No description available.

No description available.

No description available.

No description available.

No description available.

A fertility study was initiated at the Maricopa Agricultural Center in 1984 to determine how nitrogen levels influenced growth, development, and root yield of the potential domesticate, buffalo gourd (Cucurbita foetidissima). Nitrogen had little or no effect upon the following parameters: seedling emergence, early growth rates, specific leaf weights, individual root weights, consumptive water use, canopy organic N content, and nitrate and ash content of all organs. Percent root dry matter and total carbohydrate content dropped linearly as N was increased, whereas canopy dry matter production, root organic N content, petiole nitrate concentration, and leaf area indices exhibited a positive linear response. A quadratic response curve best fitted fresh weight root yields, total root dry matter and carbohydrate production, water use efficiencies, and final plant populations. A modest amount of N (84 kg ha⁻¹) provided maximum yield response in this feral species grown at 405,000 plants ha⁻¹.

Seven field experiments and two in-vitro studies were performed to elucidate hormonal control of staminate flowering in gynoecious and monoecious buffalo gourd (Cucurbita foetidissima HBK.) sex types. Objectives included development of techniques effecting staminate induction on gynoecious phenotypes which normally produce abortive stamenless male buds. Natural and synthetic growth regulants shown to modify sex expression in other cucurbits were surveyed for their masculinizing potential. Several compounds exogenously-applied to apical meristems elicited changes in shoot morphology. However, only aminoethoxyvinylglycine (AVG, an ethylene synthesis inhibitor) effected staminate induction on gynoecious segregates. Growth rate, patterns of female flowering or ontogeny of stamenless buds differentiated prior to treatment were not influenced by AVG. AVG was applied at various dosages (0-500 ppm) and produced male buds on all replicates treated at levels of 125 ppm or higher. The mean number of staminate buds induced varied linearly with dosage and averaged from 0-7.5 male flowers/shoot. A control model for staminate induction mediated by endogenous ethylene was advanced and potential benefits of this phenomenon to breeding efforts and/or to hybrid seed production were discussed. Ethephon (an ethylene releasing compound) was applied at various dosages to monoecious plants in anticipation of simulating the gynoecious phenotype. Although morphological changes were evident (i.e. reduction in shoot growth rate and floral initiation, increase in floral bud abortion and tissue senescence), ethephon failed to reduce staminate flowering or increase differentiation of antherless buds as expected. Dosage levels employed and/or confounding environmental factors may have contributed to the lack of staminate inhibition. During in-vitro studies, indirect evidence for ethylene-mediated control of male flowering was obtained by staminate proliferation in buds of gynoecious explants treated with silver nitrate (an inhibitor of ethylene action) and by formation of stamenless buds on monoecious explants treated with ethephon. However, low levels of floral induction under culture conditions employed rendered these results inconclusive. An incidental study of segregation ratios among AVG-facilitated self- and cross-pollination progeny upheld the supposition for monogenic inheritance of gynoecy in buffalo gourd.

No description available.

No description available.

The buffalo gourd, Cucurbita foetidissima HBK, is a xerophytic perennial native to the southwestern United States and northern Mexico. A vigorous spreading vine, it produces edible oil and protein in the seeds, and edible starch in its fleshy storage root. This study concerns the inheritance of content of each fatty acid in the seed oil of the buffalo gourd, including heritability studies, physiological relationships between the fatty acids, and environmental influence on the oil composition. The mechanisms of fatty acid biosynthesis and desaturation and environmental effects on them are reviewed, as is the inheritance of fatty acid composition in commercial oilseed crops. In this study, crosses were made between plants selected for low or high linoleate content and the progeny analyzed by gas chromatography, using a non-destructive half-seed method. Analyzed seed of extremely high and low linoleate content were planted, and crosses made among the resulting plants. Their progeny were analyzed and half-seeds planted again, to be selfed or sib crossed. The fatty acid composition of buffalo gourd seed was found to be determined by the embryonic genotype. Linoleate and oleate content were negatively correlated, as has been previously shown in this and other species. Heritability of oleate and linoleate content was determined by regression of progeny values on midparent values and found to be approximately 0.86 in the first year, while palmitate gave no significant regression. In the second year, palmitate exhibited a heritability of 0.39, but oleate and linoleate had heritabilities near 0.4. The notable decrease in their heritability was examined by multiple regression analysis of progeny values with environmental parameters and midparent values. A significant regression was obtained with day length for oleate and linoleate content; however, correlations also were found with high and low temperatures during the seed maturation period. The various environmental parameters tested were too strongly correlated to distinguish the causative factor with certainty.