Heritability of Resistance in Winter Wheat to Wheat Spindle Streak Mosaic Virus

Abstract

Van Koevering, M., Haufler, K. Zagula, Fulbright, D. W., Isleib, T. G., and Everson, E. H. 1987. Heritability of resistance in winter wheat to wheat spindle streak mosaic virus. Phytopathology 77:742-744. The heritability of resistance to wheat spindle streak mosaic virus in was found to be a highly heritable trait controlled by a few dominant genes. winter wheat was studied using a seven-parent diallel analysis. Parents and A two-locus genetic model was proposed to account for the observed F, progenies were evaluated for disease reaction based on virus particle resistance classification of the parents and the patterns of inheritance counts determined by immunosorbent electron microscopy. Resistance exhibited in the F, progenies. One of the most prominent virus diseases of winter wheat in the MATERIALS AND METHODS United States and Canada is wheat spindle streak mosaic (WSSM). The disease was first reported in the United States in Three Michigan cultivars and four advanced experimental lines Michigan 15 yr ago (17), and since then it has been found in most from the Michigan State University wheat breeding program, all winter wheat-growing regions (2,3,10-12,18). showing differential reactions to WS S MV, were chosen as parents Accurate yield loss data are somewhat limited, but estimates of in a diallel mating design. The parental pedigrees, which originated crop loss because of WSSM range from 2 to 59% (2,6,13,16). from widely diverse genetic backgrounds, included both red and Although a few older winter wheat cultivars show some resistance white soft winter wheat (Table 1). The seven parents were crossed to wheat spindle streak mosaic virus (WSSMV) (10,12,13,16,18), in all possible combinations to produce 42 F1 progenies. most commercially grown cultivars are susceptible (2,8,12). Preliminary analysis revealed nonsignificant maternal effects; Because recommended cultural practices such as crop rotation and therefore, reciprocal crosses were not included in the diallel late planting have not been effective in controlling the disease, it is analysis. The remaining 21 F1 progenies and seven parents were important to identify germ plasm and to develop cultivars resistant evaluated for disease reaction based on numbers of virus particles to WSSMV. in leaf tissue using ISEM (8). Diallel crosses have been used to study the heritability of Soil infested with the fungal vector Polymyxa graminis Led. was resistance to viruses in wheat (4,5) and other crops. In the analysis collected from a field in Saranac, MI, where wheat previously had of winter wheat tolerance to barley yellow dwarf virus, heritability shown severe WSSM symptoms. Four parts of infested soil were of tolerance was low, with additive genetic effects (high generalmixed with one part sterilized sand to increase soil aeration and combining ability) more important than nonadditive and drainage. Sterilized wooden flats were filled with the infested soil reciprocal effects in determining tolerance. Results from the mixture, and seeds from the 21 F1 progenies and seven parents were analysis of a five-parent winter wheat diallel cross indicated that planted in a randomized block design in rows with five seeds per resistance to soilborne wheat mosaic virus was monogenic row. Each flat represented a single replication and contained 30 dominant over susceptibility (5). Although diallel analysis has entries, including 7 parental rows, 21 F, progeny rows, and 2 some limitations (1), it does provide estimates of genetic control rows of a known susceptible cultivar (Ionia). Three parameters that serve as a basis for selection procedures used in a replications were planted in November 1983. Seeds were plant breeding program. germinated in the greenhouse, and seedlings were kept at 20 ± 3 C Haufler and Fulbright (8) recently identified several soft winter wheat cultivars and experimental breeding lines with resistance to WSSMV. Disease ratings were based on symptom expression and TABLE 1. Winter wheat cultivars and lines used as parents in diallel virus content of leaves using immunosorbent electron microscopy examining inheritance of resistance to wheat spindle streak mosaic virus (ISEM) (7). Screening the germ plasm revealed differential cultivar Experimental Common reactions to WSSMV, ranging from susceptible to resistant. or Ci No. name Origin color Reactiona Because the genetic mechanisms controlling expression of resistance to WSSMV are unknown, a diallel mating design using CI 14469 Ionia USA White S parents with known differential reactions to the virus was used to CI 17831 Augusta USA White S I 17287 Tecumseh M study the mode of inheritance and gene action of resistance to B4145 Experimental USA, White MR WSSMV. A preliminary report of a portion of this work has been line New Zealand presented (15). B7321 Experimental Russia Red MR line B6018 Experimental USA, White R line Japan B9028 Experimental Yugoslavia, Red R The publication costs of this article were defrayed in part by page charge payment. This line Mexico article must therefore be hereby marked advertisement in accordance with 18 U.S.C. § 1734 solely to indicate this fact. aS = susceptible, MS = moderately susceptible, MR = moderately resistant, and R = resistant. Disease rating (reaction) is based on virus particle ©1987 The American Phytopathological Society counts as described previously (8).