GENETIC ANALYSIS OF RESISTANCE TO FUSARIUM EAR ROT (FUSARIUM VERTICILLIOIDES) IN TROPICAL MAIZE (ZEA MAYS L.)

Abstract

Fusarium ear rot of maize is caused by Fusarium verticillioides (=F. moniliforme) and F. proliferatum, with F. verticillioides being the most widespread in Kenya. Fusarium ear rot causes yield loss in maize production and leads to contamination of maize grain with fumonisins that are harmful to both humans and livestock. Breeding for Fusarium ear rot resistance is the most economically feasible method for control of Fusarium ear rot. Knowledge of the inheritance of resistance to Fusarium ear rot infection is important in developing a breeding program for the disease. The objectives of this study were to estimate combining abilities and mode of gene action of maize inbred lines for resistance to Fusarium ear rot and evaluate the performance of single cross hybrids between mid-altitude adapted and lowland tropical inbred lines. Sixteen (16) maize inbred lines from the International Maize and Wheat Improvement Center (CIMMYT) breeding programs in Kenya and Mexico were crossed in a North Carolina design II (NCII) mating scheme to form 60 F1hybrids that were evaluated in trials laid out as alpha-lattice with two replications and two row plots at four locations (Kiboko, Kibos, Alupe, and Kakamega) in Kenya in 2014. The trials at Kibos, Alupe, and Kakamega were artificially inoculated with an isolate of F. verticillioides commonly found in Western Kenya region, and three other trials were planted at the same locations but were not inoculated. Data were collected on grain yield (GY) and agronomic traits, Fusarium ear rot incidence (FSI) and severity (FSE). Analysis of variance and combining ability analysis of the data collected were carried out using SAS. Results indicated significant differences (P < 0.001) between hybrids for GY and FSI across both artificially inoculated and non-inoculated experiments. Inbred lines with the best desirable GCA effects for FSI under artificial inoculation were CKL05024 (-6.29), CML538 (-5.66), CKL05019 (-5.15), and CKL05003 (-5.14). Inbred lines CKL05024, CKL05003, and CKL05019 that also had desirable GCA effects for FSI under natural disease infestation are therefore potentially suitable for use in pedigree breeding to develop Fusarium ear rot resistant germplasm. Inbred lines CL RCW37 (-10.79***), CKL05003 (-12.74***), CML247 (-4.82) and P502c2-185-3-4-2-3-B-2- B*6 (-3.56) had the best desirable GCA effects for FSE across artificially inoculated trials. Inbred lines CKL05003, (CKL05003/CML444//CKL05003) DH5-B, CL-RCW37 and P502c2-185-3-4- 2-3-B-2-B*6 had desirable GCA effects for both FSI and FSE in artificially inoculated trials. Hybrids CML442/CL-RCW37 (-12.83) and CKL05003/ (LaPostaSeqC7-F64-2-6-2-2-B-B B/CML495) DH19-B-B (-10.39) had the best desirable SCA effects for FSI across artificially inoculated trials. Hybrids CKL05003/CML247 (-17.53*), CKL05024/P502c2-185-3-4-2-3-B-2- B*6 (-17.03*), and CKL05003/CML264 (-15.43*) had the best SCA effects for FSE across artificially inoculated trials. These hybrids can be tested further in multiple environments to confirm low FSI and FSE, and quantify fumonisin content before they can be used as parents to develop three-way cross hybrids for the mid altitude ecology of Kenya.