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Ana Cristina M. Brasileiro, Francisco J. Lima Aragão, Sílvia Rossi, Diva Maria A. Dusi, Leila M. Gomes Barros, and Elíbio L. Rech

To develop an efficient protocol for Agrobacterium-mediated transformation of common bean (Phaseolus vulgaris L.) and tepary bean (P. acutifolius A. Gray), we have tested the susceptibility of six genotypes to eight Agrobacterium tumefaciens and two A. rhizogenes strains. The virulence of the Agrobacterium strains was shown to be genotype dependent. In general, the tumors observed on common bean cultivars were larger than those observed on tepary bean cultivars. The A. tumefaciens AT8196 and Ach5 strains and the A. rhizogenes 8196 strain induced the best responses in all genotypes tested. Polymerase chain reaction (PCR) analysis confirmed the presence of T-DNA in tumors derived from inoculation with three A. tumefaciens strains in common beans. Apical meristems of P. vulgaris cv. Jalo were bombarded with tungsten microprojectiles and then inoculated with an A. tumefaciens wild-type strain (Ach5). One month later, the explants showed a high frequency of tumor formation (50% to 70%). Similarly, when bombarded meristems were inoculated with an A. tumefaciens disarmed strain (LBA4404/p35SGUSINT), 44% of them showed substantial sectors of GUS activity, suggesting the expression of introduced gene. The bombardment/Agrobacterium system appears to be a promising method to stably transform bean through the regeneration of plants directly from transformed apical meristems.

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Geunhwa Jung, Paul W. Skroch, Dermot P. Coyne, James Nienhuis, E. Arnaud-Santana, H.M. Ariyarathne, Shawn M. Kaeppler, and Mark J. Bassett

Randomly amplified polymorphic DNA (RAPD) molecular markers were used to construct a partial genetic linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross PC-50 × XAN-159 for studying the genetics of bacterial disease resistance in common bean. The linkage map spanned 426 cM and included 168 RAPD markers and 2 classical markers with 11 unassigned markers. The seventy recombinant inbred lines were evaluated for resistance to two strains of common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] (Xcp). Common bacterial blight (CBB) resistance was evaluated for Xcp strain EK-11 in later-developed trifoliolate leaves and for Xcp strains, DR-7 and EK-11, in first trifoliolate leaves, seeds, and pods. One to four quantitative trait loci (QTLs) accounted for 18% to 53% of the phenotypic variation for traits. Most significant effects for CBB resistance were associated with one chromosomal region on linkage group 5 and with two regions on linkage group 1, of the partial linkage map. The chromosomal region (a 13-cM interval) in linkage group 5 was significantly associated with resistance to Xcp strains DR-7 and EK-11 in leaves, pods, and seeds. The regions in linkage group 1 were also significantly associated with resistance to both Xcp strains in more than one plant organ. In addition, a seedcoat pattern gene (C) and a flower color gene (vlae) were mapped in linkage groups 1 and 5, respectively, of the partial linkage map. The V locus was found to be linked to a QTL with a major effect on CBB resistance.

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Jan E. Paul Debaene and Laren Robison

Tepary beans (Phaseolus acutifolius A. Gray) are considered drought and heat tolerant, desirable characteristics for arid regions. Knowing the genetic distances among tepary lines can indicate both compatibility for intraspecific crosses and potential for Interspecific P. acutifolius × P. vulgaris hybrids. Fifteen tepary lines, including cultivars and landraces, were compared to two pinto bean varieties using random amplified polymorphic DNA's (RAPDs). At the present time polymorphisms have been clearly identified between wild and cultivated teparies and the pinto bean. An ammo acid profile is also being determined using HPLC. More work needs to be completed before relationships among cultivated teparies can be established.

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Jan E. Paul Debaene and Laren Robison

Tepary beans (Phaseolus acutifolius A. Gray) are native to north America and are considered drought and heat tolerant. Teparies are not commonly grown commercially, so little is known about their field performance. This study compared agronomic traits of 19 tepary bean lines to two pinto bean (P. vulgaris) varieties. The beans were evaluated under field conditions in a randomized complete block design with three replications. Traits examined included time to germinate, time to first trifoliate leaf, time to flower, height, seed protein content, and yield. Tepary yields ranged from 1593.0 to 656.4 kg/ha with three lines averaging 63.7 to 76.8% more than the average pinto bean yield. Tepary protein content ranged from 17.1 to 29.7% and averaged 24.7%. Tepary beans have great potential for adaptation to dry conditions while producing adequate yields and protein content.

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Kitren G. Weis and Barbara D. Webster

The drought-adapted, disease-resistant tepary bean (Phaseolus acutifolius A. Gray. var. acutifolius) is of great value as a potential gene donor of useful traits to the common bean (P. vulgaris L.). Analyses of flowering and fruiting patterns of tepary indicate that anthesis and abscission of reproductive structures within a raceme follow well-defined spatial and temporal patterns. Flowering occurs acropetally, and the probability of flowering decreases with distance from the most basal bud of the raceme. The probability of bud or pod abortion increases with distance from the basal bud, and the rate of abortion is highest in buds and pods proximal to the apex. Buds that never reach anthesis abort in the green-bud stage of development and aborting fruits cease development within the first 25% increase in pod length. In nonaborting fruits, the rate of seed abortion is 6%. A marked increase in abscission of all buds and fruits at all raceme nodes occurs before cessation of flowering.

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Harbans L. Bhardwaj and Anwar A. Hamama

Even though mothbean (Vigna aconitifolia), a drought- and heat-tolerant crop, may have potential in the eastern United States, information about its production in this region is not available. To characterize potential seed yields and preliminary nutritional quality, 54 accessions were grown near Petersburg, VA, during 2011, 2012, and 2013. The seed yields varied from 48 to 413 lb/acre. The mean concentrations of protein, calcium, iron, and zinc in mature mothbean seed were 21.9%, 0.17%, 64.8 ppm, and 37.5 ppm, respectively. These values compared well with those in mungbean (Vigna radiata) and tepary bean (Phaseolus acutifolius). The results demonstrated that mothbean has considerable potential as an alternative, new food legume crop in Virginia and eastern United States.

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Steven H. Goertz and Janice M. Coons

Seeds of two tepary bean lines (Phaseolus acutifolius Gray var. latifolius) and one navy bean cultivar (P. vulgaris L. `Fleetwood') were tested with 0.0-, – 0.3-, –0.6-, -0.9-, -1.2-, or – 1.5-MPa NaCl solutions to determine their relative salt tolerance during germination and emergence. Developmental stage was not affected at – 0.3 MPa, but with salinities more negative than -0.9 MPa, `Fleetwood' developed more slowly than the tepary lines; no plants emerged at – 1.5 MPa. Teparies tended to maintain higher water and osmotic potentials than navy over the range of NaCl concentrations used, although turgor was similar for all three genotypes. Leaf area was reduced more in navy than in white tepary at – 0.6 and – 0.9 MPa. Dry weights of navy were higher than those of either tepary bean at all NaCl concentrations, although decreases at higher salinities relative to 0.0 MPa were greater for navy than for teparies. Root: shoot ratios were higher at – 0.3 MPa than at 0.0 MPa, but were lower at the higher NaCl concentrations for all three genotypes. Overall, tepary beans tolerated NaCl better than navy. The characteristic that best indicated differences in salt tolerance was developmental stage.

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Phillip N. Miklas and Jose Santiago

Cultivated tepary bean (Phaseolus acutifolius A. Gray var. latifolius Freeman) has potential for production during the hot, dry seasons in the tropics. Bean golden mosaic virus (BGMV), however, seriously limits production of Phaseolus spp. in such environments. Twelve select tepary beans were evaluated for reaction to BGMV across four field nurseries near Isabela, Puerto Rico. Disease reaction was principally determined by measurement of seed yield (kg·ha–1) and weight (g 100/seeds). All tepary beans possessed some tolerance to BGMV, as they produced comparatively moderate seed yield despite expression of severe foliar yellow mosaic symptoms. On average, tepary bean yielded 133% of the BGMV-resistant dry bean (Phaseolus vulgaris L.) control `Dorado'. Four teparies, Neb-T-6-s, GN-610-s, Neb-T-8a-s, and PI 321637-s, expressed superior tolerance to BGMV as they yielded above the trial mean in at least three of four trials. Harvested seed quality was uniformly poor across all lines, averaging 18% less weight than in the non-BGMV trials. The combination of the observed tolerance with escape mechanisms and cultural disease control practices may enable production of tepary bean in regions and seasons that experience moderate to severe BGMV epidemics.

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Harbans L. Bhardwaj and Anwar A. Hamama

Tepary bean (Phaseolus acutifolius A. Gray), a native of southwestern U.S., is a promising plant for crop diversification and for production in short rotations with wheat. However, protein and mineral concentrations in tepary bean seed produced outside the southwestern U.S. are largely unknown. We evaluated concentrations of protein and various minerals in seed produced by eight tepary bean genotypes planted at three different dates each during 1997 and 1998 at Ettrick, Virginia. Significant year × planting date and year × genotype interactions existed for protein and other traits. Protein and zinc concentrations increased and calcium concentrations decreased with later plantings during both years. Mid-June planting had 14% higher protein concentration (24.5%) than late-May planting (21.4%) and mid-July planting had 6% higher protein concentration (25.9%) than mid-June planting. Color of seedcoat was not associated with concentrations of protein or minerals. The average concentrations of boron, calcium, copper, iron, potassium, magnesium, manganese, phosphorus, sulfur, and zinc (mg/100g) were: 1, 184, 1, 11, 1531, 192, 3, 451, 311, 4, respectively. Tepary bean seeds contained 24% protein as compared to reported average values of 22.3% in navy, 22.5% in red kidney, and 20.9% in pinto bean. The average iron concentration (mg/100g) in tepary bean seed (10.7) was higher than that in navy (6.4), red kidney (6.7), and pinto (5.9) bean. Based on protein and mineral concentrations tepary bean seed compared well with seeds of navy, red kidney, or pinto bean.

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Harbans L. Bhardwaj, Muddappa Rangappa, and Anwar A. Hamama

Our objective was to evaluate production potential of eight tepary bean (Phaseolus acutifolius A. Gray) genotypes and three planting dates. Significant variation (P < 0.05) existed among eight genotypes and three planting dates in 1997 and 1998. The genotype ×planting date interaction was nonsignificant (P > 0.05) for seed yield and harvest index. Seed yields of eight genotypes, when averaged over three planting dates and 2 years, varied from 1618 to 1988 with a mean of 1816 kg·ha-1, indicating that tepary bean is adapted to Virginia's agro-climatic conditions. The harvest index (ratio between seed and total plant weight, expressed as percentage) ranged from 38% to 47%. Seed weight varied from 12.6 to 18.8 g with a mean of 14.5 g. Genotypes with tan-colored seeds had significantly larger seed than those with black or white seeds. Planting dates significantly affected seed yield, seed weight, and harvest index. The highest seed yield (2239 kg·ha-1) and harvest index were obtained from the late May plantings.