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F1 studies on pollen sterility, pollen shedding and seed set enabled the classification of the cytoplasmic sources into three groups: (1) CK60A and Nagpur- A based on milo-A,; (2)M 35-1A and M31-2A-A2 (Tentative); (3) VZM2A and G1A - A, (Tentative). The correspondence of the A, with A, steriles reported from USA is yet to be established- These studies provided evidence for the seasonal (temperature) interaction for pollen fertility and seed set, the M35-1A and M31-2A steriles, exhibiting greater levels of fertility during summer season. in some crosses, evidence for the operation of self-incompatibility was available.
A diailel set of crosses including reciprocals with nine parents (six B lines and three R lines) enabled cytoplasmic characterisation of the B and R lines. Reciprocal differences for pollen sterility and seed set were significant. The cytoplasms of GIB and Nandyal tended to exhibit greater levels of pollen sterility while those of CK60 B and Karad local tended to promote greater levels of male fertility. Based on these studies, three cytoplasmic groups have been characterized: (1) CK 60 B and Karad local-B,; (2) M35-1 and VZM2B-B1; (3) GIB and Nandyal-B3. 'B 1′ is the most fertility inducing, whereas 'B 3′ induces greater levels of sterility. The cytoplasmic and nuclear effects in A and B lines are in opposite directions.
