Cyto-morphological studies on some species and species hybrids in the genusSorgbum

Abstract

1. The morphological characters of six species and six F1 hybrids were compared in detail in the present study. It was observed that with respect to metrical characters the hybrids were intermediate in some cases but in certain others hybrid vigour was also met with. 2. Pachytene pairing was complete and apparently normal, followed by regular meiosis at later stages resulting in high pollen fertility and good seed setting in all the parental species except the male sterile “Kafir”. Studies on the pairing properties of the differentially stained regions showed that synapsis starts from the proximal to the distal end and separation of the split chromosomes starts from the distal to the proximal. 3. Pachytene analysis in the hybrids,S. nervosum×S. sudanense and M. S. “Kafir”×S. arundinaceum revealed the presence of some minute, though cytologically detectable, structural differences such as terminal and interstitial nonpairing segments, terminal deletion etc. High percentage of fertile pollen and good seed setting were recorded in these hybrids. It is suggested that the existing chromosomal differences are quite small and do not lead to abnormal behaviour of the hybrids either in respect of morphological characters or in the meiotic process in the F1 generation. Pachytene analysis in the remaining four F1 hybrids was complete, followed by regular meiosis at later stages resulting in high percentage of stainable pollen and good seed set. 4. Cytogenetical mechanisms underlying species differentiation in the genus are discussed.