Inheritance of fall armyworm (Spodoptera frugiperda) resistance in tropical maize inbred lines

Abstract

Maize (Zea mays L.) is one of the world’s most important cereals consumed in various forms by more than 1.2 billion people worldwide. Maize yield losses range from 22–67% which is estimated between 2.5 to 6.1 billion United States dollars in sub-Saharan Africa. In addition to reduced grain yield, FAW infestation leads to approximately 20- 80 % higher mycotoxin (fumonisin) contamination when FAW larvae migrate from the leaves to the ears and damage grains compared to non-infested crops. Therefore, the objectives of this study were three: i) To determine and identify new sources of resistance to FAW in diverse tropical maize inbred lines. ii) To estimate combining ability effects for FAW resistance in diverse tropical maize inbred lines and resultant hybrids. iii) To determine the performance and stability of FAW resistance and grain yield in tropical maize hybrids. To assess levels of resistance to FAW, for study one, 112 inbred lines including four inbred line checks (CML536, CML545, CML547 and NML88) were planted in a screen house using a randomized complete block design, artificially infested with neonate larvae in a ‘Choice’ experiment to assess their levels of resistance to FAW. Further three female parents with known resistance to FAW were crossed with a selection of forty-two inbred lines in a North Carolina Design II. Ninety-four resultant hybrids were used in a study for combining ability. Performance and stability trials for FAW resistance and yield across three locations with known high FAW pressure were conducted following a 9 x 11 alpha lattice design. The study found highly significant difference (p ≤ 0.05) for the second FAW score (FAW2), third FAW score (FAW3), average fall armyworm number (AVGFAW) and area under pest progress curve (AUPPC) among the genotypes. The study found that both additive and non-additive gene action control FAW resistance. Narrow sense heritability (h2) estimates among FAW resistance traits were low to high with a range of 0.05 to 0.67. Genotype x environment interactions (GEI) were highly significant (p ≤ 0.001) for FAW resistance traits and key agronomic traits under the study. Two hybrids were the most resistant with CKDHL166087/WL429-12 having a mean of 4.17 followed by CKDHL166087/WL428-27-1A with mean resistance of 4.23. For yield, CML566/CML543 was the best-yielding hybrid with 6.08T/ha followed by CKDHL166087/CZL15088 with 5.07T/ha. Parental lines CKDHL166087, CZL15123, CKDHL120348, DJ92-687, WL429-20, WL118-5 and DJL184910 were the best combiners for FAW resistance and are recommended for utilisation as parents in the development of FAW-resistant hybrids and breeding populations.