Resistance breeding strategy for Stenocarpella maydis and Fusarium graminearum cob rots in tropical maize

Abstract

Maize cob rot caused by Fusarium graminearum and Stenocarpella maydis affects grain yield and quality. The objective of this study was to investigate the appropriateness of multiple infection as a selection and breeding strategy for multiple resistance to F. graminearum and S. maydis. Twelve tropical inbred lines with varying resistance to either or both pathogens were mated in a full diallel and the progeny and their parents evaluated for reaction to single or multiple infection. Under multiple inoculation, S. maydis suppressed colonization of cobs by F. graminearum. General combining ability (GCA) effects indicated that inbred WL 118-10 effectively transmitted resistance to both diseases. Hybrids' resistant to S. maydis was also resistant to F. graminearum, but the reverse was not true. Therefore, efficient screening should initially involve screening for S. maydis followed by F. graminearum. Overall, the suppression of F. graminearum by S. maydis shows that multiple infection cannot be used as an appropriate breeding strategy to obtain multiple resistance. The use of F. graminearum and S. maydis separately is, therefore, the best breeding strategy.Pathogen culture and inoculation: The pathogens were initially isolated from infected cobs obtained from NaCRRI fields. Inoculum was prepared wileyonlinelibrary.com Plant Breeding 132, 83-89 (2013)

Effects of Stenocarpella maydis in seeds and in the initial development of corn

“…In this study, the small difference between the cultivars in relation to the incidence of S. maydis, observed in the healthy test, showed that despite the commercial corn hybrids being rated as to their resistance to stalk and ear rot (Casa et al, 2006;Denti et al, 2002), in practice little difference was observed between the strength of the materials considered susceptible (C1) and moderately resistant (C2), which in fact, according to Tembo et al (2013), is still a challenge for breeders. Based on the results of the assessment of incidence, it was also possible to infer that 24 hours of exposure to fungal colony would be enough for 50% of the seeds are infected, which can be useful not only for assessment of materials, but also to assess seed treatment, among other purposes.…”

Evaluation for stable resistance to Stenocarpella maydis in tropical maize (Zea mays L.)

“…To curb this vice, deployment of resistant genotypes through breeding is the most cost effective way especially for the resource poor farmers in Zambia. However, resistance to S. maydis is greatly affected by underlying issues of gene interactions and the type of germplasm under study (Mukanga et al, 2011;Tembo et al, 2013). Identification of genotypes with stable resistance across locations can be utilized as the source of resistance in genotypic combinations (Tembo et al, 2013).…”

“…However, resistance to S. maydis is greatly affected by underlying issues of gene interactions and the type of germplasm under study (Mukanga et al, 2011;Tembo et al, 2013). Identification of genotypes with stable resistance across locations can be utilized as the source of resistance in genotypic combinations (Tembo et al, 2013). A higher number of resistant parental genotypes to S. maydis in mating combinations are likely to produce a larger proportion of stable resistant off-springs.…”

“…In addition, it should be realized that effectiveness of breeding for stable resistance may be influenced by the type of isolates and its interaction with the environment (Rossouw et al, 2009). Previous studies have established multiple inoculations of different ear rot pathogens, as not an appropriate breeding strategy due to antagonistic effects associated with these pathogens (Tembo et al, 2013). Little is known about the effect of multiple isolate inoculations of S. maydis in breeding for resistance.…”

“…Further breeding for stable resistance will therefore depend on the reaction effect of isolates when multiple inoculated. A previous study indicated that multiple pathogen inoculation should be employed for stable resistance if there are synergetic effects among pathogens (Chilipa et al, 2016) while this cannot clutch for pathogen combination with antagonistic effect (Tembo et al, 2013). The specific objective of this study therefore was i) to determine the appropriateness of multiple isolate inoculation on maize ear in breeding for stable resistance to Stenocarpella maydis and ii) to identify genotypes with stable resistance.…”