Studies on Cytoplasmic-Genetic Male Sterility in Cultivated Rice (Oryza sativa L.) I. Effect of different cytoplasm sources on male abnormalities at anthesis

Abstract

A study was carried out to investigate in detail about the male abnormality induced by cytoplasmic-genetic interaction at two different day/light temperatures (30/25℃, 25/20℃). Sixteen entries with different cytoplasm namely TC65(B)MS, TC65(G)MS, TC65(P.K)MS, TC65(R)MS, TC65(S)MS, TNG61(B)MS, TNG61(P.K)MS, KHS1(G)MS, KHS1(R)MS, IGG(B)MS, IGG(G)MS, TN5(B)MS, L2(B)MS, 16-3(B)MS, 34-60(B)MS, Reimei(R)MS and their pollen parents were used in this experiment. The following results were obtained: 1. Indehiscent anthers could be classified into three types a, b and c based on their appearances and pollen fertilities. The anthers of the entires with Pai-Co cytoplasm belonged to a type. With rufipogon cytoplasm, KR7 belonged to a type, 65R3, RMR3 and RMR10 to b-c types. The anther indehiscence in the entries with CBII, glaberrima and spontanea cytoplasms, was affected by temperature indicating its physiological nature of the effect. Sterility was higher at 25/20℃ than at 30/25℃ because indehiscence anther occurred more frequently at 25/20℃. The correlation coefficient between dehiscent anther percentage and seedset percentage at 30/25℃ was 0.717* and at 20/25℃ was 0.823*. 2. From anther appearance and pollen sterility of indehiscent anther, it seems that the indehiscent anther type a, b and c stopped development respectively at pollen, microspore and tetrad stages. Therefore, it could be deducted that anthers of 65P2, 61P1 and KR7 stopped development presumably at the later stage of pollen development, those of 65R3 stopped at the microspore and those of RMR stopped at the earlier stages of microspore development or about the tetrad stage. On the other hand, the cytoplasm of Pai-Co seems to affect only anther indehiscence, and rufipogon cytoplasm affects not only anther indehiscence but also the microspore development. 3. Temperature at 30/25℃ had a more favorable influence on pollen and spikelet fertilities of all entries than at 25/20℃. RMR and 65R3 having rufipogon cytoplasm were complete sterile, since their pollen fertility and seedset percentage were lower than 4% regardless of temperature treated . The correlation coefficient between pollen fertility and seedset percentage at 30/25℃ was 0.705* and at 25/20℃ was 0.897**. It was also shown that different genetic backgrounds interacted with different cytoplasms to produce different effects on pollen and spikelet fertilities. On the other hand, cytoplasms reacted differently with different nuclear genetic background. 4. The number of adhered and germinated pollens on stigma varied with varieties cytoplasms and temperature treatments. In pollen parents, there were about 150-200 pollen grains adhered to a stima when all six anthers in a spikelet dehisced, and 60 pollen grains when only three in a spikelet dehisced. With Pai-Co and rufipogon cytoplasms their anthers almost did not dehisce so that few pollens shed to the stima resulting in the production of sterility. The number of germinated pollens in the entries with CBII cytoplasm was lower than their pollen parents because of pollen immaturity. The entries with glaberrima or spontanea cytoplasm such as 65G7, IG1 did not differ from their patenals in pollen germination. 5. The abnormalities of cytoplasmic-genetic male sterility in rice varied with the entries. In 65P2 and 61P1 having Pai-Co cytoplasm, KR7 having rufipogon cytoplams and 16-3B, 34-60B, at 25/20℃, poor pollination took place due to partial and indehiscence of anthers. In the varieties having CBII and glaberrima cytoplasm (KG3), pollen immature, poor shedding of pollens and failure of pollen to germinate on stigma were the main abnormalities. As for the RMR and 65R3 with rufipogon cytoplasm there was a cessation of anther and microspore development. 6. Our results showed that the entries 65P2, 61P1, KR7 and 65R3 are probably more suitable for the use of hybrid seed production, while RMR3 and RMR10 are disadvantageous in their high rates of unopening of pelea and lemma. 將具有不同細胞質來源之16個品系及其花粉親種植於人工氣候室不同日夜溫度(30/25℃, 25/20℃)，詳細研究各種細胞質及溫度對於雄性器官之影響，並選拔穩定性之雄不稔性系統，所得之結果如下： (1)依據花藥外表形態及其所含花粉之稔性，可將不裂開花藥分為a、b及c等三型，不同細胞質對於花藥形態各有不同之影響。含白殼(Pai-Co)細胞質之65 P2及61 P1，其花藥為a型，含rufipogon細胞質之供試品種中，KR7為a型，65 R3 及RMR 為b-c型。但在含有CB II，glaberrima及spontanea細胞質之品系之花藥與其花粉親相似，其花藥不裂開主要受溫度之影響，為一種生理現象。而花藥裂開之頻度與結實率之相關係數，在30/25℃為0.717*，在 25/20℃為0.823*，顯示花藥不裂開為不稔性之主要原因之一。 (2)由a、b、c三種外表形態及其花粉發育程度，可推測各種細胞質對於小孢子及花藥構造發育之作用時期，可能分別在花粉(pollen)，小孢子期(microspore)及四分子期(tetrad)，因此，65 P2，61 P1及KR7，皆在花藥之分化後期停止，65 R3，在小孢子期產生異常，而RMR則在小孢子期或較早期已受到障礙。換言之，Pai-Co細胞質僅作用於花藥之不裂開性，而rufipogon不僅作用於花藥不裂開，而且對於花藥之發育與小孢子之發育亦有嚴重之影響。 (3)一般，在30/25℃較25/20℃之花粉率與結實率為高，但其中，65 R3 及RMR，不論何種溫度，其花粉率與結實率皆很低(0~4%)。花粉率與結實率之相關係數在30/25℃為0.705*，在25/20℃為0.897*，結實率與不裂開花藥之關係相當密切，不同細胞質與不同核遺傳因子之組合之相互作用，對於花粉率與結實率亦顯出不同程度之影響，而同細胞核不同細胞質之變異較同細胞質不同細胞核之變異為大。 (4)小穗花開後，附著在柱頭上之花粉數及花粉發芽數，因參試品系及處理而異。正常之花粉親，同一小穗花6個花藥全部裂開時約有150-200花粉附著在其本身柱頭上；若僅3個花藥裂開則僅約50粒附在柱頭上，花粉發芽百分率亦有相同趨勢。30/25℃較25/20℃都有較高百分率，在含有Pai-Co與rufipogon細胞質之品系，因其花藥不裂開或小部分裂開，以致僅僅少數花粉附著於柱頭，此為不稔原因之一，具有CB II細胞質之品系，因其所含花粉發育不飽滿(不成熟)，故其花粉數及花芽數皆少。至於其他細胞質(glaberrima, spontanea)其情形與花粉親並無顯著之差異。 (5)不同來源細胞質對於雄性器官之影響，視溫度與核遺傳因子而異，Pai-Co細胞質主要作用於花藥不裂開性。在25/20℃下，則與溫度共同影響花粉與花藥之發育，rufipogon之細胞質，主要作用於小孢子與花藥構造之發育，但視核遺因子作用而異，在KR7，僅是影響花藥不裂開，而65 R3 及RMR則兩者皆受影響。CB II與glaberrima細胞質，則主要作用於花粉後期之充實度，至於其他細胞質之作用，其與花粉親之間，並無明顯之差異。其花藥不裂開及花粉不稔性主要受溫度影響。由本實驗之結果，65 P2，61 P1，KR7，65 R3 ，RMR3 以及RMR10，皆為穩定之雄不稔系統可以適用為雜交種子生產。