Cheonan, KOREA

National Livestock Research Institute, RDA

GWACHEON, KOREA

Ministry of Science & Technology

DAEJEON, KOREA

Chungnam National University

Inheritance of ear shank length in maize (Zea mays L.)

-- Ji, HC; Lee JK; Choi GJ; Kim KY; Seong BR; Seo, S; Kim SH; Lee HB

The ear shank is called lower portion of lateral branch comprising several nodes and shortened internodes in maize (Zea mays L.). That diverged from plant vigor, plant density, genetic factor, soil conditions etc. is an unwanted factor for breeding purpose due to lodging problem and harvest trouble but the trait was not much studied. Lee et al.(1992) reported a gene located on the short arm of chromosome 2 affected ear shank length.

The inheritance of ear shank length was studied by generation mean analysis of progenies derived from crosses of the inbreds Hi38c1 and Ia453sh2. The Hi38c1 inbred, which is a tropical Hawaiian super sweet, shows long shank trait and is based on gene brittle-1. The Ia453sh2 inbred is a conversion to shrunken-2 of the Iowa sweet inbred, and has typical long shank and long husk leaves. The parents and all progenies were planted in randomized complete block (RCB) designs with three replications.

The inheritance of ear shank length in sweet corn inbreds Ia453 sh₂ (with long shank) and Hi38c1 (with short shank) was investigated by analysis of generation mean analysis (GMA). Ear shank lengths of parent lines were 4.59cm (Hi38c1) and 13.25cm (Ia453sh2). The ear shank length of F₁ hybrids was 14.66cm, while the length of F₂ lines was 12.69cm (Fig. 1). The ear shank lengths in BC₁ and BC₂ were 8.88cm and 15.32cm, respectively. The average coefficients of variation (CV) were as follows; P₁ 40%, P₂ 27%, F₁ 35%, F₂ 52%, BC₁ 56%, BC₂ 39%.

These results were analyzed by Generation Mean Analysis (GMA) Method modified from Mather & Jinks (1977). Generation mean analysis of the six generations (Table 1) revealed highly significant additive effect. The aa [additive x additive] and dd [dominance x dominance] effects were not significant but ad[additive x dominance] effects were significant.

Broad-sense heritability was 60.51% and narrow-sense heritability was 58.5%. The estimated minimum number of gene loci, using Castle and Wright formula, was 0.54. Therefore, ear shank length might depend on single gene acting without any dominance effect, and we need more study between ear shank length and other characters.

Table 1. Estimates of additive (a), dominance (d), and interaction parameters for the cross Hi38c1 (bt) x Ia453 sh2.

Parameter+	Estimate (±SE)	t test
m	12.69±0.27	18.36	^**
a	-6.44±0.43	-6.39	^**
d	3.38±1.42	0.97	^NS
aa	-2.36±1.38	-0.69	^NS
ad	-2.11±0.45	-2.03	^*
dd	1.12±2.13	0.22	^NS

+m=midpoint, a=additive effect, d=dominance effect, aa=additive x additive effect, ad=additive x dominance effect, dd=dominance x dominance effect

*, **, ^NS ; levels of significant.

P₁ P₂ F₁ F₂ BC₁ BC₂

Figure 1. Distribution of ear shank length in parents, F₁, F₂ and Backcross(BC₁, BC₂) generations.

F₁, F₂ and BC₁ and BC₂ populations were derived from the parental inbreds Hi38-71(short shank) and Ia453sh2 (long shank).

P₁: Hi38-71, P₂: Ia453sh2.