LLAVALLOL, ARGENTINA
Instituto Fitotecnico De Santa Catalina

Early waxy and high quality protein maize inbreds: study of fungal diseases
--Corcuera, VR, MarÌa C. Sandoval, MC

Since 1990 at the Institute a maize breeding plan to obtain high quality protein and waxy commercial hybrids useful for industrialization procedures, has been carried out. The characterization of the original populations, as well as the inbreds developed from them, through morphological, biochemical and resistance traits, is necessary and important to make a correct description and evaluation of the materials. It is interesting to detect the response of the different maize genotypes to pathogens in an early stage of their selection whilst inbreeding. In this paper, a summary about fungal diseases affecting maize in the Southern area of the Province of Bs. As. is presented.

Thirty-seven early maize inbreds were sown at the experimental field in a randomized block design with three replicates. Each pedigree was placed in a 7m2 plot using a density of 71,500 plants/ha. No fungicides were applied to the seeds nor to the field. Over 1,273 individual plants were scanned for the appearance of fungal diseases. The identification was done in the field and later confirmed at the lab through isolation, culture and histology techniques.

Puccinia sorghi (Schw.) was the most important pathogen detected. It appeared in all the maize genotypes at a medium degree of infection (grade 2, rust disease scale). By decreasing order of incidence on maize plants, the following pathogens were also observed: Kabatiella zeae, Sclerospora sorghi (Kulk), Physoderma maydis (Miyabe), Ustilago maydis (DC) Corda and Curvularia lunata. About Ustilago maydis it has to be said that produced not only the classic tumours or galls in the ears, but in 5 inbreds also promoted the appearance of male spikelets in ears and tassel-seed.

Table 1. Percentage of diseased waxy maize inbred plants produced by 8 different fungal pathogens.
 
Inbred A1 B2 C3 D4 E5 F6 G7 H8
54 45.00 - 10.00 - - - 10.00 -
58 43.75 - - - 12.50 - - -
63 87.50 - - - - 12.50 - -
64 38.46 53.48 - - 7.69 - - -
65 83.33 16.66 - - - - - -
71 100 - - - - - - -
72 87.50 - - 12.50 - - - -
73 90.00 10.00 - - - - - -
74 50.00 - - - - - - 50.00
75 72.22 - - - - - - 5.55
76 61.90 - - - - - - 28.57
77 63.63 22.72 - - - - - -
78 25.00 - - - - - - 25.00
79 25.00 - - - - - - 75.00
147 42.85 - 10.71 3.57 - - - -
146 61.53 - - - - - -  
141 87.57 - - 3.03 - - - -
138 94.73 - - 5.26 - - - -
134 77.27 - 9.09 - - - - -
129 50.00 10.52 - - - - - -
128 61.53 2.56 2.56 - 2.56 5.12 - -
127 57.89 - 5.26 - - - - -
126 56.66 - 6.66 3.33 - - 3.33 -
83 60.00 - - - 20.00 - - 20.00
85 88.23 - 11.76 - 5.88 - - -
87 60.00 - - - - - - 6.66
90 13.33 13.33 - - 40.00 26.66 - 0.15
80 100 - - - - - - -
151 96.29 3.70 - - - - - -
Ref: 1P. sorghi; 2H. turcicum; 3H. maydis; 4U. maydis; 5S. sorghi; 6C. lunata; 7K. zeae; 8P. maydis.

Table 2. Percentage of diseased plants produced by 8 fungal pathogens on opaque2 maize inbreds.
 
Inbred A1 B2 C3 D4 E5 F6 G7 H8
152 33.33 33.33 33.33 - - - - -
145 62.50 - 12.50 6.25 - - - -
133 100 - - - - - - -
132 84.20 - 5.26 - - 5.26 5.26 -
131 64.00 - - - - 12.00 4.00 -
130 100 - - - - - - -
Ref: 1P. sorghi; 2H. turcicum; 3H. maydis; 4U. maydis; 5S. sorghi; 6C. lunata; 7K. zeae; 8P. maydis.


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