Shandong, China
Agricultural University of Shandong
Academy of Agricultural Sciences of Laizhou
Identification and characterization of three mutational NILs in maize --Wang, ZL, Zhang, Y In developing countries that have limited adapted maize genetic resources for building up good breeding materials, induced mutations may be useful for variability. But, unfortunately theory indicates that chances are low that any new mutant (including adaptively beneficial mutants) will become established in the population and inbred lines in which they occur. On the other hand, practice indicates that mutants for so-called quantitatively inherited traits cause differences of degree (e.g. in yield, plant height, leaf number and seed size etc.) rather than kind. For this we have developed three pairs of near isogenic lines (NILs) derived from inbred female lines 478 (normal-seeded and normal-leaf 6 leaves above the top ear) and the inbred male is line 340, of the superior performance of hybrid, Yedan 13, which has a large top growing area and a long life span among Chinese major maize hybrids. The mutants were named 488-1 (big-seeded and 6 leaves above the top ear) and 488-2 ( big-seeded and 5 leaves above the top ear).

Three crosses were made among 4 inbred lines. The crosses were 478340, 488-1340 and 488-2340. The crosses and 4 inbred lines were planted 2 May 2000 in Shandong, China and 10 May in Columbia, Missouri, USA and harvested on 6 Sept, and 10 Sept respectively. There were three replications in 2000 and two replications in 2001. The three NILs were formed in 1999 (Figure 1).

Figure 1. Description of the selection processes of the mutant inbred resulting from spontaneous mutations. R.16=original inbred line, 6 leaves; BS.16= big size seed inbred line, 6 leaves; BS.15=big size seed, 5 leaves; S.M=spontaneous mutations.

Means, two standard deviations of the mean and t-test were calculated for some traits measured ( Table 1 and Table 2).

Table 1. Means of NIL traits for two years in China and the U.S.A.
Varieties Plant Height Leaf Number Leaf Length Leaf Width Culm. Circum. 100 kernel weight, g  Grainweight per ear, g
478 1802.1 60.8 811.4 12.01.6 7.40.7 24.21.0 98.67.7
488-1 1892.4 6.22.0 801.8 12.32.4 7.51.1 34.11.3 121.88.1
488-2 1822.0 5.11.9 783.2 11.42.8 7.41.5 32.92.2 120.19.3
340 1961.7 5.00.9 791.7 11.51.2 8.50.9 124.36.5
478x340 2761.8 6.21.6 93.1.9 11.52.0 8.21.4 34.24.6 197.28.0
488-1x340 2913.1 6.01.9 964.6 12.23.2 8.31.7 36.45.0 242.59.0
488-2x340 2863.4 6.02.1 924.1 12.42.9 8.12.0 36.15.9 2309.8

Table 2. t-test of NIL traits for two years in China and the U.S.A (**p<0.01 *p<0.05, NS = no significant).
Parent  478 488-1 488-2   Hybrid 478x340 478-1x340 478-2x340
t-test for plant height
478 1 * NS   478x340 1 ** *
488-1 * 1 NS   488-1x340 ** 1 NS
488-2 NS NS 1   488-2x340 * NS 1
t-test for leaf length
478 1 NS NS   478x340 1 NS NS
488-1 NS 1 NS   488-1x340 NS 1 *
488-2 NS NS 1   488-2x340 NS * 1
t-test for leaf width
478 1 NS NS   478x340 1 NS NS
488-1 NS 1 NS   488-1x340 NS 1 NS
488-2 NS NS 1   488-2x340 NS NS 1
t-test for 100 kernel weight
478 1 ** **   478x340 1 ** **
488-1 ** 1 NS   488-1x340 ** 1 NS
488-2 ** NS 1   488-2x340 ** NS 1
t-test for grain weight per ear
478 1 * *   478x340 1 ** **
488-1 * 1 NS   488-1x340 ** 1 *
488-2 * NS 1   488-2x340 ** * 1

There were only significant differences for plant height between the parent NILs, 478 and 488-1, and their hybrids for 5 replications at two locations from 2000 to 2001. But there were no significant difference for leaf length and leaf width, except for hybrids 478x340 and 488-1x340 for leaf length (Table 2).

The t-test for grain weight per ear and 100 kernel weight shows that the two mutant NILs were significantly different from the original inbred line of 478, but there is no significant difference between the two mutant NILs. However, when those NILs were crossed with paternal parent line 340, 100 kernel weight and grain weight per ear of the hybrids derived from the original inbred line of 478 were significantly different from those derived from the two mutant NILs at the P<0.01 level. For the hybrids derived from the two mutants NILs the grain weight per ear showed a significant difference at the P<0.05 level, but 100 kernel weight does not shown any difference (Table 2).

For maize genetics, mutations are of interest in two different ways. They provide us with new starting material (or building blocks) for the production of new hybrid cultivators and they give us a tool for identifying and cloning new genes. A mapping population has been established for studying the nature of genes and their way of controlling heterosis and biochemical seed size and leaf number.

This material was based upon work supported by a grant from the Shandong China foundation for basic research. Research space at University of Missouri provided by James A. Birchler. We thank James A. Birchler for his critical and grammatical review of this manuscript.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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