Genetic resistance and gene action of maize germplasm to Maize streak virus

Abstract

Maize streak virus (MSV, genus Mastrevirus, family Geminiviridae) transmitted by leafhoppers (Cicadulina spp.) can cause severe yield losses in susceptible maize (Zea mays L.) varieties. MSV is endemic in all the maize producing regions in sub-Saharan Africa (SSA). Use of maize lines and hybrids with appreciable levels of MSV tolerance remains the most effective and reliable control option. Knowledge of resistance background and mode of gene action is critical for breeding MSV-tolerant varieties. Two hundred and fifty maize inbred lines and their F1 hybrids derived from the cross with MSV–tolerant inbred Tzi3 were arranged in alpha lattice design with two replications under screenhouse and field conditions, respectively. At 2 to 3 leaf stage seedlings were inoculated using viruliferous leafhoppers (Cicadulina triangula). Disease severity (scale 1 – 5; 1 means <10 % of leaf area covered with streak symptoms; 5 implies >75 % of leaf area covered with streaks) and yield components were recorded. Resistance classes were based on Area Under the Disease Progress Curve (AUPDC) determined by plotting the data on disease severity over time. Twenty seven (10.8%), 49 (19.6%) and 53 (21.2%) lines were highly resistant, resistant and moderately resistant, respectively. Amongst the hybrids, 28 were highly resistant, whereas 45 (18%) each were resistant and moderately resistant. The highest grain (6 t/ha) and cob yield (5.6 t/ha) were recorded in the highly resistant (Plot 1445 × Tzi3) and resistant hybrids (Plot 1452 × Tzi3), respectively. Cob weight per plant (257.9 g), grain weight per plant (173.6 g), and kernel number per plant (578) were highest in the moderately resistant hybrids (Plot 1381 × Tzi3). Resistance was polygenically inherited and under the influence of both dominant and recessive genes. Simple recurrent selection would facilitate maize breeding for MSV resistance in SSA.