Weedy Accessions Research Articles

Genomic variation in weedy and cultivated broomcorn millet accessions uncovers the genetic architecture of agronomic traits.

Large-scale genomic variations are fundamental resources for crop genetics and breeding. Here we sequenced 1,904 genomes of broomcorn millet to an average of 40× sequencing depth and constructed a comprehensive variation map of weedy and cultivated accessions. Being one of the oldest cultivated crops, broomcorn millet has extremely low nucleotide diversity and remarkably rapid decay of linkage disequilibrium. Genome-wide association studies identified 186 loci for 12 agronomic traits. Many causative candidate genes, such as PmGW8 for grain size and PmLG1 for panicle shape, showed strong selection signatures during domestication. Weedy accessions contained many beneficial variations for the grain traits that are largely lost in cultivated accessions. Weedy and cultivated broomcorn millet have adopted different loci controlling flowering time for regional adaptation in parallel. Our study uncovers the unique population genomic features of broomcorn millet and provides an agronomically important resource for cereal crops.

Utilizing germinability thresholds for optimizing stale seedbed applications to control red rice (Oryza spp.) in California rice cropping systems

Abstract“Weedy” red rice is a problematic weed with phenotypic similarities to cultivated rice. Limited herbicide availability has driven a need for nonchemical control options for managing this pest. One preplanting strategy that is being explored is the stale seedbed methodology, which aims to maximize soil seedbank withdrawals via germination. This technique is adapted in rice by flooding a field, waiting for germination and emergence of weed seedlings, and completing the method with a mechanical or chemical control application. Optimization of this process is dependent on maximizing weed seed germination, which is primarily influenced by both temperature and moisture availability. Germinability across a range of these factors is not well understood in California red rice. Thus, this study aimed to determine germinability of California red rice accessions under various temperature and water potential treatments. Previously described red rice accessions 1, 2, 3, and 5, along with ‘M206’, a common California rice cultivar, were exposed to temperatures from 10 to 40 C in 5 C increments in combination with water potentials of 0, −0.2, −0.4, or −0.8 MPa until either germination or weed seed decay occurred. Statistical analysis indicated a three-way interaction between accession, temperature, and water potential. Germination reached 95% or greater when seeds were exposed to temperatures from 20 to 35 C in combination with 0 or −0.2 MPa. Germination was lowest when seeds were water stressed (−0.8 MPa) and when temperatures were colder than 20 C or warmer than 35 C. The ‘M206’ cultivar was utilized for comparison and demonstrated cold tolerance by germinating at 10 C, whereas weedy accessions 1, 2, and 3 did not. When temperatures were at or above 15 C, however, ‘M206’ germinated less often compared with all weedy accessions. Historical preplant temperatures in this region align with those required for weedy rice germination. Thus, the stale seedbed methodology is a viable strategy in years when ample floodwater is available.

Searching for Novel Oat Crown Rust Resistance in Diploid Oat Avena strigosa Schreb. Reveals the Complexity and Heterogeneity of the Analyzed Genebank Accessions

Crown rust, one of the most destructive diseases of oat, regularly occurs worldwide and leads to significant yield losses. The constant evolution of the Puccinia coronata f. sp. avenae pathogen causes a rapid decline in the effectiveness of currently used crown rust resistance genes, so new ones are urgently needed. In this study, 39 accessions of Avena strigosa Schreb. from ten countries gathered from the Polish National Genebank were evaluated at the seedling stage for crown rust reaction using a detached leaf assay and five isolates of P. coronata with diverse virulence profiles. Ten plants of each accession were tested, and 28 diverse infection profiles (IPs) were defined. One hundred and sixty-eight out of 390 plants revealed an IP of unidentified resistance. Thirty-eight (97%) of the accessions studied showed a heterogeneous infection pattern, none of the accessions displayed homogeneous susceptibility, and one (51887) was homogeneously resistant to all races used. The obtained results confirmed the complexity and heterogeneity of the accessions gathered in the genebanks. A. strigosa preserved as complex populations could be a valuable source of resistance to crown rust and potentially other pathogens. The variability of the analyzed populations was ascertained by a detailed diversity analysis of the transformed resistance/susceptibility data. The averaged resistance rating for the genebank specimens available in the databases may be an obstacle in revealing the beneficial alleles of genes hidden among the plants representing accessions preserved as complex populations. Potential donors of effective resistance may be discovered even in accessions with general susceptibility, which is a promising alternative at a time when making new collections of wild and weedy accessions is under threat from agricultural practice and climate change.

Genomics-based assembly of a sorghum bicolor (L.) moench core collection in the Uganda national genebank as a genetic resource for sustainable sorghum breeding

The Uganda National GeneBank is a key reservoir of genetic diversity for sorghum (Sorghum bicolor (L.) Moench), with over 3333 accessions which are predominantly landraces (96.48%), but also includes the weedy accessions (0.63%), breeding lines (2.5%) and released varieties (0.39%). This genetic resource from the primary center of sorghum diversity and domestication is important for broadening the genetic diversity of elite cultivars through breeding. However, due to the large size of the collection, we aimed to select a core set that captures the maximum genetic and phenotypic diversity, in order to facilitate detailed genetic and phenotypic evaluation at a reduced cost. To achieve this, we genotyped the entire collection in 2020 using Diversity Array Technology sequencing (DArTseq). A total of 27,560 SNPs were used to select a core collection of 310 accessions using the GenoCore software. A comparison of core set and the whole collection based on the polymorphism information content, observed heterozygosity, expected heterozygosity and minor allele frequency showed no significant difference between the two sets, indicating that the core collection adequately captures the genetic diversity and allelic richness present in the whole collection. The core collection captures all the five major sorghum races and the 10 intermediate hybrids. The most strongly represented race is guinea (24.5%), while caudatum-bicolor is least frequent (0.69%). Landraces account for 92.2% of the core collection, whereas breeder’s lines, weedy accessions and released varieties contribute 2.2%, 3.5% and 1.9%, respectively.

Weedy Rice Conserved Ex Situ Characterized Using Morphological and Simple Sequence Repeat (SSR) Markers

A clear understanding of genetic diversity in weedy rice is important in improving protocols for its conservation, ex situ. To this end, Asian collections of weedy rice together with accessions of the wild AA genome species Oryza nivara Sharma et Shastry and Oryza rufipogon Griffith, and the cultivated species, Oryza sativa L. were characterized using 16 qualitative morphological traits and 18 SSR markers. The Shannon-Weaver index (H’) revealed higher diversity in the weedy (mean H’ = 0.76) and wild O. nivara (mean H’ = 0.79) and O. rufipogon samples (mean H’ = 0.69) compared to the cultivated samples (mean H’ = 0.44). The weedy forms showed high preference (> 90%) for high grain shattering and awn presence. Cluster analysis based on the 16 qualitative characters revealed three major clusters where weedy accessions grouped with (1) O. rufipogon samples (2) O. nivara, O. rufipogon and indica rice samples, and (3) indica, aus, and japonica and a few O. nivara and O. rufipogon rice samples. Cluster analysis based on SSR data concurred largely with morphological analysis. Genetic diversity indices (number of alleles, observed heterozygosity, expected heterozygosity) detected by SSR markers were comparable between the weedy (1.64, 0.11, 0.23) and O. rufipogon (1.53, 0.19, 0.23) samples. Analysis of molecular variance (AMOVA) among the weedy forms revealed that differentiation within accessions accounted for 79% of the total variation.

When a Crop Goes Back to the Wild: Feralization

Feral plants have been known since the inception of modern agriculture, but the genetic changes during what seemed to be a simple reversion of a domesticated form are poorly understood. Recent studies, revealing the changes occurring in weedy rice, show an unexpected degree of differentiation in these feral escapes.

Identifying SSR markers associated with seed characteristics in Perilla (Perilla frutescens L.).

The online version of this article (10.1007/s12298-021-00933-3) contains supplementary material, which is available to authorized users.

Compositional differences in hybrids between protoporphyrinogen IX oxidase (PPO)-inhibiting herbicide-resistant transgenic rice and weedy rice accessions

We characterized the metabolites in grains of transgenic protoporphyrinogen IX oxidase-inhibiting herbicide-resistant rice and weedy accessions using GC–MS and examined whether the chemical composition of their hybrids differed from that of the parents. We found that the metabolite profiles of transgenic rice and weedy rice were clearly separated. Although the metabolite profiles of F2 progeny were partially separated from their parents, zygosity did not affect the profiles. The F2 progeny had similar or intermediate levels of most major nutritional components compared with their parents. However, levels of galactopyranose, trehalose, xylofuranose, mannitol, and benzoic acid were higher in the F2 progeny. Some fatty acids and organic acids also showed prominent quantitative differences between the F2 progeny and the parents. Changes in the metabolite levels of transgenic crop-weed hybrids compared to their parents might influence not only the ecological consequences of the hybrids, but also the nutritional quality and food safety.

Nutraceuticals, antioxidant pigments, and phytochemicals in the leaves of Amaranthus spinosus and Amaranthus viridis weedy species

Six selected weedy Amaranthus genotypes (three accessions from each species of A. viridis and A. spinosus) were evaluated in terms of nutrients, minerals, antioxidant constituents and antioxidant activity for the possibilities of weedy species as a vegetable cultivar in a randomized complete block design with three replications. As leafy vegetable, Weedy Amaranthus has remarkable protein, dietary fiber, carbohydrates, Ca, K, Mg, P, S, Fe, Mn, Cu, Zn, Na, Mo, B, chlorophylls, β-cyanins, β-xanthins, betalains, β-carotene, vitamin C, TPC, TFC, and TAC (DPPH and ABTS+) compared to any cultivated species. The A. viridis genotype WAV7 and A. spinosus genotype WAS13 had the highest nutrients, pigments, vitamins, phenolics, flavonoids, and antioxidant. Hence, these two weedy accessions could be used as an antioxidant profile enriched cultivar with high nutritional and antioxidant activity. Pigments, β-carotene, vitamin C, phenolics, and flavonoids had strong antioxidant activity and played a vital role in the antioxidant activity of weedy Amaranthus genotypes. Weedy species are an excellent source of phenolics, flavonoids, and antioxidants that have many pharmacological and medicinal effects of their traditional applications and detoxify ROS and offered huge prospects for feeding the antioxidant-deficient community to cope with the hidden hunger and attaining nutritional and antioxidant sufficiency.

Genetic diversity and population structure of Perilla frutescens collected from Korea and China based on simple sequence repeats (SSRs).

Perilla frutescens (L.) Britt. is divided into two varieties based on morphology and use. One is P. frutescens var. frutescens, which is used both as a leafy vegetable and as an oil obtained from the seeds. The other variety is P. frutescens var. crispa, a Chinese medicine or spice vegetable crop. In addition, weedy types of var. frutescens and var. crispa are occasionally grown as relict forms and are easy to find on roadsides, in waste areas and around farmers' fields or farmhouses. SSR markers have been successfully used to examine the genetic diversity and relationships of cultivated and weedy types of Perilla in many regions. In this study, we used 25 simple sequence repeat (SSR) markers were used to assess the genetic diversity and population structure of 90 Perilla accessions from Korea and China. A total of 90 accessions of Perilla were collected in Korea and China included 45 accessions from each of Korea and China. We selected 25 SSR markers representing the polymorphism of and adequately amplifying all the Perilla accessions. A total of 153 alleles were identified, with an average of 6.12 alleles per locus. The GD level and PIC value for cultivated and weedy types of P. frutescens from China were higher than those for accessions from Korea. Weedy accessions had higher GD and PIC values than cultivated accessions. In the population structure analysis using the model-based method, the 90 Perilla accessions were divided into two main group and an admixed group based on a membership probability threshold of 0.8. Based on the distance-based unweighted pair group method with the arithmetic mean (UPGMA), all accessions were classified into four major groups with a genetic similarity of 32.8%. Finally, the findings of this study will provide useful theoretical knowledge for further study of the population structure and genetic diversity of Perilla species and benefit Perilla crop breeding and germplasm conservation in Korea and China.

Gene Flow from Transgenic PPO-inhibiting Herbicide-resistant Rice to Weedy Rice, and Agronomic Performance by Their Hybrids

Hybridization of transgenic crops with their weedy relatives may spread transgenes into weedy populations and alter the ecological fitness of such hybrids. Our study objective was to quantify the rate of gene flow from herbicide-resistant transgenic rice to weedy rice and compare the performance of hybrids between them over several generations. The transgenic plants used in these experiments are resistant to protoporphyrinogen IX oxidase (PPO)-inhibiting herbicides such as oxyfluorfen, oxadiazon, and butafenacil. The rate of gene flow from those plants to five weedy accessions ranged from 0.025% to 0.139%. The F1 hybrids that resulted from gene flow from transgenic to weedy rice and subsequent F2 progeny were shorter than the weedy parents but produced significantly more and heavier grains. The F3 progeny resulting from gene flow were resistant to oxyfluorfen, which indicated that the gene associated with PPO-inhibiting herbicide resistance is dominantly inherited. The GR50 values (dose required for 50% shoot fresh weight reduction) for F3 progeny were > 69-fold greater than for the weedy rice. These results suggest that transgenes that could escape from PPO-inhibiting herbicide-resistant rice and be transferred to weedy rice might persist and disperse into weedy populations over several generations due to herbicide resistance and improved reproductive traits in the hybrids.

Genetic diversity and population structure among accessions of Perilla frutescens (L.) Britton in East Asia using new developed microsatellite markers.

SSRs were successfully isolated from the Perilla crop in our current study, and used to analyze Perilla accessions from East Asia. Analyses of the clear genetic diversity and relationship for Perilla crop still remain insufficient. In this study, 40 new simple sequence repeat (SSR) primer sets were developed from RNA sequences using transcriptome analysis. These new SSR markers were applied to analyze the diversity, relationships, and population structure among 35 accessions of the two cultivated types of Perilla crop and their weedy types. A total of 220 alleles were identified at all loci, with an average of 5.5 alleles per locus and a range between 2 and 10 alleles per locus. The MAF (major allele frequency) per locus varied from 0.229 to 0.943, with an average of 0.466. The average polymorphic information content (PIC) value was 0.603, ranging from 0.102 to 0.837. The genetic diversity (GD) ranged from 0.108 to 0.854, with an average of 0.654. Based on population structure analysis, all accessions were divided into three groups: Group I, Group II and the admixed group. This study demonstrated the utility of new SSR analysis for the study of genetic diversity and population structure among 35 Perilla accessions. The GD of each locus for accessions of cultivated var. frutescens, weedy var. frutescens, cultivated var. crispa, and weedy var. crispa were 0.415, 0.606, 0.308, and 0.480, respectively. Both weedy accessions exhibited higher GD and PIC values than their cultivated types in East Asia. The new SSR primers of Perilla species reported in this study may provide potential genetic markers for population genetics to enhance our understanding of the genetic diversity, genetic relationship and population structure of the cultivated and weedy types of P. frutescens in East Asia. In addition, new Perilla SSR primers developed from RNA-seq can be used in the future for cultivar identification, conservation of Perilla germplasm resources, genome mapping and tagging of important genes/QTLs for Perilla breeding programs.

Genetic diversity and population structure in cultivated and weedy types of Perilla in East Asia and other countries as revealed by SSR markers

In this study, 17 simple sequence repeat (SSR) primer sets were used to analyze the genetic diversity, genetic relationships, and population structure among 81 accessions of two cultivated types of Perilla crop and their corresponding weedy types in East Asia and other countries. A total of 166 alleles were identified with an average of 9.8 alleles per locus. The average gene diversity (GD) value was 0.709. The average polymorphic information content (PIC) value was 0.679. The GD of each locus for accessions of cultivated var. frutescens, weedy var. frutescens, cultivated var. crispa, and weedy var. crispa were 0.557, 0.740, 0.429, and 0.509, respectively. Both weedy accessions exhibited higher GD and PIC values than their corresponding cultivated types. The cultivated and weedy types of the Perilla crop had much higher GD and PIC values in East Asia than in other countries. Particularly, in East Asia, the Perilla accessions from China showed higher SSR diversity than those from Korea, Japan, and other countries. Population structure analysis identified three groups, Group I, Group II, and an admixed group. Phylogenetic analysis produced four major clusters, but there was no clear geographic relationship between the two cultivated types of Perilla crop and their weedy types based on their regional distribution. This study demonstrated the utility of SSR analysis for performing genetic and population analysis of cultivated and weedy types of Perilla accessions in East Asia and other countries.

The impact of herbicide-resistant rice technology on phenotypic diversity and population structure of United States weedy rice.

The use of herbicide-resistant (HR) Clearfield rice (Oryza sativa) to control weedy rice has increased in the past 12 years to constitute about 60% of rice acreage in Arkansas, where most U.S. rice is grown. To assess the impact of HR cultivated rice on the herbicide resistance and population structure of weedy rice, weedy samples were collected from commercial fields with a history of Clearfield rice. Panicles from each weedy type were harvested and tested for resistance to imazethapyr. The majority of plants sampled had at least 20% resistant offspring. These resistant weeds were 97 to 199 cm tall and initiated flowering from 78 to 128 d, generally later than recorded for accessions collected prior to the widespread use of Clearfield rice (i.e. historical accessions). Whereas the majority (70%) of historical accessions had straw-colored hulls, only 30% of contemporary HR weedy rice had straw-colored hulls. Analysis of genotyping-by-sequencing data showed that HR weeds were not genetically structured according to hull color, whereas historical weedy rice was separated into straw-hull and black-hull populations. A significant portion of the local rice crop genome was introgressed into HR weedy rice, which was rare in historical weedy accessions. Admixture analyses showed that HR weeds tend to possess crop haplotypes in the portion of chromosome 2 containing the ACETOLACTATE SYNTHASE gene, which confers herbicide resistance to Clearfield rice. Thus, U.S. HR weedy rice is a distinct population relative to historical weedy rice and shows modifications in morphology and phenology that are relevant to weed management.

Massive Sorghum Collection Genotyped with SSR Markers to Enhance Use of Global Genetic Resources

Large ex situ collections require approaches for sampling manageable amounts of germplasm for in-depth characterization and use. We present here a large diversity survey in sorghum with 3367 accessions and 41 reference nuclear SSR markers. Of 19 alleles on average per locus, the largest numbers of alleles were concentrated in central and eastern Africa. Cultivated sorghum appeared structured according to geographic regions and race within region. A total of 13 groups of variable size were distinguished. The peripheral groups in western Africa, southern Africa and eastern Asia were the most homogeneous and clearly differentiated. Except for Kafir, there was little correspondence between races and marker-based groups. Bicolor, Caudatum, Durra and Guinea types were each dispersed in three groups or more. Races should therefore better be referred to as morphotypes. Wild and weedy accessions were very diverse and scattered among cultivated samples, reinforcing the idea that large gene-flow exists between the different compartments. Our study provides an entry to global sorghum germplasm collections. Our reference marker kit can serve to aggregate additional studies and enhance international collaboration. We propose a core reference set in order to facilitate integrated phenotyping experiments towards refined functional understanding of sorghum diversity.

Water Stress in <i>Beta vulgaris</i>: Osmotic Adjustment Response and Gene Expression Analysis in ssp. <i>vulgaris</i> and <i>maritima</i>

Beta vulgaris genus comprises wild and cultivated subspecies. The “maritima” subspecies is formed by wild or weedy accessions, well adapted to low-water potential environments; it was previously shown that B. vulgaris ssp. maritima has mechanisms of osmotic adjustment more effective than the cultivated B. vulgaris ssp. vulgaris. The response to a progressive lowering of soil potential was compared in two Beta accessions, a cultivated and a wild one. Throughout the 4-months experiment under rain shelters, osmotic potential and relative water content were measured and total RNA was extracted to test the expression of six target genes known in sugar beet or in other plants to be modulated by water shortage. The mild occurrence of drought was paralleled by slow increase in transcription for sucrose synthase 1 and choline monoxygenase, in a way that was in some cases accession-dependent, e.g. the gene for choline monoxygenase was found to be up-regulated at the later stages of growth in stressed plants compared to control ones, and showed a higher constitutive transcription in sea beet compared to sugar beet. Transcription factor DREB2Aalso was slowly induced during the growth season and upon onset of water shortage, and this induction was stronger in sea beet than in sugar beet. In control plants, the transcription of all genes tested except DREB2Awere significantly higher in maritima accession compared to vulgaris one.

Genetic Architecture of Seed Dormancy in U.S. Weedy Rice in Different Genetic Backgrounds

ABSTRACTSeed dormancy (SD) is a key domestication trait closely related to preharvest sprouting tolerance. Wild and weedy rices (Oryza spp.) exhibit higher degrees of seed dormancy compared to the cultivated rice. Red rice (Oryza sativa L.), a major weed in the rice growing areas of the southern United States, was used to elucidate the genetic architecture of SD. Quantitative trait loci (QTL) analysis conducted in two recombinant inbred line (RIL) populations developed from the crosses involving two rice cultivars (Bengal and Cypress) and a red rice accession (PSRR‐1) revealed six to seven QTL for seed dormancy, which accounted for 49 to 52% of the total phenotypic variance. The magnitude of the QTL contribution to phenotypic variance was influenced by genetic backgrounds. The majority of QTL had minor effects, except the QTL linked to Rc and Sdr4. The genetic architecture for seed dormancy in U.S. red rice was distinct compared with the earlier reported weedy accessions. Four QTL were mapped onto similar positions in both populations. Both cultivars and red rice contributed alleles for increased SD. Most of the digenic epistatic interactions involved loci other than the QTL with main effects. The nucleotide polymorphisms at the Sdr4 locus could not explain the phenotypic variation for seed dormancy in our materials. The variation in SD among the rice cultivars could be attributed to segregation of minor QTL, which may be exploited to improve preharvest sprouting tolerance.

Morphological Variation in the Wild-Weedy Complex of Sorghum bicolor In Situ in Western Kenya: Preliminary Evidence of Crop-to-Wild Gene Flow?

Crop wild relatives are important components of agroecosystems and have over the years been exploited in breeding programs as sources of genes for novel traits. Information on the extent and patterns of variability is important in formulating effective conservation and utilization strategies for existing crop wild relative populations. We conducted surveys and collections of wild and weedy accessions of Sorghum bicolor (L.) Moench in Lambwe Valley in western Kenya in order to investigate occurrence, distribution, and morphological variability in the wild-weedy complex of S. bicolor under local agroecological conditions. We also attempted to understand the role, if any, of crop-to-wild gene flow in structuring variability within and among populations. The morphological data presented here showed wide variability within wild-weedy sorghum populations with respect to habitats and morphotypes. True wild sorghum populations in national parks and the sugarcane belt were clearly distinguishable from the putative hybrids or intermediate forms found in sorghum fields, in sorghum field margins, and, to some extent, by the roadside near sorghum fields. The existence of these intermediate forms is empirical evidence of introgression between cultivated sorghum and its wild-weedy relatives. Extensive introgression, especially within in situ conservation areas and/or in areas of high diversity, would lead to genetic erosion and possible depletion of these important wild sorghum genetic resources.

Histological and genetic characteristics associated with the seed-shattering habit of weedy rice (Oryza sativa L.) from Okayama, Japan

We aimed to elucidate the molecular nature of the seed-shattering habit of weedy rice Oryza sativa L. in Okayama Prefecture, Japan, which seems to be an “off-type” of the main rice varieties in Okayama. We performed time-course analyses of breaking tensile strength (BTS) and analyzed the histological features of pedicels; we also genotyped the seed-shattering genes qSH1 and sh4 of weedy rice accessions and rice cultivars. The BTS of weedy accessions and cultivars began to decrease simultaneously at three weeks after heading. The weedy accessions showed complete loss of BTS and grain dispersal at five weeks after heading. In contrast, the cultivars maintained a certain degree of BTS and did not exhibit grain dispersal. Pedicel structures, which affect BTS, differed between the weedy accessions and the cultivars. The weedy accessions had complete and cracked abscission layers, while the cultivars had incomplete and uncracked abscission layers; however, the qSH1 and sh4 sequences that influence the formation of the abscission layer showed no differences between the weedy accessions and cultivars. We surmise that the shattering habit of weedy rice in Okayama is caused by formation and degeneration of the abscission layer, mediated by unidentified shattering-related gene(s).

Leaf area of common bean genotypes during early pod filling as related to plant adaptation to limited phosphorus supply

Low phosphorus supply markedly limits leaf growth and genotypes able to maintain adequate leaf area at low P could adapt better to limited-P conditions. This work aimed to investigate the relationship between leaf area production of common bean (Phaseolus vulgaris) genotypes during early pod filling and plant adaptation to limited P supply. Twenty-four genotypes, comprised of the four growth habits in the species and two weedy accessions, were grown at two P level applied to the soil (20 and 80 mg kg-1) in 4 kg pots and harvested at two growth stages (pod setting and early pod filling). High P level markedly increased the leaf number and leaf size (leaf area per leaf), slightly increased specific leaf area but did not affect the net assimilation rate. At low P level most genotypic variation for plant dry mass was associated with leaf size, whereas at high P level this variation was associated primarily with the number of leaves and secondarily with leaf size, specific leaf area playing a minor role at both P level. Determinate bush genotypes presented a smaller leaf area, fewer but larger leaves with higher specific leaf area and lower net assimilation rate. Climbing genotypes showed numerous leaves, smaller and thicker leaves with a higher net assimilation rate. Indeterminate bush and indeterminate prostrate genotypes presented the highest leaf area, achieved through intermediate leaf number, leaf size and specific leaf area. The latter groups were better adapted to limited P. It is concluded that improved growth at low P during early pod filling was associated with common bean genotypes able to maintain leaf expansion through leaves with greater individual leaf area.