Evaluation of Tanzanian maize germplasms for identification of resistant genotypes against maize lethal necrosis

Abstract

Experiments were conducted in season 2014B at Naivasha maize lethal necrosis screening facility to evaluate Tanzanian maize germplasms for resistance to maize lethal necrosis (MLN). One hundred and fifty-two maize landraces and 33 inbreed lines were artificially inoculated with maize chlorotic mottle virus and sugarcane mosaic virus isolates in two trials arranged in a completely randomized design (CRD) and two replications. Inocula for both virus isolates were prepared, combined and applied to the trials by a 12 L backpack mist blower 4 and 5 weeks after planting. Disease incidence was assessed based on a 1 to 5 MLN rating scale 14, 28, 42 and 72 days post inoculation (dpi) for landraces and 7, 14, 21 and 52 dpi for inbred lines. Significant phenotypic variations (P<0.05) were observed on landraces for symptoms and disease severity scores. Landrace TZA-2793 had the lowest mean score of 3.5 followed by the other four landraces: TZA-3585, TZA-3543, TZA-4505 and TZA-2292, which attained a mean score of 3.75. No significant variations (P>0.05) were detected on inbreed lines as all materials were susceptible to MLN with scores ranging from 4.5 to 5 except for resistant check CML494 (mean score of 3.75). In this study, five maize landraces were identified as tolerant candidates against MLN. The identified landraces should be subjected to further MLN testing to explore their potential in breeding for MLN resistance.