Flowering time and productivity of interspecific grafts between pepper species in contrasting high tunnel-sheltered and open-field production environments in Costa Rica

Authors: VEGA ALFARO, ANDREY - UNIVERSITY OF WISCONSIN; RAMIREZ, CARLOS - THE TECHNOLOGICAL OF COSTA RICA (TEC); CHAVEZ, GERMAN - THE TECHNOLOGICAL OF COSTA RICA (TEC); LACAYO, FERNANDO - THE TECHNOLOGICAL OF COSTA RICA (TEC); Bethke, Paul; NIENHUIS, JAMES - UNIVERSITY OF WISCONSIN

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2021
Publication Date: 10/15/2021
Citation: Vega Alfaro, A., Ramirez, C., Chavez, G., Lacayo, F., Bethke, P.C., Nienhuis, J. 2021. Flowering time and productivity of interspecific grafts between pepper species in contrasting high tunnel-sheltered and open-field production environments in Costa Rica. HortTechnology. 31(6). https://doi.org/10.21273/HORTTECH04904-21.
DOI: https://doi.org/10.21273/HORTTECH04904-21

Interpretive Summary: Sweet pepper production in many locations is constrained by the presence of pathogenic organisms in the soil. One solution to this problem is to grow plants in high tunnels with hydroponic irrigation of soilless potting medium. Another way is to graft elite sweet pepper scions onto rootstocks having resistance to the pathogen. In this study, grafted plants were grown in high tunnels and in open fields and data were collected for time to flower, yield and fruit characteristics. Significant increases in yield per plant, fruit number per plant and reduced days to flower were observed in the high tunnel compared to the open-field environment. In the open-field environment, yield and fruit number were highest on scions grafted onto disease resistant rootstock. Regardless of graft treatment, the high tunnel environment resulted in significant increases in yield and fruit number compared to open-field production. No advantage of grafted plants was observed in the high tunnel production environment. In contrast, in the open-field environment, grafting sweet pepper scions onto resistant rootstock resulted in a significant increase in yield, fruit number and individual fruit size compared to control plants. These findings indicate that both high tunnel production and grafting to disease resistant rootstocks can benefit producers of sweet peppers who are confronted with soil-borne pathogens.

Technical Abstract: Production of peppers (Capsicum annuum L) is often constrained, especially in tropical environments, by susceptibility to persistent soil-borne pathogens such as Ralstonia solanacearum. Production in high tunnels using clean soil media and automatic nutrient irrigation is one way to reduce the incidence of soil pathogens. An additional strategy for disease management is the use of sweet pepper scions grafted onto rootstocks that are reistant to soil-borne pathogens. Two sweet pepper cultivars grown extensively in the tropics, ‘Nathalie’ and ‘4212’ were used as scions and were grafted onto ‘Habanero TEC’ (C. chinense) and ‘Baccatum TEC’ (C. baccatum). Self-grafted and non-grafted plants of scions were included as checks. Graft combinations were grown in a high tunnel with automatic nutrient solution irrigation and an open field with known levels of R. solanacearum inoculum. The consistent ranking of the area under disease progress curve (AUDPC) scores over two phylotypes suggests that the C. chinense cultivar ‘Habanero TEC’ and to a lesser degree the C. baccatum cultivar ‘Baccatum TEC’ may increase to R. solaacearum and therefore may be useful as cultivars or rootstocks in soils with high levels of disease inoculum. Significant increases in yield per plant, fruit number per plant plant and reduced days to flower (DTF) were observed in the high tunnel compared to the open-field environment. In contrast, individual fruit weight was reduced in the high tunnel compared to the field. Yield, fruit number, fruit weight and DTF were consistent between the scions regardless of rootstock. No differences were observed for yield, fruit number, fruit weight or DTF between self- and non-grafted scion checks. In the high tunnel, yield was higher in scions grafted onto ‘Habanero TEC’ compared to self- and non-grafted checks. In the open-field environment, yield and fruit number were highest on scions grafted onto ‘Habanero TEC’. Regardless of graft treatment, high tunnel production in tropical environments can result in significant increases in yield and fruit number compared to open-field production. No advantage of grafted plants was observed in the high tunnel production environment. In contrast, in open-field environment, grafting sweet pepper C. annuum scions onto C. chinense rootstock resulted in a significant increase in yield, fruit number and individual fruit size compared to self-and non-grafted checks. The increase is likely due to the resistance of C. chienense cultivars to soil-borne pathogens, including R. solanacearum.