Mutations Somatic mutations

Asexual propagation enables the preservation of accumulated mutations (macro and micro), which would normally be eliminated during sexual propogation. In many fruit crops, bud mutations and chimeras occur rather frequently and can provide an additional source of variability for selection. However, such reported instances are relatively few in mango. Roy and Visweswariya (1951) observed mutants of 'Puthi' in which the number of palisade cell layers differed from the original cultivar. Naik (1948) observed significant variation among trees of the same clone with respect to fruit shape, size, colour and quality, which was ascribed to bud mutations. 'Davis Haden', a sport of 'Haden', is larger than 'Haden' and its season of maturity is about a month earlier (Young and Ledin, 1954). 'Rosica' from Peru, is a bud mutant of 'Rosado de lca'. Unlike its parent, 'Rosica' is high yielding and regular bearing, and does not produce seedless fruits (Medina, 1977).

Oppenheimer (1956), after a survey of many orchards in India, reported wide variability in the performance of trees of the same clone within a single orchard. Mukherjee et al. (1983) conducted a survey of mangoes in eastern India and identified some superior clones. Singh and Chadha (1981), in a study of orchards of 'Dashehari', located four clones which were superior in performance. Singh et al. (1985) isolated two high-yielding clones from orchards of 'Langra'. Within 'Kensington', strains have also been identified that show improved resistance to bacterial black spot (Whiley et al., 1993).

Roy (1950) observed a mutant of 'Alphonso' with respect to fruit shape, and suspected it to be a mericlinal chimera. Pandey (1998) has described seven clones of 'Alphonso': 'Alphonso Behat' and 'Alphonso Bihar' from Bihar, 'Alphonso Batli', 'Alphonso Black' and 'Alphonso Bombay' from Maharashtra, 'Alphonso Punjab' from Punjab and 'Alphonso White' or 'Bili Ishada' from the North Canara district of Karnataka. Rajput et al. (1996) assembled several 'Dashehari' variants and after 14 years of observation, reported that the clone 'Dashehari 51' was superior with respect to yield and regular bearing. Other somatic mutants include: 'Cardozo Mankurad' with large fruits of attractive colour and high yields from 'Mankurad' of Goa; dwarf selections from the 'Rumani' and 'Bangalora' (Ramaswamy, 1989); development of 'Paiyur', a dwarf selection from 'Neelum' (Vijaya Kumar et al., 1991); 'Rati Bangana-palli' and 'Nuzuvid' from 'Banganapalli' (Anonymous, 1999); and 'MA-1', regular bearing and high yielding with resistance to 'spongy tissue' from 'Alphonso' (Mukunda, 2003).

In Thailand, Chaikiattiyos et al. (2000) selected clone 'SKoo7' (now known as 'Kaew Sisaket') from 320 'Kaew' plants; 'SKoo7' has higher yield and superior quality. Jintanawongse et al. (1999) also made superior selections for yield and fruit quality from 'Nam Dok Mai', 'Khiew Sawoey', 'Rad' and 'Nang Klang Wau' and DNA fingerprints of all these clones were made for comparison with the parental clone.

For these studies, it is important to conduct a replicated cultivar evaluation trial against standard commercial cultivars to establish that these variations are stable and not due to environmental responses. The use of genetic markers should be explored to confirm that the new clones are genetically distinct from the original cultivar.

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