The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that a...The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected A. gossypii strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated p-Nitroanisole O-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes viz., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in A. gossypii collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.展开更多
The melon aphid, <i>Aphis gossypii</i> Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many p...The melon aphid, <i>Aphis gossypii</i> Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected <i>A. gossypii</i> strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated <i>p</i>-Nitroanisole <i>O</i>-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes <i>viz</i>., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in <i>A. gossypii</i> collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.展开更多
Jelly seed, a physiological disorder in ‘Amrapali' mango fruit, is characterized by the excessive softening of pulp around the stone in ripe fruits. The disorder is caused by the onset of germination associated e...Jelly seed, a physiological disorder in ‘Amrapali' mango fruit, is characterized by the excessive softening of pulp around the stone in ripe fruits. The disorder is caused by the onset of germination associated events in the seed of developing fruit due to decreased level of very-longchain fatty acids(VLCFAs) in seed. Field trials involving preharvest application of spray formulations on developing fruits, between 50% and 60%maturity, showed that formulation V(10 g·L^(-1) NaCl, 25 g·L^(-1) CaCl_2, 0.5 g·L^(-1) KCl, 0.01 g·L^(-1) H_3 BO_3, 0.01 g·L^(-1) Cu SO_4, 0.01 g·L^(-1) Zn SO_4,0.01 g·L^(-1) FeSO_4, 0.01 g·L^(-1) MnSO_4, and 0.002 g·L^(-1) EDTA) was the most effective in preventing the jelly seed disorder. Further studies to understand the mode of action of the formulation in controlling jelly seed development, revealed increased synthesis of VLCFAs in seed followed by the rapid production of ABA and germination-inhibiting phenolic acids, besides increased accumulation of calcium in seed. These factors acting in unison delayed seed germination and decreased the activities of pectinolytic enzymes in pulp to produce healthy fruits, free from jelly seed disorder.There was an increase of mineral nutrient content in pulp of treated healthy fruits. Thus, the study helped to develop a remedy to prevent jelly seed besides revealing the biochemical mechanism by which formulation V acted to produce ‘Amrapali' mango fruits free of jelly seed with improved nutritional quality.展开更多
文摘The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected A. gossypii strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated p-Nitroanisole O-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes viz., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in A. gossypii collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.
文摘The melon aphid, <i>Aphis gossypii</i> Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected <i>A. gossypii</i> strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated <i>p</i>-Nitroanisole <i>O</i>-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes <i>viz</i>., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in <i>A. gossypii</i> collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.
文摘Jelly seed, a physiological disorder in ‘Amrapali' mango fruit, is characterized by the excessive softening of pulp around the stone in ripe fruits. The disorder is caused by the onset of germination associated events in the seed of developing fruit due to decreased level of very-longchain fatty acids(VLCFAs) in seed. Field trials involving preharvest application of spray formulations on developing fruits, between 50% and 60%maturity, showed that formulation V(10 g·L^(-1) NaCl, 25 g·L^(-1) CaCl_2, 0.5 g·L^(-1) KCl, 0.01 g·L^(-1) H_3 BO_3, 0.01 g·L^(-1) Cu SO_4, 0.01 g·L^(-1) Zn SO_4,0.01 g·L^(-1) FeSO_4, 0.01 g·L^(-1) MnSO_4, and 0.002 g·L^(-1) EDTA) was the most effective in preventing the jelly seed disorder. Further studies to understand the mode of action of the formulation in controlling jelly seed development, revealed increased synthesis of VLCFAs in seed followed by the rapid production of ABA and germination-inhibiting phenolic acids, besides increased accumulation of calcium in seed. These factors acting in unison delayed seed germination and decreased the activities of pectinolytic enzymes in pulp to produce healthy fruits, free from jelly seed disorder.There was an increase of mineral nutrient content in pulp of treated healthy fruits. Thus, the study helped to develop a remedy to prevent jelly seed besides revealing the biochemical mechanism by which formulation V acted to produce ‘Amrapali' mango fruits free of jelly seed with improved nutritional quality.
