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Digitized by Kansas Correctional Industries

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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.

The xerophytic gourds, Apodanthera undulata and Cucurbita digitata, hold promise as new sources of starch for industrial and domestic use as world population increases and food demands become greater. Thus, understanding of the chemical and physical properties of the starches from these arid land plants is required. Moisture content, ash, fiber and starch content of A. undulata and C. digitata roots were comparable to Solanum tuberosum (potato) and Manihot utilissima (tapioca). High lipid content was observed in A. undulata, but C. digitata was similar to tapioca in this respect. The composition of subject starches was comparable to standard starches. The lipid content of C. digitata starch was similar to that of corn starch, but A. undulata starch exhibited a higher content. A. undulata starch showed a higher iodine binding capacity, hence a higher amylose content, than C. digitata, potato and C. foetidissima starches. The number of terminal aldehyde groups and the average granule size of subject starches were comparable to tapioca starch. Interestingly, gelatinization temperature and percent sag test values were more similar to cereal starches such as corn, than to potato or tapioca. The swelling power of both starches was intermediate between corn and tapioca, while the solubility of A. undulata was similar to corn starch. The paste viscosity of A. undulata and C. digitata, when compared to corn, potato and C. foetidissima, proved to be most similar to corn. Viscosity maxima were intermediate between corn and potato. C. digitata starch was very stable, showing little change in paste viscosity after heating for one hour at 90°C. Increases in viscosity occurred during the cooling period for A. undulata, C. digitata and corn, but negligible changes occurred in C. foetidissima and potato. Starches isolated from A. undulata, C. digitata and potato were evaluated nutritionally by an in vivo study. Increases in digestibility of autoclaved starches (85% for A. undulata, 85% for C. digitata and 91% for potato) over raw starches (40% for A. undulata, 40% for C. digitata and 24% for potato) were confirmed by statistical analysis. Feed consumption and body weight gain were higher than for the potato starch diet. Autoclaving also improved net protein ratio and protein efficiency ratio. The fine structure of the macromolecular fractions amylose and amylopectin from starches of A. undulata and C. digitata were examined. The dimethyl sulfoxide method proved to be effective for fractionation of each starch. Purity of these components was confirmed by iodine binding capacity, and they were found to be similar to standard starches. Calculated values for degree of polymerization (DP) were similar to that of potato. Study of the fine structure of these components showed beta-amylolysis limits of approximately 90% for the amyloses and above 60% for the amylopectins. These values were similar to those of potato and intermediate between tapioca and cereal starches. The average chain length of the A. undulata amylopectin was found to be 25 with an outer chain length of 18 and an inner chain length of 6. The average chain length of 18 and an inner chain length of 6. The average chain length for C. digitata amylopectin was 26 with an outer chain length of 19 and an inner chain length of 6. These relatively long exterior layers with respect to the short interior layers show the amylopectins of these starches to be asymmetric molecules comparable to potato.

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.

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No description available.