The development of Synthetic Varieties is practiced commonly in some cross-pollinated crops. It involves several important steps as given below. Arrange the steps of synthetic variety development in chronological order i.e. from the beginning to the last. \begin{enumerate
• [(A).] Evaluation of the inbreds for GCA followed by selection of the inbreds as parental lines.
• [(B).] Multiplication in isolation for one or more generations followed by distribution as synthetic varieties for commercial cultivation.
• [(C).] Collection of diverse inbred lines for synthetic variety development.
• [(D).] Crossing of the inbred lines in isolation in all possible combinations followed by mixing in equal proportion of seeds from all the cross combinations. Choose the correct answer from the options given below:
• [(A).] Evaluation of the inbreds for GCA followed by selection of the inbreds as parental lines.
• [(B).] Multiplication in isolation for one or more generations followed by distribution as synthetic varieties for commercial cultivation.
• [(C).] Collection of diverse inbred lines for synthetic variety development.
• [(D).] Crossing of the inbred lines in isolation in all possible combinations followed by mixing in equal proportion of seeds from all the cross combinations. Choose the correct answer from the options given below:
Show Hint
\[ \text{Identify lines (C)} \rightarrow \text{Test GCA (A)} \rightarrow \text{Intermate (D)} \rightarrow \text{Multiply seed (B)} \]
- (C), (A), (B), (D)
- (A), (C), (D), (B)
- (B), (A), (D), (C)
- (C), (A), (D), (B)
The Correct Option is D
Solution and Explanation
Developing a synthetic variety is an important method used to improve cross-pollinated crops.
This method relies on selecting parent lines with high general combining ability (GCA) and allowing them to intermate.
Step 3: Detailed Explanation:
Let us organize the steps of synthetic variety development in chronological order:
1. Collection of diverse inbred lines (C): The first step is to collect or develop a diverse set of inbred lines or clones.
2. Evaluation of GCA and selection of parents (A): These lines are evaluated for their general combining ability (GCA) using testing methods like a topcross.
Lines that perform well in combining tests are selected as parents.
3. Intermating in all possible combinations (D): The selected parent lines are grown in isolation and crossed in all possible combinations (diallel crossing).
Equal quantities of seed harvested from each cross are mixed together to form the synthetic variety (\(\text{Syn}_0\) or \(\text{Syn}_1\)).
4. Multiplication in isolation (B): The mixed seed is planted in isolation and allowed to open-pollinate for one or more generations (producing \(\text{Syn}_2\) or \(\text{Syn}_3\)) to increase the seed volume.
This seed is then distributed to farmers for commercial cultivation.
Therefore, the correct chronological sequence is: (C) \(\rightarrow\) (A) \(\rightarrow\) (D) \(\rightarrow\) (B).
Step 4: Final Answer:
The correct chronological sequence is Option (D).
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• [(B).] The male parents of the final crosses are heterozygous and hence heterogametic.
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