Genetic Diversity and Heritability of In Vitro Leaf Regeneration Ability in Malus Species

in HortScience

Agrobacterium-mediated genetic transformation is commonly used in dicotyledon plants such as apples. The regeneration ability of the recipient is an important factor in transformation efficiency. Here, the variations in bud regeneration rate (BRR) and the number of adventitious buds (NAB) formed per explant in Malus germplasm accessions with phenological stage were estimated. Both BRR and NAB of explants at the dormancy broken and spring sprouting stages were significantly higher than those at the autumn sprouting stage. The genetic diversity and inheritance of BRR and NAB were evaluated using 153 Malus germplasm accessions and 78 hybrid trees of Jonathan × Golden Delicious. Malus sieversii 31, Liberty, and Smoothee exhibited significantly high BRR (98.33%, 98.33%, and 93.33%, respectively) and a large NAB without vitrification. BRR and NAB linearly correlated with each other but not with callus formation rate. The broad sense heritability of the regeneration rate was 92.16%. The three Malus accessions that had high regeneration ability, and some of their sexual descendants, might be outstanding genetic resources for future genetic transformation.

Contributor Notes

We thank the earmarked fund for China Agriculture Research System (CARS-27), the Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture, People’s Republic of China, and grants from the Beijing Municipal Education Commission (CEFF-PXM2017_014207_000043).

Corresponding author. E-mail: zhangxinzhong999@126.com.

Downloadable materials

  • Supplemental Materials (XLS 51 KB)
  • Supplemental Materials (DOCX 24 KB)
  • Supplemental Materials (DOCX 22 KB)
  • Supplemental Materials (PDF 22 KB)
  • Supplemental Materials (XLSX 11 KB)

Article Sections

Article Figures

  • View in gallery

    (A) Newly expanded young leaves on 1-year-old branch (bar = 1 cm). (B) Two sections of leaf blade cultured on the regeneration medium (MS + 4 mg·L−1 TDZ + 0.5 mg·L−1 NAA) (bar = 2 mm). (C) Regenerated adventitious buds cultured on the growth medium (MS + 0.5 mg·L−1 6-BA + 0.5 mg·L−1 IBA) (bar = 1 cm).

  • View in gallery

    Tissue browning and adventitious bud regeneration of the leaf explants collected from (A, D) dormancy-broken branches, (B, E) spring sprouts, and (C and F) autumn sprouts. The explants in (AC) were collected from the branches of Royal Gala (Malus domestica Borkh.), whereas the explants in (DF) were from Baleng Crab (Malus robusta (Carr.) Rehd) (bar = 1 cm).

  • View in gallery

    (A) Frequency distribution of the bud regeneration rates (BRRs) of 153 Malus germplasm accessions. The BRR was classified into four levels: Low (0% ≤ BRR < 20%), Relatively low (20% ≤ BRR < 50%), Relatively high (50% ≤ BRR < 90%), and High (BRR ≥ 90%). (B) Frequency distribution of the numbers of regenerated adventitious buds per explant of 153 Malus germplasm accessions. The number of regenerated adventitious buds per explant (NAB) was classified into four levels: None (NAB = 0), Moderate (0 < NAB < 3), Relatively high (3 ≤ NAB < 9), and High (NAB ≥ 9).

  • View in gallery

    The regeneration of leaf explants of (A) Malus sieversii 31 (M. sieversii (Ledeb.) Roem.), (B) Liberty (Malus domestica Borkh.), (C) Smoothee (M. domestica Borkh.), and (D) Royal Gala (M. domestica Borkh.) collected on dormancy-broken branches. Almost every explant of (A) M. sieversii 31, (B) Liberty, and (C) Smoothee produced numerous adventitious buds without vitrification. In comparison, their regeneration rates and numbers of adventitious buds per explant were far more than those of the commonly used cultivar (D) Royal Gala (bar = 1 cm).

  • View in gallery

    Correlation between bud regeneration rate and number of regenerated adventitious buds per explant using 60 Malus germplasm accessions with nonzero regeneration rates.

  • View in gallery

    (A) Frequency distribution of the bud regeneration rates of 78 hybrids from Jonathan × Golden Delicious. The bud regeneration rate (BRR) was classified into two levels: Low (0% ≤ BRR < 20%) and Relatively low (20% ≤ BRR < 50%). (B) Frequency distribution of the numbers of regenerated adventitious buds per explant of the 78 hybrids. The number of regenerated adventitious buds per explant (NAB) was classified into two levels: None (NAB = 0) and Moderate (0 < NAB < 3).

Article Information

Google Scholar

Related Content

Article Metrics

All Time Past Year Past 30 Days
Abstract Views 68 68 3
Full Text Views 48 48 2
PDF Downloads 7 7 3