Early detection and characterization of dwarf off types in micropropagated banana [electronic resource].

Includes references.

The present work was carried out in Pomology Department and Biotechnology Laboratory, Crop Science Department, Alexandria University, during the period from 2000 to 2003. Early detection by gibbrellic acid (GA3) was used to assess the percentage of dwarf off¬ types of four banana cultivars namely, Maghrabi, Williams, Grand Nain and Valery after 25 subcultures. Simultaneously, selecting the dwarf variant (s) of the giant cultivar 'Maghrabi'. Four hundred plantlets at deflasking stage were sprayed with 0 or 300 !-1M ,-' GA3, and were incubated under controlled-temperature glasshouse for one month. Sheath-length of the first formed leaf after spaying was measured for each plantlet. The percentage of dwarf off-types were 18, 16, 10, 2 % for Williams, Maghrabi, Grand Nain and Valery, respectively. The dwarf off-types were characterized with short pseudostem height and petioles length, narrow distance among the petioles and leaf index (leaf length /width) was less 2 as a morphological marker associated with the dwarfism in banana as compared to normal plants. The dwarf off-types clones of the gaint cultivar . Maghrabi . were identified by RAPD markers. Seventy three amplification products were obtained, out of which 95 % showed polymorphism. Primer OPJ-04 detected the band (1500 bp) which was reported in previous study as DNA marker for dwarfism in banana. Primer OPC-15 revealed a band (936 bp) which present in normal plant only and may be linked to the dwarfism in this banana cultivar. Primer OPA-OS detected a band (1334 bp)which present in all dwarf off-types only, also, may be related to the dwarfism in banana. The bands, which produced by these primers. were used to construct a similarity matrix. The genetic similarity among these tested variants ranged from 0.09 to 0.50. These variants were classified to six clusters. The use of the dwarf specific RAPD marker at the in vitro stage could be particularly useful for in vitro selection in banana breeding programme and subsequently obtaining a new genotypes in Maghrabi cultivar.

Summary in Arabic.

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