Effects of CaCl₂ concentrations on the yield,  quality and physiological disorder of potato microtubers

This study determined the microtuber yield, quality, calcium content and physiological disorder of potato in response to the various concentrations of CaCl2. Potato was cultivated in the liquid MS medium with various concentrations of CaCl2. The MS medium with zero calcium reduces the number of microtubers, tuber weight and the percent of large tubers. With the calciumfree medium, no microtubers larger than 100 mg are found, their tuber skin is yellowish brown plaques, and some tubers exhibits water-soaked decay with decay rate being 2.21%. The dry weight, starch, soluble sugar and protein contents in the microtubers cultured in the calciumfree medium are decreased by 36.8%, 41.39%, 10.7% and 39.43%, respectively, while the malonaldehyde content is increased. After being stored for six months under 4 ℃, the tuber skin shows the sign of dehydration, with physiological disorder averaging 53.77%. When stored at room temperature for three weeks, the germination rate is only 25.53% with a slow growth. With the addition of calcium to the MS medium, the number of microtubers per stem and tuber weight are increased with the increase of calcium concentrations and then decreased at higher concentrations. The percent of large tubers and the tuber skin glossiness are increased with the increase of calcium concentrations. Compared to the microtubers grown in the standard MS medium, the dry matter of microtubers in the higher calcium medium is increased by 4.43%-8.62%, the starch content is increased by 6.79%-16.49%, the soluble sugar content is increased by 2.7%-47.9%, and protein concentration is increased by 4.63%-8.29%. Average tuber calcium content is increased significantly, reaching the range from 177 g/g to 267 g/g, and the tuber skin does not show the sign of decay. After being stored for six months under 4℃, the tuber skin is normal, and the physiological disorder rate is reduced to 1%-8.9% with the increase of calcium concentration, and the coefficient of determination is 0.3812. Calcium concentrations do not affect the germination ability and bud growth. We conclude that the addition of 9 mmol/L of CaCl2 in the MS medium is the best practice for the potato cultivar Xindaping to improve its yield and quality.