Table I. Determination of nonadditive expression classes in reciprocal maize hybrids under control and water deficit conditions.

Classa	Expression Pattern	Criteria			Total No. of Genes								No. of Nonadditive Genesb
		LP ≠ H	HP ≠ H	LP ≠ HP	B73xMo17		Overlapc		Mo17xB73		Overlapc		B73xMo17		Overlapc		Mo17xB73		Overlapc
					C	WD	E	O	C	WD	E	O	C	WD	E	O	C	WD	E	O
1	LP < H < HP	Y	Y	Y	3,783	3,109	440	2,398*	3,325	3,187	396	2,351*	1,179	1,196	53	829*	1,154	1,119	48	832*
2	LP = H < HP	Y	Y	Y	3,175	3,751	445	1,519*	4,400	3,724	613	2,110*	581	1,475	32	209*	1,556	1,273	74	508*
3	LP < H = HP	Y	N	Y	5,845	5,599	1,224	3,179*	5,856	5,276	1,156	3,468*	1,437	3,180	171	754*	3,254	2,207	269	1,309*
4	LP = HP = H	N	N	N	8,559	7,224	2,313	4,821*	6,960	8,555	2,227	4,839*	3	84	0	0	55	44	0	0
5	LP < HP < H	Y	Y	Y	47	267	0	9*	148	65	0	17*	47	267	0	9*	148	65	0	17*
6	LP = HP < H	Y	Y	N	199	641	5	81*	342	259	3	92*	199	641	5	81*	342	259	3	92*
7	H < LP < HP	Y	Y	Y	134	343	2	49*	260	265	3	72*	134	343	2	49*	260	265	3	72*
8	H < LP = HP	Y	Y	N	430	1,202	19	189*	1,022	813	31	322*	430	1,202	19	189*	1,022	813	31	322*
9	Ambiguous				4,565	4,601	786	1,158*	4,424	4,593	760	1,225*	539	1,756	35	72*	1,439	1,140	61	192*
Total					26,737	26,737	5,234	13,403*	26,737	26,737	5,189	14,496*	4,549	10,144	317	2,192*	9,230	7,185	490	3,344*

^aThe classification of the relative expression of hybrids (H) compared to their parental inbred lines (HP, high parent; LP, low parent) is based on the three pairwise tests listed in the Criteria columns (N, no; Y, yes).  ^bNonadditively expressed genes were determined relative to their midparent value.  ^cExpected (E) values were calculated as (number of nonadditive genes in B73×Mo17 × number of nonadditive genes in Mo17×B73)/number of all expressed genes. The number of all expressed genes is the sum of classes 1 to 9. C, Control; O, observed; WD, water deficit. The numbers of expected and observed overlapping genes were compared using a χ² test. Significant values are indicated by asterisks: P ≤ 0.01.