12. Reciprocal crosses.

Among a large number of reciprocal single crosses tested during the past season, some exhibited differences in early plant vigor, days to silking, plant and ear height, row number, ear length and yield. It is known that the maternal effect on seed quality and early plant vigor may be great, thereby causing the large differences observed in early plant growth. It appears, in some cases, that large differences in early plant vigor are of a great enough magnitude to affect mature plant characteristics as plant and ear height, silking date, ear length and yield. Generally, these differences showed little tendeney to carry thru into the F₂ generation. If cytoplasmic factors are involved, the variability added by segregation of multiple factors in the F₂ may have prevented their detection.

Reciprocal backcrosses showed inequality in ear length and yield as shown in the following table.

Pedigree	Ear length inches	Pedigree	Yield bushels
WF9*(WF9 x R30)	6.87	187‑2(187‑2 x R30)	69.0
WF9 (R30 x WF9)	6.77	187‑2(R30 x 187‑2)	64.1
(WF9 x R30) WF9	7.26	(187‑2 x R30)187‑2	67.6
(R30 x WF9) WF9	7.04	(R30 x 187‑2)187‑2	62.2
Diff. for Sign.	.16		5.4

* Seed parent appears first in pedigree.

It is interesting to note that backcrosses were shorter eared where inbred WF9 was used as seed parent in making the backcross and when R30 was the seed parent in the original single cross. These differences cannot logically be explained on the basis of seed quality, they may possibly arise if the lines were composed of a mixture of substrains and different plants were used as male and female. However, this would be unlikely because the seed was from a bulk of approximately 12 plants. It should be stated that these differences were exceptional and not of general occurrence in the material studied.

L. F. Bauman