香蕉AAA基因組華蕉系在亞群及AAB品種胚性細胞懸浮培養之生長週期及循環生長特性

Cycling Growth Characters in Embryogenic Cell Suspension Culture of Banana AAA Cavendish Subgroup and AAB Cultivars

香蕉AAA華蕉系四個品種及AAB 'Raja'及‘粉蕉’兩品種，由幼雄花序所誘導之胚性癒合組織，接種於含2,4-D 1mg/L之修正MS液體培養基。參試之細胞系皆可在增生培養基中長期持續生長，但胚性細胞依其基因組群、胚性潛力及培養條件，生長週期呈3至8個月以上之變化。其中以呈極性發育之AAA基因組細胞系生長週期最長。其生育期可分為增生期、球狀體、伸長期、梨型增大期及重組釋放期等五個發育相，並可細分成15個生長型。增生相又可分為極性與非極性生長，前者有如前胚發生，後者則一般發育為胚性細胞團。至於極性球狀體發育相，則類似胚發生之球胚期。伸長及增大相雖有原維管束形成，但無形態雙極性分化，應屬異常偽胚發生。一般而言AAB品種及一些AAA選系之細胞系生長比AAA者較不一致，主要穿梭生長於第1或2發育相，細胞族群常共存有4-7種優勢型，同時較抗耐逆境。細胞系之再循環生長主要無性增殖途徑可分為三種模式。模式A以細胞隔離及分離為途徑，即以細胞團或失去極性生長之早期球狀體為釋放中心，籍由隔離作用而游離出胚性細胞或增生出小細胞團，供為再循環生長之繁殖體，生長周期約需2-3個月。模式B以出芽及段節為其途徑，即以初期梨形增大體I為釋放中心，始由外團細胞活化為擬分生組織，少數經直接細胞隔離，大多數為出芽（budding）與重複的芽增殖，再經由段節作用（fragmentation）釋出繁殖體，生長週期約需4-5個月。C模式主要以段節及重組為其途徑，以晚期梨形增大體Ⅲ作為中心，先以模式A釋放，分離大都數表層非胚性細胞，直至進入內環擬分生帶時，再進行細胞重組然後藉由模式B之出芽及節斷作用並伴隨A模式而重新獲得胚性懸浮細胞之增殖，此生長週期長達6個月以上。另使用未成熟體胚作為釋放增值體，可誘導類似模式A之隔離與分離增殖，即由外至內細胞漸次再分生活化與融離，約2.5個月可形成均質的胚性懸浮培養。

Succulent mate inflorescence derived embryogenic calli of Musa AAA Cavendish subgroup cultivars and AAB cultivars were serially subcultured in modified MS liquid medium supplemented I mg/L 2,4-D for up to 5 years. It was demonstrated that the longest growth cycle in polar growth of embryogenic cell lines could be divided into proliferation, globularization, elongation, pear shaped enlargement and releasing phases. The cycle also could be subdivided into 15 growth stages. The cell lines of AAB culitvars and AAA 'Robusta' selected line 44 were mainly re-shifting growth in Phase 1 and 2, and comprised of 4-7 dominant types. The major pathway of recycling growth varied with genomic groups, cultured conditions and embryogenic competency, which was categorized into three models. Model A: The pathway of A is isolation and separation, such as the embryogenic cell cluster cell mass or globular mass serving as releasing center, detached free cells or small cell cluster as propagules for next generation .The duration of A cyclic growth required 2 months. Model B: The pathway of B is budding and fragmentation. The early enlarged pear-shape body performed as reorganized center. The periphery tissue was transformed into meristematic zone, then accompanying cell detachment and repetitive budding, free cell or fragments as propagules was reproduced, The growth cycle takes up 4-5 months. Model C: The pathway of C is fragmentation and reorganization. The lately enlarged pear-shape body Ⅲ preformed as the center, first pass the isolation and separation to release all the non-embryogenic cells, until the procambium zone. Then the cells reorganized to perform as the center of budding and fragment and accompany with model A. The growth cycle takes up at lease 6 months. It was demonstrated that the immature somatic embryos were inducible to proceed A pathway, mediated cell reactivation and isolation, and able to reproduce homogeneously embryogenic suspension in 2.5 months.