Retrospect Polyploidization And Domestication Events Of Avena Species By Sequence Of Cly1-like

The barley cleistogamy gene Cly1,a member of AP2 gene family,controllsthe cleistogamy character in barleyand plays an important role in cultivated history of barley.In this study,we have obtained theorthologs of Cly1（Cly1-like）of oat and its wild relatives by homology-based cloning.The results showed that one of the orthologs is a mutant.Aco-dominance markernamed CLY1,was developed based on theexon sequences of the mutant type of Cly1-like gene.and then was usedto investigate the distributionof the mutant among 386 accessions representing 27 Avena species,including 111 A and C genome diploids,49 CmCm,AB and AC（CD）genome tetraploids,38 wild hexaploids,and 244 cultivated hexaploids（74 covered oats and 170naked oats）.In addition,one F2 population（306 individuals）and one RIL population（284 individuals）（the parents of both populations differ obviously in the spike characters）were used to investigate the separation ratio of the mutant type of Cly1-like gene.The main results are summariedas follows:1.The unnormalseparation ratio and the correlation coefficient with cultivated characters in both F₂ and F₈suggested that the mutant Cly1-like gene is closely related to many cultivated genes and it’s allele frequencyhas negative selected under natural conditions;2.After analyzing the distribution of mutant type Cly1-like gene in different Avena species,we have discovered that only four materials,excluding cultivated hexaploid species,carry the mutant type Cly1-like gene in all species,A.strigosa（PI 111261,As genome）A.brives（Roth）,A.hybrida（CAV 5806,ACD genome）and A.occidentalis（CAV 3906,ACD genome）.The result that both mutant and wild type Cly1-like gene can be found in hexaploid species supports the conclusion that hexaploid species originate from not an accidental interspecific hybridization but repeated ones happened in ancient times.Considering that mutant type allele frequency has negative selected,and the knockdown natural outcrossing rate,we hold the view that the hexaployploidization events have been affected by human factors.This result also implies that A.strigosa is likely to be involved in the evolutionary path of the hexaploid species;3.According to the geographical distribution of carrying mutant or wild type Cly1-like gene A.sativa L.and A.sativa ssp.nuda,we believe that the hulled oats enter have been taken into China from the Mediterranean region along two paths,one is through Russia and the other is through West Asia,while the naked oats may originate from Shanxi and Inner Mongolia,China,but many has a secondary origin center in Sichuan and Yunnan,China.