Explain polyploid breeding.

Explanation

(i) Majority of flowering plants are diploid (2n).
(ii) The plants which possess more than two sets of chromosome are called polyploids.
(iii) Polyploidy is a major force in the evolution of both wild and cultivated plants.
(iv) Polyploidy often exhibit increased hybrid vigour increased heterozygosity, increase the tolerance to both biotic and abiotic stresses, buffering of deleterious mutations.
(v) In addition, polyploidy often results in reduced fertility due to meiotic error allowing the production of seedless varieties.
(vi) When chromosome number is doubled by itself in the same plant, is called autopolyploidy.
Example: A triploid condition in sugarbeets, apples and pear has resulted in the increase in vigour and fruit size, large root size, large leaves, flower, more seeds and sugar content in them.
(vii) It also resulted in seedless tomato, apple, watermelon and orange.
(viii) Polyploidy can be induced by the use of colchicine to double the chromosome number.
(ix) Allopolyploids are produced by multiplication of chromosome sets that are initially derived from two different species.
Example: Triticale (Triticum durum x secale cereale) Raphanobrassica (Brassica oleraceae x Raphaims sativus).