Heat tolerant lettuce germplasm (Lactuca sativa L.) identified in romaine and butterhead types for warmer plantings

Authors: SANDOYA, GERMAN - University Of Florida; LAFTA, ABBAS - North Dakota State University; Mou, Beiquan

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2023
Publication Date: 1/5/2024
Citation: Sandoya, G., Lafta, A., Mou, B. 2024. Heat tolerant lettuce germplasm (Lactuca sativa L.) identified in romaine and butterhead types for warmer plantings. HortScience. 59(2):151-163. https://doi.org/10.21273/HORTSCI17368-23.
DOI: https://doi.org/10.21273/HORTSCI17368-23

Interpretive Summary: Warmer temperatures during crop production are not desirable for a cool season crop as lettuce (Lactuca sativa L.). Lettuce is among the top ten most consumed vegetables in the United States. Production of this vegetable is mostly concentrated in temperate areas of California and in wintertime in Arizona and Florida due to their mild climate conditions. Heat tolerant cultivars are needed for the leafy vegetable industry to continue thriving. However, there is very little information on heat tolerant varieties of lettuce that can be used as source to improve the heat tolerance in a breeding program. This is particularly important in cos (romaine) and butterhead lettuces which are two morphological types with increasing demand in the market. Therefore, this research was conducted to identify varieties that perform acceptably in warmer regions in western US. This investigation aimed to understand the reactions of varieties to different environments, a phenomenon that could help plant breeders to select and evaluate lettuce plants during the breeding process. Twenty-three and 25 varieties of romaine and butterhead lettuce were planted in five trials near El Centro, Five Point, and Salinas, California, USA under warmer temperatures. Head weight and related traits (including core length, height, width, etc.) and heat-related disorders were identified to be significantly different across the multiple experiments indicating genetic variation. The major component of the variation in these experiments was due to the different environments. Therefore, plant breeders may still need to evaluate progeny in multi trials and in multi locations to efficiently select for heat tolerant romaine and butterhead lettuce.

Technical Abstract: Warmer temperatures during crop production are not desirable for a cool season crop as lettuce (Lactuca sativa L.). Lettuce is among the top ten most consumed vegetables in the United States. Production of this vegetable is mostly concentrated in temperate areas of California and in wintertime in Arizona and Florida due to their mild climate conditions. Heat tolerant cultivars are needed for the leafy vegetable industry to continue thriving. However, there is very little information on heat tolerant germplasm of lettuce that can be used as source to improve heat tolerance in lettuce. This is particularly important in cos (romaine) and butterhead lettuce which are two morphological types with increasing demand in the market. Therefore, this research was conducted to identify germplasm that acceptably performs in warmer regions in western US. This investigation aimed to understand the genotype (G) × environment (E) interaction, a phenomenon that could help plant breeders to select and evaluate breeding lines during the breeding process. Twenty-three and 25 germplasms of romaine and butterhead lettuce were planted in five trials near El Centro, Five Point, and Salinas, California, USA under warmer temperatures. Head weight and related traits (including core length, height, width, etc.) and heat-related disorders were identified to be significantly different across the multiple experiments indicating genetic variation. The major component of the variation on these experiments was due to E and thus an analysis of the G×E suggested crossover and non-crossover interactions in the studied traits. Therefore, plant breeders may still need to evaluate progeny in multi trials and in multi locations to efficiently select for heat tolerant romaine and butterhead lettuce.