種間雜交五倍體藍莓親緣鑑定及形態與物候分析

Abstract

兔眼藍莓(Vaccinium virgatum Aiton)之原生地美國東南部氣候環境和臺灣相似，且於臺灣中北部平地種植之生長情形良好。另一方面，南高叢藍莓(V. hybrid)在美國育種歷程較長，多數品種含優良商業性狀，為驗證兩者雜交之五倍體藍莓是否具可發展為新品種或藍莓育種材料，本研究鑑定三個於2015年雜交之兔眼和南高叢藍莓組合AG (Austin x Gulfcoast)、PM (Powderblue x Misty) 及MO (Montgomery x O’Neal) 之親緣關係，並進行性狀、物候和稔性等調查。 流式細胞儀之分析結果顯示PM ‘NTU294’、PM ‘NTU295’和MO ‘NTU108’三者為五倍體，DNA含量介於2.69至2.96 pg/2C之間，而AG ‘NTU048’之DNA含量則為3.43 pg/2C，和母本‘Austin’的3.66 pg/2C接近，應為六倍體。為進一步驗證倍體數分析結果，再利用SSR (Simple sequence repeat)分子標誌VCC_K4進行鑑定，電泳結果顯示PM ‘NTU294’、PM ‘NTU295’和MO ‘NTU108’三者雜交成功，而AG ‘NTU048’之父本應非原先選定之‘Gulfcoast’。形態和性狀調查結果顯示，五倍體藍莓生長狀況良好，果實有少子特性，惟果實較小，且果實表面無果粉覆蓋。五倍體藍莓果實成熟期介於親本之間，PM ‘NTU295’於2021和2022兩年皆有最高產量。電子顯微鏡觀察PM ‘NTU294’、PM ‘NTU295’和MO ‘NTU108’三者之花粉皆顯示為四分體複合型花粉，PM ‘NTU294’和MO ‘NTU108’可觀測到發育不正常的花粉萌發孔，但體外花粉萌發率顯示所有五倍體子代花粉活力皆正常。AG ‘NTU048’之葉片、花朵、果實形態和果實成熟期都更似母本兔眼藍莓，花粉形態亦正常，判斷為純六倍體兔眼藍莓。綜上所述，本研究證實PM ‘NTU294’、PM ‘NTU295’和MO ‘NTU108’為雜交成功之五倍體藍莓，雖三者並無特別突出之優良商業性狀，但仍有作為育種材料之潛力。

Rabbiteye blueberries (Vaccinium virgatum Aiton) are promising blueberry types for central and northern Taiwan where the climate is similar to their originated habitat. On the other hand, most southern highbush blueberry cultivars (V. hybrid) possess outstanding commercial traits due to their advanced breeding progresses in the United States. In this thesis, the parentage of three hybrid combinations between the rabbiteye and southern highbush blueberry AG (Austin x Gulfcoast), PM (Powderblue x Misty), and MO (Montgomery x O’Neal) was identified. The leaf, flower, and berry morphological traits, phenology, and pollen viability of these hybrids and parental plants were then compared and investigated to evaluate the potential of interspecific hybridization in rabbiteye blueberry breeding. The results of flow cytometry indicated PM ‘NTU294’, PM ‘NTU295’, and MO ‘NTU108’ are pentaploid blueberries, with their DNA nuclear content ranging from 2.69 to 2.96 pg/2C. The DNA nuclear content of AG ‘NTU048’ was 3.43 pg/2C, being close to the number 3.66 pg/2C of its maternal parent ‘Austin’, indicating AG ‘NTU048’ was a hexaploid blueberry. Selected simple sequence repeat (SSR ) markers were then utilized to further confirm the results of the ploidy test. Through the gel electrophoresis result of SSR marker VCC_K4, PM ‘NTU294’, PM ‘NTU295’, and MO ‘NTU108’ were found to be successfully hybridized, while ‘Gulfcoast’ was verified not to be the pollen donor of AG ‘NTU048’. The pentaploid blueberries showed vigorous growth and had seedless traits but smaller berry size and lack of surface bloom. The harvest time of the pentaploid blueberries was later than their southern highbush parent but earlier than their rabbiteye parents, and PM ‘NTU295’ was found to have the highest yield in both 2021 and 2022. The pollen grain of ‘NTU294’, PM ‘NTU295’, and MO ‘NTU108’ was typical tetrahedral tetrad but abnormal pollen aperture was found in some pollen grains of PM ‘NTU294’ and MO ‘NTU108’. Nevertheless, the pollen viability of all pentaploid lines was normal. Morphological analysis indicated AG ‘NTU048’ was likely to be a pure rabbiteye blueberry. This study elucidated PM ‘NTU294’, PM ‘NTU295’, and MO ‘NTU108’ as pentaploid blueberries and these lines may have the potential of being new breeding materials.