優良單交種玉米之親本改良(二)理想族群之鑑別

Abstract

玉米族群種源之數目繁多，若没有適當的評估方法去瞭解一個族群是否攜有某些有利基因，將限制了這個族群的利用價值。本研究使用十八個遺傳背景不同之玉米族群，並設定台農１號(TA2808-176 × TA3651-377)為待改良之單交種，進行六個環境（3期作 × 2地區）之評估試驗。資料估算：(1)有利顯性基因 相對數目（relative number of favorable dominant alleles,l(p1) ̅μ ́) ;(2)不利隱性基因相對數目(relative number of unfavorable recessive alleles, j(qj) ̅μ or k(qk) ̅μ)，及⑶親疏關係值(relationship values, (I2 × Py)-(I1 × Py)+(I1 - I2)/2。藉著這三項估值之比較，發現Mezcla Amarilla, Tropical Early Yellow Flint, 三項估值之比較，發現Mezcla Ammarilla, Tropical Early Yellow Flint, RBS10 C3, RSSSC C4 及Suwan-Pathology Source等五個族群具有相當多之顯性有利基因數目，而此類有利基因是在單交種TA2808-176 × TA3651-377中所不存在的。由親疏關係值看出，僅族群RBS10 C3 與TA3651-377較相近；而族群Meacla Amarilla, Amarillo Cristalino-2, Tropical Early Yellow Flint, Tropical Early Yellow Dent及Amarillo Cristallio-1與TA2808-176較為接近。綜合評估之下，Mezcla Amarilla 及Tropical Early Yellow Dent將作為TA2808-176之重要來源；而RBS10 C3可作為改良TA3651-377之來源。由於相對有利與不利基因數目相近，在進行自交系親本改良過程中，Mezcla Amarilla × Ta2808-176、Tropical Early Yellow Dent × TA2808-176及RBS10 C3 × TA3651-377三個組合，可於F1自交分離，而不必先予回交。Mezcla Amarilla及Tropical Early Yellow Dent不僅可作為台農1號親本TA2808-176之改良來源，同時亦可直接分離自交系，以結合TA3651-377成優良單交種，而為最有價值之二個族群。 In maize (Zea mays L.) breeding program, a large number of population germplasms are available. The value of maize population has been limited by a lack of methodology for identifying populations containing favorable alleles. Eighteen maize populations were evaluated in six environments (3 crop seasons x 2 locations) for their potential as breeding sources for grain yield. Three estimats, (1)lp, µ’ -relative number of favorable dominant alleles; (2)jq ̅jµ or kq ̅kµ-relative number of unfavorable recessive alleles; and (3) [ (I1 x Py) - (l2 x Py) + (l1 - l2) / 2 ] - relationship values were calculated. The populations Mezcla Amarilla, Tropical Early Yellow Flint, RBS10 C3，RSSSC C4 and Suwan-Pathology Source had a significant number of dominant favorable alleles for grain yield not present in TA2808-176 x TA3651-377. Based on relationship values only RBS10 C3 was more closely related to TA3651-377 than TA2808-176. Populations Mezcla Amarilla, Amarillo Cristalino-2, Tropical Early Yellow Flint, Tropical Early Yellow Dent and Amarillo Cristallio-1 were more closely related to TA2808-176 than TA3651-377. Of the populations tested, Mezcla Amarilla and Tropical Early Yellow Dent would be chosen to improve TA2808-176, whereas RBS10 C3 would be chosen to improve TA3651-377. Backcrosses prior to selfing in the F! of Mezcla Amarilla x TA2808-176, Tropical Early Yellow Dent x TA2808-176 and RBS10 C3 x TA3651-377 are not necessary. Populations Mezcla Amarilla and Tropical Early Yellow Dent were most valuable populations not only for improving TA2808-176 but also as a direct sources of new lines to cross to TA3651-377.