Maize and Sorghum Research Institute

Dichotomous branched mutant (dib)

--V. E. Micu, Eugenia C. Partas and D. G. Brinzila

It was reported earlier (MNL 54:63-64, 1980) that the two-tassel maize mutant was found in 1967 in one progeny of selfing of an open-pollinated population from Afghanistan (K2858). The stalks are dichotomously branched at nodes 4-8, and two branches with normal leaves, ears and tassels develop. Very rarely twice branched plants (with four branches and tassels) are observed. The mutant was named dib, dichotomous branched. The morphological description and results of preliminary genetic and cytological analyses were published. Some new data are presented in Table 1.

Table 1. Comparative traits of dib and normal plants.
 

Traits		Number of genotypes	Normal	dib
Plant	height, cm	11	117	112
	number of nodes to ear	11	3.1	3.4
	number of nodes above ear	11	5.9	5.8
Leaf:	length, cm	11	48.9	44.7
	width, cm	11	6.1	5.3
Ear:	length, cm	35	12.3	8.9
	number	11	1.2	1.9
Tassel:	length, cm	11	26.3	24.0
	number of flowers per tassel	42	563	491
	number of flowers per plant	42	563	982
	number of branches	11	9.1	8.2
Weight of 100 anthers, g		5	0.06	0.05
Weight of anthers from 1 tassel, g		5	2.1	1.8
Weight of anthers from 1 plant, g		5	2.1	3.5
Pollen viability, %		16	74.4	80.8

The numerous progenies which were obtained from dib self-, sib- and outcross-pollinated with normal were studied. It is evident from these studies that dib is not determined by the nuclear genes as well as the cytoplasm.

In the somatic cell of dib plants a variable number (from 20 to 22) of chromosomes were found that indicate aneuploidy as a cause of dichotomous branching.

During the last ten years we made efforts to obtain progenies consisting only of branched plants. The dib plants were selfed for several generations. From 1388 progenies studied in 1991 in three of them all plants were dib, in another 8 more than 90% were dib, and in 322 more than 50% were dib.

These data indicate that it is possible to obtain entirely and constant dib progenies and lines which can be used in breeding and in seed production.

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