Alternate hosts and seed transmission of maize lethal necrosis in Ethiopia

Abstract

Maize lethal necrosis (MLN) disease caused by double infection of Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV) has become a major maize production constraint in Ethiopia. A field survey was conducted in areas where MLN infection was reported to identify naturally infected alternate hosts. MCMV host range was also studied by artificially inoculating various weed species in the greenhouse to determine potential alternate hosts. Using the serological method of double‐antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) test, MCMV was detected in 23 (20.35%), and SCMV was detected in 4 (3.53%) of 113 MLN symptomatic samples collected from the field, while combined infection of both viruses was detected in 11 (9.73%) of the samples. Poaceae family had the highest number of grass species that were alternate hosts for MLN causing viruses. Digitaria sanguinalis, Phalaris paradoxa, Oplismenus hirtellus, Echinocloa colona, Cynodon nlemfuensis, Pennisetum purpureum from Poaceae and Cyperus cyperoids from Cyperaceae family were naturally infected by MCMV. Cyperus rotundus, sugarcane (Saccharum officinarum) and sorghum (Sorghum bicolor) were infected by both MCMV and SCMV under natural field conditions. In addition, seed transmission study was conducted using growing‐on tests to determine the potential of seed transmission and its role in the spread of MLN. Overall mean seed to the seedling transmission rate was 0.073% with a range of 0 to 0.17% among 20 different maize varieties studied. Fourteen maize genotypes had some levels of seed transmission (0.03%–0.017%) for MCMV, whereas, SCMV seed transmission was observed only in a single plant of one genotype, with an overall mean of only 0.003%. Seed transmission rates of the viruses were influenced by the seed lot and maize varieties used. The wide ranges of natural and experimental alternate hosts and seed transmissibility of MLN causing viruses suggest that the viruses play a greater role in MLN epidemiology.

Occurrence, Distribution, Economic Importance and Management of Maize Chlorotic Mottle Virus: A Review

“…Depending on the host genotype, MCMV infection symptoms range from mild to severe chlorotic mottle, leaf necrosis, stunted growth, a shortened male inflorescence with few spikes, malformed or partially filled ears, and premature death of plants (Niblett and Claflin, 1978;Uyemoto et al, 1981;Regassa et al, 2021).…”

“…Severely affected plants form small cobs with little or no grain set (Fig 2 f and g). The entire crop can frequently be killed before tasseling (Niblett and Claflin, 1978;Uyemoto et al, 1980Uyemoto et al, , 1981Wangai et al, 2012;Regassa et al, 2021).…”

“…The following Table (Table 1) provides the year in which samples first tested positive for MCMV in each country it has reported in. (Wang et al, 2014;Kusia et al 2015;Mahuku et al, 2015;Regassa et al, 2021). The most recent study (Regassa et al, 2021) showed that the Poaceae family had the highest number of grass species and Cyperaceae family (Cyperus cyperoids and Cyperus cyperoides) species were alternate hosts for MCMV (Regassa et al, 2021).…”

“…Most of the natural alternative hosts identified were annual and perennial grasses in nature (Table 2), and common in the maize growing areas. Regassa et al (2021) Different types of MCMV symptoms were observed on different plant species of its natural alternative hosts. The symptoms observed included mosaic, mottling, yellowing, necrosis that develop from leaf margins to the mid-rib, and purple discoloration of leaves.…”

“…For instance, MCMV symptoms on Cyperus cyperoids and Snowdenia polystachya were expressed as yellowing, while it showed mosaic and chlorotic symptoms on Oplismenus hirtellus (Fig. 2) (Regassa et al, 2021). Bockelman et al (1982) has identified a broad range of MCMV experimental host range that includes at least 19 grass species, but it does not infect dicots.…”