• Volume 74, Issue 2

      August 1971,   pages  53-111

    • Biological control of cotton wilt - III.In vivo effect of antagonists on the pathogenFusarium vasinfectum atk

      V Arjunarao

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      By adding optimum dose of propagule suspension of antagonistic actinomycetes to pathogen amended sterilized soil, control of wilt in cotton could be effected. Gradual elimination of the pathogen both in rhizosphere of the host and soil was noticed in the presence of antagonists. Incorporation of antagonists directly into the soil controled the disease to a greater extent than “seed treatment” with propagules of antagonists. Efficient control of the disease was observed only with a few of the antagonists when seeds were soaked in their metabolites and sown. Significantly these were fromFusarium “wilt-free” soils.

    • Studies on the diurnal variations in physico-chemical and biological factors in teppakulam tank

      Sumitra Vijayaraghavan

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      1. Diurnal variations in physico-chemical and biological factors were studied in Teppakulam tank. Samples from the surface and near the bottom were collected at 3-hour intervals for 24 hours. Results of an average of five series in winter and three series in summer are presented.

      2. Water temperature increased during daytime and decreased during night hours. Diurnal variation in temperature amounted to 6·8° C at the surface and 5·1° C at the bottom.

      3. There was no marked diurnal variation in pH values both in summer and winter. Differences between the maximum and minimum levels of oxygen over 24 hours amounted to 2·4 ml/l at the surface and 2·1 ml/1 at the bottom.

      4. Carbonate and bicarbonate alkalinities revealed an inverse correlation. The variations in the above-mentioned factors during the diurnal cycle was attributed to the biological activities taking place in the medium.

      5. The phytoplankton exhibited peak of abundance at daytime and reduction at night hours at the surface. Fluctuations in chlorophyll values was found to be closely associated with Chlorophyceae which formed the dominant group among the phytoplankters.

      6. The zooplankton population was mainly composed of Copepoda and Cladocera. They revealed a characteristic diurnal pattern of daytime decrease at the surface and increase during night hours both in summer and winter.

      7. An inverse correlation between phyto- and zooplankton population recorded in the present study was attributed to the grazing activity of the zooplankton.

      8. The numerical abundance of the phytoplankton during daytime and surface concentrations of the zooplankton at night hours indicated the overall effect of light causing quantitative variations in the planktonic organisms at different hours of the day.

    • On the generic relationship ofBola coitor Hamilton, 1822 (Pisces: Sciaenidae), with a redescription of the species

      P K Talwar H P C Shetty

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      The specific nameBola coitor Hamilton, 1822 represents the type species of the two sciaenid genera,Bola Hamilton, 1822 andWak Lin, 1938. Considerable uncertainty, however, exists regarding the systematic position of this species.

      A study of large number of examples ofBola coitor, including typotypes and Day’s (1876) material, made it evident thatcoitor Hamilton should be assigned to the genusJohnius Bloch, 1793. As Hamilton’s (1822) original description of‘B’. coitor is inadequate and subsequent descriptions faulty, a redescription of the species is also given in this paper.

    • The effect of certain phenolic and related compounds on spore germination and appressorial formation inColletotrichum falcatum went

      K V Srinivasan R Narasimhan

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      The effect of twenty-one phenolic compounds and related substances on conidial germination and appressorial formation inColletotrichum falcatum was studied.

      Mono-phenol was only mildly inhibitory to spore germination at higher levels. Toxicity of di- and tri-hydroxy benzenes depended on the spatial relationship of the hydroxyl groups. The order of toxicity among the three dihydroxy isomers wasortho>para>meta. Germination inhibition followed the same pattern in the two trihydroxy isomers tested; pyrogallol was strongly toxic while phloroglucinal was without any significant effect. Methoxylation tended to abolish toxicity to spore germination as evidenced by anisole and guaiacol.

      Acylation, either nuclear or side-chain, was strongly inhibitory to germination. Introduction of a carboxyl into phenol, on the other hand, dramatically brought down toxicity. Presence of a single hydroxyl group para to a carboxyl interestingly elicited strong inhibition of appressorial formation and increase in germ tube length. The limited number of phenolic compounds tested did not reveal any relationship between molecular weight and toxicity.

      The presence on the nodal rind of certain phenolic substances may affect penetration of the pathogen into the host by suppressing appressorial formation,e.g., vanillic acid, ferulic acid, P-salicylic acid, P-coumaric acid and tyrosine. On the other hand their activity inside an infected tissue may facilitate rapid spread of the pathogen in the tissues and thereby lower the resistance of the host. It is suggested that different phenolic substances may be involved in the formation of dormant infections and have a bearing on epidemiology. Pathogenic strains are known to differ in the time of formation of hydrolytic enzymes. Since hydrolytic enzyme actionin vivo often releases phenols, it is suggested that the restricted virulence of certain strains is related to the earliness of formation of these enzymes.

    • Corynespora leaf spot of brinjal

      Y R Sarma M V Nayudu

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      Corynespora cassiicola (Berk and Curt) Wei, incitant of leaf spot of brinjal, survives at the room temperatures (28–30° C) for a period of 4 months in infected dry leaves, in infected dead stems for 10 months, and for 11 months in chicken mesh wire house where natural diurnal fluctuating temperatures prevail. Masses of bulbous conidiophore bases appearing like sclerotial bodies, conidiophores and chlamydospores may also help in the survival of the fungus. The weed hostsCroton sparsiflorus Mor.Leucas aspera Spr,Ocimum sanctum L.,Solanum nigrum L., andDigera arvensis Forsk, may act as additional reserviors of inoculum for the disease spread. The fungus survives on chilli crop during summer and this may also serve as primary source of inoculum in July for brinjal crop.

    • Induced tetraploidy inSolanum khasianum clarke

      E K Janaki Ammal Bharati Bhatt

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      Tetraploidy has been successfully induced for the first time by colchicine treatment inSolanum khasianum an important source of solasodine which is an intermediate in the synthesis of cortisone. A comparative study of the cytology and morphology of the diploid and tetraploids is reported in this paper.

    • Electron spinr esonance (ESR) study of developing and aging betel leaves

      S D Mishra I C Dave B B Singh B K Gaur

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      ESR spectra from intact developing and detached senescing betel leaves showed presence of Mn+2, Cu+2, and an unknown species exhibiting a single line (Δ H ≃ 10 gauss) at the free electron ‘g’ value in addition to a base line drift presumably from Fe−3. Leaves collected at the primordial and subsequent stages of growth indicated a sequential appearance of Mn+2 and disappearance of Cu+2 while a reverse pattern was observed with the detached senescing leaves.

    • The role of photoperiod and temperature in determining the efficiency of legume—Rhizobium symbiosis in cluster clover (Trifolium glomeratum)

      N S Subba Rao

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      A study was made on the influence of combinations of photoperiods and environmental temperatures upon symbiosis betweenTrifolium glomeratum (cluster clover) andRhizobium trifolii in environment controlled growth cabinets. Experiments were done by growing plants in unsterilized soil and also in agar slopes under bacteriologically controlled conditions. Initial nodalation was delayed as the day length was increased. Photoperiods influenced not only the development of plants but also the formation, size and number of nodules on the root system.

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