Inheritance studies on 24-chromosome tuber bearing solanum species

Abstract

The work to be described in this paper has been carried out at the Scottish Plant- breeding Station as a part of the programme of research on resistance to potato virus diseases. The general background of this work has been reported in the Annual Reports of the Scottish Plant- breeding Station for the years 1930 -1948 and details of particular investigations are to be found in papers by Cockerham (1937a,b, 1939, 1943a,b and 1945) and Cadman (1942).The present work consists of a study of the genetic background of hypersensitive responses to viruses "X'°, "A", "Y" and "C" in certain "diploid" (2n =24) species of the potato. It is concerned chiefly with the inheritance of hypersensitiveness to each virus and with the interrelationships of the various genes which appear to control this form of response.Although 24 chromosome potatoes are usually regarded as "diploids" and I2 as the basic number of chromosomes in potatoes, cytological evidence has led a number of workers (Lawrence 19310, Müntzing 1933, Ellison 1936V and Choudhuri 1943, 1944) to suggest that the basic number is 6 and that the 24- chromosome potatoes are therefore "tetraploids ". Genetic data on this material is scanty and gives no support to either point of view. Hence in the present investigation attempts have been made to thro some light on the general form of inheritance in the 24- chromosome potatoes with a view to examining the question of the polyyploid nature of 24- chromosome species from the genetic aspect.As already mentioned, the major part of the work is concerned with the inheritance of hypersensitive reactions to viruses "X", "A ", "Y" and "C ", but for the purpose of wider investigations the data obtained from the virus studies have been supplemented from a subsidiary study of the segregation of colour factors in identical and related material.