Genetic Analysis Of Deep-seeding Associated Traits In Maize

The characteristics of deep-seeding tolerance in maize can promote drought seedling in arid and semi-arid area of China. In our country, the two thirds maize is distributed in arid and semiarid regions, which mainly depend on natural rainfall. Lack of surface soil moisture often lead s to hard top soil. no germinate or irregular, which seriously affects the yield. Deep-seeding can make full use of deep soil moisture, and protect germinate to increase the yield. Through traditional breeding methods, many maize hybrids which were suitable for arid and semiarid regions were breeded. However, the genetic mechanism of the resistance to deep-seeding is still unknown, which is limit to the wide application of germplasm. Related traits of deep-seeding resistance is the length of mesocotyl. It is the the determining factor of germinate withcoleoptile. Mesocotyl is the main factor. In this research, the deep-seeding tolerance inbred CGJ and the commom inbred Zheng58 were used as materials. The differences of phenotypic characteristics, endogenous auxin and cell morphological were compared, to reveal the characteristics of deep-seeding related traits under 2cm and 20 cm deep-seeding conditions. The population with parentals of CGJ and Zheng58 were constructed to map the main QTL of deep-seeding tolerance by genetic mapping. The aim is to clone the deep sowing related gene and breeding of new varieties. The main results were as follows:(1) In this study, the deep-seeding tolerance inbred CGJ and the control inbred Zheng58 were sowed with sowing depth of 2cm and 20 cm., Some characters were investigated, such as length, length of the embryos, roots length at two leaves stage, and scanned analysis of the roots, including roots length, roots projection area, roots diameter, root nodes and root tips number. CGJ and Zheng58 had the same rate of emergence 98% under 20cm; the emergence rate of CGJ was 80% and Zheng58 couldn’t emerge. The results showed that in normal seeding depth treatments, Zheng58 was better than CGJ in coleoptiles length, roots length, roots diameter, projected area, root tips number and nodes number.Under 20 cm treatment, the roots length, the coleoptiles length, the average diameter of the roots in Zheng58 showed nosignificantly change., the length of roots and the projected area of roots decreased slightly. In addition to the average diameter of CGJ, the other traits were higher than the normal treatment, especially the length of the CGJ mesocotyl was 2.5 times of Zheng58. In summary, the main characteristics of deep-seeding tolerance maize was the significant elongation of mesocotyl under 20 cm deep sowing processing.(2) The concents of IAA, GA, ETH were measured in leaves, coleoptiles, mesocotyls and roots of CGJ and Zheng58. The results showed that under normal sowing depth, there were no significant differences between zheng58 and CGJ of auxin; the auxin content in CGJ was higher than Zheng58 under 20 cm deep sowing processing. The IAA and GA had significant growth except IAA in the leaves and coleoptiles. the content of IAA in mesocotyls and GA in leaves showed highest increased. In summary, the main effect of mesocotyl elongation was IAA.(3) Cell morphological analysis were taken in mesocotyl of CGJ and Zheng58 by scanning and transmission electron microscopy. The results show that under normal sowing depth, there was no significant difference in the cells of mesocotyl in CGJ and zheng58. Under deep sowing processing, the longitudinal length of the unit area in C GJ was significantly longer than Zheng58. There was no significant difference in the number of cells. In summary, the significant elongation of mesocotyl in CGJ was derived from the longitudinal elongation of the cells in the deep sowing treatment.(4) Inbred lines Zheng58 and CGJ were used as the parents of population BC3F1, respectively. The 823 plants were sowed in 20 cm deep-seeding. The rates of emergence were statistics. The DNA of emerging plants were extracted. The genotype were detected with five markers from Maize GDB database and six new In Del markers. According to the genetic test results, The correlation analyses between the germination rate and the marker were calculated by SAS software The result showed that the correlation between the markers and the emergence rate and markers were different. ID128C3、phi053、ID129C3、umc1102、ID136C3、ID137C3、bnlg420 and ID170C3 were closely related to the emergence rate with values from0.863 to 0.978 The markers of.umc2263、umc1504 and ID211C3 were not correlated with the emergence rates. The results of the correlation analysis between the markers and the emergence rate were consistent with the location results.