| Potato(Solanum tuberosum L.)was the fourth largest food crop in the world.In view of the research gap in the starch accumulation rule of potato planted in winter,using three varieties of potato with different starch content(’Guinongshu 1’,’Longshu 7’ and ’Longshu 12’)as testing materials,the study was carried out in the growth above and below ground,the starch content of tubers,the cell density and the distribution of various types of starch granules of tubers,yield,quality,and activity of key enzymes for starch synthesis of three potato varieties planted in winter and the effection of light,temperature,water and other environmental conditions on tuber starch acculation.The order was to explore the starch accumulation rule of tubers,provide a theoretical basis for the high-yield,high-quality and efficient cultivation of potato planted in winter and further breeding of high starch potato varieties.The main results are as follows:1.Under the winter conditions in Guangxi,’Guinongshu 1’ showed early maturity,high yield,moderate growth potential,high protein content and low content of total starch,amylose and amylopectin.’Longshu 12’ showed Medium-ripening,mediocre growth potential and the highest content of total starch,amylose and amylopectin.’Longshu 7’ showed late maturity,high yield,strong growth potential,medium content of total starch and amylose and high amylopectin content.The content of total starch and amylopectin of tubers of the three varieties showed a gradual increase with the development of tubers.2.With the development of tubers,the cell density of the inner and outer medulla and cortex of ’Guinongshu 1’ and the inner and outer medulla of’Longshu 7’ showed a single-peak change trend with a gradual increase and then decrease,it reached the maximum at 70 days after emergence.The cell density of the inner and outer pith and cortex of ’Longshu 12’ and the cortex of ’Longshu7’ showed a decreasing trend with reaching the maximum value in 35 days after emergence.The cell density in the inner medulla of ’Guinongshu 1’ and’Longshu 12’ was basically the largest,followed by the cortex and the outer medulla was the lowest.The cell density in the inner medulla of ’Longshu 7’ was basically the largest,followed by the outer medull and the cortex was the lowest.In the middle and late stages of tuber development and harvest period,the cell density in the three parts of tubers was the largest in ’Guinongshu 1’,followed by’Longshu 12’ and the lowest was ’Longshu 7’.3.With the development of tubers,the density of total starch granule and the small starch granule in the inner and outer medulla and cortex of’Guinongshu 1’,the outer medulla of ’Longshu 7’ and the cortex of ’Longshu 12’showed a single-peak change trend with a gradual increase and then decrease after the increase,it reached the maximum value 70 days after emergence.The density of the total and small starch granule in the inner medulla and cortex of’Longshu 7’ and in the inner and outer medulla of ’Longshu 12’ showed a decreasing trend with reaching the maximum value in 35 days after emergence.The density of medium and large starch granules in the inner and outer medulla and cortex of ’Guinongshu 1’,’Longshu 7’ and ’Longshu 12’ showed a gradual increasing trend and reached the maximum value in harvest period.In harvest period,the density of total and small starch granule in the inner and outer tubers and cortex of tubers of ’Guinongshu 1’ was basically the largest,followed by’Longshu 7’,and ’Longshu 12’ was the lowest.The density of middle starch granules of ’Longshu 12’ was the largest.The density of large starch granules of’Longshu 7’ was the largest.The three potato varieties were mainly accumulating small starch granules during the entire growth period,accounting for54.0 %-92 % of the total starch granules;followed by medium starch granules,accounting for about 2.9 %-36.0 % of the total starch granules;the minimum was the large starch granules,account for about 0.0 %-13.3 % of the total starch granules.High starch varieties accumulate more medium and large starch granules and were mainly distributed in cortical cells and near the vascular bundle,followed by the inner medulla cells.4.With the development of tubers,the pyrophosphorylase(SBE),soluble starch synthase(SSS)and granular coagulated starch synthase(GBSS)of’Guinongshu 1’,’Longshu 7’ and ’Longshu 12’ showed a single-peak change trend with a gradual increase and then decrease,while the starch branching enzyme(SBE)showed a increasing trend and reaching to the maximum and then stabled at a certain level.The four starch synthetases of ’Longshu 12’ were the strongest,followed by that of ’Longshu 7’ and the ’Guinongshu 1’ was the weakest.5.The content of total starch and amylopectin of ’Guinongshu 1’,’Longshu7’ and ’Longshu 12’ was mainly regulated by he pyrophosphorylase,while the amylose content was mainly regulated by the soluble starch synthase,the granular coagulated starch synthase and the pyrophosphorylase.6.Under winter conditions,the increase of light intensity,temperature difference between day and night,ground temperature and soil water content(26.7-49.9 %)could significantly promote the growth and development,the synthesis of medium and large starch granules,the accumulation of total starch and amylopectin,tereby improving starch content,yield and quality of potato.The research results provided theoretical guidance for the production of high-quality potato products planted in winter,maked up for the shortcomings of the traditional theory of lack of starch accumulation of potato planted in winter,and laied a good foundation for the promotion of potato staple food production strategy in our country’s winter seed regions. |
