Studies On The Inheritance Of Important Agronomic Traits In Pear (Pyrus)

The pear was a perennial fruit tree and its juvenile phase was long. Because of typical cross pollination, the varieties were high heterozygote at the present. Most of the characters were controlled by multigene. So it was very difficult to study the genetic development of pear traits. Predecessors had been carried out in some studies, but were not systematic. In this study, the hybrid progenies of the resources nursery in pear engineering research centre of nanjing agriculture university and the reciprocal cross seedlings of'Jingbaili'(Pyrus sinkiangensis cv. Jingbaili) and'Yali'(Pyrus bretschneideri cv. Yali) in changli institute of pomology of hebei academy of agricultural sciences were used as the materials. The genetic tendency of the important agronomic characters in the hybrid progenies of pear was studied systematically. The results were as follows:1.492 seedlings from 8 crosses of pear were used to investigate the juvenile span,first flower node number internode length and the trunk diameter. In order to provide reference for breeding work of pear, the relationship between juvenile phase and juvenile span was discussed. The results showed that the juvenile phase of 68.7% seedling progenies was 3 to 5 years at the materials, and the value of juvenile span was 214.26 centimeters. There was a positive correlation between internode length and juvenile span. The juvenile span was remarked significant positive to the first flower node number and the trunk diameter. The results also indicated that the juvenile phase was remarked significant positive to the juvenile span, and the plants of dwarfing had the potential of early bearing.2. Using the seedlings of six cross combinations and its parents as the test material, florescence inheritance was researched, and promoting flower formation was researched with the seedlings of another cross combination. The results showed that the florescence of hybrid progenies was generally shorter than its parents, especially the time from flower bud germinating to early florescence. The flowering stage was as early as the flower bud germination. Both spraying PP333 and bending branch could promote the flower formatting of the seedlings.3.'Jingbai','Yali'pear and their 400 reciprocal cross seedlings were used on studying genetic tendency of internode length. Results showed that internode length was the character controlled by multigene and tended to be longer obviously. Normal distribution was observed on internode length in filial generation, and the average transmitting ability was found to be 115.695%, in which the additive effect played the leading role. Significant heterosis in filial generation was reflected by their higher value of internode length than that of parents, with the average rate as 91.75%. There was a positive correlation among reciprocal cross seedlings (r2=0.988**, P<0.01).4.'Jingbai','Yali'pear and their reciprocal cross seedlings were used on studying genetic tendency of fruit characters. The results showed that, most of the cross fruit characters were controlled by multigene. Fruit size tended to be smaller, with the average transmitting ability as 77.14%, and average coefficient of variation as 38.26%. Normal distribution was observed on length of fruit stalk and fruit index in filial generation, and the average values were found to be lower than average value of the parents. Upturn of soluble solids content and soluble sugar content were obtained together in the hybrid fruits,97.25% and 35.28% higher than average value of the high parent respectively. Hardness and titratable acid also tended to be higher than parents, with the average transmitting ability and coefficient of variation as 123.81% and 51.1% respectively. While the Vc content showed different genetic trend between these two types of hybrids. Content of stone cells was significant higher in cross generation, and the value of average transmitting ability was up to 182.62%.