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Anwar A. Hamama and Harbans L. Bhardwaj
Wheat farmers in Virginia and southeastern US could benefit greatly from the availability of a short-duration summer crop that could be produced during the period between wheat harvest in middle of June and before planting of the next wheat crop during October. Some wheat farmers plant soybean as a double crop system, but the productivity of double-cropped soybean is extremely low and variable. Tepary bean (Phaseolus acutifolius A. Gray, Fabaceae), a highly drought and heat tolerant plant that produces nutritious, high protein seed suitable for human consumption (Thomas et al. 1983; Nabhan, 1983; Scheerens et al. 1983; Miklas et al. 1994), may have special significance in Virginia and southeastern states to be used as a short-duration summer crop.
Previous research with tepary bean, a native of southwestern US, has indicated that it can be successfully grown in Virginia as a short-duration summer crop (Bhardwaj et al. 2002). In this study, mean seed yields of 2239, 1899, and 1410 kg/ha, respectively were obtained from eight genotypes when planted during late May, mid June, or mid July during 1997 and 1998. However, information about seed composition or nutritional quality of Virginia-grown tepary bean is unknown. This information is needed to evaluate the overall potential of tepary bean as a short-duration summer crop in Virginia.
Due to high drought tolerance, tepary bean could also have potential in many parts of the world where irrigation water is unavailable. Availability of fresh water is important for enhancing and sustaining agricultural production. Even though water covers about 70% of the Earth’s surface, only about 3% of the total quantity of water is classified as fresh water, and suitable for irrigation purposes. The rest of 97% of water has too high a salt content to be used for production of crop plants. Increasing world population is also reducing the amount of irrigation water. Given that the world population increased to more than 6 billion during the latter part of 1999 and is expected to be increasing, there is an urgent need for developing of drought tolerant crop plants. The objective of this research was to determine the composition of Virginia-produced seed of tepary bean and to compare its nutritional quality with that of other beans.
Composition of seed of eight tepary bean lines was evaluated to determine contents of protein, oil, fatty acids, and minerals. These seed were obtained from a field study to compare three planting dates (May 29, June 19, and July 10) during 1997 in Petersburg, Virginia (37.14°N and 77.24°W). Each planting date experiment consisted of three replications of a randomized complete block design. The rows were 6 m long row with between row spacing of 75 cm. Approximately 200 seeds were planted in each row. These plots received no fertilizer applications. The weeds in these plots were controlled manually. All plots received one application of permethrin (60 g a.i./ha of Ambush) and one application of lambda-cyhalothrin (20 g a.i./ha of Karate) insecticides. At maturity in early October, all plots were harvested manually. Seeds from all replications of an entry in each planting date experiment during 1997 were bulked and chemically analyzed as described by Bhardwaj et al. (1998). All data were analyzed by procedures in version 6.11 of SAS (SAS 1996). The seed composition data were analyzed by using entry × planting time mean squares as the error term (Steel and Torrie 1980).
The results of tepary bean research in Virginia have been encouraging. The protein content of tepary bean lines produced in Virginia varied from 20.9% to 30.6% with a mean of 26.5% as compared to the 13.0% to 28.8% protein content in tepary beans produced in southwestern US (Table 1). The oil content of tepary bean lines produced in Virginia varied from 1.4% to 3.4% with a mean of 2.2% as compared to 0.4% to 1.9% oil in tepary beans produced in Southwestern US. The contents of saturated, unsaturated, mono-unsaturated, and poly-unsaturated fatty acids in tepary beans produced in Virginia varied from 30% to 42%, 58% to 70%, 28% to 40%, and 25% to 33%, respectively. Predominant fatty acids in the tepary bean seed oil were 16:0 (24%), 18:1 (32%), 18:2 (24%), and 18:3 (5%). Information about these characteristics of tepary bean oil were not available from seeds produced elsewhere. The contents of calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sulfur, and zinc compared favorably with those in the seeds of tepary beans produced in southwestern US.
Table 1. Composition of tepary bean seed grown in Virginia during 1997 as compared to the literature values for other dry beans.
| Variable | Tepary bean | ||||
| VA-grownz | Literaturey | Navy beanx | Kidney beanx | Pinto beanx | |
| Protein (%) | 26.5 (20.9-30.6) | 13.0-28.8 | 22.3 | 22.5 | 20.9 |
| Oil (%) | 2.2 (1.4-3.4) | 0.4-1.9 | 1.3 | 1.1 | 1.1 |
| 14:0 | 0.2 (0.1-0.3) | -- | 0.1 | 0.0 | 0.1 |
| 16:0 | 24.0 (18.7-28.6) | -- | 24.2 | 12.8 | 20.3 |
| 18:0 | 7.4 (5.6-9.2) | -- | 1.6 | 1.7 | 0.4 |
| 20:0 | 1.7 (0.2-3.9) | -- | -- | -- | -- |
| 22:0 | 0.6 (0.1-1.4) | -- | -- | -- | -- |
| 24:0 | 1.5 (0.7-2.4) | -- | -- | -- | -- |
| 16:1 | 1.9 (0.6-5.2) | -- | -- | 0.0 | 0.0 |
| 18:1 | 32.0 (23.4-34.8) | -- | 8.7 | 7.7 | 20.3 |
| 18:2 | 24.5 (19.1-28.6) | -- | 23.5 | 21.5 | 15.0 |
| 18:3 | 4.9 (1.2-9.2) | -- | 19.7 | 33.8 | 21.0 |
| 20:1 | 1.2 (0.2-2.8) | -- | -- | 0.0 | 0.0 |
| Fatty acidsw | |||||
| Saturated | 35.4 (30.1-41.7) | -- | 25.9 | 14.5 | 20.8 |
| Unsaturated | 64.6 (58.3-69.9) | -- | 74.1 | 85.5 | 79.2 |
| Mono-unsaturated | 35.2 (27.7-39.6) | -- | 8.7 | 7.7 | 20.3 |
| Poly-unsaturated | 29.4 (24.5-33.3) | -- | 43.1 | 55.3 | 36.0 |
| Minerals (mg/100 g) | |||||
| Calcium | 182.0 (110-260) | 126-446 | 155 | 83 | 121 |
| Iron | 12.1 (9.7-16.6) | 0.2-12.6 | 6.4 | 6.7 | 5.9 |
| Mg | 204.0 (170-230) | 95-281 | 173 | 138 | 159 |
| Zn | 4.7 (4.0-5.5) | 1.7-6.1 | 2.5 | 2.8 | 2.5 |
| P | 480.0 (410-560) | 60-432 | 443 | 406 | 418 |
| Cu | 1.3 (1.1-1.5) | 0.6-3.7 | 0.9 | 0.7 | 0.8 |
| Mn | 2.8 (1.9-4.4) | 0.9-3.6 | 1.3 | 1.1 | 1.1 |
| K | 1614.0 (1400-1830) | 1501-1608 | 1140 | 1359 | 1328 |
| S | 340.0 (290-410) | -- | -- | -- | -- |
zGrown in Virginia during 1997, mean over eight entries and three
planting dates, and range.
ySource: Scheerens et al. 1983.
xSource: U.S. Department of Agriculture, Agricultural Research Service.
2001. USDA Nutrient Database for Standard Reference, Release 14. Nutrient Data
Laboratory Home Page, www.nal.usda.gov/fnic/foodcomp
wFatty acids as percentage of oil.
Based on comparison of seed composition values, tepary bean had higher contents of protein, oil, calcium, iron, magnesium, zinc, phosphorus, copper, manganese, and potassium contents as compared to navy bean, kidney bean, and pinto bean seeds. The tepary bean seeds also had lower content of poly-unsaturated fatty acids as compared to navy, kidney, and pinto beans (USDA 2001). Based on seed composition traits, Virginia-grown tepary bean has great potential as a food/feed crop.
Based on experiments conducted during 1997, tepary bean seems to be a potential alternative grain crop for use as a food/feed crop. Nutritional quality is similar to that of navy, kidney, and pinto beans.