A note on the association between Thecaphora frezzii infection and peanut pod density

Authors: Bennett, Rebecca; RODRIGUEZ, ANA - Instituto De Clima Y Agua (INTA); BALDESSARI, JORGE - Instituto De Clima Y Agua (INTA); Chamberlin, Kelly; PAYTON, MARK - Oklahoma State University; WANG, NING - Oklahoma State University

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2021
Publication Date: 2/3/2021
Citation: Bennett, R.S., Rodriquez, A.V., Baldessari, J.J., Chamberlin, K.D., Payton, M.E., Wang, N. 2021. A note on the association between Thecaphora frezzii infection and peanut pod density. Peanut Science. 48(1):54-60. https://doi.org/10.3146/PS20-27.1.
DOI: https://doi.org/10.3146/PS20-27.1

Interpretive Summary: Peanut smut, which is currently present only in South America, is an emerging pathogen causing great concern. In Argentina, peanut smut can result in yield losses of up to 35% and has led to restrictions against this country's peanut exports. Proactive efforts are thus underway to breed smut-resistant peanuts for the U.S. However, one major obstacle to breeding efforts is the time and labor required to screen for disease resistance. The current screening method consists of opening each pod by hand and inspecting it visually for smut. Our research addressed this problem by examining pod densities, finding that the densities of healthy mature and immature pods differed from infected mature and immature pods. In addition, we confirmed that the presence or absence of infection is strongly correlated with the amount of disease within pods. This information can be used to develop more efficient methods than hand screening for identifying infected pods, enabling peanut breeders to develop resistant cultivars faster to protect the U.S. peanut industry.

Technical Abstract: The time and labor required to hand-screen germplasm are significant obstacles to developing cultivars resistant to peanut smut, but researchers have investigated few alternatives to manual disease evaluations. Although alternative approaches are available for separating materials based upon differences in density, it is unknown how healthy and infected pods differ in density, especially with the varying maturity levels present in real-world samples. For this reason, the pod densities from 13 peanut genotypes were estimated using a sand displacement approach. In addition, disease incidence and severity data were collected from a total of 45 plants representing 15 genotypes varying in resistance to peanut smut. As expected, the results from the pod density analyses showed significant differences between healthy mature and healthy immature pods. However, healthy mature and healthy immature pods were significantly more and less dense, respectively, than both healthy infected and immature infected pods. Thus, methods employing differences in pod density may be useful for screening germplasm. Analyses of the disease incidence and severity data showed a strong positive correlation between the two disease measures, verifying a previous report. As a result, collecting disease incidence data alone should be sufficient for screening germplasm. These results may assist in developing more efficient phenotyping methods for screening germplasm for peanut smut resistance.