Volume 70, Issue 3
September 1969, pages 111-156
pp 111-117 September 1969
The paper deals with four weeds (Digera muricata, Indigofera cordifolia, Trichodesma amplexicaule andTribulus terrestris) growing on the fields in whichBajra (Pennisetum typhoideum) is cultivated. Studies have been undertaken on the interaction of these weeds on the germination of seeds and seedling growth ofPennisetum typhoideum. The aqueous extracts from these weeds did not prove harmful as far as germination was concerned, although delay in certain cases was evident. The inhibition as well as enhancement of seedling growth was exhibited by extracts of these weeds. The best effect of growth enhancement was indicated byI. cordifolia andT. amplexicaule and that of inhibition byD. muricata andT. terrestris. Comparatively greater toxicity was caused to the first root, but the development of adventitious roots compensated for the retarding effect. Root hair formation was suppressed in the portion which remained in contact with extract, otherwise profuse root hair formation took place in other areas.
pp 118-126 September 1969
Ommatobrephus lobatum Mehra, 1928, has been redescribed from specimens collected fromVaranus bengalensis andTropiodonotus piscator at Gyanpur, Varanasi. The speciesO. lobatum najii, O. nicolli, O. chauhani andO. bengalensis is considered synonym ofO. lobatum.
pp 127-130 September 1969
pp 131-138 September 1969
This paper gives an illustrated account of 6 species ofXylosphaera Dumortier from the various localities in the North-Western Himalayas. Out of these 4 are new records for India.
pp 139-156 September 1969
Eighteen isolates ofFusarium vasinfectum Atk., from different parts of the world,viz., India, Italy, the U.S.A. and the U.S.S.R. were compared for their morphological and cultural characters, and found to be different. Light induced the formation of a uniform orange pigmentation in the cultures regardless of their being pigmented or not under dark-incubation and this is possibly due to photoactivation. The isolates maintained the observed morphological characters over a period of two years, when grown on standard medium, incubated at constant temperature and under darkness, though subcultured repeatedly.
The isolates could be differentiated into three groups on the basis of their pathogenicity to two cotton speciesGossypium arboreum L. andG. hirsutum L. The Indian and Russian isolates were pathogenic toG. arboreum while the American and the Italian, toG. hirsutum. Four of the Indian isolates were, however, pathogenic to neither of the hosts. The wilt symptoms were different on the two hosts. The roots of the host plants were invaded by all the isolates under the present experimental conditions. There was no correlation between wilt percentage and percentage of roots invaded. The pathogenic potential of the isolates is, hence, not related to their ability to invade the host roots.