Abstract
Autotetraploid inheritance has been reported and investigated in inany plants suspected of being autotetraploid in origin. Hon-ever, there are relatively few cases where segregation in artificially produced autotetraploids has been investigate,d and coinpared with that observed in the original diploid. 'The first such analysis was by Sansonle (1933), who studied the inheritance of seven characters in both the diploid and tetraploid tonlato species. Since then similar studies have been carried out on several different crops. These have been discussed by Little in his txvo reviews (1945, 1958). The present paper reports on the inheritance of resistance to cr0n.n and stem rust (caused by Pr~ccifzia coronata Cda. var. avelzae Fraser and Led. and P. g~a7~7inis Pers. f. sp. nvenae Erilcss. and Henn., respectively) in an artificially induced tetraploid of Avetza strigosn Schreb. and in the orig!nal diploid species. T h e autotetraploid segregation is analysed and compared wit11 that observed in the diploid. Materials and Methods C.D. 3820 is a strain of A. strigosa with excellent resistance to many races of crown and stem rust. Zillinslcy and Dericlc (1960) have transferred genes governing resistance to certain races of crown rust from C.D. 3820 to A. sativa by crossing an autotetraploid of C.D. 3820 with nvo cultivated hexaploid varieties. In this interspecific transfer program it was observed that C.D. 7571', an A. strigosa autotetraploid obtained from I. Nishiyama, Icyoto University, Japan, appeared Inore compatible with A. sativa than did the autotetraploid of C.D. 3820. This particular autotetraploid laclcs the disease resistance carried by C.D. 3820'. Since an autotetraploid \slit11 rhe disease resistance of C.D. 3820 ak,d the compatibility with the hesaploids of C.D. 7571' would be a great asset in a disease resistance transfer program, an investigation into the observed compatil)ility difference xvas initiated. For such a study, a knolvledge of the irheritance of crown and stem rust resistance in an autotetraploid population xvas essential. This nras carried out on F:, lines originating from three F, plants, designated as 1094, 1095 and 1099, of a cross involving the two autotetraploids, C.D. 3820' and C.D. 7574'. These data ulerc used for the autotetraploid analvI sis rep0rte.d here. The rust reaction for races 294 of crown rust and 13A of stem rust was determined for 30 or more plants of each F:, line. On the basis of their disease reaction, the IT,, lines were classified into the follonrin~ three classes: resistant, which includes lines originating from quadriplex ( A ~ ~ A A ) , triplex (AAAa) and duplex (AAaa) plants; segregating, which includes lines originating from simplex (Aaaa) plants; and susceptible, nihich includes lines originating froin nulliplex (aaaa) plants. Because of the relatively small number of plants tested in each line, it was i~npossible to separate all the duplex plants, segregat-
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