Setting of pods on male sterile plants in insect proof nets

CMS lines were grown inside the insect proof net cage of about 40X40 meter size along with some fertile restorer lines for production of hybrid by hand pollination. We have observed that there are some plants of CMS genotypes which have good pod bearing (exceeding 50 pods per plant) without hand pollination. They are confirmed to the genetic purity in respect of male sterility and other traits of the variety. Normally, we don't expect such setting inside the net and it was so in majority of the plants. We are now bothered to have the reasoning for such exception. We think that following may be the possibilities:

1. The plant is responding to the pollination through miniature insects like thripes which are abundant in pigeonpea.
2. The pod setting may be developed automatically.
3. Wind pollination from the neighboring fertile plants.

Readers are invited to share their experiences with the evidential references from the literature.