Spinach seed quality: potential for combining seed size grading and chlorophyll fluorescence sorting

Abstract

AbstractSpinach (Spinacia oleracea L.) seed quality is important for subsequent establishment of baby leaf and other spinach products. The indeterminate flowering pattern in spinach produces seeds of different sizes, and consequently a non-uniform seed lot. Sorting seeds based on novel sorting methods might therefore improve the establishment of spinach for producers. Spinach seeds were harvested at five different times (H1, H2, H3, H4 and H5) starting 3 weeks before estimated optimum harvest time. The harvested seeds were sorted according to chlorophyll fluorescence (CF) and seed size. Two harvest times 6 d apart were selected for further studies of seed development and germination counts. Analysis of mean germination time (MGT) of four germination counts (3, 7, 14 and 21 d) showed that smaller seed sizes ( < 3.25 mm) have lower MGT than seeds of larger sizes (>3.25 mm). A larger proportion of 2.5–3.25 mm size seeds had germinated on day 3 than both their larger and smaller counterparts at the later time of harvest (H4). Seeds with a diameter below 2.5 mm displayed the lowest MGT. Commercially, the use of chlorophyll fluorescence (CF)-sorted seeds, in combination with seed size sorting, may provide a useful tool for enhancing seed quality. Here our results demonstrate that a greater number of seeds with a low CF level had germinated on day 3 compared to the seeds with high CF levels. It is of relevance to develop a technology that could identify seeds that are sufficiently developed to germinate and successfully establish in the field regardless of seed size.