General Resistance in Maize to Southern Rust (Puccinia polysora Underw.)

Abstract

Southern corn rust (Puccinia polysora Underw.) is a major tropical disease that can iead to severe yield losses in the tropics. Occasionally it becomes of concern in temperate regions, as in 2010. We summarize 45 yr of research on the occurrence, genetic basis, and breeding of general resistance. Trials were conducted in Colombia, Hawaii, Nigeria, the Philippines, Texas, and Thaiiand. Temperate maize proved uniformly susceptible. No racially specific monogenes were effective. Resistance varied continuously among tropical inbreds and many of these showed stable intermediate toierance.Two diallel populations revealed high correlations of inbred values with hybrid array means and slight heterosis for resistance. Narrowsense heritabilities were 51% and 66%, and mean square ratios for gênerai to specific combining ability (GGA:SCA) were 7.8 and 10.7 to 1. Generation mean analyses were performed on six sets of families. Mean and additive effects were significant across families, while significant nonadditive effects were rare. Heritability values ranged from 19% to 49%. A set of recombinant lines segregated a primary susceptibility locus on chromosome 6. Studies of 137 near-isogenic inbred lines (NILs) of resistant tropical inbred HÍ27 revealed a dominant susceptibility quantitative trait locus (QTL) in the NIL for dwarf-1 locus, but linkage could not be confirmed. Premature senescence was associated with rust infections in many NILs, emphasizing the ubiquity of modifying genes. No correlation existed between resistance to southern and common rusts. Resistant tropical inbreds and populations were bred to serve as sources for future improvement.

QTL Mapping for Partial Resistance to Southern Corn Rust Using RILs of Tropical Sweet Corn

“…Heritability percentage of our mapping populations were categorized in high level [58]. The heritability of resistance for southern corn rust in maize has been studied and reported previously: 79% -86% [36], 93% [37], 51% -66% [12], and 53% -68% [59]. We concluded that the inheritance of resistance for southern corn rust was attributable to the influence from genotypic variation more than environmental variation (V P = V G /V E ).…”

“…The disease has emerged in Thailand since 1967 [12] it caused a severe damage of corn varieties in Nakhonratchasima, Saraburi and Tak provinces. Biodiversity and classification of the pathogens in Thailand were studied using morphology and molecular markers.…”

“…QTL of partial resistance for southern corn rust have been mapped on 6 [12] [39] and co-localization of their QTLs across studies have been done [40].…”

Inheritance of Tolerance of Maize Inbreds to Exserohilum turcicum in North Korea

“…Under the quantitatively resistance model, recurrent selection would be the most appropriate breeding method for improving tolerance. Indeed, several studies have documented significant gains from recurrent selection for NCLB resistance (Brewbaker et al, 2011;Campaña and Pataky 2005;Carson 2006;Ceballos et al, 1991;Jenkins et al, 1954;Pataky 1994) with 15 to 20% reduction in susceptibility per generation (Campaña and Pataky 2005;Carson 2006;Ceballos et al, 1991).…”

“…One tolerant hybrid to NCLB with sustainable yield potential is better than ten hybrids with several single gene controlled race specific high resistance, most of them will be broken down one day. This principle can be applicable universally, particularly under climate change (Brewbaker et al, 2011;Kim et al, 2008).…”