Evaluation Of Seed Characteristics Of Pear And The Effects Of Harvesting And Storaging On Seed Development Of ‘Cuiguan’

Pear is widely cultivated in mainland China.Its planting area and yield accounted for more than 70% of the whole world.For a long time,pear industry has made an huge contribution to the growth of agricultural production,the income of farmers and the construction of new socialist countryside.Crossbreeding is the main source of new pear varieties.Seed quality is a prerequisite for new variety selection.In this study,the morphological and physiological indexes of 101 pear seeds of different varieties were measured;In our research,‘Cuiguan’ pear seeds were selected as materials which were collected from different fruit harvest time(106、112、135 days after flowering)and different storage time(15、30、60、150 d)in 4℃.The physiological indexes of the seeds were determined and the change rules were analyzed.The aim was to find out the period of the highest seed germination rate under different harvest periods and storage time of ‘Cuiguan’ pear.Therefore,it provides reliable basis for the improvement of breeding efficiency.The results are as follows.1.The statistical results of weight and diameters of 101 different pear cultivars showed that the diameters and diameters of different pear cultivars were significantly correlated(P<0.01).The mean weight and vertical diameter of P.sinkiangensis T.T.Yu seeds were higher than those of other cultivars.But there was no significant difference in the weight and diameters of pear seeds among different cultivars.The range of soluble sugar content in pear seeds was 2.87 mg/g,the average was 2.87 mg/g.The difference between P.ussuriensis Maxim and other cultivated species reached significant(P<0.05)level.P.bretschneideri Rehd.seeds have a higher soluble sugar content.The variation range of soluble protein content in pear seeds was 1.53～5.80 mg/g,the average was 3.57 mg/g.There were significant differences in soluble protein content between P.bretschneideri Rehd.and P.ussuriensis Maxim seeds.The mean soluble protein content of P.ussuriensis Maxim seeds was highest(5.04 mg/g),the mean soluble protein content of P.bretschneideri Rehd.seeds was lowest(3.40 mg/g).The range of starch content in pear seeds was 1.56～5.17mg/g,the average was 2.86 mg/g.There was no significant difference in seed starch content between different cultivars.The average content of starch in the seeds of P.pyrifolia was the highest(2.91 mg/g),The mean starch content of P.ussuriensis Maxim seeds was the lowest.2.The antioxidant enzyme activities of 101 different pear seeds were determined showed the range of SOD activity in pear seeds was 372.89～1036.36 U/g,the average was656.40 U/g.There was no significant difference in SOD activity among different cultivars.The average value of SOD activity in the seeds of P.bretschneideri Rehd.was the highest(687.51 U/g).The average value of SOD activity in the seeds of P.pyrifolia was the lowest(636.78 U/g).The range of POD activity in pear seeds was 203.67～1470 U/g,the average was 621.36 U/g.The mean POD activity of P.bretschneideri Rehd.seeds was the highest,the mean POD activity of P.ussuriensis Maxim seeds was the lowest.The range of CAT activity in pear seeds was 5.29～33.20 μmol/min/g,the average was 15.91 μmol/min/g.The CAT activity of P.sinkiangensis T.T.Yu seeds was the lowest.Correlation analysis was carried out on the physiological indexes of pear seeds,there was a significant(P<0.01)correlation between soluble sugar content and POD activity in seeds of different pear varieties,the content of soluble protein was significantly(P<0.05)correlated with SOD activity.3.With the prolongation of harvest time,the fresh and dry weight of seeds increased,the soluble sugar content decreased,the soluble protein content decreased at first and then increased later and the starch content increased.The activity of SOD decreased with the prolonging of harvest time,and the activity of POD increased gradually.There was no significant change in CAT activity between 106 days after flowering and 122 days after flowering.The CAT activity of seeds harvested on 135 days after flowering decreased significantly.The content of ABA and GA1 in seed kernel was firstly increased and then decreased,while the content of ABA and GA1 in seed coat was firstly decreased and then increased.The germination rate of the seeds collected on 135 days after flowering was higher than that 122 days after flowering.While On 135 days after flowering,the germination rate was zero.In conclusion,the prolongation of harvest period is beneficial to seed maturation and improve seedling rate.4.With the prolongation of storage time,The FW of seeds decreased.The soluble sugar content of seeds increased at first and then decreased during storage time,the maximum was 3.45 mg(30 days after storage).The starch content of seeds increased.The soluble protein content increased at first and then decreased,the maximum content was 5mg/g(30 days after storage),there was no significant change in soluble protein content between 60 days storage and 150 days storage.During storage time,SOD activity showed a decreasing trend within 60 days and increased slightly(60 days-150 days).The POD and CAT activity increased at first(30 days after storage),then decreased(30 days-60 days),and finally increased(60 days-150 days).After seed stratification,the germination rate of the seeds increased with the prolongation of storage time(before 60 days)and the highest germination rate was presented in 60 days(95%).However between 60 days and 150 days,there was a slight decrease.In conclusion,the Cuiguan pear stored for 4℃ and 60 days after harvesting were beneficial for promoting the process of seed embryo post-maturation,breaking seed dormancy and finally improved the seeding rate.