Single Seed Descent
What is Single Seed Descent (SSD) Method – Definition?
This method is modification of bulk method. First proposed by Goulden (1939) and later modified by Brim (1966).
Instead of bulking whole seed lot of selected plants, a single seed is selected randomly from each selected plant to make bulk.
This method involves less record keeping (pedigree method) and works better where the main focus is on improvement of quantitative traits or characters such as yield and earliness, rather than qualitative traits or characters such as flesh color and disease resistance.
But, it does not involve selection process mainly artificial, so chances of loosing superior plants are comparatively more and because of the same reason does not eliminate weak plants early such as in other methods.
Procedure for Single Seed Descent Method
Single Seed Descent (SSD) Method includes stages as described below
|Hybridization||Crossing of selected parents.|
|F1 generation||F1 seeds grown and bulk harvested.|
|F2 generation||F2 seeds grown. One seed from each plant is selected randomly and mixed.|
|F3 generation||F3 seeds are grown and harvested as above.|
|F4 and F5 generation||The similar procedure as above is carried out.|
|F6 generation||F6 seeds are planted. Selection for superior plants is conducted and selected ones are harvested separately. Number of plants could range from150 to 500.|
|F7 generation||The main point in this step is individual plant progenies are grown and selected plants are harvested in bulk.|
|F8 generation||Preliminary yield trials and quality tests are conducted.|
|F9 to F10 or F13 generation||Co-ordinated yield trials and tests for resistance and quality are conducted.|
|F11 of F14 generation||Seed multiplication for distribution|
For advantages and disadvantages of single seed descent method visit Single Seed Descent – Advantages.