Abstract
White rust (causative pathogen Puccinia horiana) is a destructive disease of commercial chrysanthemum crops. A panel of 19 accessions of commercial chrysanthemum near-relatives (four Ajania species, 11 Chrysanthemum species including five accessions of Chrysanthemum indicum) were screened for their reaction to white rust infection in separate greenhouse trials carried out at two independent sites in eastern China, one in 2010 and the other in 2012. The reaction of the accessions to artificial inoculation ranged from immune to highly susceptible. Accessions of Chrysanthemum indicum, C. yoshinaganthum, C. makinoi var. wakasaense, C. nankingense, C. vestitum, C. lavandulifolium, C. crassum, and Ajania tripinnatisecta were immune, and strong resistance was present in C. japonense, C. × shimotomaii, and A. przewalskii. Most of the accessions behaved similarly in the two trials, but two of the C. indicum accessions produced inconsistent results, each being highly resistant in one trial but susceptible in the other. Because wide crosses are relatively easy to achieve in the chrysanthemum complex, these immune and highly resistant accessions represent promising germplasm for white rust resistance breeding.
Chrysanthemum white rust (causative pathogen Puccinia horiana Hennings) is a notifiable disease, which infects chrysanthemum plants grown for the cut flower and pot plant trade, largely because they are routinely cultivated under glass or in plastic tunnels where the microclimate favors the growth of the pathogen. The global trade in chrysanthemum has dispersed the disease from the site of its first documentation in Japan in 1895 to China, South Africa, and Europe (Baker, 1967; Firman and Martin, 1968; Whipps, 1993) and by now has become endemic to most chrysanthemum-growing areas (Cook, 2001; Göre, 2008; O’Keefe and Davis, 2012). The pathogen is an obligate biotroph, which colonizes young leaves and flower buds (Yamada, 1956). Under conditions of high humidity and mild temperature, its teliospores, which develop within a pustule on the abaxial leaf surface within 14 to 18 d post-infection (Zandvoort et al., 1968b), germinate to form a promycelium. Each promycelium bears a mean of two infective propagules (basidiospores) (Kapooria and Zadoks, 1973), which can be dispersed by wind over a distance of up to 700 m (Zandvoort, 1968b).
Although white rust can be chemically controlled (Dickens, 1990; Zadoks et al., 1969; Zandvoort et al., 1968a), the use of fungicides is associated with both environmental hazards and an increased production cost (Waard et al., 1993); overdependence on their use has already led to the appearance of tolerant strains (Abiko et al., 1977; Cook, 2001). The more sustainable strategy of exploiting genetically determined resistance requires the identification of sources of resistance, as first attempted by Dickens (1968) and Martin and Firman (1970). DeJong and Rademaker (1986) have suggested that resistance is most commonly under monogenic control.
Outside of the primary gene pool, a number of related species have been shown to harbor variation of relevance to aphid tolerance (Sun et al., 2012), to Alternaria leaf spot resistance (Xu et al., 2011), and to tolerance of various abiotic stresses (Guan et al., 2010; Yin et al., 2009). Several Chrysanthemum spp. have been reported as resistant to white rust (Dickens, 1968; Hiratsuka, 1957) and an intergeneric hybrid between chrysanthemum and Artemisia sieversiana has been shown to be more resistant than the chrysanthemum parent (Furuta et al., 2004). Hybridization between commercial chrysanthemum and various Ajania and Chrysanthmum spp. has been repeatedly achieved (Cheng et al., 2011; Deng et al., 2011), so wide crossing could have considerable potential for white rust resistance breeding. Here, we report the evaluation for the white rust resistance shown by a panel of 19 Ajania and Chrysanthemum spp. involving two independent trials. To our knowledge, this represents the first such survey of the potential of Ajania and Chrysanthemum spp. to provide a source of genetic resistance to white rust.
Materials and Methods
Plant materials and inoculation.
The set of 19 accessions including species from Ajania (four species) and Chrysanthemum (10 species with five accessions of Chrysanthemum indicum) (Table 1) was obtained from the Chrysanthemum Germplasm Resource Preserving Center, Nanjing Agricultural University, Nanjing, China. The commercial cultivar Jinba served as a white rust-susceptible control to indicate inoculations were succeeded or not. Screening was carried out on plants grown in two different plastic greenhouses in eastern China, one in 2010 (“Trial 1”) and the other in 2012 (“Trial 2”). For Trial 1, morphologically uniform 3-week-old rooted cuttings (eight to 10 leaf stage) were grown at a site located at lat. 34.06° N, long. 118.28° E. The plastic house was initially treated with carbendazim and mancozeb, after which a minimum of 30 cuttings per accession were planted in a single 10-m row with an interplant spacing of 20 to 30 cm and an interrow spacing of 0.5 m. The experiment was arranged as a randomized complete block with three replications (McIntosh, 1983). Overhead irrigation was provided with a sprinkler. No fertilizer or fungicide was applied during the whole experimental process (1 May to 30 June). Seven days after planting, the cuttings were inoculated with teliospores collected from diseased cv. Jinba plants. To minimize disease escape, they were inoculated first using the fraction method elaborated by Zhu et al. (2011), then a day later using a spray method derived from Zandvoort (1968a); briefly, the infected leaves containing white rust pustules were cut into small pieces and were dispersed in deionized water and filtered through medical gauze to remove any plant debris. The concentration of the pathogenic spore suspension was then adjusted using a hemacytometer slide to a concentration of 1 × 106 zoosporangia/mL with deionized water containing one drop of Tween 20 before application to the plants until runoff using a handheld sprayer. The plants were covered with a black polythene sheet for the first 48 h post-inoculation both to maintain a high relative humidity and to exclude light (Yamada, 1956). Thereafter the temperature was kept within the range 15 to 25 °C, and supplementary light was given to provide a 16-h photoperiod. The relative humidity was kept above 80% by the use of 360° rotating sprinklers for overhead sprinkling, in which water pressure was 200 Kpa, flow was 27.8 L·h–1, and maximum range was 3.5 m (Lemiao Irrigation Equipment Factory, Zhejiang, China) every 2 h during the day. The Trial 2 plastic house was sited at lat. 34.32° N, long. 118.12° E. Planting period, plant layout, inoculation procedure, and field management were as for Trial 1. The fungal inoculum used in this trial was collected from diseased cv. Iwanohakusen.
Latent period, infection type, disease index, and host response of 19 accessions of Ajania (four species) and Chrysanthemum (eleven species) tested for reaction to chrysanthemum white rust inoculation in two independent trials.
Disease monitoring and classification.
The latent period, infection type, disease severity, and disease incidence were recorded at the time when teliospore-containing pustules had become well developed. Monitoring was continued until 52 d post-inoculation (dpi). The latent period was defined as the number of days elapsed between inoculation and the first appearance of symptoms (Browne and Cooke, 2004). Infection type was represented by a 0 to 5 scale, which was observed from the majority (15 or greater) of individual data, adapted from Pathan and Park (2006) and Zhu et al. (2011), in which “0” indicated no visible symptoms, “1” indicated rare visible yellowish hypersensitive flecks are discernible, “2” indicated a few small yellowish flecks and very little telia on the back, “3” indicated more small or few large yellowish necrosis and clear telia on the back, “4” indicated large and continuous yellowish necrosis and clear telia on the back, and “5” indicated massive large and continuous yellowish necrosis and diffusible telia on the back and some leaves even roll or rot. Disease incidence (I) was given by the ratio between the average number of diseased and non-diseased leaves on a plant from 30 individuals per accession. A mean disease severity measure (Ŝ, given by the mean proportion of leaf area infected) was calculated from ≈30 infected leaves per accession; both the area of diseased leaf surface and the overall leaf area were obtained from scanned images of the leaves following Igathinathane et al. (2006). A disease index (DI) was then derived from the expression I × Ŝ × 100 based on rule for resistance evaluation of wheat to leaf rust (Puccinia triticina) (Ministry of Agriculture of the People's Republic of China, 2007).
Statistical analysis.
SPSS 17.0 software (SPSS Inc., Chicago, IL) was used for all statistical calculations. A one-way analysis of variance, in conjunction with the Duncan multiple range test, was used to assess whether accessions differed significantly from one another for their reaction to infection.
Results
Trial 1.
The latent period ranged from 9 to greater than 30 dpi (Table 1). The earliest accession to display disease symptoms was A. shiwogiku var. kinokuniense followed 3 d later by A. pacifica. The disease symptoms started as pale green to yellow flecks of diameter up to 5 mm (Fig. 1A). Over time, the flecks turned necrotic, and buff- to pink-colored pustules formed on the leaf’s surface (Fig. 1B). The pustules lost their color as they matured. In some cases, both surfaces of the leaf became postulated, leading to leaf collapse (Fig. 1C). With respect to infection type, 12 of the 19 accessions (A. tripinnatisecta, A. przewalskii, four of the C. indicum accessions, C. yoshinaganthum, C. makinoi var. wakasaense, C. nankingense, C. vestitum, C. lavandulifolium, C. crassum) were symptom-less (type “0,” see Fig. 2) and therefore were classed as immune. C. japonense and C. × shimotomaii had developed a small number of yellowish flecks by the end of the monitoring period (type “1,” see Fig. 2) and were classed as highly resistant. C. japonense var. ashizuriense and C. ornatum leaves carried rather more yellowish flecks and developed small pustules on their abaxial surface (type “2,” see Fig. 2) and were classed as moderately resistant. Finally, C. indicum from Huangshan, A. pacifica, and A. shiwogiku var. kinokuniense were classed as, respectively, moderately susceptible, susceptible, and highly susceptible (types “3” to “5,” see Fig. 2). The DI classification exposed significant differences (P < 0.01) between the accessions, ranging from 0 (the 12 immune accessions) to 41.6. The DIs of the two highly resistant accessions were 0.2 and 3.7, that of the moderately resistant C. japonense var. ashizuriense was 13.5, and C. ornatum was 0.9, which classified as highly resistant, whereas those of susceptible accessions A. pacifica, C. indicum (Huangshan), and A. shiwogiku var. kinokuniese ranged from 28.8 to 41.6 (Table 1).
The development of white rust pustules on the abaxial surface of an A. pacifica leaf at (A) 10 d post-inoculation (dpi), (B) 20 dpi, (C) 30 dpi. Bar = 5 mm.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
The development of white rust pustules on the abaxial surface of an A. pacifica leaf at (A) 10 d post-inoculation (dpi), (B) 20 dpi, (C) 30 dpi. Bar = 5 mm.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
The development of white rust pustules on the abaxial surface of an A. pacifica leaf at (A) 10 d post-inoculation (dpi), (B) 20 dpi, (C) 30 dpi. Bar = 5 mm.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
Infection type of accessions inoculated with white rust, measured at 30 d post-inoculation (dpi) in Trial 1. Bar = 10 mm. 0 = no visible symptoms, as exemplified by C. nankingense; 1 = a very small numbers of yellowish flecks, as exemplified by C. × shimotomaii; 2 = several yellowish flecks and a few pustules, as exemplified by C. ornatum; 3 = the development of chlorotic and necrotic areas, and the formation of a few pustules on the abaxial leaf surface, as exemplified by C. indicum (Huangshan); 4 = the development of extensive areas of chlorosis and necrosis, and the formation of many pustules on the abaxial leaf surface, as exemplified by A. pacifica; 5 = merged pustules on the abaxial leaf surface and the development of leaf distortion and collapse, as exemplified by A. shiwogiku var. kinokuniense.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
Infection type of accessions inoculated with white rust, measured at 30 d post-inoculation (dpi) in Trial 1. Bar = 10 mm. 0 = no visible symptoms, as exemplified by C. nankingense; 1 = a very small numbers of yellowish flecks, as exemplified by C. × shimotomaii; 2 = several yellowish flecks and a few pustules, as exemplified by C. ornatum; 3 = the development of chlorotic and necrotic areas, and the formation of a few pustules on the abaxial leaf surface, as exemplified by C. indicum (Huangshan); 4 = the development of extensive areas of chlorosis and necrosis, and the formation of many pustules on the abaxial leaf surface, as exemplified by A. pacifica; 5 = merged pustules on the abaxial leaf surface and the development of leaf distortion and collapse, as exemplified by A. shiwogiku var. kinokuniense.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
Infection type of accessions inoculated with white rust, measured at 30 d post-inoculation (dpi) in Trial 1. Bar = 10 mm. 0 = no visible symptoms, as exemplified by C. nankingense; 1 = a very small numbers of yellowish flecks, as exemplified by C. × shimotomaii; 2 = several yellowish flecks and a few pustules, as exemplified by C. ornatum; 3 = the development of chlorotic and necrotic areas, and the formation of a few pustules on the abaxial leaf surface, as exemplified by C. indicum (Huangshan); 4 = the development of extensive areas of chlorosis and necrosis, and the formation of many pustules on the abaxial leaf surface, as exemplified by A. pacifica; 5 = merged pustules on the abaxial leaf surface and the development of leaf distortion and collapse, as exemplified by A. shiwogiku var. kinokuniense.
Citation: HortScience horts 48, 10; 10.21273/HORTSCI.48.10.1231
Trial 2.
The latent period was generally slightly shorter than in Trial 1, although it was the same (9 dpi) for the earliest accession to show disease symptoms (A. shiwogiku var. kinokuniense). The order of symptom displayed thereafter was A. pacifica (10 dpi), C. indicum (Nanjing) (11 dpi), C. × shimotomaii (13 dpi), C. ornatum (15 dpi), C. japonense (26 dpi), A. przewalskii (27 dpi), and C. indicum (Huangshan) (29 dpi). The other accessions remained symptomless (Table 1). Some of the recorded infection types differed from what had been seen in the earlier trial. Thus, the classification of A. przewalskii changed from “0” to “1” (immune to highly resistant) and that of C. japonense var. ashizuriense from “2” to “0” (its DI fell from 13.5 to 0) and so was classified as immune. C. indicum (Huangshan) was reclassified as being highly resistant (previously moderately susceptible) and C. indicum (Nanjing) as moderately susceptible (previously immune) (Table 1). To determine if these host responses were consistent across two different field locations, Spearman rank correlation tests were performed. Significant and positive correlations between Trial 1 and Trial 2 (r = 0.652; P < 0.01) were found.
Discussion
Reliable sources of genetically determined resistance are the sine qua non of a disease resistance breeding program. Here, the white rust infection type and disease index of a set of near relatives of commercial chrysanthemum were established. The panel of 19 accessions was evaluated in two independent trials separated from one another with respect to both time and place, and the outcomes were highly (but not entirely) consistent with one another. Notable among the discrepancies were the changed classification in infection type accorded to C. indicum (Huangshan) and C. indicum (Nanjing). Such variation may because of the change of a combination of factors such as spatial and temporal variations in inoculum levels, environmental conditions, age of plants, and soil conditions, etc. (Akhtar et al., 2013). The most likely basis for this phenomenon, as seen in many host/fungal pathogen interactions, lies in present in the inoculum (Lindeberg, 2012; Zhou et al., 2007). Races of white rust were first discovered and supposed by Dickens (1968), and there may exist four races of white rust, which was reported in Japan by Kudo and Okamura (1998). A differential response in the chrysanthemum/white rust system has been recorded by Yamaguchi (1981), and this finding was later confirmed by De Backer et al.’s (2011) study of the response of 36 cultivars to 22 different white rust strains, where differential patterns of resistance were displayed. Over half of the accessions proved to be immune or at least highly resistant, despite the large inoculum load imposed on them, and most of these resistant types belonged to the genus Chrysanthemum, rather than to the more distant genus Ajania.
According to the evaluation result (Table 1), we can combine latent period, infection type, and disease index together (Table 2). These evaluation systems could be useful for the evaluation for P. horiana tolerance of chrysanthemum. In this study, we found that latent period is a reliable and simpler component for evaluation for resistance to P. horiana. Infection type and DI have been widely used in disease resistance screens (Farias Neto et al., 2008; Kolmer, 1996). The former has the advantage of speed and simplicity, because it is based on primary data; its disadvantage is that it is somewhat subjective. The DI combines disease incidence and disease severity, thereby producing a measure, which is much more objective; however, its acquisition is more laborious and requires the means to measure the area of diseased and non-diseased leaf surface.
Latent period, infection type, and disease index for chrysanthemum white rust (Puccnia horiana) resistance evaluation.
The leaves of A. pacifica and A. shiwogiku var. kinokuniense typically develop a denser mat of leaf trichomes (especially on their abaxial surface) than do those Chrysanthemum spp. In Arabidopsis thaliana at least, it has been suggested that the presence of trichomes aids the adhesion of fungal spores to the leaf surface (Calo et al., 2006). A dense system of leaf trichomes can be expected to produce a microclimate where the level of relative humidity remains high, and this would certainly favor the germination of the white rust spores, so it may be that greater susceptibility shown by the Ajania spp. is a pleotropic effect of trichome density.
The relative ease of making wide hybrids between commercial chrysanthemum and related species from the genera Chrysanthemum and Ajania opens the way to introgressing white rust resistance into the crop species. Primary hybrids tend to form poor-quality inflorescences, but this feature should be correctable by building in a sufficient level of backcrossing (Zhao et al., 2012). Apart from the white rust resistance, the related species in question provide a reservoir of genes, which could be exploited to improve the commercial chrysanthemum’s level of tolerance to a number of abiotic stresses, of resistance to a range of other diseases and pests, and possibly also to manipulate flowering time.
Literature Cited
Abiko, K., Kishi, K. & Yoshioka, A. 1977 Occurrence of oxycarboxin-tolerant isolates of Puccinia horiana P. Hennings in Japan Ann. Phytopathological Soc. Jpn. 43 145 150
Akhtar, K.P., Sarwar, G., Sarwar, N. & Elahi, M.T. 2013 Field evaluation of sesame germplasm against sesame phyllody disease Pak. J. Bot. 45 1085 1090
Baker, J. 1967 Chrysanthemum white rust in England and Wales 1963–66 Plant Pathol. 16 162 166
Browne, R. & Cooke, B. 2004 Development and evaluation of an in vitro detached leaf assay for pre-screening resistance to fusarium head blight in wheat Eur. J. Plant Pathol. 110 91 102
Calo, L., García, I., Gotor, C. & Romero, L.C. 2006 Leaf hairs influence phytopathogenic fungus infection and confer an increased resistance when expressing a Trichoderma α-1,3-glucanase J. Expt. Bot. 57 3911 3920
Cheng, X., Chen, S., Chen, F., Deng, Y., Fang, W., Tang, F., Liu, Z. & Shao, W. 2011 Creating novel chrysanthemum germplasm via interspecific hybridization and backcrossing Euphytica 177 45 53
Cook, R.T.A. 2001 First report in England of changes in the susceptibility of Puccinia horiana, the cause of chrysanthemum white rust, to triazole and strobilurin fungicides Plant Pathol. 50 792
De Backer, M., Alaei, H., Van Bockstaele, E., Roldan-Ruiz, I., van der Lee, T., Maes, M. & Heungens, K. 2011 Identification and characterization of pathotypes in Puccinia horiana, a rust pathogen of Chrysanthemum × morifolium Eur. J. Plant Pathol. 130 325 338
DeJong, J. & Rademaker, W. 1986 The reaction of chrysanthemum cultivars to Puccinia horiana and the inheritance of resistance Euphytica 35 945 952
Deng, Y., Chen, S., Chen, F., Cheng, X. & Zhang, F. 2011 The embryo rescue derived intergeneric hybrid between chrysanthemum and Ajania przewalskii shows enhanced cold tolerance Plant Cell Rpt. 30 2177 2186
Dickens, J. 1968 The resistance of various cultivars and species of chrysanthemum to white rust (Puccinia horiana Henn.) Plant Pathol. 17 19 22
Dickens, J. 1990 Studies on the chemical control of chrysanthemum white rust caused by Puccinia horiana Plant Pathol. 39 434 442
Farias Neto, A.L.D., Schmidt, M., Hartman, G.L., Shuxian, L. & Diers, B.W. 2008 Inoculation methods under greenhouse conditions for evaluating soybean resistance to sudden death syndrome. Brazil Agr. Res. 43 1475 1482
Firman, I. & Martin, P. 1968 White rust of chrysanthemums Ann. Appl. Biol. 62 429 442
Furuta, H., Shinoyama, H., Nomura, Y., Maeda, M. & Makara, K. 2004 Production of intergeneric somatic hybrids of chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura] and wormwood (Artemisia sieversiana J. F. Ehrh. ex. Willd) with rust (Puccinia horiana Henning) resistance by electrofusion of protoplasts Plant Sci. 166 695 702
Göre, M. 2008 White rust outbreaks on chrysanthemum caused by Puccinia horiana in Turkey Plant Pathol. 57 786
Guan, Z., Chen, F., Teng, N., Chen, S. & Liu, P. 2010 Study on the NaCl tolerance in five plant species from Dendranthema and its relatives Scientia Agr. Sinica 43 787 794
Hiratsuka, N. 1957 Three species of chrysanthemum rusts in Japan and its neighbouring districts Sydowia Ser 2 (Beiheft 1) 34 44
Igathinathane, C., Prakash, V.S.S., Padma, U., Babu, G.R. & Womac, A.R. 2006 Interactive computer software development for leaf area measurement Comput. Electron. Agr. 51 1 16
Kapooria, R. & Zadoks, J. 1973 Morphology and cytology of the promycelium and the basidiospore of Puccinia horiana Eur. J. Plant Pathol. 79 236 242
Kolmer, J. 1996 Genetics of resistance to wheat leaf rust 1 Annu. Rev. Phytopathol. 34 435 455
Kudo, H. & Okamura, M. 1998 Pathogenic variation in Puccinia horiana P. Henn. on chrysanthemum cultivars in Japan Ann. Phytopathological Soc. Jpn. 64 436
Lindeberg, M. 2012 Genome-enabled perspectives on the composition, evolution, and expression of virulence determinants in bacterial plant pathogens Annu. Rev. Phytopathol. 50 111 132
Martin, P. & Firman, I. 1970 Resistance of chrysanthemum cultivars to white rust (Puccinia horiana) Plant Pathol. 19 180 184
McIntosh, M. 1983 Analysis of combined experiments Agron. J. 75 153 155
Ministry of Agriculture of the People's Republic of China 2007 The principle of the agricultural standard in the people's republic of China NY/T 1443.2-2007. Rules for resistance evaluation of wheat to diseases and insect pests part 2: Rule for resistance evaluation of wheat to leaf rust [Puccinia triticina (=P. recondite Roberge ex Desmaz. f. sp. tritici)]. China Agricultural Press, Beijing, China
O’Keefe, G. & Davis, D. 2012 First confirmed report that Puccinia horiana, causal agent of chrysanthemum white rust, can overwinter in Pennsylvania Plant Dis. 96 1381
Pathan, A.K. & Park, R.F. 2006 Evaluation of seedling and adult plant resistance to leaf rust in European wheat cultivars Euphytica 149 327 342
Sun, Y., Guan, Z., Chen, S., Fang, W. & Chen, F. 2012 Identification of aphid resistance in eleven species from Dendranthema and Artemisia at seedling stage Acta Ecol. Sinica 32 319 325
Waard, M.A.D., Georgopoulos, S., Hollomon, D., Ishii, H., Leroux, P., Ragsdale, N. & Schwinn, F. 1993 Chemical control of plant diseases: Problems and prospects Annu. Rev. Phytopathol. 31 403 421
Whipps, J.M. 1993 A review of white rust (Puccinia horiana Henn.) disease on chrysanthemum and the potential for its biological control with Verticillium lecanii (Zimm.) Viégas Ann. Appl. Biol. 122 173 187
Xu, G., Liu, Y., Chen, S. & Chen, F. 2011 Potential structural and biochemical mechanisms of compositae wild species resistance to Alternaria tenuissima Russ. J. Plant Physiol. 58 491 497
Yamada, S. 1956 Experiments on the epidemiology and control of chrysanthemum white rust, caused by Puccinia horiana Ann. Phytopathological Soc. Jpn. 20 148 154
Yamaguchi, T. 1981 Chrysanthemum breeding for resistance to white rust Jpn. J. Breeding 31 121 132
Yin, D., Guan, Z., Chen, S. & Chen, F. 2009 Establishment of evaluation system for waterlogging tolerance and identification of waterlogging tolerance in Chrysanthemum morifolium and its related genera plants J. Plant Genet. Resources 10 399 404
Zadoks, J., Kodde, A. & Hoogkamer, W. 1969 The effect of derivatives of 1, 4-oxathiin on Puccinia horiana in Chrysanthemum morifolium Eur. J. Plant Pathol. 75 193 196
Zandvoort, R. 1968a Methods for the inoculation of Chrysanthemum morifolium with Puccinia horiana Eur. J. Plant Pathol. 74 174 176
Zandvoort, R. 1968b Wind dispersal of Puccinia horiana Eur. J. Plant Pathol. 74 124 127
Zandvoort, R., Groenewegen, C. & Zadoks, J. 1968a Chemical control of Puccinia horiana in Chrysanthemum morifolium Eur. J. Plant Pathol. 74 170 173
Zandvoort, R., Groenewegen, C. & Zadoks, J. 1968b On the incubation period of Puccinia horiana Eur. J. Plant Pathol. 74 128 130
Zhao, H., Chen, S., Tang, F., Jiang, J., Li, C., Miao, H., Chen, F., Fang, W. & Guo, W. 2012 Morphological characteristics and chromosome behaviour in F1, F2 and BC1 progenies between Chrysanthemum × morifolium and Ajania pacifica Russ. J. Genet. 48 808 818
Zhou, E., Jia, Y., Singh, P., Correll, J.C. & Lee, F.N. 2007 Instability of the Magnaporthe oryzae avirulence gene AVR-Pita alters virulence Fungal Genet. Biol. 44 1024 1034
Zhu, P., Zhao, N., Qi, D., Liu, N. & Duan, Y. 2011 Optimization of identification standards and artificial inoculation methods in vitro on resistance to chrysanthemum white rust Chin. Agr. Sci. Bul. 27 149 152
