Analisis jarak genetik berdasarkan marka ssrs dan morfologi serta analisis daya gabung untuk pembentukan hibrida jagung manis (Zea mays L. Var. Saccharata)

Abstract

The objective of the research were to grouping sweet corn lines resistant to downy mildew, high specific and general combining ability and high heterosis to select parental line to breed single cross hybrid of sweet corn. The first research was done to study genetic variability of 39 sweet corn lines based on SSR and morphological marker to select good parental lines of hybrid sweet corn. There were high genetic variability among genetic material, showed by genetic distance value about 0.18 to 0.78, indicates wide genetic variability of sweet corn. The results shows that among 20 lines having genetic similarity between 0.25 – 0.82 or genetic distance from 0.18 to 0.75; based on morphological trait 0.27 – 1.00. Correlation value between similarity matrix based on SSR and morphology was high on 0.88 of goodness of fit criteria. The aim of second research was to study general combining ability of sweet corn lines for yield and resistant to downy mildew for hybrid varieties improvement. Six of 45 lines having high fresh ear yield per plot and best general combining ability, such as Mr4/SC/BC4-2-1B, Mr4/SC/BC4-6-1B, Mr11/SC/BC4-2-1B, Mr11/SC/BC4-4-1B, Mr12/SC/BC4-6-1B, and Mr12/SC/BC3-3-1B. All of testing lines have resistance to downy mildew with severity about 0.0 to 7.1%. The lines having high GCA value would be good combiner to other lines to develop high yielding hybrid sweet corn and resistant to downy mildew. The third research was done to study general and specific combining ability of sweet corn lines and higher heterosis of downy mildew resistance supporting the hybrid corn development. The combination of A x D lines (Mr12/SC/BC4-6-1B x Mr11/SC/BC4-2-1B) were medium genetic distance and having highest GCA, heterosis and heterobeltiosis for fresh ear yield per plot character. The D x C combination (Mr11/SC/BC4-2-1B x Mr4/SC/BC4-2-1B) have wide genetic distance and high fresh ear yield per plot, heterosis and heterobeltiosis, but have negative SCA value. The combination of E x C (Mr12/SC/BC3-3-1B x Mr4/SC/BC4-2-1B) have a wide genetic distance but low productivity. The best hybrid is not always obtained from parents with the high genetic distance, but also can be obtained from the low or medium genetic distance as well.

Penelitian ini bertujuan untuk memperoleh pengelompokan galur jagung manis yang tahan terhadap penyakit bulai, dengan nilai daya gabung umum, daya gabung khusus, serta nilai heterosis yang tinggi sehingga diperoleh jagung hibrida silang tunggal yang mempunyai potensi hasil tinggi. Penelitian pertama untuk mengetahui keragaman genetik 39 galur jagung manis memanfaatkan marka SSRs dan karakter morfologi untuk seleksi tetua hibrida. Hasil percobaan menunjukkan keragaman genetik cukup tinggi dari materi yang diuji. Hal ini ditunjukkan dengan nilai jarak genetik berkisar dari 0,18 sampai 0,78 yang mengindikasikan variabilitas genetik galur jagung manis yang dikarakterisasi cukup luas. Hasil penelitian 20 galur berdasarkan SSRs menunjukkan koefisien kemiripan genetik pada galur yang diuji berkisar antara 0,25 – 0,82 atau pada jarak genetik 0,18 - 0,75; berdasarkan karakter morfologi menunjukkan nilai rata-rata koefisien kemiripan genetik 0,27 – 1,00. Nilai korelasi antara matrik kemiripan berdasarkan SSRs dengan matrik kemiripan berdasarkan morfologi tergolong baik berdasarkan kriteria goodness of fit (0,88). Kegiatan pada penelitian kedua dilakukan untuk untuk mengetahui nilai daya gabung umum galur-galur jagung manis (Zea mays L. var. saccharata) untuk karakter hasil dan ketahanan terhadap penyakit bulai (downy mildew) dalam rangka perakitan varietas hibrida. Dari 45 galur yang diuji terpilih enam galur yang mempunyai hasil tongkol segar per petak dan nilai DGU tertinggi yaitu Mr4/SC/BC4-2-1B, Mr4/SC/BC4-6-1B, Mr11/SC/BC4-2-1B, Mr11/SC/BC4-4-1B, Mr12/SC/BC4-6-1B, dan Mr12/SC/BC3-3-1B.