Dry Beans and Pulses Production, Processing, and Nutrition. Группа авторов

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Fig. 2.7. Canned beans with differences in processing quality: (a) Navy beans with many splits and poor processing quality; (b) Navy bean with acceptable processing quality; (c) Black bean that appears brown following processing; and (d) Black bean that maintains black color following processing. (For color detail, please see color plate section.)

      Source: Original images by author, K. A. Cichy.

      Iron biofortification has been a major bean breeding initiative since 2003, primarily implemented through the International Center for Tropical Agriculture in collaboration with various national programs. HarvestPlus set iron biofortification targets at increases of at least 22 mg/kg above locally consumed varieties (Andersson et al. 2017). To date, at least 60 high iron bean varieties have been released in over 12 countries in eastern and southern Africa and Latin America (Saltzman et al. 2017; Beebe 2020). Breeding progress has been made largely through phenotypic selection for increased levels of raw seed iron concentrations. The large variability for iron and zinc levels in dry bean germplasm has facilitated breeding progress. Screening of the CIAT core collection of 1072 bean lines of Mesoamerican, Andean, and mixed‐origin beans has revealed genetic variability for seed Fe and Zn concentrations ranging from 34 to 96 mg/kg and 21 to 60 mg/kg, respectively (Islam et al. 2002). Iron concentrations as high as 152 mg/kg have been reported for some bean genotypes from race Chile (Paredes et al. 2009).

While there have been at least seven QTL studies published on the inheritance of iron and zinc, applying these to marker assisted selection has not proved to be worthwhile (Freyre et al. 1998; Blair et al. 2009, 2010, 2011; Cichy et al. 2009, 2014; Blair and Izquierdo 2012). Any one QTL typically only provides the potential for a few ppm increase in iron or zinc, and these small levels would easily be confounded with environmental variation. Levels of Fe and Zn in the seed are influenced by the environment, especially soil fertility levels (Cichy et al. 2009; White and Broadley, 2009; Katuuramu et al. 2021). Genomic selection may hold promise to improve breeding gains. Future work is also likely to be more directed to iron bioavailability, as opposed to iron concentration, to achieve the maximum nutritional benefits to the consumer (Katuuramu et al. 2021).

Niche Markets

       Organic dry beans

      Organic dry beans are a high‐value specialty crop of multiple market classes, including black, dark red kidney, and white kidney beans. Dry beans are an appealing option for organic farmers, since consumer demand is strong. The price premium for organic dry beans is 1.5–3 times that of conventionally produced beans. Controlling weeds and insect pests effectively without the use of pesticides is a major challenge for organic producers (Frick et al. 2017). Despite these constraints many larger producers continue to produce high‐quality organic beans but at resulting lower yields. In side‐by‐side studies over three years in Michigan, 36 bean varieties grown under organic production systems averaged 18% lower yields than under conventional systems (Heilig and Kelly 2012).

      Currently, organic producers use varieties developed for conventional production systems and some of these may not perform as well under organic production systems. Prior dry bean breeding research suggests that breeding under organic systems is more valuable in some market classes than others. Genetic variability for seed yield under organic vs. conventional showed that for black and navy beans the best lines under organic were also the best performers under conventional (Heilig and Kelly 2012). This is likely because of the goals of conventional breeding programs are beneficial for all producers. For example, traits such as disease or insect resistance, overall productivity, and improved plant architecture are valuable for both conventional and organic producers. Heilig and Kelly (2012) found that in the case of kidney beans the best lines under conventional were not necessarily the best under organic. Therefore, selecting kidney lines under organic conditions would be beneficial to improve germplasm for organic production. Breeding for organic production systems is underway in multiple public breeding programs around the US.

Slow darkening (SD) pinto beans

Consumer preference for pinto beans is often dictated by seed color. Most pinto bean cultivars possess a brown mottled color on beige background; however, this pigmentation changes with postharvest aging. The bright beige background darkens with storage and has been used as a means for purchase decisions in traditional markets for discriminating between fresh/new crop (bright color) and old/aged (dark color) beans. Plant breeders were able to isolate this characteristic as a heritable trait (recessive sd gene). This has resulted in the recent release of several SD cultivars (Vibrant, Radiant, Lumen, Gleam, Palomino, Staybright) that take considerably longer to darken during storage (Rodrigues et al. 2019; Miklas et al. 2020). SD pinto beans produced in controlled field trials exhibited slightly better canning quality than standard pintos. The distinctive color of SD pintos requires strict segregation as a market class to assure lot uniformity.

Heirloom beans

      Heirloom beans is another niche opportunity for bean breeders. Demand for heirloom and specialty beans is increasing, and this trend is due in part to direct‐to‐consumer bean sellers such as Rancho Gordo, that have effectively created demand by framing stories around the beans which appeal to consumers (King et al. 2021). Some popular heirloom beans include Jacob’s Cattle, Calypso, Soldier, and Hidatso Red. There is also interest on the part of breeders to improve heirloom beans for agronomic characteristics and disease resistance. Studies of the yield and SNF capacity of heirloom vs conventional showed comparable yields for some heirlooms and reductions for others suggesting they can be incorporated into parents in breeding programs without major yield drag (Swegarden et al. 2016; Wilker et al. 2019). Five improved heirlooms were recently released by UC Davis, including a Rio Zape and Tiger’s Eye. Each was improved by backcrossing with the I gene to add BCMV resistance while maintaining the heirloom seed types (Parker et al. 2021a,b,c,d,e).

GENOMIC RESEARCH AND TRANSGENIC BEANS

      Genomic research

      The Phaseolus vulgaris genome sequence of the Andean landrace, Chacha Chuga (G19833) was released in 2014 (Schmutz et al. 2014); v2.1 is the most current version available, which has been updated with long read PacBio sequencing. The sequence is available СКАЧАТЬ