Inbred line B73 derived from Iowa Stiff Stalk Synthetic C5 has a tendency to break at upper nodes during the tassel-bagging operation. Crosses of B73 with four different inbred lines (non-brittle types) were made and F2 progenies were obtained. The F1 plants in each cross were normal (non-brittle). The F2 data given below indicated a 3:1 segregation for normal:brittle node in each cross:
 

	F2 Plants
Cross No.	Normal	Brittle Node	c2 for 3:1 Ratio	P
1	95	22	2.247	0.2-0.1
2	94	20	3.38	0.1-0.05
3	90	28	0.101	0.8-0.7
4	98	34	0.04	0.9-0.8

Therefore, brittle node trait appears to be controlled by a single recessive gene. Tests for allelism with bk2 (brittle stalk) and a study to locate the brittle node gene using waxy-marked translocations are planned. The brittle stalk (bk2) mutant has been described as "Leaves and stalk very brittle, easily broken. Plant shows [in picture] leaves shattered by moderate winds" (Neuffer, M. G., L. Jones and M. S. Zuber, 1968, The Mutants of Maize). The brittle node trait is different from brittle stalk in that leaves remain intact even against strong winds, but breakage occurs at the node when the tassel is handled. If tests for allelism with bk2 are negative, the new gene will be designated btn1.

This information may be useful to breeders in manipulating the brittle node trait depending upon their objectives (for example to facilitate detasseling in seed production fields).

M. S. Kang

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