Studies On The Minituber Seed Vigor And Regulation Mechanism In Potato

The vigor of potato minitubers plays a very important role in seed tuber production. Although the factors of determining and affecting the vigor are complex,the main factors should be seeked out so as to find out the methods for detecting and increasing it.Up to now,the reports on minituber vigor and its mechanism as well as the methods for increasing it are very poor.In order to find out the available methods for determining and increasing the vigor,the systematic researches were carried out.Because the minituber vigor determination and increasing are a very urgent need resolving problem,the study results have important theoretical and practical significance.In the studies,the potato minitubers with different weight from different varieties were taken as the testing material to study effects of minituber vigor under different storage conditions,temperature,periods and also the effects of different chemical treatments.Also,the mechanism between endohormones,such as GA₃,IAA,ABA,and minituber vigor changes under different storage conditions were also studied.The main results were as follows:1.Effects of varying storage periods and different varieties on minituber vigor had extremely significant difference.The minituber vigor of 'Atlantic' and 'Shepody' after 91 days storage was lower because of just breaking its dormancy,and then,the vigor increased with the lengthening storage time,and the highest vigor was found after 183 day's storage.Then the vigor decreased.The vigor index of 'Atlantic' minituber stored for 183 days was 0.0633,69.67%higher than those stored for 91 days and 71.3%higher than those stored for 275 days.The vigor index of 'Shepody' minitubers was 0.0345, 60.87%and 52.44%higher than those stored for 91 and 275 days respectively.It was indicated that suitable storage time for minitubers should be 183 days.It was the best time to get best yield in the fields.If longer or shorter,it would reduce minituber vigor.2.The minituber vigor of 'Atlantic' and 'Shepody' changed greatly after stored under different storage conditions.The index of vigor under cold storage was highest among them.The vigor of 'Atlantic' was 0.0949,20.44%and 33.51%higher than those under cellar and room storage respectively and that of 'Shepody' was 0.0784,20.28%and 35.46%higher than those under cellar and room storage respectively.It showed that the advantage order for storage conditions was cold＞cellar＞room.Therefore,the cold storage is the most suitable condition for potato minitubers.3.The effect of minituber weight on the vigor was very significant.The vigor index rised with the weight increasing,ie.the higher the weight,the stronger the vigor.It was indicated that the differences of vigor index among different weight reached extreme significant level.The minituber vigor of 'Atlantic' with 7-8g weight was 0.0436,and 0.91%,26.54%,40.28%,42.05%,69.72%,74.16%and 76.71%higher than that of the minitubers with 6-7g,5-6g,4-5g,3-4g,2-3g,1-2g,and≤1g respectively;In'Shepody',it was 0.0383 in 7-8g weight minitubers,and it was 10.83%,38.79%,40.41%,48.8%, 55.44%,72.43%and 76.76%higher than the same weight minitubers in "Atlantic" respectively.Therefore,when purchasing or planting minitubers,if it is possible the bigger ones should be selected in order to gain high yield.4.The vigor differences of minitubers among different varieties were great.Dry sprout weight and yield were closely related with vigor,so that it affected vigor very much.The minituber vigor of Longshu No.3 was 0.0531,it was 4.9%,15.82%,41.05% and 69.49%higher than that of Xingdaping,Atlantic,Favorite and Shepody respectively.5.Seed soaking treatment with different chemicals for 2 hours could improve minituber sprouting,and increase its length,but it was weaker,and could restrain sprouting after 12 hours.PEG,riboflavin treatment could not only improve minituber vigor,but also promote sprouting,emergence and young seedling growth.Soak treatments with PEG2000 in high concentration,riboflavin in low concentration and PEG8000 in low concentration could promote sprouting and emergence,the rate of promotion was 73.03%,68.44%and 58.89%respectively;Soak treatments with GA₃ in medium concentration,PEG8000 in low concentration,NaCl in low concentration or PEG8000 in medium concentration could improve minitubers vigor greatly,which was 112.73%,100%,76.36%and 72.73%higher than that of control.6.Under different storage conditions the content of endohormone and vigor of minitubers with different weight and varieties varied remarkably.The GA₃ content of minitubers was 97.97%higher than IAA,86.73%higher than ABA,but IAA content was only 3.8%higher than ABA.The results showed that the content of GA₃ was much higher than that of IAA or ABA but IAA content was almost the same as ABA content. Under cold,cellar and room storage conditions,GA₃ content of the two varieties all were much higher than IAA,ABA content,and ABA was much higher than IAA;The vigor index of the two varieties was highest under cold storage condition,medium under cellar condition and low under room condition.Aslo it could be seen that the proportion of GA₃, IAA and ABA was almost unchanged in different varieties and under different storage condition,but in the same endohormone,the content and the changing trend of minituber seed vigor were not alike.