Reaction of popcorn germplasm to polysora rust under field conditions and natural inoculation

Abstract

Polysora rust, caused by Puccinia polysora, is one of the most economically important foliar diseases of maize, and the use of resistant genotypes is the most efficient and economically appropriate measure to control this disease. In popcorn, damage caused by this disease is equivalent to that found in common maize. However, studies on the identification of sources of resistance in popcorn are much more scarce. This study aimed to evaluate the reaction of popcorn genotypes regarding polysora rust resistance. For this purpose, 37 temperate and tropical popcorn genotypes were evaluated in randomized block experiments with four replicates in two crop seasons, in Campos dos Goytacazes, RJ, Brazil. Disease intensity was estimated by quantifying incidence and severity using a diagrammatic scale, based on the plant and the leaf immediately below the first ear. We found that incidence can efficiently replace severity at low epidemic levels, facilitating field diagnostics. Also, we observed genetic variability for traits related to polysora rust resistance. The landraces PARA 172, ARZM 05083 and the line L80 are recommended to integrate breeding populations for Puccinia polysora resistance as they may carry favorable alleles for disease control.

The combining ability of popcorn S7 lines for Puccinia polysora resistance purposes

“…Nevertheless, Kurosawa et al (2016), in a similar study, discriminated popcorn accessions tolerant to Puccinia polysora from the germplasm bank of UENF. They conducted some diallel analyses to estimate the combining abilities aiming at identifying superior hybrids (Hallauer et al 1988;Pinto et al 2007).…”

Research Article Combining ability of popcorn lines for resistance to the fungus <i>Puccinia</i> <i>polysora</i> (Pucciniaceae)

“…To establish hybrids, crosses were made based on a complete diallel design with reciprocals, as proposed by Griffing (1956). To this end, eight popcorn lines were used, previously identified as of interest for introgression of southern rust resistance genes by Popcorn lines resistant to polysora rust 3 Kurosawa et al (2016). The lines (S 7 ) belong to the UENF Popcorn Breeding Program and formed 56 hybrid combinations in paired crosses.…”

“…Although it is a very popular food in Brazil, popcorn grain yields fall short of those of field maize (Santos et al, 2017). One of the reasons for this low production is the higher pest and disease susceptibility of popcorn (Kurosawa et al, 2016).…”

“…However, the use of genetic resistance in popcorn, especially against P. polyssora, is still rare (Mafra et al, 2018). In this context, with a view to the introgression of leaf-disease resistance genes, the popcorn breeding program of the Northern Fluminense State University Darcy Ribeiro (UENF) has been working since 2013 to characterize the resistance of popcorn in the UENF genebank with regard to the complex of corn leaf and ear fungal diseases (Kurosawa et al, 2016;Schwantes et al, 2017;Kurosawa et al, 2018;Mafra et al, 2018), in order to breed improved hybrids.…”

“…Considering the economic losses that occur in popcorn as a result of the attack of the southern rust pathogen, as well as the genetic variability in the UENF genebank (Kurosawa et al, 2016;Santos et al, 2016;Schwantes et al, 2017;Kurosawa et al, 2018), which comprises accessions from various soil-climate regions, the selection of promising genotypes is highly relevant in breeding programs. We evaluated the combining ability and hybrid performance of popcorn lines in this genebank for the development of resistance to southern rust in popcorn.…”