Variability In Carotenoid Content and Profiles In Cucurbita maxima and Cucurbita moschata Squash

Carotenoid studies of specific cultigens of squash have been limited, but nonetheless, have shown that some squash cultigens contain substantial amounts of the nutritionally beneficial carotenoids, α-carotene, β-carotene and lutein, but not zeaxanthin.  Our study focused primarily, but not exclusively, on comparing carotenoid content and profiles in breeding lines and cultivars of C. maxima Duchesne and C. moschata Duchesne developed at the University of New Hampshire (UNH).  Plants were grown at the UNH experimental farms in Durham and Madbury, NH, using randomized complete block designs with either three or four replications and two fruit samples per treatment per plot.  Comparisons were made over three seasons (2008 to 2010), and with different harvesting and storage periods.  Squash mesocarp samples were stored at -80 C.  Carotenoid content was determined spectrophotometrically in acetone, and profiles were determined by HPLC. There was appreciable variability in carotenoid content across seasons, but carotenoid profiles among squash cultigens were relatively stable.   In most cultigens there were progressive and often linear increases in carotenoids from harvest at  40 days after pollination (DAP) to 60 DAP, and with longer storage time, either 30 d or 60 d at 14^oC.  Maximum total carotenoid values for all cultigens varied between 84 and 185 mg/g DW for C. moschata and between 204 and 518 mg/g DW for C. maxima.  Cultigens of C. maxima contained substantial amounts of lutein and β-carotene, and a few cultigens contained appreciable amounts of zeaxanthin.  However, between 54 to 67% of the carotenoids in C. maxima were tentatively identified as principally esterified forms of neoxanthin and lutein epoxide, neither considered nutritionally important.  In C. moschata, cv.Waltham Butternut had relatively low amounts of total carotenoids (109 mg/g DW after 60 d storage), but about three-fourths of the total were nutritionally beneficial carotenoids -  lutein (33 to 36 %), β-carotene (30 to 38%) and α-carotene (5 to 7%).  In C. moschata inbred lines derived from a common F₂ population, carotenoid content and profiles varied considerably.  Carotenoid content in line NH421 was 216 mg/g DW, and 50 to 60% was β-carotene.  Line NH851 had higher amounts but similar proportions of β-carotene and lutein  as ‘Waltham,’ but unlike the latter, most lutein was non-esterfied.   A third line, NH910, had lower proportions of lutein and β-carotene than ‘Waltham,’ but α-carotene comprised about 33% of carotenoid content.  Our results indicate a potential for maximizing contents of specific beneficial carotenoids in squash through selective breeding.