ISSR profiling of Indian cultivars of mulberry (Morus spp.) and its relevance to breeding programs

Mulberry, Morus spp. has a wide range of use, the chief among them is to feed the silk producing caterpillar Bombyx mori L. (Bombycidae; Bombycoidea). As a homeland of mulberry, India has a number of indigenous mulberry species, of which a few are widely cultivated. In the present investigation genetic distance among such eleven mulberry cultivars originated from six different states of India covering a wide geographic area extending from 15degreesN to 32degreesN latitude and 72degreesE to 89degreesE longitude was studied using inter-simple sequence repeat primers. Out of the 20 primers tested, 13 primers, viz, nine di-nucleotide, three tri-nucleotide and one penta-nucleotide repeats, gave clear and reproducible band profiles. While the (AT)(n) rich primers could not amplify the DNA, the (GA)n, (AC)n and (AG)n rich primers gave excellent amplification profiles. The genetic distance among the cultivars varied from a minimum of 0.053, between Punjab local and Bombay local, to a maximum of 0.431, between Almora local and Sujanpur-5. Clustering of the cultivars according to nearest neighbor method created three groups. The north-Indian cultivars made a separate and distinct group while the cultivars originated from eastern and southern India occupied a distinct position. Almora local was found quite different from others. The first two canonical functions identified through discriminant function analysis accounted for 91.2% of the total variability. Distribution of cultivars belonging to six different zones on canonical matrix realized from Discriminant Function Analysis (DFA) revealed wider variability for West Bengal, Karnataka and Punjab which reaches the group centroids of Uttar Pradesh and Himachal Pradesh. This attests to the past contribution of West Bengal in east and Karnataka in south towards development of mulberry cultivars in different parts of India. Step-wise linear regression analysis, further, identified two markers (825.(1400) and 835.(750)) associated with leaf yield, which also satisfied the Beta estimation, thereby testifying strong association of these two markers with leaf yield. This finding along with the classification of the eleven cultivars bear strong relevance to mulberry breeding for different agro climatic areas.