Changes in total cyanide content of tissues from cassava plants infested by mites (Mononychellus tanajoa) and mealybugs (Phenacoccus manihoti)

Ayanru, D. K. G.; Sharma, V.C.

doi:10.1016/0167-8809(84)90059-8

Cited by 17 publications

(9 citation statements)

References 14 publications

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“…A toxin was thought to be injected into the plant during feeding by the mealybug, but there is no evidence to support this claim. Cassava plants exhibit various deformities in response to CMB infestation , but, more importantly, the plants also undergo physiological changes, exemplified by changes in the cyanide content of the leaves, stems and tubers, in response to the combined attack by CMB and a complex of mites (Ayanru & Sharma, 1984). Such a spreading response to herbivore damage has also been demonstrated in potato and tomato plants (Green & Ryan, 1972).…”

Section: Resultsmentioning

confidence: 95%

The role of host‐ and host‐plant odours in the attraction of a parasitoid, Epidinocarsis lopezi, to the habitat of its host, the cassava mealybug, Phenacoccus manihoti

Nadel

Alphen

1987

Entomologia Exp Applicata

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In the field, the encyrtid wasp, Epidinocarsis lopezi (DeSantis) can find its host, the cassava mealybug (Phenacoccus manihoti Matile‐Ferrero) on cassave plants when the host is scarce. As a step towards understanding the parasitoid's effectiveness we investigated the cues with which it locates its host‐habitat. Using a four‐armed olfactometer, we determined the attactivity of various host‐ and host‐plant odours to female E. lopezi which had been previously exposed to infested plants. Attractivity or preference of an odour was determined from the proportion of 50 choices made between the odour and a blank, or between two odours. Female E. lopezi were attracted by mealybug‐infested cassava leaves (CML), but not by the odour of cassava mealybugs (CMB) alone or by uninfested plants (ULU). An artificial combination of CMB and ULU was also not attractive. CML was preferred over ULU and CMB + ULU. These results suggest that the attractive element arises from the cassava plant itself in response to CMB infestation. We therefore tested the attractivity of uninfested leaves from partly infested plants, and found that these were indeed attractive. E. lopezi probably uses the odour which is emitted from infested cassava plants to guide it to its host in the field. Zusammenfassung Die Rolle des Geruchs von Wirt und Wirtspflanzen für die Anlockung des Parasitoiden, Epidinocarsis lopezi, zur Umgebung seiner Wirte, die Cassava‐schmierlaus. Epidinocarsis lopezi ist imstande, seine Wirte auf den Cassavapflanzen zu finden, auch wenn die Wirte nur in geringer Dichte vorkommen. Die Reaktion der Schlupfwespe auf Gerüche der Wirte und der Wirtspflanzen wurde untersucht. Weibchen der Schlupfwespe, die vorher mit Schmierläusen auf Cassavapflanzen zusammengebracht worden waren, wurden individuell in einem vierarmigen Olfaktometer verschiedenen Kombinationen dieser Gerüche ausgesetzt. Die relative Attraktivität jedes Geruchs wurde bestimmt anhand von 50 Entscheiden zwischen dem Geruch und einer Kontrolle oder zwischen zwei Gerüchen. E. lopezi Weibchen wurden von schmierlausinfizierten Blättern angezogen, aber nicht von Cassavaschmierläusen (CMB), oder von uninfizierten Cassavapflanzen (ULU). Die künstliche Mischung von CMN und ULU wurde auch nicht anlockend. CML war relativ mehr attraktiv als ULU und als die Mischung. Die Vermutung liegt vor dass E. lopezi von einem Pflanzenduft angezogen wird, der von mit Schmierläusen infizierten Cassavapflanzen ausgeschieden wird. Die Parasitoide wurden auch von uninfizierte Blättern teilweise infizierter Pflanzen angezogen. Wahrscheinlich wird im Freiland der Geruch infizierter Cassavapflanzen durch E. lopezi zur Auffindung weiterer wirtstragenden Cassavapflanzen gebraucht.

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Section: Resultsmentioning

confidence: 95%

The role of host‐ and host‐plant odours in the attraction of a parasitoid, Epidinocarsis lopezi, to the habitat of its host, the cassava mealybug, Phenacoccus manihoti

Nadel

Alphen

1987

Entomologia Exp Applicata

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“…To minimize the experimental work to identify a transgenic cassava line that does not contain cyanogenic glucosides in leaves and tubers, it was desirable to be able to define the earliest plant stage and the type of plant tissue suitable for robust screening to avoid growing all transgenic lines to the tuber stage. A good correlation between leaf and tuber cyanide potential in cassava grown in the field has been reported (Cooke et al, 1978;Mahungu, 1994), but the existence of an association between root and leaf cyanide potential has subsequently been refuted (Ayanru andSharma, 1984/1985;Makame et al, 1987;Mkong et al, 1990;Bokanga et al, 1994). In tissue culture of cassava, cyanogenesis arises late in the regeneration process (Joseph et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…In tuber-producing cassava plants, the main site of synthesis is the shoot apex (de Bruijn, 1973;Andersen et al, 2000). In young cassava plants derived from stakes, the highest concentration of cyanogenic glucosides has generally been found in young leaves (de Bruijn, 1973;Ayanru andSharma, 1984/1985). In plants with a high cyanide potential, the cyanogenic glucoside content of leaves has been reported to increase with plant age, whereas the cyanogenic glucoside content in leaves decreased with plant age in cassava plants with low cyanide potential (Indira and Ramanujam, 1987).…”

Section: Discussionmentioning

confidence: 99%

Cassava Plants with a Depleted Cyanogenic Glucoside Content in Leaves and Tubers. Distribution of Cyanogenic Glucosides, Their Site of Synthesis and Transport, and Blockage of the Biosynthesis by RNA Interference Technology

et al. 2005

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Transgenic cassava (Manihot esculenta Crantz, cv MCol22) plants with a 92% reduction in cyanogenic glucoside content in tubers and acyanogenic (,1% of wild type) leaves were obtained by RNA interference to block expression of CYP79D1 and CYP79D2, the two paralogous genes encoding the first committed enzymes in linamarin and lotaustralin synthesis. About 180 independent lines with acyanogenic (,1% of wild type) leaves were obtained. Only a few of these were depleted with respect to cyanogenic glucoside content in tubers. In agreement with this observation, girdling experiments demonstrated that cyanogenic glucosides are synthesized in the shoot apex and transported to the root, resulting in a negative concentration gradient basipetal in the plant with the concentration of cyanogenic glucosides being highest in the shoot apex and the petiole of the first unfolded leaf. Supply of nitrogen increased the cyanogenic glucoside concentration in the shoot apex. In situ polymerase chain reaction studies demonstrated that CYP79D1 and CYP79D2 were preferentially expressed in leaf mesophyll cells positioned adjacent to the epidermis. In young petioles, preferential expression was observed in the epidermis, in the two first cortex cell layers, and in the endodermis together with pericycle cells and specific parenchymatic cells around the laticifers. These data demonstrate that it is possible to drastically reduce the linamarin and lotaustralin content in cassava tubers by blockage of cyanogenic glucoside synthesis in leaves and petioles. The reduced flux to the roots of reduced nitrogen in the form of cyanogenic glucosides did not prevent tuber formation.Cassava (Manihot esculenta Crantz) is the most important root crop in the world and ranks second among African staple crops (Nweke et al., 2002). Cassava is vegetatively propagated through stem cuttings and produces well on poor soils. The tubers may be kept in the soil for extended time periods. This secures rural farmers a carbohydrate source in years with adverse growth conditions where other crops fail and famine would otherwise prevail. These features and high crop yield contribute to the importance of cassava in Africa, South East Asia, and South America Industrial cassava starch production is important, especially in South East Asia (Bokanga, 1994). Cassava leaves are not widely used as a food source despite their high protein content (Ngudi et al., 2003).Major drawbacks of the cassava crop are the low tuber protein content, rapid tuber perishability following harvest, and high content of the cyanogenic glucosides linamarin and lotaustralin in all tissues. Upon tissue disruption, the cyanogenic glucosides are brought in contact with b-glucosidases and a-hydroxynitrile lyases and degraded into cyanohydrins, hydrogen cyanide, and ketones (Conn, 1980). When cassava products are used as a primary staple food, careful processing to remove these toxic constituents is required to avoid chronic cyanide intoxication (Onabolu et al., 2002). Incomplete processing may result in hi...

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“…Kojima et al 1983 found increased CNP in wounded roots, especially in the outer parenchyma tissue next to the cortex. Ayanru and Sharma (1984) found enhanced CNP of root parenchyma caused by infestation by Cassava green mite (Mononychellus tanajoa Bondar) and Cassava mealybug (Phenacoccus manihoti MatileFerrero) compared with noninfested plants sprayed with insecticides. They found that the overall mean of CNP of the entire plants did not differ between infested and noninfested plants and concluded that translocation of cyanogen from other tissues to the root parenchyma must have occurred as a response to the biotic stresses.…”

Section: Discussionmentioning

confidence: 95%

“…Cassava leaves invariably have high CNP, whereas cassava roots are much more variable. High and low parenchymal CNP values do not correspond with CNP in the leaves (Bruijn 1973, Pereira et al 1981, Ayanru and Sharma 1984.…”

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confidence: 95%

Cyanogenic Potential in Cassava and Its Influence on a Generalist Insect Herbivore <I>Cyrtomenus bergi</I> (Hemiptera: Cydnidae)

Riis¹,

Bellotti²,

Bonierbale³

et al. 2003

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The hypothesis that cyanogenic potential in cassava is a defense mechanism against arthropod pests is one of the crucial questions relevant to current efforts to reduce or eliminate cyanogenic potential (CNP) in cassava. The generalist arthropod Cyrtomenus bergi, which attacks cassava roots, was used in a bioassay relating oviposition and survival to CNP, concentration of nonglycosidic cyanogens, and linamarase (beta-glycosidase) activity in twelve selfed cassava siblings and their parental clone, which has segregated for different levels of cyanogenesis. Electron microscopic evaluation revealed an intracellular pathway of the stylet of C. bergi in the cassava root tissue to rupture cell walls. This feeding behavior causes cyanogenesis and increased linamarin content in the hemolymph of C. bergi while feeding on a cyanogenic diet. This diet resulted in a significant reduction in oviposition, especially at levels of CNP above 150 ppm (expressed as hydrogen cyanide) on fresh weight basis (or 400 ppm on dry weight basis) in cassava roots. An exponential decline in oviposition was observed with increasing levels of CNP, beginning 12 d after exposure to the cyanogenic diet. Cyanogenic potential and dry matter content showed a positive effect on survival. No relationship was found between concentrations of nonglycosidic cyanogens or linamarase activity in the cassava root and either oviposition or survival. According to our results, there is a significant difference between potentially noncyanogen and high cyanogen clones, but there may not be a significant difference between potentially noncyanogen and low cyanogen clones. Consequently, more frequent outbreaks or higher levels of damage might not be anticipated in potentially noncyanogen cassava clones than that anticipated in low cyanogenic clones. The negative effect of cyanogenesis on oviposition concurrent with a positive effect on survival of this pest is most likely the result of a physiological trade-off between survival and oviposition. The question of whether ovipositional rates could be recovered after a long-term exposure to cyanide remains unanswered.

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Changes in total cyanide content of tissues from cassava plants infested by mites (Mononychellus tanajoa) and mealybugs (Phenacoccus manihoti)

Cited by 17 publications

References 14 publications

The role of host‐ and host‐plant odours in the attraction of a parasitoid, Epidinocarsis lopezi, to the habitat of its host, the cassava mealybug, Phenacoccus manihoti

The role of host‐ and host‐plant odours in the attraction of a parasitoid, Epidinocarsis lopezi, to the habitat of its host, the cassava mealybug, Phenacoccus manihoti

Cassava Plants with a Depleted Cyanogenic Glucoside Content in Leaves and Tubers. Distribution of Cyanogenic Glucosides, Their Site of Synthesis and Transport, and Blockage of the Biosynthesis by RNA Interference Technology

Cyanogenic Potential in Cassava and Its Influence on a Generalist Insect Herbivore <I>Cyrtomenus bergi</I> (Hemiptera: Cydnidae)

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