Final answer:
In a typical Mendelian cross, if the red color is dominant and we have a 3:1 ratio of red to white, planting 100 seeds from a test cross would result in approximately 75 red and 25 white seeds.
Step-by-step explanation:
If you are performing a test cross in garden pea plants and need to predict the phenotype of seeds in terms of color (red versus white), first, it is important to understand the genetics involved. Without the actual genetic cross provided in the question or the ratios of previous generations, we cannot determine the precise distribution of seed color. However, typically you'd see mention of dominant and recessive traits in a Mendelian cross, where dominant traits tend to manifest in offspring even if only one parent contributes the gene for that trait.
In your example, you mentioned a count of 600 blue flowers and 200 red flowers from a previous cross which suggests a phenotypic ratio. If this ratio represents the outcome of a simple Mendelian inheritance pattern, the ratio of 3:1 (red to blue) would suggest that red is dominant over blue. For seed color, assuming a similar dominant-recessive relationship where white is recessive and red is dominant (most common scenario in typical genetics problems), about 75% of the offspring should display the dominant phenotype and 25% the recessive phenotype. If you plant 100 seeds from this hypothetical test cross, you would therefore expect approximately 75 red and 25 white seeds, provided that the ratio applies.