INDUCTION OF RESISTANCE BY CHEMICALS AND PLANT EXTRACTS IN CHICKPEA AGAINST Ascochyta rabiei

Abstract

A series of experiments were conducted to determine the ability of different chemicals and plant extracts to induce resistance in chickpea plant against A. rabiei disease in the Department of Plant Pathology, University of Agriculture, Faisalabad, Pakistan. Firstly two hundred and seventy seven advanced lines/cultivars of chickpea obtained from various International and Indigenous Organizations were screened during the Rabi season 2005-06 for the source of resistance against chickpea blight disease by artificial inoculation of the germplasm with pycniosspore suspension of the pathogen. The screening revealed 02, 38, 39, 49 and 149 lines/cultivars to be highly resistant (immune), resistant, moderately resistant, susceptible and highly susceptible while in the next experiments 49 susceptible lines/cultivars were sown for the purpose of induction of resistance in high yielding lines/cultivars by comparing their yield potential under disease free and artificially inoculated The results revealed that the three chickpea cultivars C-44 with (575 kg h -1 ), Bittle-98 (543.75 kg h -1 ) and Pb-91 (533.50 kg h -1 ) gave highest yield under disease free as well as under artificially inoculated conditions with yield (144.6 kg h -1 ), (132.8 kg h -1 ) (111.2 kg h -1 ) of C-44, Bittle-98, and Pb-91 respectively. Upon induction of resistance by chemicals i.e. salicylic acid, Bion ® , KOH and plant extracts i.e. Azadirachta indica, Datura metel and Allium sativum revealed that significant disease reduction (79%) was provided by Bion ® in the cultivar C-44 at 1.2mM dose rate as compared to salicylic acid, however, the least was showed by KOH. Among the plant extracts the maximum disease reduction (43.5%) against the disease was observed by the application of Azadirachta indica leaf extract while Datura metel and Allium sativum did not prove effective in reducing the disease at the same time this resistance was remained persistent for 14 days. The analysis of mineral contents of induced un-inoculated and induced inoculated chickpea plants after seven and fourteen days revealed there were increased after the induction of resistance but this increase was more significant (P ≤ 0.05) upon inoculation with the pathogen after 14 th day time interval by the application of chemical but it was not significant in case of plant extract expect neem. Only Na content was decreased in Bion applied plant in the cultivar C-44 and Pb-98 further more Cu content was also decreased in salicylic acid, Bion and neem leaf extract treated plants in the cultivar C-44. The amino acids contents were also determined of both the induced un-inoculated and induced inoculated chickpea plants showed that the quantity of methionine, isolucine, tyrosine and phenylalanine content increased after induction and inoculation in three cultivars of chickpea and comparatively higher than induced un-inoculated plants. Increase in lysine content was more in C-44 upon inoculation in case of Bion and salicylic acid treatment but it decreased in Bittle-98. Arginine and aspartic acid contents also increased in all the cultivars expect in Bittle-98, however, aspartic acid content increased in case of garlic application. Variable response was also shown by threonine content by the application of chemicals and inoculation with pathogen in all the cultivars. Serine contents decreased in KOH, neem and datura extracts application in Bittle-98. Glutamic acid show variable response while proline decreased in C-44 and Bittle-98 after application of garlic extract. Glycine content decreased in Bittle-98 otherwise it increased in all the other cultivars. Garlic application showed decrease in alanine content in Pb-91 and Bittle-98.