Influence of seed coat compactness around cotyledons, protein andmineral composition on mechanical strength of soybean[Glycine max (L.) Merrill] seed coat

The critical problem of soybean seed is susceptibility to mechanical processes due to structural limitations of seed and seed coat. The X-radiography of soybean seed revealed the orientation of seed coat around the cotyledons and cultivars like JS 335, JS 9752, JS 71-05, JS 95-60, MACS 124, Pusa 40, Punjab 1 and Type 49 had very compact seed coat around cotyledons. In NRC 12, NRC 37, RKS 18 and SL 525 where the gap between seed coat and cotyledons was significantly very high and non uniform making seed coat very much vulnerable to cracking. Seed coat minerals- calcium, silicon, zinc, iron and lignin content were found to vary significantly among cultivars. Significant genotypic variability for strength of seed coat was observed among the soybean cultivars. A very close relationship was found between strength of seed coat and seed coat compactness. Highly significant correlation was found between mechanical strength and seed coat lignin, iron and zinc content. Quantitative and qualitative variation for seed coat protein among soybean cultivars was revealed and higher protein content was found linked with mechanically strong seed coat. The result revealed that selection for these seed coat parameters in varietal improvement programme may be very fruitful for development of varieties having resistance to field weathering and mechanical damage.