Thirty-one clones of Saccharum officinarum, collected from New Guinea, were analysed and the somatic chromosome number was determined. Of the 31 clones, 29 showed 2n = 80 (typical clones), while two clones, NG 77-56 and NG 77-26, were atypical with 2n = 116 and 70 respectively. Chromosome number was determined for 62 clones of S. spontaneum, available in the world germplasm collection, through root tip mitosis. Variable numbers were identified from the same area of collection. Clones collected from north-western regions (Gujarat and Rajasthan) of India showed a majority of 2n = 80 types and 2n = 64 types, whereas 62% of clones collected from Meghalaya (north-east) showed 2n = 64. This is the first time that 2n = 80 cytotypes of S. spontaneum have been reported from the western sector of India. The clones collected from Himachal Pradesh and Uttaranchal showed lower number, e.g. 2n = 56 and 2n = 60.
Summary Microsporogenesis was analyzed in a rare intergeneric hybrid of sugarcane produced from a Sorghum Saccharum cross. The original hybrid was found to be non-flowering. Some of the somaclones of this hybrid obtained by irradiating the callus at four Kr showed flowering. However, the somaclones were found to be male sterile. Here we report the occurrence of syncyte formation and subsequent chromatin degeneration in the somaclones of this hybrid. Syncytes were recorded in 58.3-85.7% pollen mother cells of somaclones that flowered. Meiosis progressed normally in microsporocytes till leptotene where the uninucleate cells appeared normal with loosely tangled, long thread-like chromosomes. Later, the whole nuclear mass divided into two or more groups, forming syncytes with multiple nuclei and micronuclei. Cytokinesis fractionated the syncyte into abnormal meiotic products. Degeneration of chromatin content was observed in both syncytes as well as in the uninucleate cells, resulting in anther sacs with fragmented chromatin mass. Complete pollen sterility resulted from these abnormalities. However, these plants were found to be female fertile and hybrids could be obtained by using it as a female parent in crosses with sugarcane.
SummaryThe influence of hybrid vigor on callus induction, culture efficiency, callus weight, regeneration capacity of the callus and number of regenerated plants from callus culture of sugarcane was studied. For the study a total of 6 parents (clones of S. officinarum and S. spontaneum) and 12 F1 hybrids were used. The statistical analysis of the results revealed that positive heterosis was noticed for callus induction, callus weight and number of regenerated plants.
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