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28 THE BRITISH SMUT FUNGI large stainable bodies in addition to the nucleolus, may represent diakinesis. The intranuclear spindle is so small and narrow that in many cases the number of chromosomes cannot be accurately determined. jIt is possible that the diploid number is four. Nuclear divisions continue in the spore until ten to sixteen nuclei are present and these finally pass out into the promyceUum and so into the sporidia. Helton (1935) discovered that the distribution of nuclei between spore and promycelium diifers in two races of T. caries. In Cintractia montagnei the diploid nucleus leaves the spore and meiosis occurs in the promycehum. Some figures of dividing nuclei in vegetative cells and in promyceHa of Ustilago avenae, U. maydis, and Tilletia caries were given by Kharbush (1927, 1928). The two relatively large chromosomes, seen on the spindle of the first division in the promycelium, were accepted as bivalents, those seen in later divisions and in cells of the parasitic mycelium as monovalents, and two is suggested as the haploid number in smuts. D. T. Wang (1932, 1934) confirmed this in the following species: U. nuda, U. hordei, U. violacea, U. longissima, Sphacelotheca sorghi, S. cruenta, and Tilletia caries. In her experiments spores were germinated at 17° to 20° C. except that a lower temperature was used for T. caries. Reduction occurred always at the first division which took place either in the chlamydospore or in the promycelium. That segregation is not restricted to the first and second divisions of the diploid nucleus, but may even occur in the second or third division, is suggested by some genetical data (see p. 36). Cytological evidence on this point is meagre, but C. S. Wang (1943), working with Ustilago crameri {n = 2) observed four chromosomes at meiosis in promycelia,which already contained two or four nuclei, and accepts this as evidence that reduction had not been completed in the first division of the zygote. Hiittig (1933) suggests that external factors can influence the moment of chromosome reduction in some smuts. Yen (1937) has also studied nuclear division in the smuts and agrees with previous workers that Tilletia caries has a haploid number of two. His conclusions (p. 292) regarding the chromosome number in species of Ustilago are somewhat contradictory. Leach & Ryan (1946) failed to distinguish chromosomes in a form of U. striiformis which they believe to be homothaUic. They estimate that nuclei in the young germ-tube measure 2-3 /x. The vacuome and the chondriome of smuts have been studied by Moreau (1914), D. T. Wang (1934), and Yen (1937). In the chlamydospore the vacuome consists of numerous small vacuoles with dense contents which take up water and unite to form larger vacuoles, prior to germination. When growth begins, they fragment and pass into the promycelium, and as sporidia are formed, minute vacuoles pass into them (D. T. Wang, 1934). Yen (1937), using vital stains, demonstrated the presence of metachromatic granules which showed Brownian movement in the young vacuoles near the tips of growing hyphae. The chondriome was represented in material stained with aniline fuchsin and light green, by long, wavy, sometimes branched chondriosonies (chondrioconts) running parallel with the long axis of the ceU. They were particularly abundant in the cells destined to form spores. D. T. Wang (1934) found that the chondriosomes had the form of spherical corpuscles in all the species studied except U. hordei where some were filamentous. According to Moreau (1914), who studied the chondriome (cytome) in Entyloma ficariae, the chondriosomes were chiefly filamentous in the mycelium, corpuscular in the spore.
GENETICS INCOMPATIBILITY KNIEP'S discovery (1919) of heterothallism in smuts initiated the successful application of modern genetical principles to the study of this group. It is now an. accepted fact that new races of smuts can be produced by hybridization, though it is not yet clear how often this happens in nature or how it may affect breediag for resistance in the host. The majority of species so far studied are heterothallic (Kniep, 1928) and, in some of them, fusion of sporidia is governed by a single pair of allelomorphs. In these species, if large numbers of monosporidial lines are tested for compatibility (see p. 42), they fall into two equal groups. Any member of group A wiU fuse with any member of group B but the hnes within a group are incompatible. As Dickinson (1928, 1931) showed, segregation for compatibiUty factors can take place at either the first or second division of the diploid nucleus during the growth of the promycelium. If it occurs at the first division, the arrangement of sporidia will be either A, A, B, B, or B, B, A, A; if, at the second division, four types of distribution are possible, A, B, A, B; B, A, B, A; A, B, B, A; and B, A, A, B. A gametes can only be distinguished from B by reference to a culture arbitrarily taken as the standard. The nuclei carrying A or B factors show no polarity, A occurring in the apical segment of the promycelium as often as B. This type of segregation (2:2) was first observed by Kniep (1919) in Ustilago violacea and later found in U. hordei from oats and barley, U. avenue from oats, U. avenae (medians) from barley (Dickinson, 1927,1928,1931;Holton, 1931 b, 1932; Allison, 1937; Bever, 1945), and U. striiformis from Elymus glaucus (Fischer, 1940). Segregation of incompatibility factors is not so simple in all species, and fusion is probably governed in some by a series of multiple allelomorphs. Thus in U. maydis, while the sporidia of one chlamydospore may fall into two equal groups, in others segregation ratios may be 4:0;3:1;1:1:2; or 1:1:1:1 (Christensen in Stakman et al., 1929, 1931; Hanna, 1929; Bauch, 1932 a). Work with V. maydis is complicated by the fact that a few exceptional monosporidial lines infect maize and produce galls (Eddins, 1929 a; Sleumer, 1932). Three out of 31 lines intensively studied by ChristeHsen (in Stakman et al., 1929) were thus 'solo-pathogenic', but Schmitt (1940) met this peculiarity in only three among 4,000 monosporidial Unes examined. Unusually large numbers of solo-pathogenic lines were derived from the promycelia of crosses between Unes carrying factors for lysis (Chilton, 1940,1943). It is thought that irregular meiosis, rather than mutation, accounts for the origin and behaviour of solo-pathogenic hnes, since segregation for incompatibility factors does occur in subsequent generations. Chrisxiensen (1931) obtained three successive crops of chlamydospores in which reduction for incompatibiUty failed. In solo-pathogenic lines segregation for other factors such as colour and pathogenicity may take place normally and mutation is not unknown. Cytological evidence for the abnormal behaviour of these lines is lacking. Multiple factors for incompatibility h4ve been found also in Sphaceloiheca reiliana (Hanna, 1929); S. sorghi (Rodenhiser, 1932, 1934; Isenbeek, 1935;
Page 1 and 2: THE BRITISH SMUT FUNGI ^ (USTILAGIN
Page 3: FOREWORD THIS volume was started wh
Page 6 and 7: 6 PBEFACE We also acknowledge the b
Page 9 and 10: INTRODUCTION THE smut fungi, which
Page 11 and 12: INTRODUCTION H of bushels of wheat
Page 14 and 15: FIG. 1. Vstilago avenae on Arrhenat
Page 16: ^^ THE BBITISH SMUT FUNGI Young hea
Page 19 and 20: BIOLOGY 15 less than the normal, in
Page 21 and 22: BIOLOGy 17 and united with it, fina
Page 23 and 24: BIOLOGY 19 eermination in a collect
Page 25 and 26: BIOLOGY 21 genus, and the manner of
Page 27 and 28: BIOLOGY 23 species of Entyloma, and
Page 29 and 30: 3036^ BIOLOGY 25 in others. Dickins
Page 31: CYTOLOGY THE discovery of nuclei in
Page 35 and 36: GENETICS • 31 direction of growth
Page 37 and 38: GENETICS 35 when a few sporidia fro
Page 39 and 40: GENETICS 37 lines retained their di
Page 41 and 42: TECHNIQUE COLLECTION AND EXAMINATIO
Page 43 and 44: TECHNIQUE 41 be undesirable. Weak a
Page 45 and 46: TECHNIQUE 43 in one season (see p.
Page 47 and 48: TECHNIQUE 45 barley with loose smut
Page 49 and 50: TECHNIQUE 47 (1939), Holton & Heald
Page 51 and 52: TECHNIQUE 49 Allen's, modification
Page 53 and 54: CLASSIFICATION THE morphological ch
Page 55 and 56: THE BRITISH SMUT FUNGI MOST of the
Page 57 and 58: FIG. 2. Spore geimination in Ustila
Page 59 and 60: THE BRITISH SMUT FUJJGI 57 from one
Page 61 and 62: THE BRITISH SMUT FUKGI 59 of exsert
Page 63 and 64: THE BRITISH SMUT FUNGI 61 noticeabl
Page 65 and 66: THE BRITISH SMUT FUNGI 63 Evidence
Page 67 and 68: THE BRITISH SMUT FUNGI 65 winter in
Page 69 and 70: THE BRITISH SMUT FUNGI 67 Ustilago
Page 71 and 72: THE BRITISH SMUT FUlJGI 69 material
Page 73 and 74: THE BRITISH SMUT FUNGI 71 results o
Page 75 and 76: THE BRITISH SMUT FUNGI 73 TTstilago
Page 77 and 78: THE BRITISH SMUT FUNGI 75 Species i
Page 79 and 80: " TJSE BRITISH SMUT FUNGI 77 Ustila
Page 81 and 82: THE BKITISH SMUT FUNGI 79 On Carex
Page 83 and 84:
THE BRITISH SMUT FUNGI 81 Exsiccati
Page 85 and 86:
THE BRITISH SMUT FUNGI 83 Tilletia
Page 87 and 88:
THE BRITISH SMUT FUNGI 85 bunt ball
Page 89 and 90:
THE BEITISH SMUT FUNGI 87 globose t
Page 91 and 92:
THE BRITISH SMUT FUNGI 89 FIG. 13.
Page 93 and 94:
FIG. 15. Spore geimination in Taboi
Page 95 and 96:
FIG. 17. Spore germination in Urocy
Page 97 and 98:
THE BRITISH SMUT FUNGI 95 separate
Page 99 and 100:
THE BRITISH SMUT FUNGI 97 8ori in t
Page 101 and 102:
THE BRITISH SMUT FUNGI 99 Urocystis
Page 103 and 104:
30390 THE BRITISH SMUT FUNGI 101 pr
Page 105 and 106:
FIG. 20. Spore geimination in Entyl
Page 107 and 108:
THE BRITISH SMUT FUNGI 105 Sori in
Page 109 and 110:
On Ranunculus ficariae and B. scler
Page 111 and 112:
THE BRITISH SMUT FUNGI 109 Infectio
Page 113 and 114:
THE BKITISH SMUT FUNGI 111 [Sporidi
Page 115 and 116:
THE BRITISH SMUT FUNGI 113 Ustilago
Page 117 and 118:
REFEEENCES 115 BBETT, M. A. (1940).
Page 119 and 120:
REFERENCES 117 ^ DniON WESTON, W. A
Page 121 and 122:
REFERENCES 119 GRIFFITHS, MAEIOK A.
Page 123 and 124:
REFERENCES 121 HtjTTiG, W. (1933).
Page 125 and 126:
REFEBENCES 123 LiMBOtruN, E. J. (19
Page 127 and 128:
REFERENCES 125 NOBLE, E. J. (1934).
Page 129 and 130:
REFERENCES 127 RoDENHiSEE, H. A., &
Page 131 and 132:
BEFERENCES 129 STAKMAK, E. C, XCEEN
Page 133 and 134:
EEFEEENCES 131 WAXTBE, J. M. (1934)
Page 135 and 136:
INDEX to generic and specific names
Page 137 and 138:
Muscari Ustilago vaillantii, 59 Myo
Page 139 and 140:
Ustilago ficuum Reich., 113 —flps
Page 141 and 142:
2i}:y0 ANDHRA PRADESH AGRICULTURAL
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