Floral structures of six cowpea （Vigna unguiculata） cultivars were analysed for secondary plant metabolites （polyphenols, terpenoids and flavonoids） to study their relationships with resistance to Megalurothrips s...Floral structures of six cowpea （Vigna unguiculata） cultivars were analysed for secondary plant metabolites （polyphenols, terpenoids and flavonoids） to study their relationships with resistance to Megalurothrips sjostedti （Trybom）. Polyphenols varied significantly （P 〈 0.001） among the floral structures of the cultivars at the same growth stage. Significant negative correlations were obtained between polyphenols and damage indices （r = -0.57）, mean adult counts （r = -0.56） and mean larval counts （r = -0.64） of resistant cowpea cultivars especially in the late season, indicating that polyphenols play a significant role in cowpea resistance to M. sjostedti. High levels of polyphenols obtained from Sanzibanili and Sewe cultivars, coupled with highly significant correlations between the polyphenols and thrips population on resistant cultivars, and their damage indices, suggests that these polyphenols could be inhibitors or deterrents in this case. Terpenoid extracts （10 mg/mL） of IT90K-277-2, Sewe, Sanzibanili, TVu 1509 and KV - 404-8-1 racemes; KV ~ 404-8-I and TVu 1509 floral buds; IT90K-277-2, Sewe and Sanzibanili flowers caused significant （P 〈 0.001） larval mortalities, since mortality ranged between 56.7%-96.7%. Hence terpenoid extracts from floral structures of the cultivars are biologically active and confers antibiotic resistance to M. sjostedti larvae; this compound could be promising candidates for genetic transformation of cowpea cultivars.展开更多
Field experiments were conducted at two key locations in two successive seasons in Nigeria to determine the role of habitat manipulation in the bio-control of African rice gall midge, Orseolia oryzivora using Platygas...Field experiments were conducted at two key locations in two successive seasons in Nigeria to determine the role of habitat manipulation in the bio-control of African rice gall midge, Orseolia oryzivora using Platygaster diplosisae an endoparasitoid of the midge. The habitat manipulation strategy tested in the study was to plant seedlings ofPaspalum scrobiculatum on one meter strip of land at the border of each rice plot early in the cropping season to conserve P. diplosisae in its alternative host, Orseolia bonzii that infest P. scrobiculatum. The Paspalum seedlings were allowed to be fully established, infested naturally by 0. bonzii and parasitized by P. diplosisae before transplanting rice varieties in each plot. The control plots were planted with only rice seedlings leaving the border empty without any Paspalum. Rice plots with Paspalum at the edge had much lower levels of O. oryzivora infestation than the control plots. The percentage number of gall midge parasitized by P. diplosisae showed that rice plots with Paspalum at the edge had more parasitized galls than the control plots without Paspalum. The role of the Paspalum border was substantiated with the negative correlation results recorded with the infestation indicating significant decrease in the percentage tiller infestation as the percentage parasitism increased. That resulted in higher grain yield in the plots surrounded with Paspalum treatment than in the control. The present study therefore demonstrated that management of P. scrobiculatum on a strip of land around the edge of rice crops could significantly increase parasitoid carry-over into the crop.展开更多
文摘Floral structures of six cowpea （Vigna unguiculata） cultivars were analysed for secondary plant metabolites （polyphenols, terpenoids and flavonoids） to study their relationships with resistance to Megalurothrips sjostedti （Trybom）. Polyphenols varied significantly （P 〈 0.001） among the floral structures of the cultivars at the same growth stage. Significant negative correlations were obtained between polyphenols and damage indices （r = -0.57）, mean adult counts （r = -0.56） and mean larval counts （r = -0.64） of resistant cowpea cultivars especially in the late season, indicating that polyphenols play a significant role in cowpea resistance to M. sjostedti. High levels of polyphenols obtained from Sanzibanili and Sewe cultivars, coupled with highly significant correlations between the polyphenols and thrips population on resistant cultivars, and their damage indices, suggests that these polyphenols could be inhibitors or deterrents in this case. Terpenoid extracts （10 mg/mL） of IT90K-277-2, Sewe, Sanzibanili, TVu 1509 and KV - 404-8-1 racemes; KV ~ 404-8-I and TVu 1509 floral buds; IT90K-277-2, Sewe and Sanzibanili flowers caused significant （P 〈 0.001） larval mortalities, since mortality ranged between 56.7%-96.7%. Hence terpenoid extracts from floral structures of the cultivars are biologically active and confers antibiotic resistance to M. sjostedti larvae; this compound could be promising candidates for genetic transformation of cowpea cultivars.
文摘Field experiments were conducted at two key locations in two successive seasons in Nigeria to determine the role of habitat manipulation in the bio-control of African rice gall midge, Orseolia oryzivora using Platygaster diplosisae an endoparasitoid of the midge. The habitat manipulation strategy tested in the study was to plant seedlings ofPaspalum scrobiculatum on one meter strip of land at the border of each rice plot early in the cropping season to conserve P. diplosisae in its alternative host, Orseolia bonzii that infest P. scrobiculatum. The Paspalum seedlings were allowed to be fully established, infested naturally by 0. bonzii and parasitized by P. diplosisae before transplanting rice varieties in each plot. The control plots were planted with only rice seedlings leaving the border empty without any Paspalum. Rice plots with Paspalum at the edge had much lower levels of O. oryzivora infestation than the control plots. The percentage number of gall midge parasitized by P. diplosisae showed that rice plots with Paspalum at the edge had more parasitized galls than the control plots without Paspalum. The role of the Paspalum border was substantiated with the negative correlation results recorded with the infestation indicating significant decrease in the percentage tiller infestation as the percentage parasitism increased. That resulted in higher grain yield in the plots surrounded with Paspalum treatment than in the control. The present study therefore demonstrated that management of P. scrobiculatum on a strip of land around the edge of rice crops could significantly increase parasitoid carry-over into the crop.
