香蕉作物栽培種之起源

Origin of Cultivated Bananas

香蕉作物栽培種的原種主要是Musa acuminata與M. balbisiana，此外在一些栽培種的遺傳組成中亦可找到M. schizocarpa與M. texitile的基因組。從野生種演化為栽培種的關鍵為果實單為結果與植株雌不稔。至少三個顯性因子控制單為結果，且具此特性的品種均帶有M. acuminata ssp. banksii或M. acuminata ssp. errans的基因組。相伴隨的雌不稔性則可能為遺傳控制或染色體異常與受環境影響而引起，絕對的雌不稔保證了栽培種之可食性，而部分的雌不稔則為栽培種的雜種化與多倍體化開啟一扇大門。2n配子的產生使得香蕉作物可以經由單向有性雜交的方式而三倍體化，在高溫、高光照與低濕的環境下較易產生2n雌配子，且主要是因發生了第二次減數分裂回復（second division restitution，SDR）而產生的；2n雄配子則僅在栽培種觀察到，且至少一個基因座參予其形成。菲律賓群島-印尼群島東部-巴布亞及新幾內亞等地是香蕉作物最初栽培化的地區，最初的三倍體尖蕉在印尼群島東部以外之島嶼東南亞與大陸東南亞等地產生，而三倍體菜蕉則可能在印尼群島東部。 Most banana cultivars are derived from two species, Musa acuminata (A genome) and M. balbisiana (B genome), however M. schizocarpa (S genome) and M. textiles (T genome) also been found in the genetic constitute of several landraces. Edibility of mature fruits came out as a result of parthenocarpy and female sterility. Parethnocarpy was controlled by at least three dominant genes, and showed to be linked to M. acuminata ssp. banksii and/or M. acuminata ssp. errans. Female sterility may be controlled by genetic or caused by chromosome abnormality or by environment. Absolute female sterility proved to be essential for the edibility of cultivars, however partial female sterility offered the opportunity of hybridity and polyploidization. The presence of 2n gametes in diploid species suggests that unilateral sexual polyploidization (2n x n) could have been involved in the origin of triploid Musa species. The generation of 2n eggs probably came out as a result of second division restitution (SDR). Relatively high production of 2n eggs was under high temperature, high solar radiation and low relatively humidity conditions. 2n pollens were observed only in cultivated genotypes and was controlled by at least one locus. M. acuminata ssp. banksii became domesticated first in the Philippines – eastern Indonesia-New Guinea area and later progressively in the rest of eastern Indonesia and mainland Southeast Asia, where AAA triploids were generated. When M. balbisiana moved southward through the Philippines and the Moluccas to the eastern Indonesia, produced the first AAB hybrids.