Development and Identification of an Interspecific Hexaploid Hybrid Between an A.hypogaea Cultivar and a Wild Species Arachis sp.30119 in Peanut
[Objective]Wild Arachis species containing many elite disease and insect resistant genes are an important gene pool for the improvement of cultivated peanut A.hypogaea L.,so the introduction of chromatin from wild species into cultivated peanut remains an important task for distant hybridization of peanut.Unfortunately,only a few wild species have been successfully involved in the development of interspecific hybrids,despite the existence of a huge amount of wild germplasm resource.The wild species A.sp.30119 contains multiple disease resistance.However,no interspecific hybrid between it and the cultivated peanut has been reported.[Method]After crossing allotetraploid peanut cultivar Baitu 131 with diploid wild species A.sp.30119 and followed by the embryo rescue,the interspecific hybrid F1(W1212)was obtained.However,interspecific hybrid F1 did not produce seed when selfed.In order to reveal the reason for infertility and continue the generation,the chromosome number of root tip cells was counted and chromosome pairing in pollen mother cells during meiosis of W1212 observed.The chromosome of W1212 was doubled through colchicine treatment during the in vitro culture W1212 plantlet.Finally,we harvested four one-seeded pods from the established W1212 plants;one of the pods undergone in vitro cultured and a number of plants were established from the culture and named as Am1212.The chromosome composition of Am1212 was analyzed by sequential GISH/FISH and SSR marker.Additionally,phenotypic characteristics of Am1212 were investigated.The metaphase chromosome numbers of 8 randomly selected F3 plants were analyzed by rDNA FISH to evaluate the genetic stability of Am1212.[Result]The average chromosome configuration during meiosis of pollen mother cells of W1212 was 1 Ⅲ+6Ⅱ+15Ⅰ,and the abnormalities in chromosome pairings lead to the high sterility of F1 plants.The pollen viability of peg-setting branches of W1212 was significantly improved after chromosome doubling treatment.Sequential GISH/FISH of Baitu 131,A.sp.30119 and Am1212 indicated that A.sp.30119 may be a diploid with A genome.Am1212 has 60 chromosomes consisting of all chromosomes of both Baitu 131 and A.sp.30119,which confirmed its nature of a hexaploid hybrid,but 37.5%F3 plants derived from Am1212 exhibited chromosome number variation.After conducting the screening of SSR molecular markers and phenotypic investigation,we obtained 17 dominant or co-dominant markers for specifically tracking wild species chromosomes and clarified the genetic characteristics of Am1212.[Conclusion]In this study,we successfully created a new hexaploid peanut Am1212 which incorporated A.sp.30119 chromatin.However,Am1212 exhibited instability in chromosome numbers and inherited unacceptable agronomic traits from wild species,such as small pods.Therefore,it is necessary to develop more accurate and efficient chromosome manipulation techniques to minimize the unfavorable gene linkage and generate alien chromosomal lines that possess compensatory effects and favorable traits for future breeding purposes.
peanutwild specieshexaploidoligonucleotide fluorescence in situ hybridizationmolecular markers
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