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Two accessions of tepary (phaseolus acutifolius Gray var. latifolius) and navy (P. vulgaris L. 'Fleetwood') beans were studied for salt tolerance at several• developmental stages. Genotypes were germinated at 0.0 through -2.5 MPa NaCl at 25°C and 35°C for nine days. Tepary accessions had higher germination percentages and rates than navy for ≤ - 2.0 MPa at 250C and ≤ - 1.5 MPa at 35°C. Fresh weights of root plus hypocotyl decreased severely with the first increment of NaCl (-0.5 MPa) for all genotypes. Fresh weight of navy was reduced more at 35°C than at 25°C. Genotypes were stressed in vermiculite-filled trays with 0.0 through -1.5 MPa NaCl for 14 days. Final growth stage and rates of emergence were reduced at salinities ~ -0.6 MPa NaCl, and were higher in tepary than navy at -1.2 MPa. Tepary beans tended to maintain higher water and osmotic potentials, and at -0.9 MPa had less reduction in leaf area than navy beans. Fresh weights, dry weights and root:shoot ratios declined in all genotypes with increasing salinities. Plants grown hydroponically were stressed with -0.10, -0.25, and -0.50 MPa NaCl during either vegetative or reproductive stages. Navy had equal or greater fresh and dry weights of leaf, stem, and pods at -0.10 MPa, but tepary beans had equal or greater weights at the highest salinity relative to navy. Tepary had the greatest pod weight with -0.50 MPa NaCl applied during the reproductive stage. Carbon exchange rates (CER) were lower in navy than one or both tepary beans at some sampling times. Tepary beans tended to have higher leaf water and osmotic potentials than did navy. Transpiration and stomatal resistance values were similar in all genotypes, while leaf temperatures were different in white tepary versus navy. Tepary beans yielded higher than navy when grown in low and high salinity fields. Transpiration rates, leaf water and osmotic potentials, and CERs were similar or higher, while stomatal resistance and leaf temperatures were similar or lower in tepary than in navy. Plant height and stand count also were measured. Tepary was more salt tolerant than navy, exhibiting greater tolerance to NaCl at every growth stage.

Shoot and root fresh and dry weight, shoot length, leaf area, leaf area index and relative growth rate of 14 day old tepary bean (Phaseolus acutifolis Gray) and navy bean (Phaseolus vulgaris L.) seedlings were reduced following treatment with NaCl solution exhibiting osmotic potential of either -0.25, 0.50, and -0.75 MPa. Salinity reduced the growth of navy bean more than tepary bean. The physiological basis of the adaptive response of tepary bean seedlings to salt stress was explored by determining the water and osmotic potentials, relative water content, free amino acid and sugar concentrations, distribution and levels of inorganic ions within the seedlings and ATPase activity of the root plasma membrane. Salinity led to an osmotic adjustment in the leaves and the proximal part of the root of tepary bean. Turgor remained almost constant whereas osmotic and water potential and relative water content declined following the salt treatments. The osmotic adjustment of the leaves and proximal part of the roots was -1.7 MPa and -1.2 MPa, respectively, in seedlings treated with -0.75 MPa NaCl solution. Free amino acids and sugars increased under salinity stress in both species but they increased more in the tepary bean. Glucose was the most abundant free sugar. The nonstructural carbon solutes contributed -0.15 MPa to the seedling's osmotic adjustment whereas Na, Cl, K and Ca ion levels contributed -0.85 MPa. However, the levels of these solutes were not large enough to account for the total osmotic adjustment observed in the salt treated seedlings. This study shows that tepary bean has specific strategies to overcome the impact of salinity through osmotic adjustment and exclusion of Na and Cl ions from the stems and leaves by retaining these ions in the proximal part of root and stem base. (Abstract shortened with permission of author.)

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One of the advantages of intercropping has been the increase in yield over the monocultures. Intercrop yield can be improved by selecting for compatible cultivars and by efficient spacing arrangements of the component crops. A field experiment was conducted in the 1990 growing season to compare two spacing arrangements for the pepper/bean intercrop, to observe the effects of three bean cultivars on the system, and to examine whether there is any interaction between cropping system and bean cultivar. Three bean cultivars (Frenchie, Earliserve, and E-Z Pick), differing in their morphology and time to maturity, and one pepper cultivar (Hybrid Bell Boy) were used in the study. In the intercrop, the beans were sown at 50% of the optimum bean monocrop density while the peppers were planted at 100% or 50% of the optimum pepper monocrop density, resulting in 50:50 and 100:50 pepper/bean intercrop treatments. The experiment was repeated the following growing season with the addition of light transmission measurements, an $ sp{15}$N experiment to test for the possibility of nitrogen transfer, and the addition of three monocrop treatments (one for each cultivar) with the same intra-row spacing as in the intercrops. Beans were generally the dominant crop for both years. When compared to the optimum monocrops on a per plant basis, intercropping increased bean yields by 52% and 31% and decreased pepper yields by 49% and 21% in 1990 and 1991, respectively. The LER (Land Equivalent Ratio) ranged from 0.96 to 1.23 in 1990 and from 1.09 to 1.42 in 1991, with the 100:50 intercrops usually having the higher values. Frenchie and E-Z Pick were best suited for intercropping in 1990 and 1991, respectively. The overall increase in yields in intercropping was probably due to the larger bean intra-row spacing and the greater utilization of light, water and nutrients, as well as the increased population pressure in the 100:50 intercrop. Bean cultivars generally performed the same relative t

The extension of frozen-thawed epidermal strips prepared from the first centimetre below the hypocotyl hook of six day old dark grown Phaseolus vulgaris seedlings while immersed in various buffers and under various tensions was characterized. This was done in an attempt to determine if the acid wall loosening phenomenon, which according to the Acid-growth theory (Taiz, 1984) is thought to mimic part of the auxin mechanism of action, is mediated by unspecified wall loosening enzymes. Epidermal strips were found to be significantly loosened by media pH 6.0 to pH 2.6 (0.05M citric acid-O.lOM disodium phosphate) relative to pH 7.5. A minimum stress between 1.6 and 7.6 grams was required for the acid-extension of strips 4.5±0.5 mm wide. Regardless of tension, extension by tissues in an acid medium was largely transient For example, tissues tensioned by a 16.0 gram load reached a maximum extension rate of 6.18 ±1.37% of initial length per hour (L°/hr) between 4 and 6 minutes after immersion in pH 4.8. The rate was 1.29±0.17% L°/hr between 55 and 60 minutes and 1.05±0.14% L°/hr between 220 and 240 minutes. Total acid-extension over four hours was 4.24±0.57% L°. The extension response was found to be stable; newly harvested tissues whether frozen or not performed similarly to strips aged up to 15 days at -12°C before being extended. The performance of strips immersed in unbuffered solutions indicated that tissues were self-buffering at an acid pH probably because of the fixed carboxyls within the wall. The capacity for acid-extension by epidermal strips was lost in mature tissues harvested 4-5 cm below the hypocotyl hook. Temperature coefficients from extension rates were determined at several pHs. The results were highly variable. The acid-extension of strips boiled 15 minutes in ethanol or extracted in 3M NaCl for 4 hours at 4°C or 6M LiCl for 8 hours was determined in several pHs. The impact of the treatments was largely a suppression of the initial burst of acceleration. Extension rates following the initial surge were relatively unaffected. Glycosidase activities in untreated, ethanol-boiled, or salt extracted strips were determined. β-glucosidase was found to be most active in untreated strips with lesser levels of β-galactosidase and β-xylosidase and a trace of α-galactosidase being detected. Ethanol-boiling and LiCl-extraction removed or deactivated all four activities from the strips and NaCl-extraction lowered all four activities 70-80%. NaCl proved to have solubilized most of the missing β-glucosidase and β-galactosidase when the extraction solution was assayed following desalting and concentration. LiCl solubilized most of β-xylosidase. It was concluded that glycosidases and any other similarly soluble enzyme cannot be responsible for long term acid wall loosening in bean epidermis. If an enzyme is involved, it must be extremely stable and tightly bound to the wall. The acid-extension performance of frozen-thawed longitudinally halved hypocotyl sections in comparison to epidermal strips, as well as other evidence was considered support for another hypothesized mechanism of acid wall loosening, the displacement of calcium bridges. / Science, Faculty of / Botany, Department of / Graduate

Double infection by cowpea strains of southern bean mosaic virus (CP-SBMV) and of tobacco mosaic virus (CP-TMV) caused additive growth reductions in California blackeye cowpea. Plant height, weight and numbers of seed and pods were significantly reduced by double infection and by CP-TMV single infection compared to healthy and CP-SBMV-sing 1 y infected plants. Singly and doubly inoculated California blackeye cowpea plants developed CP-SBMV symptoms on the primary leaves, but CP-SBMV symptoms in doubly infected trifoliates were masked by CP-TMV symptoms. CP-TMV symptoms did not mask CP-SBMV symptoms in systemically infected trifoliate leaves of another cowpea variety, V45-Bots. CP-TMV infection conditioned systemic infection of V45~Bots by CP-SBMV, as indicated by infectivity,serology and analytical sucrose density gradient centrifugation. CP-TMV also induced susceptibility of Pinto to infection by CP-SBMV, as ascertained by infectivity, immunodiffusion and electron microscopy. Analytical sucrose density gradient centrifugation measurements demonstrated that in doubly inoculated primary leaves of California blackeye cowpea CP-SBMV and CP-TMV were synthesized less than in the same leaves singly inoculated. CP-SBMV synthesis in trifoliate leaves, following simultaneous inoculations of primary leaves, was enhanced 5 times that in singly infected trifoliate leaves, whereas CP-TMV synthesis was not greatly affected. When CP-TMV preceded CP-SBMV in the primary leaves by 2k and 72 hr CP-SBMV synthesis was enhanced more in trifoliate leaves that were undifferentiated at the time of inoculation than in those of plants simultaneously inoculated. When CP-TMV preceded CP-SBMV into preformed 3rd trifoliate leaves by 22 hr, the ratio of CP-SBMV concentration in doubly infected tissue to that in singly infected tissue was 2.7 versus 1.9 when both viruses arrived simultaneously at these leaves. When either virus preceded the other by 72 hr into preformed 3rd trifoliate leaves the synthesis of the challenging virus was greatly retarded. CP-SBMV synthesis was also enhanced by CP-TMV infection under differential temperature synchronous system of infection. Although virions of both viruses were detected in the same cell no genomic masking was detected by infectivity neutralization test. It is theorized that CP-TMV infection predisposes the host cells to infection by CP-SBMV and thus the enhanced synthesis of CP-SBMV. The effect of CP-TMV infection on CP-SBMV synthesis in cowpea seems to be a physiological one. CP-SBMV, but not CP-TMV, was transmitted through planted seed and decontaminated embryos of California blackeye cowpea. Buffer extracts made from decontaminated embryos also were infectious for CP-SBMV. Seed coats contained both viruses. Double infection of California blackeye cowpea decreased seed transmission of CP-SBMV from 13-5 to 7.6%. Buffer extracts of healthy seed were inhibitory to infectivity of both viruses. Germination of seed reduced infectivity of CP-SBMV in the seed coats, but not of CP-TMV. It is also concluded that seed transmission of CP-SBMV is a result of embryo infection rather than contamination with virus in the seed coats. / Land and Food Systems, Faculty of / Graduate

Pulses (i.e. beans, lentils, and chickpeas) are enriched in plant-based proteins and non-digestible carbohydrates (e.g. fibre) that may beneficially impact intestinal and metabolic health. The objectives of this thesis were to determine if i) consumption of diet supplemented with kidney beans would improve biomarkers of intestinal and metabolic health, ii) dark-colored beans would provide additional health benefits compared to light-colored beans, and iii) background diet composition would impact the health effects of kidney bean consumption. Study 1: 5-week-old male C57Bl/6 mice were fed either a basal diet (BD; 20% casein, wt/wt), or isocaloric diets supplemented with 15% cooked white kidney beans or dark red kidney beans for 9 weeks (n=12/group); Study 2: 5-week-old male C57Bl/6 mice were fed either a high-fat diet (HF; 60% kcals from fat) or HF diet supplemented with 15% cooked white kidney beans or dark red kidney beans. In both studies, consumption of diets supplemented with beans improved microbiota community structure and activity, as indicated by increased abundance of short-chain fatty acid (SCFA) producing bacteria (Prevotella and S24-7) and intestinal SCFA concentrations, with dark kidney beans inducing the greatest effects. Furthermore, biomarkers of colonic inflammation, barrier integrity, and metabolic health were beneficially impacted by kidney bean consumption, however, the effects were greater in mice consuming low-fat vs. high-fat diets. In conclusion, this thesis demonstrated that while kidney bean consumption led to improvements in intestinal and metabolic health, the results were influenced by seed coat color and the nutrient composition of the background diet.

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