Study On Combining Ability And Heterosis Of Main Agronomic Traits In F₁ Between Upland Rice And Lowland Rice Sterile Lines

This research was divided into three parts which included three-line method, two-line method ,and paddy-upland rice crossing method to study the utilization of upland rice heterosis. Eleven characters correlated to drought tolerance and yield components were investigated by exceeding parent heterosis index and competitive heterosis . The GCA of parents and SCA of combinations were investigated as well. The rules of parents mating were also explored . The main results were summarized as follows :1. Three-line MethodFourty-four cross combinations were obtained by crossing four cytoplasmic male sterile rice line (CMS ) were with 11 upland rice varieties as male parents acorrding to NC II design . The heterosis of 11 characters of Fl hybrids were investigated by exceeding male parent heterosis index (EMHI) and competitive . The results indicated that GCA(general combining ability) play an important role in drought tolerance correlated characters and yield characters.One elite combination was obtained , it is Zhenshan97A/IRAT109.2. Two-line MethodOne hundred and twenty cross combinations were obtained by crossing 8 photo-thermo sensitive genie male sterile lines (PGMR) and with 13 upland rice varieties and two paddy rice (as check) acorrding to NC design . Eleven characters of Fl hybrids were investigated .The results indicated that F1 hybrids were shown exceeding male parent heterosis on drought tolerance correlated characters ,but when it comes to yield characters , the Fl hybrids crossing by upland rice with indica PGMR were not shown heterosis , but those crossing by upland rice with japonica one were shown exceeding male parent heterosis and competitive heterosis .The analysis combining ability indicated that GCA of drought tolerance wre high on most upland rice varieties ,but the one of yield characters were low on a few male parents. The GCA of yiele characters on indica PGMS were lower than that on japonica ones. And GCA of the parents have no specific rule with SCA of the cross combinations . Some elite cross combinations were obtained , such as 612S/Handao502, N422S/Handao616 , 42S/1RPAR9, N422S/IRAT109, 372S/Haogelao> 582S/IRPAR9.3. Paddy-unpland rice Crossing MethodThe Fl hybrids by paddy rice and upland rice crossing have more stronger exceeding upland rice parent heterosis on drought tolerance and biological yield ,but most hybrid combinations have very low seed setting ratio and few panicle number per plant .And the exceeding parent heterosis and competitive heterosis were not shown on the characters correlated to yield components. Some elite combinations were obtained such as Handao 277/1004 .4. The results indicated that two-line method on the utilization of upland rice heterosis is an promising approach at present .The parents should be selected according to the rule that the parents have high GCA on drought tolerance and yield characters . On the other hand , GCA of the cross combinations and genetic divergence between the parents are should be appropriate.