Location: Crop Improvement and Protection ResearchTitle: Phenotypic characters and inheritance of Yellow Spot malady in lettuce
|PENG, HUI - University Of California|
|SMITH, RICHARD - University Of California|
Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2022
Publication Date: 8/1/2022
Citation: Peng, H., Zhao, R.B., Smith, R., Simko, I. 2022. Phenotypic characters and inheritance of Yellow Spot malady in lettuce. American Society for Horticultural Science Annual Meeting, July 30-August 3, 2022, Chicago, Illinois.
Technical Abstract: Lettuce (Lactuca sativa L.) is one of the most important vegetable crops grown worldwide. An unknown malady that causes Yellow Spot (YS) blemishes on leaves has recently appeared in commercial fields in California, potentially reducing lettuce yield and/or quality. YS occurred on all morphological types of cultivated lettuce regardless of their color, with the highest (0.90) and lowest (0.09) rate found in non-leaf (stem and oilseed) and leaf lettuce, respectively. The spots that range in diameter from 0.5 to 3.1 mm (depending on genotype) mostly appeared on the adaxial leaf surface of mature or nearly mature plants. YS symptoms began as light-yellow circular spots that later became more intensely yellow and eventually turned necrotic. The YS-affected area displayed decreased chlorophyll fluorescence and photosynthesis. The malady was not caused by the effect of fungi, bacteria, viruses, insects, or foliar nematodes. Among 31 tested chemical elements, four macronutrients (P, Ca, Mg, and S) and eight microminerals (B, Cd, Cu, Li, Mn, Ni, Si, and Sn) displayed significantly changed concentration in the YS-affected leaves. A relatively high broad-sense inheritability (H2 = 47.9% ~ 68.4%) was observed for the trait in four experiments conducted at two locations in three years. The genome-wide association study (GWAS) involving 479 accessions identified eight loci (qYS2.1, qYS3.1, qYS3.2, qYS4.1, qYS5.1, qYS5.2, qYS6.1, and qYS7.1) defined by 10 SNP markers significantly associated with YS. A total of 162 genes were predicted in the identified chromosomal regions, with four oxidation-reduction (redox) catalyzers being potentially the most promising candidate genes involved in the regulation of this physiological disorder.