Indica-japonica Cross Research Articles

A gamete abortion locus detected by segregation distortion of isozyme locus Est-9 in wide crosses of rice (Oryza sativa L.)

A locus for male gamete abortion in hybrids for Japonica and Indica rice was identified with the aid of marker genes Rc and Est-9 on chromosome 7. In an Indica-Japonica cross, AKAMAI 1/IR50, the Indica allele Est-9 2 was transmitted via the male gamete with a ratio of 0.29 instead of the normal 0.5, whereas no segregation distortion was observed for the Rc locus. The recombination value (p) for Est-9 and Rc was estimated to be 0.38 by a least square method after adjusting Mendelian segregation ratios with the male transmission ratios of 0.29 (Tr) for Est-9 2 and 0.71 (1-Tr) for Est-9 1. The recombination value (q) for the new locus for male gamete abortion, ga-11, and Est-9 was estimated to be 0.23 by using 56 F3 lines from F2 plants which were heterozygous for the Est-9 locus. No linkage for Rc and ga-11 was found. Therefore, the two markers and ga-11 were located in the order of ga-11-Est-9-Rc. Using the estimated recombination value (q), the male transmission rate (k) of ga-11 a was estimated to be 0.11 with the F2 data and-0.07 with the F3 line data. Thus, it was apparent that male gametes possessing ga-11 a were frequently aborted in the Indica-Japonica hybrid.

Development of new cytoplasmic genetic male sterile lines through Indica × Japonica hybridization in rice

From 28 Indica-Japonica crosses, two Indica cultivars, V.20B and Sattari were identified to possess male sterile cytoplasm with fertility restoring genes. It was possible to develop a new Japonica cytoplasmic genetic male sterile line (Zhunghua-1) on Indica male sterile cytoplasm (V 20B) by repeated backcrossing the complete pollen sterile plants of V 20B x Zhunghua-1 to the recurring male parent, Zhunghua-1. The study indicated that it would be possible to develop male sterile lines rom indica-japonica crosses only when there is sufficient amount of reciprocal differences with respect to pollen sterility. Further, it was inferred that it would be easier to develop Japonica male sterile lines on Indica cytoplasm than developing Indica male sterile line with japonica cytoplasm.

Multiple alleles controlling F1 sterility in remote crosses of rice (Oryza sativa).

We reported previously that Indonesian rice varieties belonging to the so-called Javanica varieties could be classified into some different types in respect to F1-sterility relationships with a set of Indica and Japonica testers. Firstly, in this study, we observed that the F1 Plants between these different types were fertile with a few exceptions. Secondly, to look into the genetic basis of the sterility of the F1 hybrids between a variety, Penuh Baru II and Indica or Japonica testers, we made threevarietal crosses involving Penuh Baru II, a “wide-compatibility” variety Ketan Nangka, and IR 36 or IR 50 (Indica tester). The progeny of the three-varietal crosses showed an association of spikelet fertility with certain gene markers. The segregation pattern for the spikelet fertility was explained by a model of one-locus allelic interaction. It was postulated that the Japonica tester as well as Penuh Baru II have the same allele S-5j while the Indica tester has S-5i at the S-5 locus belonging to linkage group I, and that female gamates with S-5j are aborted in plants with the genotype of S-5i/S-5j. Ketan Nangka was found to have a wide-compatibility allele S-5n which does not confer sterility in combination with other alleles. The F1 sterility of Penuh Baru II with Japonica tester appeared to be controlled by sterility genes other than those at S-5 locus. The wide-compatibility gene S-5n can be usefull in the breedig of Indica-Japonica crosses and also in developing Indica-Japonica F1 varieties.

Female Sterility in an Indica-Japonica Cross of Rice

日本のイネ品種`藤坂5号'を母とし，インドネシア品種`Tjina'を父とする雑種F1に藤坂5号を4回戻し交雑した後代系統の中から，遺伝様式の単純な雌性不稔が見出された。雑種系統における種子稔性の分離に2遺伝子が関与し，この二重劣性ホモで雌性不稔が生ずると推定された。雌性不稔個体では，正常な花粉が生ずるが，胚のうが形成されなかった。しかし，1穂に2ないし3粒の頴花が結実し，この種子によって雌性不稔は次代に伝達された。

Breeding of Blast Resistant Lines (BLI to 7) from Indica-Japonica Crosses of Rice

Breeding of Blast Resistant Lines (BLI to 7) from Indica-Japonica Crosses of Rice