Identification of Tropical and Temperate Maize Populations Having Favorable Alleles for Disease Resistance

Abstract

A possible use of nonelite germplasm is as a source of alleles for disease resistance. Our objective was to determine the value of tropical and temperate maize (Zea mays L.) germplasm accessions as sources of alleles to improve disease resistance of the Corn Belt hybrid FR1064 × LH185. A group of tropical populations and hybrids from the Germplasm Enhancement of Maize Project (GEM) crossed to either Mo17 or B73 (temperate inbreds), was studied. In addition, a group of temperate accessions was evaluated. Reaction to southern corn leaf blight (SCLB) [Bipolaris maydis (Nisikado & Miyake) Shoemaker = Helminthosporium maydis Nisikado & Miyake], northern corn leaf spot (NCLS) [Bipolaris zeicola (G. L. Stout) Shoemaker = Helminthosporium carbonum Ullstrup Races 2 and 3], gray leaf spot (GLS) (Cercospora zeae‐maydis Tehon & E.Y. Daniels), northern corn leaf blight (NCLB) [Exserohilum turcicum (Pass.) K. J. Leonard & E. G. Suggs = Helminthosporium turcicum Pass., Races 1, 1, 2, 23N and three unidentified races] and common rust (Puccinia sorghi Schwein) was studied using Dudley's method for identifying populations with favorable alleles. All accessions had favorable dominant alleles for resistance not present in FR1064 × LH185 for common rust, GLS, and SCLB. Four accessions had a number of favorable alleles for resistance not significantly different from the best accession for all five diseases. Crosses of the accessions containing Mo17 to FR1064 and LH185 were less susceptible to SCLB, NCLB, and rust than crosses of accessions containing B73. At least seven of the best 10 populations were tropical × Mo17 crosses for SCLB, NCLB, and rust when populations were ranked for presence of favorable alleles for resistance not present in either LH185 or FR1064. Net value statistics for tropical × B73 and tropical × Mo17 accessions differed in indicating whether backcrossing or selfing from the F1 is more desirable. Therefore, if tropical populations are crossed to Corn Belt inbreds to increase adaptation, comparisons among tropical populations should only be made when all populations being compared have been crossed to the same Corn Belt inbred.

Maize Hybrids Response to Nitrogen, Potassium Fertilization and Its Relation to Some Fungal Diseases

“…On the other hand, there was no significant difference between the other two hybrids in both seasons. These results are in agreement with those reported by Williams and Hallauer (2000); Kraja et al (2000) who showed that the difference of genotypes in disease severity was due to diversity in their genetic makeup.…”

Mapping QTL Controlling Southern Leaf Blight Resistance by Joint Analysis of Three Related Recombinant Inbred Line Populations

“…With few exceptions (Jiang et al, 1999; Zwonitzer et al, 2010), these studies used populations derived from crosses between two temperate adapted lines. Tropical lines tend to be more resistant than temperate lines to SLB and a number of other diseases due, presumably, to disease being a much more important selection pressure in tropical environments (Goodman, 1999; Kraja et al, 2000). Furthermore, with the exception of Kump et al (2011), each study reported results from analyses of single populations involving the segregation of alleles from two parents.…”

Germplasm Architecture Revealed through Chromosomal Effects for Quantitative Traits in Maize

“…For the five traits studied, PH207‐type inbreds are intermediate to the B73‐ and Mo17‐type inbreds and the Oh43‐ and A321‐type inbreds (Schaefer and Bernardo, 2013b). The Mo17‐type inbreds are known to be resistant to most leaf diseases (Kraja and White, 2000). The signs of the regression coefficients in Fig.…”