Characterization of the Rice Floral Organ Number Mutantfon3

A spontaneous rice mutant named floral organ number 3 (fon3) had major mutations in floral organ numbers. Genetic analysis indicated that fon3 acted as a single recessive gene. Microscopic observation showed that the number of floral organs in fon3 increased centripetally. For example, the number of pistils was the more frequently increased than organs in the outer whorls. Homeotic conversion of lodicules and glumes into palea/lemma-like organs was observed in some flowers. Scanning electron microscopy observation showed that the size of flower meristems was maintained the same or similar until the lemma primordium started to differentiate, at which time the floral meristem became enlarged, suggesting abnormal development of the inner whorls of rice florets. The relationship of fon3 with other similar rice mutants is discussed.

An Exploratory Study on Allelic Diversity for Five Genetic Loci Associated with Floral Organ Development in Rice

Allelic diversity for five genetic loci (DL, FON4, OsMADS24, OsMADS45 and Spw1) associated with floral organ development were investigated among a small heterogeneous rice population which included one wild species (O. rufipogon Griffiths), one indigenous less popular natural floral organ mutant (O. sativa var. indica cv. Jugal), one indigenous normal line (O. sativa var. indica cv. Bhutmoori) and one improved high yielding line (O. sativa var. indica cv. IR 36). Detailed spikelet morphology showed that var. Jugal had variable number (1 - 3) of carpels within a single spikelet which was unique and resulted in variable (1 - 3) number of kernels within a single matured spikelet (grain). The genomic DNA of each investigated line was amplified with primer sequences designed from the selected genetic loci and the derived polymorphism profiles were used for study of allelic diversity for the studied loci. The derived genetic distances among the rice lines were used for dendrogram construction. In constructed dendrogram, the mutant genotype (Jugal) showed highest similarity with the wild rice (O. rufipogon) instead of the rice lines. To verify this finding, the genomic DNA of each studied line was also amplified with four SSR loci, tightly linked to saltol QTL, mapped to rice chromosome 1. The amplified products were screened for polymorphism and another dendrogram was constructed to reveal the genetic distance among the lines for selected salt tolerance linked SSR loci. In SSR derived dendrogram, the wild rice (O. rufipogon) got totally separated from the all three rice genotypes though all the studied four lines showed equal sensitivity for salt sensitivity in a physiological screening experiment. From the combined experiment, it can be concluded that genetic architecture of floral organ development loci in var. Jugal may have some uniqueness which is not present in normal rice but common to O. rufipogon, a species which is regarded as immediate progenitor of present day modern rice (O. sativa). Though this uniqueness was not confirmed by second set genetic loci associated with salt tolerance in rice, the information resulted from this experiment was preliminary and based only on allelic size (molecular weight of amplicon), which should be confirmed through sequence analysis for further analysis.

水稻花器官数目突变体fon6的研究初报

fon6是在籼稻恢复系乐恢188/明恢62杂交F3代发现的花器官数目突变体,表型分析结果表明:该突变体小花颖壳畸形扭曲、内颖长于外颖不闭合;每朵小花内外颖壳总数目2～4片;雄蕊数目为1～14枚;雌蕊数目增加,子房数目2～6个,胚囊畸形。突变体套袋自交结实率为14.06%,花粉活力较高,平均花粉可染率为91.86%。自交种子能正常萌发成苗,突变性状表现稳定的遗传特性。以突变体为父本分别与蜀恢527、明恢63杂交,F2代群体中正常株与突变株的分离均符合3∶1的比例,F3代及BC1F2代进一步的观察与统计结果均表明,该突变性状受1对隐性核基因控制,将该突变基因暂定名为fon6(floral organ number6)。