I have a ripe crop of serrano chilli peppers (Capsicum annuum). I'm planning to save some seeds for a future crop, and have done some research on what I need to do to dry and store them properly for maximum viability.
With respect to selecting seeds to keep for later propagation, many sources mention that the seeds need to have come from a fully ripe fruit, and should appear off-white in color (in contrast to 'bright' white seeds from unripe fruit). Ideally, the plant from which the fruit was harvested from should also appear healthy, i.e. free of signs of diseases, especially signs of mosaic virus infection or signs of the various bacterial leaf-spot and wilt diseases.
However, I cannot find any information on a phenomenon I've noticed in a few of the seeds in each of my fruit: around 5-10% of seeds in each fruit appear less convex than the rest, and appear to have 'darker' cores, which is especially visible when backlit. The attached image shows two seeds close up, the left seed is 'normal' like the majority of the other seed in the fruits, while the right seed is an example of one that is less convex with a 'dark' core.
My question is: does anyone know why these seeds have 'dark' cores, and are they potential vectors of disease, or are they simply more developed than the rest of the seeds (closer to actually germinating)?
Edit: The plant itself appears to be mostly healthy and disease free, although aphids have been a persistent problem throughout the season, causing minor damage to a few leaves. The seed in the image were freshly extracted and were not been dried at all.