Metabolic profiling of mango cultivars to identify biomarkers for resistance against Fusarium infection

Infection of mango panicles and young leaf shoots by Fusarium results in significantly lower fruit yields. Some mango cultivars are known to be tolerant to blossom malformation, while others are highly susceptible. Previous researchers linked the ability of certain cultivars to confine Fusarium infection to the production of high levels of mangiferin. This study further elucidates the role of phenolic metabolites contributing to tolerance. Phenolic profiles of mature leaf extracts from cultivars with varying degrees of resistance to Fusarium infection were obtained by ultrahigh performance liquid chromatography–time-of-flight-mass detection. Chemometric models constructed from the data revealed a clear distinction between the profiles of tolerant and susceptible cultivars and permitted the identification of biomarkers associated with susceptibility to infection. The presence of elevated levels of mangiferin, maclurin and maclurin O-galloyl-glucoside in the leaves were associated with a higher degree of tolerance. In contrast, high levels of iriflophenone glucosides were linked to increased susceptibility of the cultivars to infection. These models can serve as an important tool to investigate appropriate cultivars, prior to their introduction to areas prone to the disease.     

Effect of rootstock on mango fruit susceptibility to infestation by Anastrepha obliqua

The effect of the use of rootstock Criollo on the susceptibility of Manila mango fruit to infestation by Anastrepha obliqua (Macquart) was determined in the present investigation. Growth, quality parameters (Soluble solids content (%), citric acid content (%), firmness, monoterpene volatiles (3-carene, limonene, alpha-pinene, and beta-myrcene), main flavonoids content (milligrams/100 g fresh pulp), and larvicidal activity of methanolic extracts, as well as the degree of infestation during preharvest development of the fruits were analyzed. The results indicated that the rootstock did not have any significant effect on growth, soluble solids content, or citric acid content; although it increased firmness as well as 3-carene levels and main flavonoids content, resulting in a greater resistance to infestation by A. obliqua. The obtained results support the use of this rootstock because of the beneficial effects observed on the resistance of mango fruit to infestation by this fruit fly.     

Invasive mango blossom gall midge, Procontarinia mangiferae (Felt) (Diptera: Cecidomyiidae) in Reunion Island: ecological plasticity, permanent and structured populations

Mango blossom gall midge, Procontarinia mangiferae (=Erosomyia mangiferae Felt), is an invasive pest that causes economic damage worldwide. The objectives of our study were to highlight the genetic and ecological abilities of this monophagous gall midge to invade new habitats and to evaluate its genetic structure on an isolated island. This study, carried out in subtropical Reunion Island, is based on data from population dynamics surveys and from molecular analyses (mitochondrial DNA and microsatellites). Using 11 microsatellite loci and an extensive sampling of 27 populations at 17 sites, we tested the genetic differentiation between populations sampled on different mango organs and cultivars at different seasons and under different climatic and cultural environments. We checked for the existence of a seasonal bottleneck. Our results showed that a single species, P. mangiferae, was present all year round with no genetic bottleneck at any of the sites sampled, regardless of the climatic and cultural conditions, and that it fed on inflorescences and young leaves. These characteristics showed the ecological plasticity of P. mangiferae, despite its low genetic diversity and, consequently, the invasive potential of this species. Populations in Reunion Island are structured into two clusters in sympatry and present in different proportions at each site. One cluster was more frequently found in the cultivated mango area. This work provides insights into the relationships between gall midges and tree host plants in a subtropical agro-ecosystem, as well as into the role of the population genetic structure in the establishment process of a monophagous invasive cecid fly.     

Olive Volatiles from Portuguese Cultivars Cobran?osa,Madural and Verdeal Transmontana: Role in Oviposition Preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fly, Bactrocera oleae (Rossi), a serious threat to the olive crop worldwide, displays ovipositon preference for some olive cultivars but the causes are still unclear. In the present work, three Portuguese olive cultivars with different susceptibilities to olive fly (Cobrançosa, Madural, and Verdeal Transmontana) were studied, aiming to determine if the olive volatiles are implicated in this interaction. Olive volatiles were assessed by SPME-GC-MS in the three cultivars during maturation process to observe possible correlations with olive fly infestation levels. Overall, 34 volatiles were identified in the olives, from 7 chemical classes (alcohols, aldehydes, aromatic hydrocarbons, esters, ketones, sesquiterpenes, and terpenes). Generally, total volatile amounts decrease during maturation but toluene, the main compound, increased in all cultivars, particularly in those with higher susceptibility to olive fly. Sesquiterpenes also raised, mainly α-copaene. Toluene and α-copaene, recognized oviposition promoters to olive fly, were correlated with the infestation level of cvs. Madural and Verdeal Trasnmontana (intermediate and highly susceptible cultivars respectively), while no correlations were established with cv. Cobrançosa (less susceptible). No volatiles with inverse correlation were observed. Volatile composition of olives may be a decisive factor in the olive fly choice to oviposit and this could be the basis for the development of new control strategies for this pest.     

Effect of mango weevil (Coleoptera: Curculionidae) damage on mango seed viability in Tanzania

Studies were conducted at the horticulture unit of Sokoine University of Agriculture, Morogoro, Tanzania, to assess the incidence and effect of mango weevil, Cryptorhynchus mangiferae (F.) (Coleoptera: Curculionidae), infestation on mango, Mangifera indica L., seed viability. Three polyembryo mango cultivars ('Sindano nyeusi', 'Sindano nyeupe', and 'Dodo') as well as three monoembryo mango cultivars ('Ex-horticulture', 'Tango', and 'Bongwa') were collected and examined for the presence of C. mangiferae. The effect of seed damage on viability was assessed for both naturally and artificially damaged seeds. However, for artificially damaged seeds, the viability was assessed by cutting away 0, 25, 50, or 75% of the cotyledon before planting. In this experiment, only monoembryo mango cultivars were used. All the examined cultivars were infested by C. mangiferae, although at varying levels. Polyembryo mango cultivars were relatively more infested than monoembryo cultivars. Bongwa and Tango were least infested, whereas Sindano nyeusi recorded the highest C. mangiferae incidence. Germination rates of damaged seeds of polyembryonic cultivars differed significantly from the uninfested control, except for Sindano nyeusi. There were no significant differences in germination percentage among the three monoembryo cultivars, and all the cultivars differed significantly from the uninfested control. The germination rates of seeds with 25% of their cotyledons removed did not differ significantly from the undamaged seeds, indicating that monoembryo cultivar seeds can withstand up to 25% damage and germinate successfully.     

Comparison of the volatile components of some mango cultivars

Three cultivars of mango from Sri Lanka (Jaffna, Willard and Parrot) were analysed for their volatile aroma components. The total concentrations of volatiles obtained were ca 251, 422 and 628 μg per kg of fresh fruit, respectively. Terpenes were the main volatiles of all three cultivars, with monoterpene hydrocarbons contributing 50–63 % w/w of the total volatiles and sesquiterpene hydrocarbons 14–19 %. Whilst the major volatile of Jaffna mango was cis-β-ocimene (38 %), α-terpinolene was the major volatile of the other two cultivars (32 % and 35 %). Esters were produced by all cultivars (2–16 %), Jaffna yielding most, the majority being unsaturated (12 %). Willard mango gave particularly high levels of non-terpene hydrocarbons (19 %), including a range of six long-chain alkanes (8 %), not detected in the other cultivars.     

Terpenes associated with resistance against the gall wasp,Leptocybe invasa,in Eucalyptus grandis

Leptocybe invasa is an insect pest causing gall formation on oviposited shoot tips and leaves of Eucalyptus trees leading to leaf deformation, stunting, and death in severe cases. We previously observed different constitutive and induced terpenes, plant specialized metabolites that may act as attractants or repellents to insects, in a resistant and susceptible clone of Eucalyptus challenged with L. invasa. We tested the hypothesis that specific terpenes are associated with pest resistance in a Eucalyptus grandis half‐sib population. Insect damage was scored over 2 infestation cycles, and leaves were harvested for near‐infrared reflectance (NIR) and terpene measurements. We used Bayesian model averaging for terpene selection and obtained partial least squares NIR models to predict terpene content and L. invasa infestation damage. In our optimal model, 29% of the phenotypic variation could be explained by 7 terpenes, and the monoterpene combination, limonene, α‐terpineol, and 1,8‐cineole, could be predicted with an NIR prediction ability of  .67. Bayesian model averaging supported α‐pinene, γ‐terpinene, and iso‐pinocarveol as important for predicting L. invasa infestation. Susceptibility was associated with increased γ‐terpinene and α‐pinene, which may act as a pest attractant, whereas reduced susceptibility was associated with iso‐pinocarveol, which may act to recruit parasitoids or have direct toxic effects.     

Diversity analysis,pathogen load and gene expression studies of mango cultivars infected by mango malformation disease

Mango (Mangifera indica L.) is known as “king of fruits” in India. More than 1000 mango varieties are currently cultivated in Indian Sub-continent. However most of the orchards of mango are infected with mango malformation disease (MMD), which every year leads to huge losses in yield of mango in range of 40 to 80?% in India. Till date there is no effective control measure against MMD. Floral Malformation, in contrast to vegetative one, is very virulent and can cause the loss of the entire crop. In the present study, six mango cultivars commonly grown in Gujarat, and all infected with various degrees of MMD were taken for studying their molecular relatedness, pathogen load and defense responsiveness via gene expression to rate whether hybrids or landrace among mango cultivars are better equipped to fight MMD. Genetic diversity analysis was performed using 30 SSR markers in order to bring out clustering pattern among the six cultivars belonging to orchards of Balisana and Prantij, Gujarat. The diversity analysis gave clues to the existence of wide genetic base among the six cultivars. Fungal load studies using Real Time PCR lead to the ranking of cultivars based on maximum and minimum infection load of pathogen. Absolute quantitation studies found that cultivars like Totapuri, Neelam and Amrapali were more resistant to MMD than highly popular cultivars like Kesar. The six mango cultivars were further quantified for pathogen responsiveness with 21 defense responsive genes using Real Time PCR. Among the 21 genes selected for the study, 11 genes were directly part of defense responsive pathways like Phenyl propanoid pathway and jasmonic acid pathway. Gene expression studies aided in ranking mango hybrid like Amrapali having better systemic acquired resistance response as 11 defense responsive genes were found upregulated in this cultivar followed by landrace Neelam which is in fact a parental line of Amrapali. If MMD remains unchecked it may lead to evolution of more virulent strains of Fusarium; propelling devastating consequences in mango cultivation. Hence mango hybrids developed via molecular and expressional screening will fasten process of establishment of resistant mango cultivars.     

Attraction of the West Indian fruit fly to mango fruit volatiles

In this study, we investigated the attraction of West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae), to volatiles of three mango [Mangifera indica L. (Anacardiaceae)] cultivars in field cage tests. The number of flies captured with Multilure traps baited with Amate mature green mangoes was significantly higher than that captured in traps baited with Coche and Ataulfo fruits. There was no significant difference between the number of flies captured in traps baited with Coche or Ataulfo mangoes. Gas chromatography‐mass spectrometry analysis of mango fruit volatiles identified 24, 22, and 19 compounds for Amate, Ataulfo, and Coche mango cultivars, respectively. A principal component analysis of the volatiles revealed that the Amate mango was more distant from the Ataulfo mango, and the latter cultivar was closer to the Coche mango. The compounds myrcene, α‐pinene, β‐selinene, and trans‐β‐ocimene were the most abundant in Amate mangoes, whereas 3‐carene, β‐selinene, terpinolene, and α‐pinene were the predominant compounds of Ataulfo cultivars. In the Coche mango, the predominant compounds were 3‐carene, β‐selinene, terpinolene, and limonene. Traps baited with a blend of myrcene, α‐pinene, and trans‐β‐ocimene captured more A. obliqua females and males than control traps. Flies were more attracted to the Super Q volatile extracts of Amate mango than to the three‐component blend formulated in a ratio of 1:1:1. However, there was no significant difference between the number of flies caught by traps baited with Amate mango extracts and that caught by traps baited with the three‐blend component when this was formulated according to the relative proportions in the mango extracts. Traps baited with myrcene, the major component, caught fewer flies than traps baited with Amate mango extracts.     

云南元江芒果园桔小实蝇成虫日活动规律及空间分布格局

利用甲基丁香酚引诱剂和黄板对桔小实蝇Bactrocera dorsalis成虫日活动规律及飞行高度进行了研究,同时根据多种聚集度指标对桔小实蝇成虫的空间分布格局进行了分析。结果表明:元江县挂果期芒果园内桔小实蝇日活动量高峰出现在10:00、16:00左右,活动量低谷出现在8:00、14:00和19:00左右,日间温湿度与其日活动量之间无线性相关关系;成虫飞行高度随时间变化,受降雨影响,雌雄成虫飞行高度存在差异。上午、中午成虫多近地飞行,午后多在1.5 m以上高度飞行,降雨导致成虫飞行活动量大幅减退,多分布于1.5 m以上枝叶附近。株高8 m的3a芒果树4 m高度处黄板捕获虫量最大,其次是2 m高处,6m以上虫量较少。雄性成虫在芒果园中呈聚集分布,原因之一是其自身的聚集行为;雌虫空间分布不均,主要呈聚集分布,少数部分为均匀分布,其聚集由环境因素造成。     

Volatile flavour components of mango fruit

An essence of fresh Venezuelan mango fruit obtained by well-established procedures possessed the characteristic aroma of the fruit. It was analysed by GC/MS using both EI and Cl. The fruit produced a relatively small quantity of aroma volatiles (ca 60 μg/kg fresh fruit), less than that obtained from many similar tropical fruits. Terpene hydrocarbons comprised ca 68% of the sample, eight monoterpenes contributing ca 54% and four sesquiterpenes contributing ca 14%. Important constituents included α-pinene, car-3-ene, limonene, γ-terpinene, α-humulene, β-selinene, acetophenone, benzaldehyde and a dimethylstyrene. Car-3-ene (26%) was the major constituent, and on odour evaluation of separated components at an odour port during GC, the peak due to this compound was described as having an aroma of mango leaves. This compound has not previously been detected among mango volatiles. The only other component providing mango aroma was a dimethylstyrene, and this too is a new mango volatile.     

Responses of embryogenic mango cultures and seedling bioassays to a partially purified phytotoxin produced by a mango leaf isolate of Colletotrichum gloeosporioides penz

Summary Colletotrichum gloeosporioides Penz., the causal agent of mango anthracnose, produces a phytotoxin in vitro. The partially purified phytotoxin, presumably colletotrichin, caused anthracnose-like symptoms on young mango leaves, was toxic to embryogenic suspension cultures of two mango cultivars, ‘Hindi’ and ‘Carabao,’ and inhibited in vitro seed germination of two nonhosts, lettuce and tobacco. There were linear relationships between concentration of the partially purified phytotoxin and mortality of mango embryogenic cultures. Embryogenic cultures grown in the presence of the partially purified phytotoxin showed significantly lower growth rates than the controls. Similarly, embryogenic cultures grown in the presence of 40% (vol/vol) fungal culture filtrate showed significantly lower growth rates than unchallenged controls. Medium containing 40% (vol/vol) Czapek-Dox fungal broth did not reduce growth of embryogenic cultures, indicating the production of phytotoxin in vitro. The results suggest that either fungal culture filtrate or purified phytotoxin can be used as in vitro selection agents to screen for resistance to this fungus.     

Field superparasitism by Diachasmimorpha longicaudata attacking Anastrepha spp. larvae on mango fruits

The incidence of superparasitism in field populations of Diachasmimorpha longicaudata (Ashmead), a solitary larval–pupal endoparasitoid, attacking Anastrepha fruit fly species was determined. From 14,550 fruit fly larvae infesting mango fruits in the field, 68.9% (10,038) survived to the pupal stage. Of these pupae, 3780 (37.7%) were parasitized, of which 2075 (54.9%) were superparasitized. The number of oviposition scars per pupa ranged between 1 and 29, although high numbers were rare. The presence of one or two scars per host was frequent, but only 8.6% of pupae had more than three scars. Fruit size was positively related to the level of infestation by Anastrepha spp. and was significantly correlated with the numbers of parasitized and superparasitized pupae by D. longicaudata. The length and width of host pupae were positively related to superparasitism, and superparasitism was positively correlated with a sex ratio biased toward females. Our data show that superparasitism is present in natural populations of D. longicaudata at remarkable rates and confers some advantageous features such as a female-biased sex ratio. These findings favor the election of this species as a viable biocontrol agent for augmentative releases because the favorable proportion of adult females emerging from superparasitized pupa should contribute to better pest control.     

Relation of fruit color,elongation, hardness,and volume to the infestation of olive cultivars by the olive fruit fly,Bactrocera oleae

The susceptibility of olive cultivars to the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), has seldom been studied. This article examines factors associated with olive fruit fly infestation of 16 commonly planted Sicilian olive cultivars. Total infestation data were simultaneously correlated with categorical and quantitative factors using ordinal logistic regression. When all factors were included in the analysis, year, sampling date, cultivar, and fruit color were highly significant, but the quantitative factors fruit volume, fruit elongation, and fruit hardness were not. When the analysis was repeated excluding cultivar, all quantitative factors were significant, and elongation and volume were highly significant. Spherical, large, and hard fruit seemed to be preferred by B. oleae over fruit that are elongate, small, and soft. Therefore, fruit color, elongation, volume, and hardness provide useful information regarding the susceptibility of cultivars. In both organic and conventional olive cultivation, information about olive cultivar susceptibility to olive fruit fly will help orchard managers to produce quality oil and table olives while reducing treatments for olive fruit fly control.     

Susceptibility of low-chill blueberry cultivars to Mediterranean fruit fly, oriental fruit fly, and melon fly (Diptera: Tephritidae)

No-choice tests were conducted to determine whether fruit of southern highbush blueberry, Vaccinium corymbosum L., hybrids are hosts for three invasive tephritid fruit flies in Hawaii. Fruit of various blueberry cultivars was exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquillet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal development and adult emergence. Each of the 15 blueberry cultivars tested were infested by oriental fruit fly and Mediterranean fruit fly, confirming that these fruit flies will oviposit on blueberry fruit and that blueberry is a suitable host for fly development. However, there was significant cultivar variation in susceptibility to fruit fly infestation. For oriental fruit fly, 'Sapphire' fruit produced an average of 1.42 puparia per g, twice as high as that of the next most susceptible cultivar 'Emerald' (0.70 puparia per g). 'Legacy', 'Biloxi', and 'Spring High' were least susceptible to infestation, producing only 0.20-0.25 oriental fruit fly puparia per g of fruit. For Mediterranean fruit fly, 'Blue Crisp' produced 0.50 puparia per g of fruit, whereas 'Sharpblue' produced only 0.03 puparia per g of fruit. Blueberry was a marginal host for melon fly. This information will aid in development of pest management recommendations for blueberry cultivars as planting of low-chill cultivars expands to areas with subtropical and tropical fruit flies. Planting of fruit fly resistant cultivars may result in lower infestation levels and less crop loss.     

Characterization of embryogenic mango cultures selected for resistance to Colletotrichum gloeosporioides culture filtrate and phytotoxin

 Embryogenic nucellar cultures of two polyembryonic mango cultivars, ‘Hindi’ and ‘Carabao’, were selected for resistance to the culture filtrate and phytotoxin of a virulent strain of Colletotrichum gloeosporioides Penz. that was isolated from mango leaves. The cultures were recurrently selected either with progressively increasing concentrations of culture filtrate or by continuous challenge with the same concentration of either culture filtrate phytotoxin. Mycelium growth was inhibited when the pathogen was cocultured with the selected, resistant embryogenic cultures. Conditioned plant growth medium containing macerated resistant embryogenic cultures did not inhibit mycelium growth, confirming that extracellular antifungal compounds were involved in the defense response. Enhanced secretion of chitinase and glucanase was observed in the plant growth medium in which resistant embryogenic cultures and regenerated somatic embryos were grown in comparison with the controls. Received: 6 February 1997 / Accepted: 4 November 1997     

Egg adhesion of the codling moth Cydia pomonella L. (Lepidoptera, Tortricidae) to various substrates: I. Leaf surfaces of different apple cultivars

Codling moths, Cydia pomonella L. (Lepidoptera, Tortricidae), of the first generation deposit eggs on apple leaves in the vicinity of small fruits. The choice of the suitable oviposition sites and proper fixation of eggs are expected to be crucial factors for the survival of the offspring. In this study, we investigated egg adhesion of the codling moth to leaf surfaces of different cultivars of the domestic apple, Malus domestica Borkh., by measuring the pull-off force required to detach the eggs from leaves. Since surface features may influence insect egg adhesion, morphological and physicochemical properties (wettability, free surface energy) of these leaf surfaces were analyzed. Furthermore, eggs and their adhesives covering leaf surfaces were visualized. Eggs on the smooth upper leaf surfaces of all tested cultivars required significantly similar pull-off forces to be detached, at a total average of 6.0?mN. Up to 2?C3 times stronger pull-off forces had to be applied to detach eggs from trichome-covered lower leaves, and these forces differed significantly between cultivars. The role of leaf surface properties is discussed in the context of egg adhesion, oviposition site choice, female attachment, as well as neonate locomotion speed and survival. The obtained results shed light on the susceptibility of various apple cultivars and leaf surfaces to the infestation of apple trees by first-generation codling moths.     

Epicuticular wax composition in relation to aphid infestation and resistance in red raspberry (Rubus idaeus L.)

Epicuticular waxes from the aphid-resistant red raspberry (Rubus idaeus) cultivar Autumn Bliss and the aphid-susceptible cultivar Malling Jewel were collected from the newly emerging crown leaves, and also from the group of four more mature leaves immediately below the crown. Resistance and susceptibility status of the leaves to infestation by the large raspberry aphid, Amphorophora idaei, were determined by bioassay with the insect just prior to collection of the wax. Analysis showed the waxes to consist of a complex mixture of free fatty acids; free primary alcohols and their acetates; secondary alcohols; ketones; terpenoids including squalene, phytosterols, tocopherol and amyrins; alkanes and long chain alkyl and terpenyl esters. Compositional differences which may relate to A. idaei-resistance status were noticeably higher levels of sterols, particularly cycloartenol, together with the presence of branched alkanes, and an absence of C₂₉ ketones and the symmetrical C₂₉ secondary alcohol in wax from the resistant cultivar Bliss. There were also differences between the cultivars in the distribution of individual amyrins and tocopherols and in the chain length distribution for homologues of fatty acids, primary alcohols and alkanes, and these may also be related to resistance to A. idaei. Emerging leaves had lower levels of primary alcohols and terpenes, but higher levels of long-chain alkyl esters, and in general, more compounds of shorter chain-length than the more mature leaves. During bioassay A. idaei displayed a preference to settle on the more mature leaves. This may be due to greater wax coverage and higher levels of the compounds of shorter chain length found in the newly emerged younger leaves at the crown of the plant.     

ISSR鉴定亲缘关系非常近的芒果栽培品种

用ISSR技术鉴定7个吕宋芒品种(系)和柳州吕宋芒。从30个引物中筛选出6个多态性好的ISSR引物建立DNA指纹图谱用于区分吕宋芒品种(系)。分析DNA指纹图谱,发现这6个引物中每个引物都能区分吕宋系列品种(系),表明ISSR-PCR技术对芒果品种(系)的鉴定非常有效,能区分亲缘关系很近的品种(系)。基于69条多态性条带的聚类分析结果,发现吕宋芒和其它供试的7个品种(系)同源性低,而这7个品种(系):高州吕宋芒、湛江吕宋芒、田阳香芒、金钱芒、柳州吕宋芒、粤西一号、攀西红吕宋同源性较高,可归为一类。