Tetraploid soybeans

Abstract

• 1. Polyploidy could be induced in four varieties of soybean, both by soaking the seeds in colchicine solution and by treating the apical bud of the germinating seedling through a cotton-wad, the latter being a more successful method. Even though several doses and replicates were tried, the number of polyploids obtained were few and out of four varieties with tetraploid sectors only in the progenies of two of them tetraploid plants were recovered.

• 2. Imbibation of water is hampered in the tetraploid seeds; this reduces the germination percentage and delays germination.

• 3. The changed growth and development due to tetraploidy is affected by varietal and climatic difference but in no case they are shorter than those of the diploids and flowering is always delayed and prolonged. The number of branches is, however, reduced. Enlargement of parts is observed in stem, leaves, all floral parts, fruits, and seeds. There was reduction in fruit number and number of seeds per fruit. The thickness and colour of leaves were practically unaffected.

• 4. The frequency of different chromosome configurations was found to be IV-9.9, III-1.85, II-14.9 and I-5.2 per cell. The maximum number of quadrivalents in a PMC was 17. In two thirds of the cells examined, the chromosome distribution was 40-40. No supernumerary-spored quartet was seen.

• 5. Only 1–3 per cent. of the progeny were abnormal looking, but none could be confirmed as aneuploid.