**5. References**


susceptible genotypes will accumulate high seed [Fe] even when excess Fe is available; (4) seed [Fe] or content at harvest, more so than VCS, can also reflect responses to management practices designed to reduce or alleviate Fe deficiency; (5) when soybean is grown on chlorosis-prone soils, increasing seeding density can markedly increase grain yield and seed [Fe] of both susceptible and resistant cultivars, whereas applying higher rates of Fe-EDDHA especially benefits susceptible cultivars; (6) increasing rates of added fertilizer nitrate have little influence on Fe deficiency of resistant cultivars, but severely depress plant height, grain yield and harvest seed [Fe] of susceptible cultivars; (7) genotypic rank correlations of visual chlorosis scores across locations within a year are reasonably consistent and reliable; however, rank correlations across years are not; (8) classifying genotypes using VCS can result in heterogeneous class variances indicating that VCSs may not be appropriate (consistent, reliable) measures of Fe efficiency; (9) measures of genetic resistance to Fe deficiency should include measures of seed [Fe] or content; and (10) the slow improvement in genotypic resistance to Fe deficiency may be related to the plant trait used

Seed [Fe] is very useful for identifying superior genotypes in management and agronomic performance trials; it also provides a consistent, reliable estimate of resistance to Fe

Aktas, M., and F. van Egmond. 1979. Effect of nitrate nutrition on iron utilization by an Feefficient and an Fe-inefficient soybean cultivar. Plant Soil 51:257-274. Ambler, J. E. and J. C. Brown. 1974. Iron supply in soybean seedlings. Agron. J. 66:476-478. Beebe S.A., V. Gonzalez and J. Rengifo. 2000. Research on trace minerals in the common

Beeghly, H.H., and W.R. Fehr. 1989. Indirect effects of recurrent selection for Fe efficiency in

Blair, M.W., C. Astudillo, M.A. Grusak, R. Graham, and S.E. Beebe. 2009. Inheritance of seed

Blair, M.W., J.I. Medina, C. Astudillo, J. Rengifo, S.E. Beebe, G. Machado, and R. Graham. 2010.

Bouis, H.E., B.M. Chassy, and J.O. Ochanda. 2003. Genetically modified food crops and their

Brown, J.C., J.E. Ambler, R.L. Chaney, and C.D. Foy, 1972. Differential responses of plant

Brown, J.C., R.S. Holmes, and L.0. Tiffin. 1958. Iron chlorosis in soybeans as related to the

Chaney, R.L., B.A. Coulombe, P.F. Bell, and J. Scott Angle. 1992. Detailed method to screen

Cianzio, S. Rodriguez de, W.R. Fehr, and I.C. Anderson. 1979. Genotypic evaluation for iron

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genotypes to micronutrients. *In* J.J. Mortvedt, P.M. Giordano, and W.L. Lindsay

dicot cultivars for resistance to Fe-chlorosis using FeDTPA and bicarbonate in

deficiency chlorosis in soybeans by visual scores and chlorophyll concentration.

to measure resistance.

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deficiency, thereby enhancing genotype selection.

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209.


**3** 

*1,3,4Japan 2China* 

**Positional Cloning of the Responsible Genes for** 

*2Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin,* 

The change from vegetative to reproductive growth is a critical developmental transition in the life of plants. Various external cues, such as photoperiod and temperature, are known to initiate plant flowering under the appropriate seasonal conditions. Endogenous cues include a system of juvenile to adult transition that affects competence to flower. To understand the molecular mechanism of flowering, extensive studies have been performed using model plants, *Arabidopsis thaliana* and rice (*Oryza sativa*), and these have revealed the numerous regulatory network components associated with flowering (Jung & Muller, 2009; Amasino, 2010). The general concept of the photoperiodic induction of flowering (photoperiodism) and the range of response types among plant species was established by Garner and Allard (1920). Among the external cues, light is the most important, being received by several photoreceptors including phytochromes, cryptochromes and phototropins. The role of phytochromes, that is the R-light- and FR-light- absorbing photoreceptors, in flowering has been investigated in several plant species. In *Arabidopsis*, a quantitative long-day (LD) plant, a phyA mutant flowered later in either long-day or short-day (SD) conditions with a night break (Johnson et al., 1994; Reed et al., 1994). In rice, a SD plant, the phyA monogenic mutant exhibited the same flowering time as the wild type under LD conditions, while, in the phyB and phyC mutant backgrounds, the flowering was greatly accelerated relative to phyB and phyC monogenic mutants (Takano et al., 2005). In pea, a LD plant, loss- or gainof-function phyA mutants displayed late or early flowering phenotypes, respectively (Weller et al., 1997, 2001). Day length is found to be perceived by leaves by Knott (1934). Because flowering occurs in the shoot apical meristem (SAM), the leaves must transmit a signal to the SAM and this signal is referred to as florigen (Chailakhyan, 1936). In *Arabidopsis*, three genes, *CONSTANS* (*CO*), *GIGANTEA* (*GI*) and *FLOWERING LOCUS T* (*FT*) were found to be involved in the production of a flowering promoter in LD conditions (Koornneef et al., 1991; Kardailsky et al., 1999). FT protein is now known to be florigen, and CO and GI are key players in the activation of FT expression. CO is a zinc-finger protein that

**1. Introduction** 

**Maturity Loci** *E1, E2* **and** *E3* **in Soybean** 

Yasutaka Tsubokura1, Naoki Yamanaka3 and Toyoaki Anai4

*3Japan International Research Center for Agricultural Sciences, Tsukuba,* 

Kyuya Harada1, Satoshi Watanabe1, Xia Zhengjun2,

*1National Institute of Agrobiological Sciences, Tsukuba,* 

*4Faculty of Agriculture, Saga University, Saga* 

