Paper. Taiwan Sugar Corfioration and Taiwan Sugar Exfieriment Station 5O4 CYTOLOGICAL STUDIES OF SUGARCANE AND ITS RELATIVES

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1 5O4 CANE BREEDING SECTION DISCUSSION MR. GRASSL paid a compliment to the Indian worlrers, and gave it as his opinion that the collection of spontaneum types was of great interest and importance. His remarlrs were supported by MR. STEVENSON and DR. BRANDES and it was decided that a resolution should be forwarded to the Committee of the I.S.S.C.T., expressing the appreciation of sugarcane breeders of the collection work in India and on previous U.S.A., Australian and Hawaiian expeditions to collect original sugarcane types. Paper CYTOLOGICAL STUDIES OF SUGARCANE AND ITS RELATIVES * H. W. LI, T. H. MA and K. C. SHANG Taiwan Sugar Corfioration and Taiwan Sugar Exfieriment Station In the past, there were two attempts made in the cytological studies of the hybrids involving P.O. J and Miscanthus japonicus. Studies were made in.1948 (LI et al, 1948) on several of the hybrids between P.O. J and Miscanthus japonicus, which were made by the Japanese in There were two types of hybrids: I. OMM type with 126 somatic chromosomes. P.O. J has 107 and M, japonicus 38 somatic chromosomes respectively: This is the "noblized" type or "normal" type of MORIYA (1940). 2. OM type with somatic chromoson~es. This is the "intermediate" type of MORIYA. There was larger proportion in OOM type than OM type in the few eeedlingsstudied. However, this does not represent the true picture for there is no way of telling how many seedlings the Japanese obtained to start with: Later (LI et al, 1951) one seedling out of the original 40 seedlings obtained was found to be OOM type or "patroclinous" type. The same cross was involved, i.e. P.O. J and M. japonicus. Since the other 39 seedlings were discarded before any attempt was made to reveal their cytological identity, nothing is known about them. According to MR. SHANG who made the crosses, few of the seedlings were more or less similar to the female parent, P.O. J. 2725, (00M type) ; others were intermediate (OM type). The one OMM type saved for propagation resembled very closely the Miscanthus parent used. In fact OM and OMM types were not separated from the standpoint of the morphological difference at the t~me selection was made. It is apparent however, that there are 3 types of hybrids cropped out in the very cross. Unfortunately this is only a guess work at the best. In 1950, another attempt of the same intergeneric cross was made. Instead of using P.O. J as the female parent as ~t was ordinarily done in the past, an early tasseling seedling variety was used at the time when Miscanthus was tasseling. This seedling was also male sterile and is a hybrid between FP 180 and FP 172, It has 127 somatic chromosomes (Fig. I). Its chromosomal configurations in the first meiotic mitosis are scored as presented in Table I : (Fig. 2). The un~valents range from 7 to 15 and there are one or two tetravalents present in soine of the PMCs examined. The presence of univalents would undoubtedly induce lagging in IA. (Fig. 3). Refevences p 508.

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3 50~ CANE BREEDING SECTION TABLE I1 CHROMOSOMAL NUMBER OF HYBRIDS BETWEEN AND MISCANTHUS JAPONICUS Plant IAt chro~nosomal cornfiguration number IA zn Remarks 5 I11 I11 I I0 110 I I11 I11 I ca. I12 I I11 I I00 ca. I ca. Fig X M. japonicus. (3-4-1) IA, 2n: 113. Fig x M. japonicus. (3-4-1) IM, , 4 The chromosomal numbers of these 13 hybrids examined range from Outwardly, the four hybrids whose chromosomal number was not determined are not different from their sister plants. It is therefore highly probable that their chromosomal number would fall within this range,

4 H. W. LI, T. H. MA, K. C. SHANG As the hybrids do look very much alike the Miscanthus parent, it is s they are all "patroclinous" type, OMM. This would mean that it is the co the reduced gamete of and the unreduced gamete of Miscanth As there is a preponderance of hybrid plants with chromoson~es with , 11 out of 13 or 85 %, it would merit some consideration. From the study of the meiotic mitosis of the it was found that there are 7-15 univalents in IM. These univalents do lag behind in IT, and their distribution would be at random even though some of them do i I I Plate I. Mature plants of (Q), hybrid (F,) and Miscantl~us japoilicus (d), from left to right respectively. Plate 2. Stallrs of the same. split in the first division (Fig. 3). Consequently, gametes produced by , the femaie parent used, would vary depending on the number of univalents that are induced in the two successive divisions. The question that comes next is to offer a plausible explanation for the fact that the entire population of this intergeneric cross is only of the odd type OMM. There are several possibilities : I. Even though the clone of Miscanthus used in making this cross was examined cytologically alid was found to be a true diploid with 19 pairs of ci~romosomes. There is still a possibility that the tassel used was a tetraploid. In our collection of Miscanthus there is a triploid with 57 chromosomes. In combining with the reduced gametes from the female parent, excl~~sively OM11 would be obtained. However, since the shoot from which the tassel was talien was not recognizable, whether or not it was a tetraploid, it call not be rechecl~ed for certainty. In using haploid Miscanthus pollen on P.O. J Refevences p. 508.

5 50s CANE BREEDING SECTION as described earlier, 3 types of hybrids might be obtained, i.e. OOM, OM and OMM. In case diploid Miscanthus gametes are used, there-is a high possibility of getting some hybrid plants of 00MM type. Its absence might be the result of small hybrid population or other unknown cause or causes. 2. The possibility of bispermy or polysperm is rather tenab1e:this would involve the entering of two pollen tubes into each ovary; one sperm nucleus of each tube fused with the egg gives rise to OMM. The other sperm nucleus from each tube will fuse with polar nuclei. Instead of the nor~nal triple fusion, there might be a quadruple fusion. Or else, one sperm nucleus of one tube would wander about and deteriorate later on. 3. Another possibility is rather tenable. The vegetative nucleus of pollen tube enters the ovary and fuses with the egg at the time when sperm nucleus enters into normal fusion with the egg. Prof. C. Y. YU of the National Taiwan University gave us the information that such phenomenon was known in rice, but gave no exact citation to substantiate his claim. 4. There is still another possibility. Both sperm nuclei of the pollen tube will fuse with the egg in the ovary, leaving the polar nuclei to fuse among themselves, and to be devoid of the normal triple fusion. Should any of the last three possibilities postulated as above be the right explanation, then either of these would differ widely from the normality. Any one of these would be sufficient to explain a chance variation, but far from being sufecient to explain the result that the whole progeny is alike. In order to explain this, another supposition must be offered to supplement the one already given. That is, the abnormal behaviour must be genetically controlled. The functioning of the vegetative nucleus as postulated in possibility 3 would be that the clone of Miscanthus used in this very cross must differ from other clones of the same species and is controlled genetically so that all the vegetative nuclei in any pollen tube will function in fertilizing the egg. Likewise double spermy or lack of double fertilization and triple fusion as postulated in possibility 2 and 4 respectively is a peculiar function of the female parent used and this function is also genetically controlled. The same cross is remade. Which one of the possibilities postulated would be correct remains to be verified later on. SUMMARY The piogeny of the cross and Miscanthus laponicus had chromosomes railging from and outwardly they resembled the male parent used had 127 somatic chromosomes and M lapon~cus 38 It seems that all the hybrids belonged to OMM type or the "patrocl~nous" type ' Hypothesis weie postulated to account for this peculiar result It seems that the tassel of Miscailthus parent used 111 this very cross mlght be a tetraploid instead of normal diploid This hypothesis seems to be more plausible 111 preference to other REFERENCES 1 LI, 1-1 W, C S LOH, C L LEE 1948 Cytological studies of Sugarcane and its relatives I ~ybrids between S Officinarum, Miscanthiis ~apo~licus and S spontaneum. Bot Bull Acadevnza Sznzca 2: LI, H. W., T. H. MA and K. C. SHANG. 1g5r Cytological studies of Sugarcane and its relatives IX, Further studies of hybrids of intergeneric ancl iilterspecific crosses. Report Taiwan Sugar Experiment Statioqz 7 : 1-14.