A Rice Black-Streaked Dwarf Virus Replication Curve Model to Evaluate Maize Rough Dwarf Disease Resistance

Resistance to maize rough dwarf disease (MRDD), a major cause of crop losses, depends on external conditions such as the virus transmission period and the rate of viruliferous small brown planthoppers, Laodelphax striatellus. The precise identification of MRDD contributes to the utilization of resistant germplasm and the cloning of resistant genes. In this study, eight maize varieties were artificially inoculated in a greenhouse with viruliferous planthoppers. The viral titers in maize seedlings were detected by quantitative fluorescence RT-PCR, and the viral replication curves were analyzed by regression. A logistic model fit the Rice black-streaked dwarf virus (RBSDV) replication data for five susceptible varieties well, whereas a linear model fit the data for three resistant varieties. Among the five susceptible varieties, the time points with the maximum replication rates (t) of the highly susceptible Ye478 and XH6 were significantly earlier than those of the three susceptible varieties, Mo17, Zheng58, and Zhengdan958. P138, the most highly resistant variety, had the lowest slope of the best fit line, followed by moderately resistant Chang7-2 and Dan 340. The RBSDV replication curve model developed in this study can accurately identify the resistance of maize germplasm to MRDD at the molecular level. Our results also suggested that t and the slope of the RBSDV replication curve can be considered new criteria to evaluate maize resistance to MRDD.