Maize Genetics Cooperation Newsletter 80. 2006.

 

LLAVALLOL, ARGENTINA

Instituto Fitot�cnico de Santa Catalina (FCAF, UNLP)

 

Evaluation of incidence and severity of Puccinia sorghi and other diseases in the inbreds of Andino-Patagonico in Argentina

--Llama, AM; Benigni, MR; Dulau, D; Garc�a Stepien, LE; Astiz Gass�, MM; Molina, MC

 

       During the 2004/05 growing seasons, Andinas-Patagonicas inbreds were evaluated for response to the attack of the fungal pathogen responsible for maize rust and other leaf diseases.  The selected lines were from the Institute Fitot�cnico de Santa Catalina:  SC1, SC3, SC4, SC6, SC7, and SC9 were harvested from the west Patagonica zone in Argentina and X Region in Chile.  Also included were one early line, F2 (France), and two lines of average cycle, B73 and Mo17 (USA).  The materials were sown on 2 dates, with the second 20 days after the first.  The severity of attack was determined for three leaves:  Leaf 1: under ear, Leaf 2: ear leaf and Leaf 3: above the ear.  Plants with one pustule or less were considered to be tolerant (t).

       Most lines present a high incidence (>70 %) of P. sorghi for both plantings, with the exception of SC1 (46%) (Table 1).  Lines SC4 and SC6 exhibited reduced severity (Table 2).  We also observed the presence of other diseases, such as leaf spot caused by Helminthosporium sp. and also corn smut, caused by U. maydis.  These were of lesser severity.  In the majority of cases, the incidence was more obvious for the first planting (Table 2).

 

Table 1.  Frequency of Puccinia sorghi  infection.

 

 

Lines

1st Planting

% infected

2nd Planting

% infected

SC1

46

100

SC3

87.7

100

SC4

96.9

88.4

SC6

76.4

86

SC7

85.1

81

SC9

95.2

85.6

F2

76.9

100

B73

47.5

89.4

Mo17

100

47.9

 

Table 2.  Severity of Puccinia sorghi infection in leaves.

 

 

1st Planting

P. sorghi

leaf 1

%

P. sorghi

leaf 2

%

P. sorghi

leaf 3

%

 

Other diseases

SC1

0-t

0-t

0-t

Helminthosporium spp

SC3

0-1

0-1

0-1

Helminthosporium spp

SC4

0-1

0-1

0-1

U. maydis,

Helminthosporium spp

SC6

0-1

0-1

0-1

Helminthosporium spp

SC7

0-1

0-1

0-1

U. maydis, Helminthosporium spp

SC9

0-5

0-5

0-5

Helminthosporium spp

F2

0-10

0-15

0-10

------

B73

0-10

0-10

0-10

------

Mo17

0-15

0-10

0-10

U. maydis

 

2nd Planting

P. sorghi

leaf 1

%

P. sorghi

leaf 2

%

P. sorghi

leaf 3

%

 

Other diseases

SC1

0-20

t-30

t-30

------

SC3

0-5

t-10

t-10

Helminthosporium spp

SC4

0-t

0-1

0-1

------

SC6

0-t

0-1

0-1

------

SC7

0-1

0-1

0-1

U. maydis

SC9

0-1

t-5

0-1

------

F2

t-5

t-5

t-5

------

B73

0-t

0-t

0-t

------

Mo17

0-1

0-1

0-1

------

Scoring:  None ------ ; average: 0-30% ; t : tolerant.

 

       The lines SC4 and SC6 were selected to continue improving tolerance to maize rust and other diseases in the materials employed in this breeding.

 

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