Studies on the Compatibility and Heterosis of Different Indica-Japonica RILs Crosses of Rice
|School||Hunan Agricultural University|
|Course||Crop Genetics and Breeding|
|Keywords||Rice(Oryza sativa L) indica-japonica differation RILs Compatibility Heterosis of F1 hybrids|
The recombinant inbred lines （RILs） of different indica-japonica differentiation derived froman indica/japonica cross were studied for the relationship between the indica-japonica diversity andcompatibility, combining ability as well as heterosis through identifying characteristics ofdifferentiation, examining compatibility and heterosis of hybrid F1. The main results are as follows:1. There is difference in characteristics of indica-japonica identification by Cheng’s index orby resistance of seedlings to KClO3, and the resistance of seedlings to KClO3 was a little moreclosely in relation to cold tolerance than that of Cheng’s index although the classification of coldtolerance was the same. Analysis on the esterase of seedlings in different indica-japonica riceshowed seven isozyme bands, of which, the four of EST-2,4,5 and 6 appeared in all the materialswhile the EST-1, EST-3 and EST-7 appeared difference as parents or types, and the bands ofseedlings are much more clear and dense than that of the germinating seeds.2. The F1 characteristics of indica-japonica diversity of indica, quasi-indica and quasi-japonicaRILs crossing with indica, quasi-indica two-line steriles belong to indica and quasi-indica, most ofindica; while those with the typical indica-japonica varieties show the middle-parental valuesranged from 27.7% to 82.4% of the male and female parents, of which ones with indica femaleparent are indica type like female and with japonica are the middle-parental type. The Cheng’sindexes of indica×japonica F1 in typical indica-japonica inter-varietal crosses are indica-clinewithin 20.4%～51.9%, that of the reciprocal （japonica×indica） in 26.1%～53.1%; while indica×indica are ranged from 48.2% to 101.9% of the parental values and japonica×japonica are46.3%～53.3% as the middle-parental value.3. The percentages of classification for different indica-japonica F1, are 66.7% quasi-indica,22.2% indica and 11.1% quasi-japonica in the indica×japonica crosses, and japonica×indica as thesame besides more quasi-indica ratio, ratio of indica to japonica 1:1 in indica×quasi-japonicacrosses, while the ratio 3:1 in quasi-indica×quasi-japonica and 66.7% quasi-japonica, 33.3%quasi-indica in the japonica×quasi-indica crosses. The performing trend of F1 Cheng’s indexaffected by parents is indica type more than japonica type and female more than male, and thereason of those are more dominant components of indica than japonica in the indica-japonicaclassification traits such as the reaction to phenol of grains. The dominant trait of indica can bestexplain the difference why the results were different as the researchers studied materials.4. The F1 pollen fertility in crosses of RILs with indica testing varieties ranged from 68.5% to98.5%, and showed normal fertile spikelets, while F1 pollen fertility below 50% and very low spikelet fertility for crossing with japonica testing varieties, of which quasi-japonica type has bettercompatibility. The percentage of F1 pollen fertility was no relation to the parental relationship, andthe difference of reciprocal crosses was related to parent itself not to the indica-japonica type. Thespikelet fertility of typical indica-japonica crosses was obviously lower than the pollen fertility, andthe reciprocal in spikelet fertility （seed setting rate） of indica×japonica hybrids was no difference.5. The F1 pollen fertility of indica×japonica was changed by treating with short days, someincreased, the others decreased and the spikelet fertility was increased. F1 pollen fertility of thosewith wide-compatible parent decreased greatly from normal fertility to half fertility by treatment,but the spikelet fertility has little changed near to normal fertility. It is hardly to say that thewide-compatible genes are the specific genes controlling the wide-compatible character, whichobtained in the past and may be some genes related to environments and the formation as well asthe development of the gametes.6. The type quasi-indica or quasi-japonica is the best in general combining ability （gca） ofdifferent differentiation RILs. It should be chosen the better comprehensive gca for female sterilelines, which a little easily obtain from the quasi-japonica type derived from indica-japonica crosses,and selected the better gca of grain characters such as filled grains per panicle, density of spikeletsand grain weight per panicle for male parent and pay attention to the glume color better toquasi-indica type; but the lower gca of heading days and panicle length for both of parents.7. The F1 heterosis of yield per plant for two-line sterile lines×RILs crosses showed themean of 31.95% positive over male parent and the number of positive combinations was 93.3% ofthe total. The F1 heterosis of main characters over male parent from high to low were the filledgrains per panicle （33.35%）, followed by spikelets per panicle （29.13%）, density of spikelets（21.95%）, plant height （20.00%）, heading days （13.98%）, panicle length （6.86%）, 1000-grainweight （4.30%）, seed setting rate （4.12%） and panicles per plant （-4.60%）.8. According to the relationship between grain yield per plant and the main characters, theyield of F1 hybrids was determined by the yield components of panicles per plant, filled grains perpanicle, seed setting rate and 1000-grain weight, which are related to the F1 plant height. As theplant height increased the spikelets per plant increased and the panicles per plant decreased, whilethe panicles per plant is the most important component of the yield. The optimal heterosis ofpanicles per plant is a prerequisite for obtaining higher spikelet heterosis, however, spikelets perplant was highly negatively significant correlated to seed setting rate. It is necessary for adjustingthe characters of plant height, panicles per plant and spikelets per plant （especially the filled grainsper panicle） to the best degree of advantage.9. For obtaining high yield per plant of F1 hybrids and its heterosis, the male parent should behad the characters of suitable heading days, dwarf plant height, middle panicle length and high yieldper plant. For obtaining large filled grains per panicle the male parent should be selected with thecharacters of high spikelets per panicle, high filled grains per panicle but panicles per plant and 1000-grain weight lower, while for high 1000-grain weight （grain plumpness） of F1 hybrid the maleparent should be had suitable spikelets per panicle and high panicle per plant. For using the strongheterosis of indica-japonica F1 hybrids without too long maturity, too long heading days and lowseed setting rate, the principle is the panicle length at the middle type and the grain plumpness at thehigh level.10. The heterosis of F1 hybrids was increased as the japonica degree increased of female parentand increased in indica degree of male parent. The F1 heterosis of yield per plant will decrease asthe mean of japonica degree increased in parents and the indica-japonica difference of the parents.The heterosis of 1000-grain weight and seed setting rate was increased as the F1 japonica degreeincreased. For obtaining the highest heterosis of indica-japonica hybrids, the pattern of combinationshould be adopt as the japonica female and indica male, which are selecting the differentindica-japonica sterile lines of indica-compatible japonica line with japonica cytoplasm, and thebetter male indica parents. This strategy of selecting interspecific crosses combines both theapproach of indica-compatible japonica lines by Zhang guiquan and the suitable difference ofparental indica-japonica degree by Yang zhenyu, so that get the great high yield of the hybrids.