Pod Harvest Index Research Articles

Agronomic and morpho‐physiological response of Andean genotypes of common bean to terminal drought

AbstractDrought is a major production constraint of common bean (Phaseolus vulgaris L.) worldwide. The objectives of this study were to (i) assess the agronomic and morpho‐physiological response of Andean genotypes to terminal drought, and (ii) identify Andean genotypes with an ideal combination of agronomic and morpho‐physiological traits for enhanced drought tolerance. Twenty Andean genotypes and seven checks were evaluated for drought tolerance in three field trials conducted in three locations. Agronomic and morpho‐physiological traits including seed yield, seed weight, shoot dry weight, pod number, pod harvest index, harvest index, and carbon isotope discrimination (CID) were measured. Strong positive correlations were observed between seed yield, and partitioning efficiency metrics and CID (r = 0.57***) under drought, which suggested the important role of assimilate partitioning and water use efficiency in the observed drought tolerance. The heritability estimates for pod harvest index (H2 = 0.88) and harvest index (H2 = 0.87) were higher than for seed yield (H2 = 0.43) and other morpho‐physiological traits, thus they can be used to indirectly select for drought tolerance. Based on the relationship between seed yield and CID under drought stress, 12 genotypes were identified as drought tolerant with high water use efficiency. Among these, three were classified as water savers, while nine as water spenders. Genotypes with an ideal combination of superior shoot dry weight, partition efficiency, water use efficiency, and superior seed yield under both drought stress and non‐stress conditions were identified. The identified genotypes can be used for genetic improvement of drought tolerance in the Andean gene pool of common bean.

Genotypic Variation Studies in Biomass Partitioning Patterns during Post-flowering Stages under the Late Sown Conditions of Chickpea (Cicer arietinum L.) Germplasm

This study conducted during the 2021-2022 year under field conditions investigates the genotypic variation in biomass partitioning among different chickpea genotypes during post-flowering stages, with a specific emphasis on late sown conditions. The main aim of the study was to elucidate the efficiency of resource allocation toward pod production, measured by the pod harvest index. This research enhances understanding of chickpea performance under delayed sowing conditions by examining genotypic variations in key parameters during critical post-flowering stages, specifically pod filling and seed filling. Biomass partitioning in branches and pods varied considerably during both growth stages, with branches playing a crucial role in pod development during pod filling. The transition from pod filling to seed filling stage resulted in increased biomass partitioning in pods, highlighting their importance as storage organs for seed development. Seed yield exhibited significant variability among genotypes, with some surpassing 2000 kg/ha, while pod harvest index ranged from 35.62% to 70.48%, indicating differences in resource allocation efficiency. Regression analysis showed varying degrees of association between biomass partitioning and pod harvest index, with seed yield and pod harvest index, biomass partitioning in pods exhibiting the highest explanatory power during seed filling. By studying the adaptation of plants towards biphasic and allometric allocation patterns during unfavorable conditions can result in developing the resource use efficient climate resilient varieties. These findings contribute to our understanding of crop productivity under varying environmental conditions and inform strategies for optimizing chickpea yield and resilience.

Adaptive Responses of Biofortified Common Bean Lines to Acidic Soil and High Temperatures in the Colombian Amazon Region

One of the strategies to combat micronutrient malnutrition is by developing biofortified common bean lines (Phaseolus vulgaris L.) capable of tolerating different stress conditions. In this study, the adaptive responses of different biofortified bean lines grown under combined stress of acidic soil and high-temperatures were evaluated in the Colombian Amazon. A total of 247 common bean lines from the Mesoamerican gene pool were used to determine the adaptive response in terms of phenological, physiological, and agronomic behavior under combined stress conditions. The lines tested were obtained from different single crosses, double crosses, and backcrosses between different bean materials, of which 146 were obtained from F4 families with high iron (Fe) content in seed and 99 common bean lines from F5 families. Different bean lines had grain yields (GY) higher than 1400 kg ha−1 from the F5 (lines: 859, 805, 865, and 657) and F4 (lines: 2853 and 2796) families. The superior performance of these lines was related to a higher photosynthate partitioning that has allowed an increase in pod formation (pod partitioning index, PPI) from the canopy biomass (CB) and grain filling (pod harvest index, PHI; harvest index, HI), resulting in higher values of GY. Values of GY were correlated with CB (r = 0.36), PPI (r = 0.6), PHI (r = 0.68), and HI (r = 0.8, p < 0.001). This increase in agronomic performance is due to a greater allocation of energy to the photosynthetic machinery (ΦII) and its dissipation in the form of heat (ΦNPQ), with increases in the leaf temperature difference (LTD). Based on the results obtained, six biofortified lines of common bean (lines F5: 859, 805, 865, and 657; lines F4: 2853 and 2796) showed traits of tolerance to combined stress and can serve as progenitors to increase Fe and Zn concentration in the seeds of lines that tolerate the combined stress from acidic soil and high temperature in the Colombian Amazon region.

Genetic dissection of yield-related traits in response to drought stress in common bean

Drought stress severely impairs common bean production. For facilitating drought-resistance breeding in common bean, molecular markers were identified in a genome-wide level marker–trait association study. A panel of 210 common bean accessions showed large variation in 11 agronomic traits at the adult stage (plant height, pod number per plant, seed number per pod, seed number per plant, seed yield per plant, pod length, harvest index, pod harvest index, days to maturity, hundred-seed weight, and seed yield) under two water conditions. The coefficient of variation ranged from 6.21% for pod harvest index to 51.00% for seed number per plant under well-watered conditions, and from 4.05% for days to maturity to 40.72% for seed number per plant under drought stress. In a genome-wide association study, 119 quantitative-trait loci were associated with drought resistance, including 41 adjacent to known loci. Among these loci, 12 were found to be associated with at least two traits. Three major loci were identified at Pv01 and Pv02. A set of candidate genes were found that encode MYBs, AREBs, WKRYs, and protein kinases. These results reveal promising alleles that control drought resistance, shedding light on the genetic basis of drought resistance and accelerating future efforts for drought resistance improvement in common bean.

Simulating drought tolerance of peanut varieties by maintaining photosynthesis under water deficit

Over two-third of global peanuts are grown mainly in seasonally rainfed regions across arid and semi-arid zones where drought is a major yield limiting factor. Breeders are targeting drought adaptive traits by selecting high yielding genotypes under water-limited environments. Recently, several peanut varieties have been developed that exhibit drought tolerant characteristics. Crop models can be used to simulate the impact of these traits for different environments. The overall goal of this study was to develop an approach to simulate drought tolerant traits using the CROPGRO-Peanut model and assess the long-term yield response to these desired traits. Four peanut varieties and one advanced breeding line variety with varying degrees of drought tolerance response were grown under both field and rainout shelter conditions in 2019 and 2020. The trait of maintaining photosynthesis under water deficit was observed in the rainout shelter experiments and incorporated into the crop model as a new drought tolerance cultivar coefficient. The evaluation results with independent data showed that the modified model simulated peanut growth and yield under water-limited conditions reasonably well. The rainfed yield, seasonal evapotranspiration (ET), and grain water use efficiency (WUE) were simulated for both drought tolerant and baseline peanut varieties at two representative sites using weather data from 1998 to 2020. The drought tolerant mechanism of maintaining photosynthesis under water deficit was shown to be an advantageous trait for peanut varieties, which produced higher simulated rainfed yield with enhanced seasonal ET and grain WUE, especially for dry seasons. The simulated photosynthesis and yield were sensitive to values of the drought tolerant factor over an expected range of values. Further research is needed on other potential drought tolerant mechanisms, such as maintaining nitrogen fixation, pod harvest index and leaf growth under drought.

ResidualBradyrhizobiuminoculation effects on soybean performance and selected soil health parameters

AbstractThe persistence of inoculants from year to year in soybean [Glycine max (L.) Merr.] cultivation and the residual benefits in soybean production are pertinent to adopting such practices in sub‐Saharan Africa countries such as Ghana. A study was conducted to determine the residual effect of commercial rhizobium inoculants on soybean and selected soil health parameters after three cropping seasons. The experimental design was a split‐plot. The main plot consisted of three soybean cultivars (Jenguma, Afayak, and Songda), and the subplot comprised of three peat‐based commercial bradyrhizobium inoculants (Biofix, Legumefix, and NoduMax) and an uninoculated control. Assessments were made on nodulation, shoot dry matter (DM), grain yield, grain total N uptake, permanganate‐oxidizable carbon (POXC), soil pH, and potentially mineralizable C. Among the soybean cultivars, Afayak produced greater nodule mass on the lateral root and the whole root system compared with the other cultivars. Jenguma and Afayak yielded greater shoot DM relative to Songda. Regarding the inoculants, Biofix increased nodule mass on the lateral root and the whole root system compared with the control. Biofix and NoduMax produced superior grain yield relative to the control. Biofix also produced greater grain yield than Legumefix. A superior pod harvest index and an improved grain total N uptake were produced by Biofix compared with Legumefix and the control. Commercial inoculants enhanced POXC availability at harvest, whereas potentially mineralizable C declined with inoculation treatments. Commercial inoculants (Biofix and NoduMax) enhanced nodulation, grain yield, and selected soil health indicators 3 yr after inoculation.

Effect of Drought and Low P on Yield and Nutritional Content in Common Bean

Common bean (Phaseolus vulgaris L.) production in the tropics typically occurs in rainfed systems on marginal lands where yields are low, primarily as a consequence of drought and low phosphorus (P) availability in soil. This study aimed to investigate the physiological and chemical responses of 12 bush bean genotypes for adaptation to individual and combined stress factors of drought and low P availability. Water stress and P deficiency, both individually and combined, decreased seed weight and aboveground biomass by ∼80%. Water deficit and P deficiency decreased photosynthesis and stomatal conductance during plant development. Maximum rates of carboxylation, electron transport, and triose phosphate utilization were superior for two common bean genotypes (SEF60 and NCB226) that are better adapted to combined stress conditions of water deficit and low P compared to the commercial check (DOR390). In response to water deficit treatment, carbon isotope fractionation in the leaf tissue decreased at all developmental stages. Within the soluble leaf fraction, combined water deficit and low P, led to significant changes in the concentration of key nutrients and amino acids, whereas no impact was detected in the seed. Our results suggest that common bean genotypes have a degree of resilience in yield development, expressed in traits such as pod harvest index, and conservation of nutritional content in the seed. Further exploration of the chemical and physiological traits identified here will enhance the resilience of common bean production systems in the tropics.

Genetic Correlation Between Fe and Zn Biofortification and Yield Components in a Common Bean (Phaseolus vulgaris L.).

Common bean (Phaseolus vulgaris L.) is the most important legume for direct human consumption worldwide. It is a rich and relatively inexpensive source of proteins and micronutrients, especially iron and zinc. Bean is a target for biofortification to develop new cultivars with high Fe/Zn levels that help to ameliorate malnutrition mainly in developing countries. A strong negative phenotypic correlation between Fe/Zn concentration and yield is usually reported, posing a significant challenge for breeders. The objective of this study was to investigate the genetic relationship between Fe/Zn. We used Quantitative Trait Loci (QTLs) mapping and Genome-Wide Association Studies (GWAS) analysis in three bi-parental populations that included biofortified parents, identifying genomic regions associated with yield and micromineral accumulation. Significant negative correlations were observed between agronomic traits (pod harvest index, PHI; pod number, PdN; seed number, SdN; 100 seed weight, 100SdW; and seed per pod, Sd/Pd) and micronutrient concentration traits (SdFe and SdZn), especially between pod harvest index (PHI) and SdFe and SdZn. PHI presented a higher correlation with SdN than PdN. Seventy-nine QTLs were identified for the three populations: 14 for SdFe, 12 for SdZn, 13 for PHI, 11 for SdN, 14 for PdN, 6 for 100SdW, and 9 for Sd/Pd. Twenty-three hotspot regions were identified in which several QTLs were co-located, of which 13 hotpots displayed QTL of opposite effect for yield components and Fe/Zn accumulation. In contrast, eight QTLs for SdFe and six QTLs for SdZn were observed that segregated independently of QTL of yield components. The selection of these QTLs will enable enhanced levels of Fe/Zn and will not affect the yield performance of new cultivars focused on biofortification.

Physiological and genetic characterization of heat stress effects in a common bean RIL population.

Heat stress is a major abiotic stress factor reducing crop productivity and climate change models predict increasing temperatures in many production regions. Common bean (Phaseolus vulgaris L.) is an important crop for food security in the tropics and heat stress is expected to cause increasing yield losses. To study physiological responses and to characterize the genetics of heat stress tolerance, we evaluated the recombinant inbred line (RIL) population IJR (Indeterminate Jamaica Red) x AFR298 of the Andean gene pool. Heat stress (HS) conditions in the field affected many traits across the reproductive phase. High nighttime temperatures appeared to have larger effects than maximum daytime temperatures. Yield was reduced compared to non-stress conditions by 37% and 26% in 2016 and 2017 seasons, respectively. The image analysis tool HYRBEAN was developed to evaluate pollen viability (PolVia). A significant reduction of PolVia was observed in HS and higher viability was correlated with yield only under stress conditions. In susceptible lines the reproductive phase was extended and defects in the initiation of seed, seed fill and seed formation were identified reducing grain quality. Higher yields under HS were correlated with early flowering, high pollen viability and effective seed filling. Quantitative trait loci (QTL) analysis revealed a QTL for both pod harvest index and PolVia on chromosome Pv05, for which the more heat tolerant parent IJR contributed the positive allele. Also, on chromosome Pv08 a QTL from IJR improved PolVia and the yield component pods per plant. HS affected several traits during the whole reproductive development, from floral induction to grain quality traits, indicating a general heat perception affecting many reproductive processes. Identification of tolerant germplasm, indicator traits for heat tolerance and molecular tools will help to breed heat tolerant varieties to face future climate change effects.

Genetic mapping for agronomic traits in a MAGIC population of common bean (Phaseolus vulgaris L.) under drought conditions

BackgroundCommon bean is an important staple crop in the tropics of Africa, Asia and the Americas. Particularly smallholder farmers rely on bean as a source for calories, protein and micronutrients. Drought is a major production constraint for common bean, a situation that will be aggravated with current climate change scenarios. In this context, new tools designed to understand the genetic basis governing the phenotypic responses to abiotic stress are required to improve transfer of desirable traits into cultivated beans.ResultsA multiparent advanced generation intercross (MAGIC) population of common bean was generated from eight Mesoamerican breeding lines representing the phenotypic and genotypic diversity of the CIAT Mesoamerican breeding program. This population was assessed under drought conditions in two field trials for yield, 100 seed weight, iron and zinc accumulation, phenology and pod harvest index.Transgressive segregation was observed for most of these traits. Yield was positively correlated with yield components and pod harvest index (PHI), and negative correlations were found with phenology traits and micromineral contents. Founder haplotypes in the population were identified using Genotyping by Sequencing (GBS). No major population structure was observed in the population. Whole Genome Sequencing (WGS) data from the founder lines was used to impute genotyping data for GWAS. Genetic mapping was carried out with two methods, using association mapping with GWAS, and linkage mapping with haplotype-based interval screening. Thirteen high confidence QTL were identified using both methods and several QTL hotspots were found controlling multiple traits. A major QTL hotspot located on chromosome Pv01 for phenology traits and yield was identified. Further hotspots affecting several traits were observed on chromosomes Pv03 and Pv08. A major QTL for seed Fe content was contributed by MIB778, the founder line with highest micromineral accumulation. Based on imputed WGS data, candidate genes are reported for the identified major QTL, and sequence changes were identified that could cause the phenotypic variation.ConclusionsThis work demonstrates the importance of this common bean MAGIC population for genetic mapping of agronomic traits, to identify trait associations for molecular breeding tool design and as a new genetic resource for the bean research community.

Adapting the CROPGRO model to simulate chia growth and yield

AbstractChia (Salvia hispanica L.) seeds are becoming increasingly popular as a superfood in Europe. However, broad experience in growing chia in temperate climates is missing. Crop simulation models can be helpful tools for management and decision‐making in crop production systems in different regions. The objective of this study was to adapt the CROPGRO model for simulating growth and yield of chia. Data sets from a field experiment conducted over 2 yr in southwestern Germany (48°74′ N, 08°92′ E, 475 m above sea level) were used for model adaptation. The initial starting point was the CROPGRO–soybean [Glycine max (L.) Merr.] model as a template for parameterizing temperature functions and setting tissue composition. Considerable iterations were made in optimizing growth, development, and photosynthesis parameters. After model calibration, the simulation of leaf area index (LAI) was reasonable for both years, slightly over‐predicting LAI with an average d‐statistic of 0.95 and root mean square error (RMSE) of 0.53. Simulations of final leaf number were close to the observed data with d‐statistic of 0.98 and RMSE of 1.36. Simulations were acceptable for total biomass (d‐statistic of 0.93), leaf (d‐statistic of 0.94), stem (d‐statistic of 0.94), pod mass (d‐statistic of 0.89), and seed yield (d‐statistic of 0.88). Pod harvest index (HI) showed good model performance (d‐statistic of 0.96 and RMSE of 0.08). Overall, the model adaptation resulted in a preliminarily adapted model with realistically simulated crop growth variables. Researchers can use the developed chia model to extend knowledge on the eco‐physiology of chia and to improve its production and adaption to other regions.

Dry Bean [Phaseolus vulgaris L.] Growth and Yield Response to Variable Irrigation in the Arid to Semi-Arid Climate

Understanding the crop growth and yield response to variable irrigation and the relationship between crop eco-physiological and morphological parameters is critical for identifying a balanced irrigation management strategy and developing decision support systems for early detection and information for on-ground decisions. Experiments were conducted to evaluate the effect of variable irrigation treatments on dry bean [Phaseolus vulgaris L.] growth traits (plant height, leaf area index, normalized difference vegetation index), seed yield (SY), and yield components (pods plant−1, seeds pod−1, 100-seed weight (SW), and pod harvest index (PHI)) and to develop empirical models between dry bean growth and environmental conditions, SY, and yield components. Five irrigation treatments i.e., FIT (full irrigation treatment), 125% FIT, 75% FIT, 50% FIT, and 25% FIT were investigated. Water deficit at the beginning of the crop growth [vegetative growth (V1-V2) stage], dramatically reduced dry bean growth and development and resulted in a significant reduction in SY. However, the degree to which vegetative growth and SY was reduced depends on the weather conditions. Reducing irrigation by 25% below FIT resulted in an average reduction of 30% in SY. This reduction in SY was significantly correlated with a decline in pods plant−1 and SW. Moreover, the empirical models between growth traits and growing degree days (GDD) have a strong correlation, while growth traits and SY and yield components are moderately correlated. The data and empirical models presented in this research provide valuable information in predicting and estimating dry bean SY in-season and allow for corrective management decisions.

Using Carbon Isotope Discrimination to Assess Genotypic Differences in Drought Resistance of Parental Lines of Common Bean

Accurate assessment of crop water uptake (WU) and water use efficiency (WUE) is not easy under field conditions. Carbon isotope discrimination (Δ13C) has been used as a surrogate of WUE to examine crop yield responses to drought and its relationship with WU and WUE. A 2‐yr study was conducted (i) to characterize genotypic variation in Δ13C, grain yield, and other physiological parameters in common bean (Phaseolus vulgaris L.) parental lines, and (ii) to examine the relationships between grain Δ13C, shoot Δ13C, and grain yield under well‐watered and terminal drought stress conditions. All measured plant traits were strongly influenced by water availability, and genotypic differences in grain yield, shoot Δ13C, and grain Δ13C were found in both watered and terminal drought stress environments. The parental lines were classified into two drought adaptation groups, drought resistant and drought sensitive, based on a yield drought index. High yields under drought conditions were related to (i) greater water uptake, as indicated by high Δ13C in genotypes previously shown to have deeper roots (e.g., SEA 5 and BAT 477), and (ii) increased WUE, denoted by lower Δ13C and greater pod harvest index (PHI) (e.g., SER 16). Coupling of Δ13C measurements with measured yield and yield components analyses, such as PHI, provided an avenue to distinguish different physiological traits among drought resistant genotypes underlying adaptation to water deficit stress.

Effects of Foliar Boron Treatments on Yield and Yield Components of Fenugreek (Trigonella foenum graecum L.): Detection by PCA Analysis

ABSTRACTIn this study, effects of foliar boron treatments on yield and yield components of fenugreek plants were assessed with the aid of principal component analysis (PCA) analysis. Experiments were conducted over the experimental fields of Erciyes University Agricultural Research and Implementation Center during the summer growing seasons of the years 2017 and 2018. Gürarslan fenugreek variety was used as the plant material of the experiments. Four different foliar boron (H3BO3) doses (control, 100, 200, 400, and 800 mg lt−1) were applied to fenugreek plants. Plant height, number of branches per plant, number of pods per plant, number of seeds per pod, pod length, the first pod height, thousand-seed weight, biological yield, seed yield, and harvest index were measured. Variance analysis revealed that only the seed yield of 2017 was significant (p < .05) and the other parameters were not found to be significant (p > .05). PCA analysis was performed to classify and characterize boron doses based on yield and yield components of fenugreek plants. PC1 and PC2 explained about 82% in total variation in 2017 and about 83% in 2018. In both years of the experiments, the greatest biological and seed yields were obtained from 800 mg lt−1 boron treatments. Therefore, 800 mg B lt−1 was recommended to get high seed yield from fenugreek plants.

Effect of drought stress on the genetic architecture of photosynthate allocation and remobilization in pods of common bean (Phaseolus vulgaris L.), a key species for food security

BackgroundCommon bean is the most important staple grain legume for direct human consumption and nutrition. It complements major sources of carbohydrates, including cereals, root crop, or plantain, as a source of dietary proteins. It is also a significant source of vitamins and minerals like iron and zinc. To fully play its nutritional role, however, its robustness against stresses needs to be strengthened. Foremost among these is drought, which commonly affects its productivity and seed quality. Previous studies have shown that photosynthate remobilization and partitioning is one of the main mechanisms of drought tolerance and overall productivity in common bean.ResultsIn this study, we sought to determine the inheritance of pod harvest index (PHI), a measure of the partitioning of pod biomass to seed biomass, relative to that of grain yield. We evaluated a recombinant inbred population of the cross of ICA Bunsi and SXB405, both from the Mesoamerican gene pool, to determine the effects of intermittent and terminal drought stresses on the genetic architecture of photosynthate allocation and remobilization in pods of common bean. The population was grown for two seasons, under well-watered conditions and terminal and intermittent drought stress in one year, and well-watered conditions and terminal drought stress in the second year. There was a significant effect of the water regime and year on all the traits, at both the phenotypic and QTL levels. We found nine QTLs for pod harvest index, including a major (17% of variation explained), stable QTL on linkage group Pv07. We also found eight QTLs for yield, three of which clustered with PHI QTLs, underscoring the importance of photosynthate remobilization in productivity. We also found evidence for substantial epistasis, explaining a considerable part of the variation for yield and PHI.ConclusionOur results highlight the genetic relationship between PHI and yield and confirm the role of PHI in selection of both additive and epistatic effects controlling drought tolerance. These results are a key component to strengthen the robustness of common bean against drought stresses.

Influence of Season, Variety and Phosphorus Fertilization on Herbage Yield of Groundnut (&lt;i&gt;Arachis hypogaea &lt;/i&gt;L&lt;i&gt;.&lt;/i&gt;) in Bauchi State Nigeria

An experiment was conducted at teaching and research farm of the Abubakar Tafawa Balewa University Bauchi, during the dry and rainy seasons of 2016 to evaluate the influence of variety and phosphorus fertilization on herbage yield of groundnut (Arachis hypogaea L.). The treatment consisted of two groundnut varieties (Samnut 24 and Samnut 25) and two levels of phosphorus fertilizer (25kg and 50kg/ha and a control) factorially combined to give six treatment combinations. These treatments were laid out in a randomized complete block design (RCBD) with four replications. Data was collected on number of branches, 100 pod weight, Harvest index, biomass yield and stover yield. All data collected were subjected Analysis of variance (ANOVA) and DMRT was adopted in separating the means. The result of the experiment revealed a significant (P = 0.05) difference in both seasons on all the parameters observed. The results further revealed that, application of 25 and 50 kgP/ha gave statistically (P = 0.05) similarly result but all the treatments were better than the control. Variety on the other hand, samnut 25 gave significantly (P = 0.05) higher herbage yield than samnut 24. Based on the result of this findings, application of 25 kg P/ha to Samnut 25 should be adopted by farmers for groundnut herbage production in the study area.

Response of Haricot Bean (Phaseolus Vulgaris L.) Varieties to Drought Stress at Different Growth Stages

Drought is considered as the single most devastating environmental factor, which decreases crop yield more than the collective effect of other environmental factors. Varieties also differ in their reaction to drought stress, when they exposed to drought stress at different growth stages. Pot experiment was conducted at Hawassa College of Agriculture, southern Ethiopia, with objectives of identifying relatively drought tolerant haricot bean varieties and yield correlated traits under drought stress at different growth stages. Ten improved haricot bean varieties were subjected to drought stress by withholding water for 15 days at vegetative, flowering and pod-setting stages. The analysis of variance showed that phenology, growth and yield components were affected by both drought stress and varieties. However, their interaction effect was significant only for number of seeds plant -1 , seed yield and pod harvest index. Drought intensity indices at vegetative, flowering and pod setting stages were 0.046, 0.335 and 0.249 respectively. Drought at vegetative, flowering and pod setting stages reduces seed yield by 2.91, 33.53 and 25.11% respectively as compared to full irrigation. Plant height, branches, pods and seeds plant -1 and 100 seed weight were reduced most by the stress induced at flowering followed by pod setting stages. However, there was no statistical difference between the effects of drought stress at vegetative stage and full irrigation on all measured parameters. Varieties with higher yields under flowering stress were H/dumme (21.96g plant -1 ), Wajo(21.38g plant -1 ) and Nasir(17.45g plant -1 ) on the other hand Wajo (30.57g plant -1 ), H/dumme(22.6g plant -1 ) and Ibbado(30.45g plant -1 ) had better yield performance under full irrigtaion. Seed yield had significant and positive correlation with pod harvest index, days to maturity, number of pods on the main stem, seed plant -1 , 100 seed weight and plant height, which can be used as a selection index to screen drought tolerant haricot bean varieties. To achieve high yield, drought must be avoided during flowering and pod-setting stages, and varieties H/dumme, Wajo and Nasir can be recommended for drought prone areas. Keywords: Drought stress, drought tolerance, Phaseolus vulgaris L . DOI : 10.7176/JBAH/9-1-05

Effect of intermittent drought on phenotypic traits of F5 RIL Andean intra-gene cross population (BRB 191 X SEQ 1027) of common bean

Drought is a major constraint to common bean ( Phaseolus vulgaris L.) production in East Africa, where irrigation for the crop is very uncommon. The objective of this study was to identify drought tolerant lines and phenotypic traits underlying drought tolerance among 128 F5 recombinant inbred lines (RILs), derived from intra gene pool population, between drought tolerant BRB 191 (source of bc-3) and SEQ 1027. The population was evaluated with eight experimental checks that included BAT 477, CAL 96, DAB 441, DAB 494, and Diacol Calima, NABE 4, SCR 9 and SEQ 1003. A total of 20 phenological, morphological and physiological shoot traits were evaluated, under drought and non-stress conditions, in the field for 2 years (2014 and 2015) at Kawanda in Uganda. New sources of drought tolerance, and previously identified sources of drought tolerance in common bean (BAT 477, DAB 441 and DAB 494), were confirmed based on their superior geometric means and low drought susceptibility. Drought stress in the field significantly affected all measured traits, except harvest index and stem dry weight reduction (P<0.001). Drought significantly reduced yield, yield components and pod harvest index (P<0.01). However, chlorophyll content, canopy temperature, stem dry mass reduction, and 100 seed weight remained stable under season by genotype by water regime treatment interactions (S x G x T). The stability of these traits highlighted their usefulness in selecting for drought tolerance across different environments. Furthermore, pod partitioning index (PPI), harvest index (HI), chlorophyll content and stem dry weight reduction also remained stable under G x T effects. Significant correlations (P<0.001) were maintained between HI and PPI with seed yield under drought stress in field conditions, indicating that photosynthate remobilisation increases yield under drought stress conditions. Key words: Phaseolus vulgaris , photosynthate remobilisation

QTL analyses for tolerance to abiotic stresses in a common bean (Phaseolus vulgaris L.) population.

Common bean productivity is reduced by several abiotic stress factors like drought and low soil fertility, leading to yield losses particularly in low input smallholder farming systems in the tropics.To understand the genetics of stress tolerance, and to improve adaptation of common bean to adverse environments, the BAT 881 x G21212 population of 95 recombinant inbred lines (RILs) was evaluated under different abiotic stress conditions in 15 trials across four locations in Colombia, representing two higher altitude (Darién, Popayán) and two lower altitude (Palmira, Quilichao) locations. Stress vs non-stress treatments showed that yields were reduced in drought trials in Palmira by 13 and 31%, respectively, and observed yield reductions in low phosphorus stress were 39% in Quilichao, 16% in Popayán, and 71% in Darién, respectively. Yield components and biomass traits were also reduced. Traits linked to dry matter redistribution from stems, leaves and pods to seed, such as pod harvest index and total non-structural carbohydrates, were found to be important factors contributing to yield in all conditions. In contrast, early maturity was correlated with improved yield only in lower altitude locations, whereas in higher altitudes delayed maturity promoted yield. Superior RILs that combine stress tolerance and high cross-location productivity were identified. Lines that showed good yield under strong stress conditions also performed well under non-stress conditions, indicating that breeder’s selection can be applied for both conditions at the same time.Quantitative trait loci (QTL) analyses revealed a stable yield QTL on chromosome Pv04, detected individually in all locations, several stress treatments and in best linear unbiased predictions (BLUPs) across all trials. Furthermore, two QTL hotspots for maturity traits were identified on Pv01 and Pv08, which are the most stable QTL. The constitutive yield QTL could serve as a good candidate for marker development and could be used in marker assisted selection.Increased understanding of the physiology of abiotic stress tolerance, combined with the availability of superior germplasm and molecular tools, will aid breeding efforts for further improvement of these plant traits.

Improving adaptation to drought stress in white pea bean (Phaseolus vulgaris L.): Genotypic effects on grain yield, yield components and pod harvest index

AbstractCommon bean (Phaseolus vulgaris L.) is the most important food legume crop in Africa and Latin America where rainfall pattern is unpredictable. The objectives were to identify better yielding common bean lines with good canning quality under drought, and to identify traits that could be used as selection criteria for evaluating drought‐tolerant genotypes. In all, 35 advanced lines were developed through single seed descent and evaluated with a standard check under drought and irrigated conditions at two locations over 2 years in Ethiopia. Grain yield (GY), pod number per m2, seed number per m2 and seed weight decreased by 56%, 47%, 49% and 14%, respectively, under drought stress. Eight genotypes had better yield with good canning quality under drought compared to the check. Moderate to high proportion of genetic effects were observed under drought conditions for GY and yield components compared to genotype × environment effects. Significant positive correlations between GY and pod harvest index (PHI) in drought suggest that PHI could be used as an indirect selection criterion for common bean improvement.