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  • Author or Editor: Carl E. Motsenbocker x
  • Journal of the American Society for Horticultural Science x
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Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.

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Of eight genotypes of cayenne pepper (Capsicum annuum L.) examined, two were identified that differ significantly in ease of fruit detachment force. Greenhouse and field-grown plants of these genotypes, Cajun 1-9027 and Cap-9004, were investigated for differences in cell type and organization at the fruit and receptacle junction. Scanning electron microscopy revealed that mature Cajun 1-9027 fruit that did not separate exhibited a distinct region of sclerified cells that extended from the periphery of the fruit into the receptacle for 25 to 30 cell layers. In contrast, mature fruit of the more readily detachable Cap-9004 had 10 to 15 layers of sclerified cells at the region of detachment. Histochemical and stereological techniques indicated that Cajun 1-9027 had a greater volume of sclereids than Cap-9004. Cajun 1-9027 exhibited smaller cortical cells in the detachment region than Cap-9004. Neither genotype exhibited a well-defined abscission zone at maturity in the detachment region. The presence of more sclerified cells and increased lignification in Cajun 1-9027 compared to Cap-9004 probably contributed to the differences in ease of detachment between the two genotypes.

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