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Title: Ploidy manipulation and mutation studies in papaya
Authors: M, Mahadevamma
Guide/Chairperson: I S, Yadav
Keywords: Ploidy
Issue Date: 1997
Year of Submission: 1997
Abstract: Ploidy manipulation has been used in fruit crops to advantage by getting better sized fruits. In case of papaya with its chromosome number being 2n=18, there is good scope for making heading in breeding. In case of variety Sunrise Solo, the fruits are quite small, but the quality is good. The variety Coorg Honey Dew has big sized fruits with poor keeping quality. Hence these two varieties were selected for mutagenic treatment to create variability. In this experiment GA was used as a pretreatment chemical for seed material before mutagenic treatment to study the effect of various mutagens viz., gamma rays, EMS and colchicine on various growth parameters, mitosis and fix LD50 dosage, Seedlings, callus and shoot tips of Coorg Honey Dew were also used to know their response and to find LD50 dosage. Germination and survival percent was the highest (85.16 and 80.16) in control and the lowest (22.00 and 12.99) in 20 kR respectively. A dosage of 30 kR and above were found to be lethal. Germination and survival percent was the higher in Sunrise solo (53.67 and 44.22) than in Coorg Honey Dew (45.33 and 36.11). LD50 dose for Germination percent and survival percent for pretreated seeds with gibberellic acid was 9.5 kR and 7 kR for Sunrise solo and 7.5 kR and 4.5 kR for Coorg Honey Dew respectively. For seeds without pretreatment the LD50 dose for Germination percent was 39 kR for Sunrise solo and 27 kR for Coorg Honey Dew. Gamma rays significantly influenced the seeding height both at and 30 days after Germination which decreased with increase in gamma rays dosage and was minimum (5.68 cm and 9.44 cm)with 20 kR maximum (7.15 cm and 11.93 cm) with control. Total chlorophyll content decreased with increase in gamma rays dosage and was the lowest (1.54 mg/g tissue) at 20 kR and the highest (2.15 mg/g tissue) with control. Both stomatal length and breadth increased with increased in concentration of EMS but decreased with increase in duration of treatment. The maximum stomatal length (15.55 μ and 13.61 μ) and breadth (7.86 μ and 7.86 μ) were observed at 0.3% EMS and 8h duration treatment respectively compared to control which recorded minimum stomatal length (10.41 μ) and breadth (5.75 μ). EMS treatment significantly reduced the plant height, plant spread, plant girth and intermodal length at the time of first flowering in Sunrise Solo variety. EMS treatment 0.3% recorded minimum plant spread at North-South (72.46 cm) and East-West (71.52 cm) direction, Plant girth (3.130 and intermodal length (3.59 cm) while control plants recorded maximum. Ovules excised 60 days after pollination continued growth on half strength MS media supplemented with 60 g sucrose, 400 mg glutamine and 20% coconut water which recorded the maximum ovule length (3.43 mm) and breadth (2.08 mm) after 60 days in culture compared to ovules excised 90 days after pollination which recorded maximum ovule length (2.77 mm) and breadth (1.85 mm). Sixty days upon culture, the highest percent of green and enlarged ovules (29.00) was also noticed from ovules excised of sixty days after pollination while it was lowest (10.5) from ovules excised 90 days after pollination. 86
URI: http://www.erepo.iihr.ernet.in/handle/123456789/378
University in which they received their degree: University of Agricultural Sciences, Bangalore
Degree Level: M.Sc

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