--R. L. Phillips, J. Suresh and S. Kaeppler

In recent studies by Steffensen et al. (MNL 61:97-98, 1987) a relationship was reported between maturity and knob heterochromatin. This report represents an initial screening of seven inbreds differing in maturity (Table 1) for the level of a repetitive sequence found in maize heterochromatic knobs. The maize lines selected were ND101, CG 16, Mt42, Wilbur's Knobless Flint, A86-9, R225 and NC254.

Table 1. Maturity of seven maize inbreds used for slot blot hybridization.
 

	Inbreds	Maturity (Days to 50% pollen shed)
1	ND101	71
2	CG16	76
3	Mt 42	77
4	Wilbur's Knobless	90
5	A86-9	75
6	R225	118
7	NC254	115

Figure 1. Hybridization data of 185bp sequence to DNA from seven inbreds.

DNA extracted from leaf tissue (Hoisington - personal communication, Missouri, 1988) and CsCl purified (Maniatis, Molecular Cloning, p. 93) was blotted (50-100ng) on nitrocellulose filter paper using a slot blotter (Schleicher and Schuell). The nitrocellulose filter was hybridized (procedure from Cuno Laboratories Connecticut) with a 32P-labelled probe synthesized (A. Biochem. 137:266-267, 1984) from a 185bp sequence localized in heterochromatic knobs (Peacock et al. PNAS 70:4490-4494, 1981). Later each slot of the nitrocellulose filter was cut out and counted in a scintillation counter.

In these maize lines no obvious relationship was observed between maturity and proportion of the 185bp sequence (F = .015 NS and correlation coefficient = .17 NS).

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