Volume 3, Issue 6
June 1936, pages 425-551
pp 425-431 June 1936
The behaviour of certain Coimbatore sugarcane varieties with reference to the mosaic disease has been discussed, showing that those containingSaccharum spontaneum blood are generally resistant or at least tolerant.
Preliminary data regarding the supposed correlation between bristles and mosaic resistance have been presented, which indicate that at least in certain cases there appears to be no positive correlation between the high number of bristles and disease resistance, nor in the protection supposed to be afforded by the bristles to the stomata.
pp 432-437 June 1936
Observations on the varieties of the coconut collected from the different parts of the world and grown at the Agricultural Research Station, Pilicode (District: South Kanara), showed that the precentage of infections varied from 37—the lowest in a variety from the Philippines—to 87 in a variety from Mysore.
The disease occurs largely among the palms of three to nine years of age, and thereafter the trees are generally less susceptible to the disease. The susceptibility to the disease is more pronounced in the trees planted on the surface, than in the trees planted at a depth of three feet. The incidence of disease is considerably reduced when potassium sulphate is applied to the soil. The bearing of these observations on the subject of natural and induced resistance to the disease is discussed.
pp 438-443 June 1936
pp 444-449 June 1936
The study of physiological characteristics of virus diseases will be found useful in (1) diagnosing the disease at an early stage and (2) in discovering resistant strains. Such studies have hardly been begun with sandal. Holmes (1932) has recently developed a technique of iodine staining which renders local lesions, due to virus, conspicuous and reveals the points of infection. Such studies may be profitably extended to sandal spike. Resistant varieties are generally characterised by low acidity and poor oxidase activities. Other factors of disease resistance, such, for instance as, phenols, glocosides, alkaloids, etc., have to be investigated. The study of active groups in tissue fluids for which a scheme was recently outlined (Sastri and Sreenivasaya, 1934) may usefully be undertaken in this connection. The possibility of nurturing sandal through appropriate hosts to impart resistance to disease has been amply demonstrated by the work of Sreenivasaya and the study of physiological characters of such plants would give results of great significance.
pp 450-458 June 1936
The disease,piricularia, was first noticed in Madras when it appeared in an epidemic form attacking a particular variety of rice,korangusamba, in portions of the Tanjore district. The studies on the fungus by the Mycologist had shown that there was a wide range of susceptibility of rice varieties to the disease, some remaining practically immune while varieties like the Tanjore one showing 70 to 80 per cent. incidence.
Work of breeding forms resistant topiricularia was undertaken by the Paddy Specialist in 1926. Two of the strains evolved by him, GEB. 24 and Co. 4 which were determined to be highly resistant, were crossed with the susceptible variety from Tanjore. The inheritance of disease resistance appeared to be simple in the cross GEB. 24×korangusamba and more complicated in the cross Co. 4 ×korangusamba. In the former cross disease-free selections from F3 onwards bred pure for freedom and two of these after two years’ trial both at Coimbatore and Aduturai have been found to give a big increase in yield over the susceptible variety (10–50 per cent.), the increase being more or less according as the susceptible variety gets the infection or not. Selections from the other cross are still under study and appear even more promising than the first.
We are indebted to the Superintendent, Agricultural Research Station, Aduturai, for the figures of yield trials conducted there.
pp 459-469 June 1936
pp 470-480 June 1936
pp 481-490 June 1936
From the foregoing, it is seen that (1) great differences in susceptibility to mosaic are exhibited by the varieties of sugarcane, (2) that most commercial varieties are susceptible to this disease, (3) that some highly susceptible varieties are tolerant to the disease, (4) that a few immune varieties exist and could be made use of as parents, (5) that certain varieties which escape infection under one set of conditions may take the disease under other conditions, and (6) that though the disease is systemic, certain varieties recover from the disease and there is a possibility of the recovering plant acquiring permanent immunity.
pp 491-492 June 1936
pp 493-497 June 1936
pp 498-501 June 1936
It is a well-known fact that Indo-American cottons are immune toFusarium wilt in India.
These cottons as well as the recently introduced American varieties also proved to be immune to an American strain of the fungus when growing in Indian soils.
The Indo-American cottons were tested in America on American cotton soils and there they proved to be as susceptible as the American cottons to the American strain of the fungus, but they were still immune to the Indian fungus.
The American and the Indian strains ofF. vasinfectum show, therefore, a very strict parasitic specialisation, the American form being unable to attack Indian cottons in any circumstances, andvice versa.
Indian cottons grown on American cotton soils are much less susceptible to the Indian form than when they are in India.
American cotton soils where wilt is common, are light, sandy and acidic but the Indian cotton soils where wilt is predominant are heavy, clayey and alkaline. The above experiments strongly suggest that the reason the IndianFusarium weakly attacks its Indian host in American soils and the AmericanFusarium is almost non-pathogenic to its American and Indo-American host in Indian soils, is to be sought for in the fact that these soils have different texture and reaction.
pp 502-526 June 1936
pp 527-534 June 1936
pp 535-551 June 1936