Preliminary studies to determine the degree of resistance to
Ustilago maydis D.C. Corda in wild and cultivated species of the
genus Zea
--Astiz Gassó, MM; Molina, MC
The purpose of the current work is to determine the degree of
resistance of wild and cultivated species of the genus Zea to
Ustilago maydis D.C. Corda (Um), which will subsequently be used
in crosses to obtain new forage plants (Molina M.C. and Rosales
;T.P., Rev. Facultad Agr. 54:579-586, 1984). The host materials
used were the population cv. Colorado Klein and the inbreds
SC66, B73 and E642A88 of Zea mays ssp. mays as well as clones
of Z. diploperennis and Z. perennis.
All the materials were inoculated with a strain of Um belonging
to the collection of the Phytopathology Lab. of the Instituto
Fitotécnico de Sta. Catalina. The strain was cultivated in a liquid
medium of 2% C.P.G, under shaking for 8 days running at 25 C.
The pathogen was inoculated using a hypodermic syringe. The
trial involved three replications, in which 60-30 seedlings were
inoculated (Hirschhorn, E., Las Ustilaginales de la Flora
Argentina CIC 530 p., 1986). The plants were evaluated using a
reaction scale (Table 1) to determine the mean percent infection
of the Um fungus.
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The results obtained point out that the population cv.
Colorado Klein and the inbred SC66 (Z. mays ssp. mays), as well
as the clones of Z. perennis and Z. diploperennis, are the most
tolerant and show a good response to Um. Some plants of the
inbreds B73 and E642A88 were lightly susceptible or
susceptible (Table 2).
Table 1. Reaction scale in hosts.
| Behaviour | Host reaction |
| Immune (0) | No reaction |
| Resistant(1) | Chlorosis partial |
| Medium resistant (2) | chlorosis accent and /or presence stripe or anthocyanin stain |
| Medium susceptible (3) | Necrosis and diminution growth in plants |
| Susceptibles (4) | Formation of tumors (galls) |
Table 2. Result of the reaction in species of Gro. Zea with isolates of U. maydis. (Sta.
Catalina) in Argentina.
| Hosts | No.
Plants | Total plants
Infected | Means of the reaction in plants (%) |
| | 0 1 2 3 4 | 0 1 2 3 4 |
| Colorado Klein | 60 | 5 25 26 4 0 | 1.66 8.33 8.66 1.33 0.00 |
| SC66 | 60 | 5 25 25 4 0 | 1.66 8.33 8.33 1.33 0.00 |
| B73 | 60 | 4 19 20 10 7 | 1.33 6.33 6.66 3.33 2.33 |
| E642A88 | 60 | 1 17 22 16 4 | 0.33 5.66 7.33 5.33 1.33 |
| Zea perennis | 30 | 15 4 8 2 1 | 5.00 1.33 2.66 0.66 0.33 |
| Zea diploperennis | 30 | 11 7 10 1 1 | 3.66 2.33 3.33 0.33 0.33 |
| Testigo | 30 | 0 0 0 0 0 | 0.00 0.00 0.00 0.00 0.00 |
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors
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