represented the highest number of tree cavity nesting species in status. In the 35 avifaunas examined, the mean percentage of cavity nesting species ranged from 17% to 21%. The cloud forest reserve of “El Triunfo” with 43 species, is the area with the highest concentration of cavity nesting species in Mexico.     

Expansion of Leptochloa fusca ssp. uninervia and Leptochloa fusca ssp. fascicularis in rice fields in Valencia,eastern Spain

Due to the rapid spread of two subspecies of Leptochloa fusca through the Valencia rice‐growing region in the east of Spain, a 3‐year field study was carried out to establish the frequency, distribution and infestation level of the two subspecies in rice paddies in the area. A total of 3650 fields were visited, of which 1235 were visited in each year of the study period. Leptochloa fusca ssp. uninervia and Leptochloa fusca ssp. fascicularis were found to be widely distributed in the area, increasing from a frequency of 5.3% in 2008 to 20.1% in 2010. Leptochloa fusca ssp. uninervia was the largest contributor to the infestations, but subspecies fascicularis is now on the increase and represents a serious threat to rice crops, as it is found within the rice fields themselves. The irrigation system and the farm machinery used in the rice fields also contribute to the rapid spread of these weeds. Severe infestations have been caused by periodic water shortages, and the fact that new herbicides used to control Echinochloa spp. do not affect Leptochloa subspecies. Spatial differences in the distributions of the two subspecies are attributed to the different water management systems and also to differences in the germination and dormancy of both subspecies.     

Plant folk medicines for gastrointestinal disorders among the main tribes of Sonora, Mexico

This paper describes the herbal remedies used by ethnic groups from Sonora, Mexico, for treatment of gastrointestinal diseases. Twelve types of these illnesses are cured using 85 different species which belong to 38 families. Thirty nine spp. are used to treat diarrhea, 28 for stomach-ache, 12 for constipation, 9 for intestinal parasites, 6 for indigestion, 3 for stomach or intestinal cancer, 3 for stomach inflammation and only 1 to treat gastrointestinal sicknesses, ulcers, gastritis, colitis and colic. Regarding the use of species of plant per ethnic group the following was observed: Mayo 47; Seri, 27; Yaqui, 13; Guarijio, 12, Pima, 5 and Papago, 3. The plants are used by two or more tribes, for the same or different illness but always related to the gastrointestinal system.     

尤力克柠檬上一种新病害的生物学特性及RT-PCR检测

近年我国云南瑞丽市的一果园尤里克柠檬上出现一种引起叶片皱缩、反卷或呈船形,叶背水浸状、侧脉脉明、黄化的柑橘新病害。为明确该病害的病原及其生物学特性,通过田间观察、病样接种、电镜观察,并基于柑橘黄脉病毒(Citrus yellow vein clearing virus,CYVCV)外壳蛋白基因设计引物对病样进行RT-PCR检测。结果表明,该病是一种嫁接传染性病害,能侵染柠檬和酸橙品种且症状明显,并能摩擦接种到辣椒和豇豆等草本植物。该病发病最适温度为18~24℃。春梢嫩叶症状表现明显,夏梢和秋梢基本不表现症状,而晚秋梢也表现出较春梢稍弱的典型症状。引致该病的病毒为(13~15)nm×(400~1 000)nm大小的联合丝状病毒。RT-PCR扩增产物为614 bp,且其与CYVCV外壳蛋白序列相似性达97%以上,表明该病害是由CYVCV引起的柑橘黄脉病,并初步建立了该病的RT-PCR检测技术。