The Heterosis Performance And Potential Utilization Of P Germplasm In Temperate Maize Breeding

The main agronomic traits and photoperiod sensitivity of 9 P germplasm inbred lines of maize were systematically studied. Hybrids of P line x temperate line(9×8), and PX tropical population (9×5) were used to study the genetic relationships and the heterosis performance. The photoperiod sensitivity of hybrids of P germplasm inbreds × tropic-subtropical populations was also studied in this paper. The results were as follows:1. The speciality of P gemplasm lines were: (1) the seedling leaf and sheath color of were distinct from that of Chinese elite temperate lines; (2)the plant type was normally half-copact; (3)the growth days were longer than that of Chinese elite temperate lines; (4)the grain yield was comparatively low with bad kernel setting in ears; (5) they were stronger in biological and abiological stress and higher in 100-kernel weight and kernel bulk weight.Their photoperiod sensitivity was mainly reflected in some traits related with vegetative growth such as plant and ear height, the number of tassel branch, but not in traits related with reproductive growth. There still expressed strong photoperiod sensitivity in some P group inbreds such as Shen 137, Qi 319 and 1127.2. NC II design was used to make 72 hybrids between 9 P gemplasm lines and 8 lines from Chinese 4 major groups. And strong heterosis was found in F1 yield, which suggested P group was a relatively special group. The main heterosis patterns were P×Reid, P×Ludahonggu, P×Tangsipingtou and P×Lancaster.3. Strong heterosis was found in the hybrids of P lines×Pop49(Tuxpeno-based) ,Pop 32(ETO-based), P 3 and Pool34, but not in the hybrids of P lines× Suwan population, which implied kindredship between the two kinds of germplasm.4.In contrast to tropic-subtropical population parent, the hybrids of P × tropic-subtropical population showed insensitivity to photoperiod in many traits and enhanced adaptability in temperate region and lodge-resistance. Hun008, X178 and 1145 within P group showed better ability to improve photoperiod sensitivity of tropic-subtropical population and lodge-resistance.5. It was found that the values of RDs under long day was in direct proportion to the proportion of tropical germplasm. RDs was a simple quantitative genetic trait, the gene effect of which was additive. The gene number of RDs was dependent on the proportion of tropical germplasm.