Dry bean (Phaseolus vulgaris L.) is a nutritious crop that is high in protein, fiber, vitamins and minerals and provides a large portion of dietary protein in the human diet. Beans require significant time to cook making them inconvenient for consumers potentially reducing the consumption rate. Considerable genetic variability exists for cooking time in P. vulgaris, but the underlying genetic causes of cooking time differences are largely unknown. To elucidate the genetic control of cooking time in dry bean, two Andean bean genotypes (TZ-27 and TZ-37) from Tanzania were identified with contrasting cooking times but similar seed color and plant growth habit. The average cooking time was 72.3 min and 33.1 min for TZ-27 and TZ-37, respectively, across nine growing locations globally. Additionally, TZ-37 had a 100 dry seed weight 1.2 to 1.5 times greater than TZ-27 in all test environments. The concentration of Ca and Mn were 1.7 and 1.3 times higher in TZ-27 than in TZ-37 respectively, while TZ-37 had 1.1 times the level of phytate than TZ-27.TZ-27 and TZ-37 were used to develop a biparental recombinant inbred line population (RIL) of 161 genotypes. The RIL population was evaluated for cooking time, hydration capacity, seed coat percentage, protein concentration, and other agronomic traits in Arusha and Morogoro in Tanzania in 2016 and 2017. Morogoro typically has higher temperatures, lower altitude, and lower soil fertility soil than Arusha. Significant variation was found for cooking time within the RIL population with a range of 21.4 min to 134.6 min across both years and locations. An environmental influence on cooking time was observed with the average cooking time in Morogoro being 15 min longer than Arusha. Five lines were identified that cooked faster than TZ-37 showing transgressive segregation for cooking time. Seed weight, hydration capacity, and protein concentration were inversely correlated with cooking time, while seed coat percentage was directly correlated.A quantitative trait loci (QTL) analysis was conducted using 2,427 single nucleotide polymorphism (SNP) markers discovered through genotyping by sequencing. Ten QTL were discovered for cooking time. A previously reported QTL, CT1.1, was found in Arusha in 2016 and 2017. CT3.2 was found in Arusha and Morogoro in 2017 and explained 20.5% of variation for the trait. CT6.1 was identified in both locations in 2017 and co-localized with multiple traits including hydration capacity, protein concentration, and 100 seed weight. CT10.1 was identified in Morogoro in both years. These 4 QTL, collectively, resulted in a reduction of cooking time by 16 minutes. Genes of interest within the cooking time QTL included one for polygalacturonase and another for the inhibitor of pectin methylesterase, which have previously been shown to affect cooking time. The QTL described serve as potential targets for improvement of cooking time in commercial dry bean genotypes and could be used to increase the efficiency in a breeding program by selecting for genotypes with multiple QTL for fast cooking. Developing faster cooking varieties would eliminate a major barrier for consumption. Faster cooking beans would be especially helpful in developing countries by reducing fuel burned as well as time required to gather firewood, which allows more time for other tasks.
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