Abstract
ABSTRACT The present study resulted from the lack of information on the genotypic expression ruling the resistance to rust and on the main traits of economic importance to the herein addressed crop. The combining ability of 16 popcorn lines and hybrids was assessed in partial diallel cross in two representative locations in Rio de Janeiro State, Brazil, where forty simple hybrids were obtained. The experiments followed a completely randomized block design with four repetitions and were conducted under natural infestation conditions in order to test the southern rust severity in the entire plant (SSW) and in the leaf of the first ear (SFPE), as well as the morpho-agronomic traits of greater interest: grain yield (GY) and popping expansion (PE). Additive gene effects prevailed in PE and the non-additive ones stood out in GY; however, both gene effects were important to the southern rust resistance characteristics (SSW and SFPE). Hybrids L65 × P10 and P7 × L70 presented appropriate specific combining ability (SCA) values in all traits; therefore, they were promising for the selection of superior genotypes. Lines L80, L76 and L77 expressed negative general combining ability (GCA) values in SSW and SFPE; line P10 recorded high and positiveGCA values in GY and PE.
Highlights
Southern rust has become one of the main diseases affecting corn crops in Brazil, mainly those subjected to high temperature and humidity conditions (Ramirez-Cabral et al 2017; Casela and Ferreira 2002)
Significance was detected at 1% probability in all general combining ability (GCA) environments in almost all assessed traits, and it allowed assuming that additive effects are relevant to their expression
Similar to results recorded by Vieira et al (2011), the present study showed the significant effect of specific combining ability (SCA) on SFPE in places other than the Campos dos Goytacazes environment (Tables 1 and 2)
Summary
Southern rust has become one of the main diseases affecting corn crops in Brazil, mainly those subjected to high temperature and humidity conditions (Ramirez-Cabral et al 2017; Casela and Ferreira 2002). Some factors such as the use of susceptible hybrids and monocropping in no-till systems in association with weather conditions favorable to inoculant outspread have increased the occurrence of this disease in Brazilian crops (Colombo et al 2014; Costa et al 2012). Vieira et al (2011) estimated the economic importance and the combining ability of popcorn rustresistance traits via partial diallel They concluded that the additive effects were more important to the poppingexpansion expression and to southern rust severity. They concluded that the additive effects were more important to the poppingexpansion expression and to southern rust severity. Vieira et al (2012) assessed the possibility of breeding popcorn to achieve blotch and Cercospora leaf spot resistance and found that the additive genes were very important to the expression of these diseases
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