Bionomics and control of root_knot nematodes in wheat_rice cropping system

Investigations were under taken within the laboratory, green-house, microplots and real fields s i tuat ions with the following broad objectives: 1. To study the survival of Meloidogyne triticoryzae in relation to soil moisture . 2. To study the population dynamics of root-knot nematodes under five rice-based cropping systems. 3 . To study the effect of tillage and water management on the population behaviour of rootknot nematodes in rice. 4. To study the effect of some nematicides on the population density of root-knot nematodes and performance of the rice crop. 5. To devise and test a practical and economical method for integrated management of root-knot nematodes in wheat-rice cropping system. 6. To investigate the role of a cyanobacteria, Aulosira fertilissima in the bio-regulation of root-knot nematodes in rice. 7. Histopathology of wheat roots infected with rootknot nematodes, Af. triticoryzae. The results of the above experiments are summerized below: The root-knot nematode, M. triticoryzae could survive longer in moist and wet soil than in air-dried soil. In sterilized soil very few second stage juveniles (J2) survived or remained infective after 45-75d. The J2 of M. triticoryzae were very susceptible to desiccation but the population appeared to survive in egg stage. The rate of water loss in sub-saturated conditions was higher in M. triticoryzae than in M. incognita J2. The J2 of both the species survived only for a short time (5-40 min) in vitro at 60-90% RH levels, M. incognita was relatively more tolerant to desiccation than M. triticoryzae. Desiccation tolerance was related to the kind of mois ture regimes experienced by the two species in their na tu ra l habi ta ts . Population dynamics of Af. triticoryzae h a s been studied in five rice-based cropping sys tems . Replacing wheat with mus ta rd could reduce the populat ion density while berseem increased it. Incorporation of organic matter as greengram crop residue also reduced the equilibrium population density. The s tudies on the tillage and water management have revealed tha t puddling reduced the bulk density of soil and decreased the hydraulic conductivity in the upper layers but not in the deeper layer at soil. Aeration was reduced due to high moisture levels re ta ined in the puddle soil. Population density of M. triticoryzae declined in puddled soil. The invasion of the roots by the second-generation infective juveniles was reduced. The populat ion density of the root-knot nematodes was higher in the non-puddled soil especially in unsubmerged condition compared to puddled and submerged soil. However, if the seedlings were already infected before transplanting and submergence , the nematode could survive well and reproduced within the aerenchyma of the root. The reduction in nematode population levels achieved by soil solarization and nematicides in nursery-beds resulted in significantly improved hea l th of the rice seedlings which when t ransplanted in the main field gave better crop in treated and un t rea ted in the main field. Application of nematicides phorate or carbofuran after soil solarization gave greater reduct ion in nematode infection and increased weight. However, soil solarization had the major influence. Besides paddy yield the shelling percentage was improved due to nematode control. The grain filling was adversely affected due to nematode damage to roots. Fur ther application of the nematicide in the solarized main field gave 53.2% higher yield over untreated control which was only 3.8% higher than that from unt rea ted main field. Soil solarization could be a practical, feasible and environmentally safer alternative to nematicides. The hatching of M. triticoryzae J2 was suppressed in cul ture filtrates and standard aqueous extracts of the blue-green alga, Aulosira fertilissima. Sudden resumption in hatch was observed when the aqueous extract was replaced by fresh GDW. Very low concentration of the aqueous extract s t imulated hatching whereas high concentration of the same was nematostat ic , Meloidogyne incognita eggs hatched very rapidly and completed most of the hatching within 2-3 wk. In contrast, M. triticoryzae eggs hatched very slowly over 9 wk. The root-knot nematode, M. triticoryzae also infected wheat. Histopathological studies on wheat root showed that syncytium was well developed. The vascular bundles were dislocated, the cortical parenchyma had hyperplasia and was extensively damaged. The root wall was broken with partially protruding females and eggsacs, while in rice root female and eggsacs usual ly remained inside the root aerenchyma. BIONOMICS AND CONTROL OF ROOT-KNOT NEMATODES IN WHEAT-RICE CROPPING SYSTEM THESfS SUBMITTED TO THE ALIGARH MUSLIM UNIVERSITY. ALIGARH IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF \^-^ ^ doctor at $Ijilo! s;QpI)p HI AGRICULTURE \ ;^ (NEMATOLOGY) / ^ <f " € J BY / ^^^^ SHEFTA TASNEEM CHANDEL R. A. K. INSTITUTE OF AGRICULTURAL SCIENCES ALIGARH MUSLIM UNIVERSITY ALIGARH 2000