Indian Agricultural Research Institute, New Delhi
A detailed study of chromosome morphology, meiotic behaviour and plant growth and morphology was made in some monosomics (2n=41) and nullisomics (2n=40) of the bread wheat varieties, Chinese Spring and Redman. Pairing behaviour was critically studied at metaphase I of meiosis in nullisomics of homeo-logous group five (chromosomes V, IX and XVIII) in order to ascertain whether any multivalent formation occurs in them. One trivalent was found in some cells of nulli-V of Redman but in the others pairing was normal. Some degree of chromosome stickiness was observed in all the three nullisomics. The chromosome V of both Chinese Spring and Redman in our material was not, however, of the pronounced heterobrachial type described by Sears (1954). The significance of the multivalent suppressor gene system discovered in chromosome V by Riley and Chapman (1958) and Sears and Okamoto (1958) is discussed and it is pointed out that further critical studies of this important problem are needed.
