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20241
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Subject: Vegetable Science × Author: Nidhi × End date: 2024 × Thesis Type: Ph.D ×
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    Development of monoecious lines in muskmelon (Cucumis melo L.) through marker assisted selection
    (Punjab Agricultural University, 2024) Nidhi; Sharma, Sat Pal
    In heterosis breeding, monoecious sex expression offers significant advantages over andromonoecy in muskmelon, as it eliminates emasculation and produces fruits with desirable traits, such as earliness, high TSS, thick flesh, small scar size, and large fruit size. Thus, development of stable monoecious lines possessing desirable horticultural traits is critical for hybrid breeding in this crop. This investigation was aimed to identify molecular markers linked to monoecious trait and to transfer this trait to a popular melon cultivar through marker assisted selection. For this purpose, stability of monoecism was assessed under varying environments and identified 18 stable monoecious using the andromonoecious index. A set of identified lines was used to develop KASP markers for the sex-determining gene, CmACS-7, which revealed two mutations in exons 1 and 2, with one SNP at 170th, followed by insertion of ‘GA’ at 222nd nucleotide position. Upon validation, KASP-CT-2 accurately separated homozygous andromonoecious and monoecious parents and was also successfully validated on F2 population segregating for monoecious trait. Subsequently, marker-assisted backcross breeding was carried out to transfer the dominant gene 'A' controlling the monoecious trait into the Punjab Sunheri, a popular muskmelon cultivar. Heterozygous plants in BC1F1 and BC2F1 and homozygous plants in BC2F2 with high recurrent parent genome recovery and monoecious trait were advanced using the cleaved amplified polymorphic sequence (CAPS) marker. In the BC2F2 population, homozygous monoecious plants were identified using the CAPS marker. These plants were self pollinated to generate a BC2F3 progenies, of which 11 out of 13 lines had phenotypic similarities with the recurrent parents. These 11 lines were self pollinated to generate 34 BC2F4 progenies. Eight BC2F4 lines, viz. Mono-6R2, Mono-IOB1, Mono-2OB3, Mono-7R3, Mono-2OV2, Mono-1OB2 were selected based on TSS, TSS/TA ratio, β-carotene, low titratable acidity, pH, flesh thickness, fruit shape index, and yield. The information and developed associated molecular marker will be useful in developing new stable monoecious lines. Furthermore, the generated monoecious lines can potentially be utilized as a female parent for F1 hybrid development in muskmelon.