In vitro micro-propagation and haploid production in muskmelon (Cucumis melo L.)
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Induction of haploids in muskmelon was attempted through two methods,
parthenogenesis and ovule culture. In parthenogenesis, four genotypes, MS-1, MM Sel.-103,
MH-27 and Muskan were used. Pollen grains of MS-5, the male parent, were irradiated with
γ-rays (60Co) from 250 to 400 Gy for induction of parthenogenic embryos upon fertilization.
Higher number of haploids were obtained at 300 Gy in each genotype, except in Muskan. The
ploidy level of putative haploids was determined through chromosome count, stomatal
density and dimensions and chloroplasts count in guard cells. The root meristematic cells
exhibited 12 and 24 chromosomes in haploid and diploid plants, respectively. The stomatal
density was higher in haploids than in diploids (29.2 vs.10.9 stomata/mm2). However, the
number of chloroplasts per guard cell was less in haploids as compared to diploids (4.0 vs.
12.9). Furthermore, the stomatal cavity diameter (10.9 vs. 14.4 µm) and length (13.0 vs. 24.3
µm) exhibited the same trend. In ovule culture, muskmelon genotype, MM Sel.-103 recorded
higher number of embryo like structure (ELS) than MS-5. No pre/ post-temperature treatment
was effective to enhance the percent callusing and ELS formation. The MS medium
supplemented with TDZ (0.04 mg L-1) recorded the highest callusing (100%), while the
highest ELS (16.3/20 mm2) formation was observed in MS medium supplemented with
Proline (560 mg L-1), Kinetin (0.5 mg L-1), 2, 4-D (2.5 mg L-1) and Coconut water (10%). On
culturing in differentiation media, MM Sel.-103 exhibited 3.3% and 26.8% rooting in two
media, MS+BAP (0.5%) and MS+adenine sulphate (30 mg L-1), respectively. In micropropagation
of MS-5, a male sterile line, MS+BAP (0.5mg L-1) and MS+IAA (1.0 mg L-1)
were observed to be the optimum medium for shoot (55%) and root (90%) induction,
respectively.
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