Sorghum Germplasm Tolerant to Greenbug (Homoptera: Aphididae) Feeding Damage as Measured by Reduced Chlorophyll Loss

Publication Type

Journal Article

Journal Name

Journal of the Kansas Entomological Society

Publication Date

4-1-1998

Abstract

The SPAD chlorophyll meter was used to assess tolerance to feeding damage by the greenbug, Schizaphis graminum (Rondani). Grain sorghum [Sorghum bicolor (L.) Moench] cultivars considered tolerant by the tolerance index (TI) and measurements of proportional dry weight change (DWT) measurements, also were found to be tolerant in terms of reduced chlorophyll as quantified by the SPAD chlorophyll meter. This result indicated that the SPAD meter could be used as a rapid method of assessing plants tolerant to aphids. Damage progression tests, in which SPAD readings taken days after greenbugs were removed, confirmed earlier work that chlorophyll loss continued in the absence of greenbugs; the rate of chlorophyll loss varied among cultivars studied. The susceptible sorghum cultivar 'KS 86' lost chlorophyll twice as fast as the tolerant cultivar 'Cargill 607E' did. The proportional chlorophyll loss, represented by the SPAD Index, at a specified point in time, as well as the rate of chlorophyll loss (damage progression) could be utilized as a method of assessing tolerance. Sorghum germplasm accessions were screened for tolerance to greenbug biotype I using the SPAD Index. Out of 51 accessions screened, 11 were tolerant enough, as compared to 'NC+ 160' (control), to be tested further. The pooled test of these accessions showed that the germplasm accession PI 550610 was highly tolerant to biotype I greenbug feeding damage; PI 550610 only lost 22.9% as much chlorophyll as the susceptible check. Eight other entries also lost significantly less chlorophyll due to biotype I greenbug feeding damage, than the susceptible check.

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