Study On The Heterotic Groups Of Maize Inbred Lines Used In Sichuan With SSR Markers

The materials used in this study were 33 maize inbred lines utilized in Sichuan since the 1980's, of which the genetic diversities and heterotic groups were studied by SSR molecular markers. The research discussed the choice of primers and analysised heterotic patterns of the populized maize hybrids between 1990 and 2002 and their parents' genetic distance. The main results of the present study were summarized as follows:1. Simple sequence repeats (SSRs) were used to detect genetic diversities among 33 maize inbred lines. Seventy-two SSR primers produced 289 polymorphic amplified fragments. The average number of alleles per SSR locus was 4.1, ranging from 2 to 7. Genetic similarities among the 33 inbred lines ranged from 0.5866 to 0.9247 with an average of 0.7056. So the genetic diversities of the studied materials were in abundance.2. Thirty-three inbred lines were classified into four groups, of which the first group were divided into six sub-groups by UPGMA(Unweighted Pair Group Method Agrithmetic Average) based on SSR markers: the first sub-group of the first group including S37, 75-1, 48-2A, 48-2, R08; the second sub-group of the first group including 7922, 32, 478, 5003, NY75, 238; the third sub-group of the first group including 698-3, R15, Mol7, 7327; the forth sub-group of the first group including 273, 81565, 0951, S28; the fifth sub-group of the first group including ES40, Huangzaosi, R18white, 77; the sixth sub-group of the first group including R09, Cheng687, Qi205, 200B, Zi330; the second group including Yu612, Yu5, the third group including Dan340; the fourth group including Nan21-3, 286-4. The clustering result was consistent with the grouping based on the available pedigree. Average genetic similarities among groups were smaller than that within group. Most of the parents of populized maize hybrids came from different groups or sub-groups. So SSR markers could be applied to classification.3. The study selected 14 primers based on PIC value and prime's location in chromosome, which could amplified the stabilized band and had the high PIC value. The primers, including umc1136, phi015, phi072, phi96100, phi083, phi078, bnlg391, phi109275,phi328175, umc!545, phi453121, phi063, phi032, umcll53, could be used as core-primes to screen and identify the samples of accession preliminarily. My study proved that it needed at least 44 primers to get a relativly good result.4. The parents of populized maize hybrids had the big genetic distance, but the hybrid combinations whose parents had the big genetic distance didn't get high yield .The parents' genetic distance of some populized hybrid such as XiyuNo.3, Qisan simple cross, Chuandanl8, Chuandanl3, Chuandanl6, Yandan14 were smaller than the average genetic distance. Because the relativity between the heterosis and genetic distance was not distinct, SSR marker couldn't predict heterosis at present.5. The heterotic patterns utilized in Sichuan presently were sub-group of Mo 17 sub-group of Zi330, group of Reid xgroup of Tangsipingtou, group of Reidx sub-group of Zi330, group of tropic germplasmxgroup of Reid, group of Tangsipingtouxsub-group of Zi330 and so on. The germplasm bases of hybrids grown on more than that in 1980's.