Mode of inheritance of bitterness and spine colour in cucumber fruits (Cucumis sativus L.)

The mode of inheritance of bitterness and spine colour in cucumber was investigated. Two cucumber lines, namely 'IIHR-82-2' which is a cultivated bitter free advanced line and a wild species namely Cucumis sativus var. hardwickii which is highly bitter in taste were taken for the present study. The two parents, diverse with respect to spine colour (i.e. 'IIHR-82-2' is white and C. sativus var. hardwickii being brown), self pollinated for three successive generations, fixed the character under the study. Crosses were made between the parents to produce F-1, F-2, BC1P1 and BC1P2 populations. The fruits from all the F-1 plants were bitter, indicating dominant inheritance of bitterness in C. sativus var. hardwickii. The segregating F-2 plants showed ratio 3: 1 (bitter : non bitter) which confirmed that bitterness trait was governed by a single dominant gene Bt. This interpretation was largely confirmed by segregation ratio of 1: 1 (bitter : non bitter) in BC1P1 generation and in BC1P2, where all bitter plants were obtained.. For spine colour, the F-1 generation plants bore brown spines on fruits indicating that brown spine was dominant over white spine. The F-2 generation showed segregation ratio of 3: 1 (brown spine : white spine) indicating monogenic control of spine colour. This was confirmed by segregation ratio of 1: 1 (brown spine : white spine) in BC1P1 generation and in BC1P2, where all fruits obtained showed brown spine. The presence of spine colour was controlled by single dominant gene.