Westermann, D. T., Terán, H., Muñoz-Perea, C. G. and Singh, S. P. 2011. Plant and seed nutrient uptake in common bean in seven organic and conventional production systems. Can. J. Plant Sci. 91: 1089–1099. Knowledge of plant and seed nutrient uptake by crop cultivars in organic and conventional production systems (PS) is essential for breeding the most appropriate genotypes for each PS. The objective was to determine the plant and seed uptake of nitrogen (N), phosphorus (P), potassium (K), copper (Cu), manganese (Mn), and zinc (Zn) by 16 common bean genotypes. We also identified genotypes efficient in plant and seed nutrient uptake across seven organic and conventional PS. A randomized complete block design with four replicates (one plot per replicate) was used for evaluation in each of seven organic and conventional PS in 2003 and 2004. The effects of plant and seed uptake of nutrients, genotypes, PS, and the genotype × PS interaction were significant (P≤0.05). Plant and seed uptake of nutrients decreased in on-station continual dry bean and drought-stressed and on-farm organic low-input compared with on-station conventional irrigated and on-farm organic high-input PS. Common bean genotypes with higher biomass yield, in general, also had higher nutrient uptake, regardless of PS. In general, N and P uptakes were high and that for Mn was markedly low among common bean genotypes. Pinto CO46348, Bill Z, and Othello and Mexican red NW-63 and UI 239 were high-yielding and used nutrients more efficiently across seven organic and conventional PS and years. Other cultivars either had low biomass and seed yield (e.g., Common Pinto, Topaz, Common Red Mexican, UI 59) or were more efficient at whole-plant uptake or seed uptake of nutrients, but not both (e.g., Matterhorn, UI 465). Use of the above five genotypes should be maximized for production in both organic and conventional PS, and for breeding high-yielding broadly adapted cultivars efficient in plant and seed nutrient uptake in organic and conventional PS.

White mold (WM) is a widely distributed and severe disease of common bean in North America. The objective of this study was to determine the effectiveness of gamete (GS) and recurrent (RS) selection methods for improving WM resistance. Two double-crosses, namely USPT-WM-1/CORNELL 601//USPT-CBB-1/92BG-7 and ‘Chas’/I 9365-25//ABL 15/A 195 were made. Equal numbers of progenies from both crosses were subjected to GS and RS. The GS was practiced from F₁ to F₄ by selecting WM resistant single plants followed by progeny testing in the subsequent generation. Two cycles of RS were practiced by intermating selected WM resistant plants in each cycle. Thirteen selected families in each method and parents were evaluated at 16, 23, and 33 days post first inoculation in replicated trials in two greenhouse environments. Higher frequencies of families with lower WM scores were obtained from GS than RS. The average genetic gains due to GS and RS were 19.6 and 7.9%, respectively. Employing multiple-parent-crosses involving parents of diverse evolutionary origins delayed WM evaluation, and application of GS are recommended for improving physiological WM resistance in common bean.Key words: Interspecific breeding line, introgressing resistance, multiple-parent crosses, Phaseolus vulgaris, pyramiding resistance, Sclerotinia sclerotiorum

White mold (WM) caused by Sclerotinia sclerotiorum (Lib.) de Bary is the most devastating disease of common bean (dry and snap or garden bean) (Phaseolus vulgaris L.) in North America. The use of a reliable screening method (SM) in common bean is crucial to improve physiological resistance to WM. The objective of this study was to compare the efficacy of three SM to identify physiological resistance in dry bean genotypes with different evolutionary origins and levels of resistance. Screening methods tested were: (i) the modified straw test or cut–stem (CSM); (ii) infected bean flower (IFL); and (iii) infected oat seed (IOS). A 195, ICA Bunsi, Othello, and VCW 54 dry bean were tested with the three SM. The experimental design was a split plot in randomized complete blocks with three replications in 2007 and 2008. Two independent inoculations 1 wk apart for each SM were made. The WM reaction was scored at 16, 23, and 33 d post-inoculation (DPI) using a 1 to 9 scale. There were highly significant differences between SM and its interaction with years. The CSM and IFL were the most consistent and highly correlated (r > 0.70, P < 0.01). Interspecific breeding line VCW 54 consistently had the highest WM resistance across years, SM, and evaluation dates, followed by A 195. White mold scores increased with delayed evaluations. Thus, CSM or IFL with disease assessed 33 DPI should be used for identifying common bean genotypes with high levels of physiological resistance to WM.Key words: Common bean, growth habit, race Mesoamerica, race Nueva Granada, Phaseolus vulgaris, Sclerotinia sclerotiorum