19. Ditelosomic alien addition lines of rice (Oryza sativa L.) carrying a pair of telocentric chromosomes of 0. punctata Kotschy Hideshi yasui and Nobuo iwata

Plant Breeding Laboratory, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-81, Japan

 Ditelosomic alien addition lines (DtAALs) of rice carrying an extra pair of telocentric chromosomes of 0. punctata in addition to normal 24 chromosomes were obtained in the selfed progenies of three monotelosomic alien addition lines (MtAALs). Three DtAALs were isolated in the selfed progenies of each MtAAL, that is, an unidentified MtAAL (MtAAL X), in which the alien chromosome has not been specified, MtAAL 7 (Yasui and Iwata 1994) and MtAAL 11, respectively. These MtAALs were unstable and gave rise to the respective DtAALs at frequencies ranging from 2.5 % in the progeny of MtAAL 7 to 11.1% in that of MtAAL II. The morphological features of the DtAALs deviated from those of normal disomics and their respective MtAALs. The extra pair of telocentric chromosomes in addition to the normal diploid complement, was identified by karyotype analysis. Among the DtAALs, DtAAL X carried an additional pair of telocentric chromosomes with medium length, while DtAALs 7 and 11 carried an additional pair of telocentric chromosomes with short length.

The meiotic chromosome behavior of DtAALs was investigated at pachytene, diakinesis and MI of PMCs by acetocarmin squash methods. The typical meiotic stages of DtAAL 7 are shown in Fig. 1. One short telocentric bivalent in addition to relatively long 12 bivalents were observed at pachytene stage in the three DtAALs (Fig. 1 a). More than 90 % of PMCs in those DtAALs formed 1211 + It II (Fig. la, b, d) and remainings

Research Notes 81
Fig. 1. Meiotic chromosome behavior in ditelosomic alien addition line (DtAAL) of rice carrying an extra pair of telocentric chromosome 7 of 0. punctata Kotschy. (a) Pachytene, 12II + It II, (b) Diakinesis, 12II+ 1t II, (c) Diakinesis, 12II + 2t I, (d) Metaphase 1, 1211+It II, (e) Metaphase 1, 12II+2t I, (f and g) Anaphase I showing 13:13 segregation. Arrows indicate a pair of alien telocentric chromosomes. Arrowheads indicate univalents of alien telocentric chromosomes. Bar = 5mm.


were 12II + 2tI (Fig. lc, e) showing frequently precocious separation. Most of the PMCs showed 13:13 segregation in anaphase I (Fig. If, g).

The degree of morphological deviation of three DtAALs from disomic plants were intensified than that of parental MtAALs. DtAAL X had slender kernels than those of the parental MtAAL. DtAAL 7 was characterized by rounder kernels and more brownish pericarp than those of the parental MtAAL. DtAAL I I gave rise to slender kernels than those of the parental MtAAL. In addition, the panicles of DtAAL II exerted incompletely when compared with those of the parental MtAAL. The pollen fertility of the three DtAALs was quite high, especially the value of DtAAL 11 was almost same as that of disomics. The seed fertilities of DtAALs 7 and 11 were high, while that of DtAAL X was low. All the three DtAALs were recovered in each selfed progeny and more than 95% of the selfed progenies had at least one alien chromosome. Especially, DtAAL I I showed complete transmission of the alien chromosome in the selfed progeny.

The three DtAALs of rice isolated in the present study may be used for breeding materials transferring alien traits from 0. punctata to 0. sativa. Those DtAALs showed relatively stable transmission of alien telosome(s), through the male and female gametes. The fact suggests that small fragments with functional centromere, could be transmitted stably to the progenies. In addition, pollen and seed fertilities were considerablly restored in DtAALs carrying small fragments such as telocentric chromosomes 7 and 11 of 0. punctata. We propose a following procedure to develop materials for the use of practical breeding program: Firstly screening MtAALs derived from spontaneous misdivision of the additional alien univalents in the monosomic alien addition lines, and secondly selecting fertile DtAAL stocks for respective 24 chromosome arms of 0. punctata.

References

Yasui, H. and N. Iwata, 1994. Cytological identification of three monotelosomic and a monoacrosomic alien addition lines in rice (Oryza sativa L.) having a telocentric chromosome 2, 7, and 9, and an acrocentric chromosome 4 of Oryza punytata Kotschy. Breed. Sci. 44 (Suppl. 2): 128.