Identification and diversity of tropical maize inbred lines with resistance to common rust (Puccinia sorghi Schwein)

Abstract

Common rust (CR) caused by Puccinia sorghi Schwein is one of the major foliar diseases of maize (Zea mays L.) in Eastern and Southern Africa. This study was conducted to (i) evaluate the response of elite tropical adapted maize inbred lines to Puccinia sorghi and identify resistant lines (ii) examine associations between CR disease parameters and agronomic traits, and (iii) assess the genetic diversity of the inbred lines. Fifty inbred lines were evaluated in field trials for three seasons (2017–2019) in Uganda under artificial inoculation. Disease severity was rated on a 1–9 scale at 21 (Rust 1), 28 (Rust 2), and 35 (Rust 3) days after inoculation. Area under disease progress curve (AUDPC) was calculated. The genetic diversity of the lines was assessed using 44,975 single nucleotide polymorphism markers. Combined ANOVA across seasons showed significant (P < .001) line mean squares for the three rust scores and AUDPC. Heritability was high for Rust 2 (0.90), Rust 3 (0.83), and AUDPC (0.93). Of the 50 lines, 12 were highly resistant to CR. Inbred lines CKL1522, CKL05010, and CKL05017 had significantly lower Rust 3 scores and AUDPC compared to the resistant check CML444 and are potential donors of CR resistance alleles. The genetic correlations between CR disease resistance parameters were positive and strong. A neighbor‐joining (NJ) tree and STRUCTURE suggested the presence of three major groups among the lines, with lines highly resistant to CR spread across the three groups. The genetic diversity among the highly resistant lines can be exploited by recycling genetically distant lines to develop new multiple disease resistant inbred lines for hybrid development and deployment.

Studies of Evaluation Methods for Resistance to Fusarium Wilt Race 4 (Fusarium oxysporum f. sp. vasinfectum) in Cotton: Effects of Cultivar, Planting Date, and Inoculum Density on Disease Progression

“…In this study, highly susceptible Pima S-7 had the highest regression coefficients on each planting date, while FM 2334 RF had the lowest regression coefficients on two planting dates (5/7 and 6/17), and PHY 725 RF and Pima PHY 881 RF had similar and intermediate regression coefficients. Thus, the regression coefficient (slope) can be used to compare levels of resistance among different cotton germplasm lines instead of using DSR or MR at only one-time point, in addition to the area under the disease progress curve (AUDPC) that is used to quantitatively summarize disease severity over time, for comparison among cultivars (Simko and Piepho, 2012 ; Fernández-Campos et al, 2020 ; Serumaga et al, 2020 ; Zhu et al, 2021a , b ). Fernández-Campos et al ( 2020 ) recently showed that logistic models (polycyclic) provided the best fitting disease progress curve in all eight tested wheat cultivars against the wheat blast disease, which was followed by the Gompertz model; however, epidemiological parameters differed between genotypes.…”

Introduction to the special Crop Science issue: Celebrating the International Year of Plant Health

“…Finally, Sserumaga et al. (2020) studied tropical maize lines with resistance to common rust ( Puccinia sorghi Schwein) evaluated in Uganda. They also assessed the genetic diversity and population structure within these lines.…”

Use of remote sensing for linkage mapping and genomic prediction for common rust resistance in maize

“…Common rust (CR) in maize ( Zea mays L. ), caused by an obligate fungal pathogen Puccinia sorghi Schwein, is one of the most pervasive diseases in many maize-growing regions ( Sserumaga et al, 2020 ), and yield losses of up to 49% were reported in susceptible germplasm ( Groth et al, 1983 ). Because of the severity of the disease, several authors have investigated the genetic basis of resistance to CR and have identified different quantitative trait loci (QTL) ( Kerns et al, 1999 , Danson et al, 2008 , Zheng et al, 2018 , Ren et al, 2021 ).…”