Morphological characterization and nutritional bioassay of different mulberry (Morus alba L.) varieties with silkworm (Bombyx mori L.)

Five varieties of mulberry were used to determine the (1) morphological characters, (2) protein, starch, fiber and moisture content of the leaves, (3) effect of flood value of these lines of mulberry on the performance of silkworm and quality of silk produced, and (4) correlation of the biochemical composition of mulberry leaves and the performance of silkworm fed with these leaves. The different varieties vary in their morphological characters. Alfonso and S13 had elliptic base shape, Batac and S54 had cordate and Kanva-2 had ovate leaf shape. Except for S13 which had serrate leaf margin and purple color of the young leaves; all the varieties had create leaf margin and green young shoots. S34 had drooping branching nature, Batac had semi-erect, and Alfonso, S13 and Kanva2 had erect nature of branching. Leaf yield ranged from 262.83-416.64 g/plant, with Batac having the lowest leaf yield and S54 having the highest yield. Plants varied significantly in their biochemical composition with position and variety. Top leaves had significantly higher protein, starch and moisture than the bottom leaves. Leaves of Alfonso had significantly the highest protein and moisture while Batac had the lowest. Food utilization, cocoon quality and length of filament were better in bivoltine silkworms than the multivoltine silkworm. Raw silk percentage, denier size and reel ability, however, were similar in both silkworm strains. Pearson correlation analysis indicates that protein and moisture content of the leaves were positively correlated to the weight of food ingested, efficiency conversion of digested and ingested food, approximate digestibility, survival rate, weight of mature larvae and cocoon shell percentage but negatively correlated to the consumption index. This indicates that as the protein and moisture contents of the leaves become higher, the more efficient were the leaves converted into body substance. Apparently, high degree of utilization and better cocoon and silk quality were caused by high protein and moisture but low fiber and starch contents in mulberry leaves. Under the prevailing conditions of DMMMSU, bivoltine silkworm outperformed the multivoltine silkworms in terms of survival rate, weight of mature larvae, leaf cocoon ratio, effective rearing rate, efficiency in converting food into body substance and length of filament. Likewise, Alfonso variety proved to be the best for silkworms both in bivoltine and multivoltine strains. Based on the foregoing results, Alfonso variety is recommended for silkworms feeding in both bivoltine and multivoltine silkworms. However, bivoltine is preferred over multivoltine for better cocoon and silk productivity.