Textures do not fill objects, they are like paint, that is put on the object surface. Objects are defined by geometries and are always hollow. When you cut a geometry, you need to add another geometry to fill in the gap. For a sphere, you can use RingGeometry:
Thank you so much
I tried applying texture for filling the gap between spheres using ring geometry , but texture is applied as plane color , can you please help me with this ?
Most likely there is a bug in your code. By looking at the image I cannot tell what the bug is.
When I apply a texture of small squares on the middle rings, the texture shows up fine:
https://codepen.io/boytchev/pen/RwOVMPZ
should you not be getting the gaps any way, since the tesselation would be a bit different between the ring and the sphere 
edit yep, here they are:
These gaps are caused by the subdivisions when their number is not the same, or their starting angle is not aligned (code is modified, do you see gaps again).