small percentage of these sporidia appeared to grow 

 perfectly normally (55). 



Lysis. — Sometimes, abnormal germination of chla- 

 mydospores is associated with lysis of the promycelia. 

 Chilton (50. 51. 52) found that chlamydospores from 

 certain crosses produced gnarled and distorted promy- 

 celia that either lysed before producing sporidia or 

 developed only a few sporidia in an irregular manner. 

 The factors for lysis were carried only in certain 

 haploid and diploid lines. By making the appropriate 

 crosses, he proved that the tendency for lysis was 

 partially dominant and that at least 2 or more genetic 

 factors were involved, as distinctly different degrees 

 of lysis occurred in different crosses. This type of 

 abnormal germination was usually associated with large 

 chlamydospores and the tendency to produce diploid 

 sporidia. Both the haploid and diploid lines that car- 

 ried the factors for lysis grew normally on nutrient 

 agar. According to Christensen (55), diploid lines are 

 not always associated with lysis of promycelia. 



Formation of chlamydospores. — Moore ('229 1. in 

 1932. found that 3 dicaryophytes. derived by pairing 

 haploids from the same chlamydospore, differed greatly 

 in their ability to form chlamydospores on corn plants, 

 even though they developed numerous galls containing 

 abundant mycelium. One dicaryon rarely produced 

 chlamydospores — and in some galls, none — although it 

 induced large overgrowths. The number of chlamydo- 

 spores formed also varied with the variety and line 

 of corn inoculated. 



Later. Stakman. et al. (320) mated many "white" 

 monosporidial lines in various combinations. Although 

 compatible combinations produced large galls with 

 the normal amount of stout mycelium, no mature 

 chlamydospores developed. When some of these white 

 lines were crossed with tester lines, they developed 

 normal chlamydospores. Apparently, the nuclei of the 

 lines have the necessary factors for attraction and 

 association and growth that enable them to produce the 

 dicaryon and cause infection, but lack the necessary 

 factors for nuclear fusion or factors essential for 

 chlamydospore maturation. 



Pathogenicity. — Although it has been repeatedly 

 demonstrated that dicaryon and diploid ( solopathogen) 

 lines differ distinctly in their ability to attack different 

 varieties and lines of corn, very little is known about 

 the inheritance of virulence. Even dicaryons derived 

 from the same chlamydospores may differ greatly in 

 pathogenicity, as do solopathogens derived from the 

 same cross (54. 55. Ill i. Some are very pathogenic 

 and produce large galls, others are virtually non- 

 pathogenic and produce small or incipient galls, and 

 still others are more or less intermediate in their 

 parasitic behavior. Similar differences also occur in 

 the production of chlorosis and anthocyanin pigment 

 on certain inbred lines of corn (54, 111). 



Great diversity in virulence also frequently arises 

 by mutation in both haploid and diploid lines ( 54. 

 111. 314. 322). Although most of the changes are 

 associated with loss of virulence, occasionally there 

 is a gain in virulence. Changes in virulence are most 

 easily detected in solopathogenic lines. It is generally 

 accepted that virulence is conditioned by several 

 factors as indicated by great range of virulence among 

 biotypes. especially in diploid lines (54, 55, 111. 280). 



Toxic Effect of Smut. — Whether corn smut was 

 injurious and toxic to man and animals was con- 

 troversial from about 1 760 to the early part of the 

 twentieth century. According to Burger (38), Tillet 

 and Imhof claimed that chlamydospores of U. maydis 

 when eaten by men and animals or when introduced 

 into wounds were not harmful. Imhof (156), in 1784. 

 ate chlamydospores before breakfast for 2 weeks and 

 introduced them into wounds and used the spores 

 as snuff, but detected no injurious effect. Bonafous 

 (25), in 1936. also ate chlamydospores of corn smut 

 without ill effect. 



According to Arthur and Stuart (5), Roulin. in 

 1829. reported that corn smut was very injurious to 

 men and animals in the low land in Colombia. South 

 America; whereas it could be eaten without deleterious 

 effect in the mountainous upland. 1 Corn smut has been 

 used for human food for a long time and it still is in 

 some of the Latin American countries (2, 5. 211). 

 Several Mexican publications give recipes for prepara- 

 tion of U. maydis dishes. Martinez (211) states that 

 cuitlocoche (smut galls) is collected in the field and 

 carried to the market to sell. Many people use it as 

 food. They chop it into pieces and then fry smut 

 with hot peppers, salt, and several spices. The result- 

 ing mixture is put inside of "tortillas" forming 

 "quesadillas." Obviously, the people who eat and relish 

 corn smut do not consider it harmful. 



Recent studies show that corn smut can cause 

 human diseases, particularly allergy. Wittich and Stak- 

 man (361i and Harris (125) proved that smuts 

 including corn smut, were responsible for certain 

 respiratory allergies. Preininger's (268) work indi- 

 cated that corn smut was the cause of a derma- 

 tomycosis in man. 



Dragisic and Yaricak (82) and Mayerhofer and 

 Dragisic (213) concluded that corn smut was the 

 cause of an acrodynia-like disease in children. Later, 

 this type of poisoning was called "Ustilagism" (82). 



Several investigators have attempted to isolate the 

 toxic material produced by U. maydis. According to 

 Arthur and Stuart (5), several of the early workers 

 thought the active principle had some resemblance 

 to the toxin in ergot. Rademaker and Fischer (269) 

 called the alkaloid substance "ustilagin.'* Other chem- 

 ists could not verify their findings. Mitchell (228) 

 found that an extract from the chlamydospore acted 

 on the nervous system of frogs, the action being some- 

 what similar to potassium bromide. 



Some of the investigators did not use pure cultures 

 of U. maydis and some were not aware of the tremen- 

 dous genetic variation within the species of U. maydis. 

 This could lead to differences in results. Further, the 

 smut galls produced in nature often harbor many 

 foreign species of fungi and bacteria and these im- 

 purities in the material also may help to account for 

 some of the conflicting results. 



Most of the early reports on the injuriousness of 

 corn smut spores to animals were not based on ade- 



1 Since this paper was written, ergot has been reported 

 on corn in Mexico. Thus it is possible that erratic effects 

 of toxicity from corn smut could arise from ergot mixed 

 with smut. [Fuentes, S., Maria de Lourdes de la Isla, A. 

 J. Ullstrup. and A. E. Rodriguez. 1962. Ergot of maize in 

 Mexico. (Abstr.) Phytopathology 52:733.] 



31 



