Abstract
ABSTRACT The genetic resistance to diseases in plants represents an important support pillar in modern agriculture. This study aimed to determine the genetic inheritance to anthracnose stalk rot resistance in tropical maize. Nine segregating families were obtained from contrasting inbred lines crosses. The parental lines and the filial generations (F1, F2, BC1 and BC2) were evaluated for antrachnose stalk rot resistance in an experiment in randomized blocks, with three replications. The treatments were arranged in a split-plot design, with family effect in the plots and generation effect in the split-plots. The results showed a similar inheritance among the families, with predominance of additive genetic effects. The inbreed lines (LR 04-2, LR 03-2 and LR 23-1) were very effective in transmitting resistance genes to their descendants because they allowed sharp decreases in the lesions length in the stalks. It was also possible to notice an oligogenic inheritance involved in the anthracnose stalk rot resistance for the evaluated families. It may be inferred that genetic gains from artificial selection could be successful for developing maize inbred lines more resistant to anthracnose stalk rot.
Highlights
In Brazil, the maize-on-maize succession and increase in no-till crop areas over crop residues, without crop rotation, have contributed to a favorable environment for development of stalk rot diseases (Fusarium verticillioides, Giberella zeae, Stenocapella sp., Colletotrichum graminicola) that previously had been considered of secondary importance for the crop (Costa et al 2008, Matiello et al 2012)
The inoculation of the maize stalks with C. graminicola in the different generations of the respective families confirmed, according to the internal length of the lesion (ILL) and number of discolored internodes (NDI) variables, that the pathogen isolate was pathogenic, because it always conferred a greater length of lesions in the stalks in susceptible lines (LS 71-1, LS 95-1 and LS 99-4)
The analysis of the mean values for ILL and NDI confirmed highly contrasting differences among the maize inbred lines used in the families development, in relation to the reaction to C. graminicola (Table 1)
Summary
In Brazil, the maize-on-maize succession and increase in no-till crop areas over crop residues, without crop rotation, have contributed to a favorable environment for development of stalk rot diseases (Fusarium verticillioides, Giberella zeae, Stenocapella sp., Colletotrichum graminicola) that previously had been considered of secondary importance for the crop (Costa et al 2008, Matiello et al 2012). Anthracnose stalk rot, caused by Colletotrichum graminicola (Ces.) Wils, can bring significant crop damage and considerable economic losses. In Brazil, a predominance of C. graminicola (62.7 %) was observed among the main pathogens associated with stalk rot in maize (Costa et al 2008). Damage caused by rotting at the stalk base is still not common in Brazil. Matiello et al (2013) estimated a significant In the Paraná state, Nazareno (1989) reported damage to yield of 1240 %, depending on the year, location and hybrid used. Matiello et al (2013) estimated a significant
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