Significant Genotypic Variation Research Articles

Relative performance of white clover (

Assessment of the relative performance of white clover (Trifolium repens L.) cultivars, using multi-year and multi-location seasonal growth trials, is key to identification of material with specific and broad adaptation. This paper is based on a multi-year and multi-location study of 56 white clover entries comprising 14 commercial cultivars and 42 experimental synthetic lines evaluated for seasonal growth under rotational grazing across four locations in New Zealand over 4 years. The four locations (and animals grazing) were: Kerikeri (beef cattle), Aorangi (beef cattle), Ruakura (dairy cattle), Lincoln (sheep). Significant (P < 0.05) genotypic variation among the 56 entries, and genotype × year, genotype × location and genotype × season interactions, were estimated. We were able to identify cultivars and experimental synthetics with specific and broad adaptation to the three grazing management types. Cvv. AberDance, Apex, Demand, Prestige, Quartz and Riesling, with leaf size ranging from small to medium–large, showed highly above-average performance under sheep grazing. Synthetic lines 15 and 45 also had highly above-average performance under sheep grazing. Cvv. Legacy and Kopu II showed above-average performance under cattle and dairy grazing. Synthetics 15, 48, 49, 44, 22 and 18 and cv. Quartz had above-average performance under all three grazing managements. Synthetics 27, 33 and 38 had highly above-average performance across all three grazing managements and were superior to all 14 cultivars evaluated. Several of these superior synthetics are being tested across multiple grazing environments. Among the 14 cultivars evaluated, Legacy and Quartz showed superior seasonal growth performance across the three grazing managements. Quartz is being evaluated in several on-farm trials across temperate regions of the world.

Dissecting the phenotypic response of maize to low phosphorus soils by field screening of a large diversity panel

Maize (Zea mays L.) is an important crop worldwide, but in many regions is increasingly faced with the issue of phosphorus (P)-deficient soils. The aim of this study was to screen for low P-tolerance in maize and to dissect the underlying phenotypic response. To this end, we evaluated a panel of 380 diverse inbred lines in the field under low and normal P conditions for 17 morphological, biomass- and yield-related traits. All traits showed a significant genotypic variation and a moderate to high repeatability for each P condition. Under P deficiency, all traits were significantly lower compared to the control with normal P availability. The variance due to the interaction between genotype and P condition was significant for most traits, but generally small compared to the genotypic variance. Regarding the low P tolerance index, i.e. the phenotype under low P relative to the control, we observed a generally similar response within the morphological, biomass- or yield-related traits. Interestingly, genotypes showing little yield reduction under low P appear to achieve this tolerance through different strategies. Based on our results, low-P tolerant and low-P sensitive lines were identified, which can be used for further genetic research as well as to improve this globally important trait in maize breeding.

Rootstock Genotypes Shape the Response of cv. Pinot gris to Water Deficit

Understanding the physiological basis underlying the water stress responses in grapevine is becoming increasingly topical owing to the challenges that climate change will impose to grapevine agriculture. Here we used cv. Pinot gris (clone H1), grafted on a series of tolerant (1103Paulsen; P), sensitive (SO4) and recently selected (Georgikon28; G28, Georgikon121; G121, Zamor17; Z17) rootstocks. Plants were either subjected to reduced water availability (WS) or maintained at pot capacity (WW). Photosynthetic (light response curves), stomatal and in vivo gas exchange analysis were carried out as well as dynamics of daily water use (WU), leaf area accumulation with affordable RGB imaging pipelines and leaf water potential. Significant genotypic variation was recorded between rootstocks for most of the traits analyzed under optimal conditions with P and SO4 showing a more vigorous growth, higher CO2 assimilation rate, stomatal conductance and stomatal density per unit of leaf area than G28, G121, Z17 (p < 0.001). Under WS, rootstocks induced different water stress response in Pinot gris, with G28 and G121 showing a higher sensitivity of water use to reduced water availability (WS) (p = 0.021) and no variation for midday leaf water potential until severe WS. P, Z17 and to some extent SO4 induced a pronounced near-anisohydric response with a general WU maintenance followed by reduction in leaf water potential even at high levels of soil water content. In addition, G28 and G121 showed a less marked slope in the linear relationship between daily water use and VPD (p = 0.008) suggesting elevated sensitivity of transpiration to evaporative demand. This led to an insensitivity for total dry weight biomass of G28 and G121 under WS conditions (p < 0.001). This work provides: (i) an in-depth analysis for a series of preferable traits under WS in Pinot gris; (ii) a characterization of Pinot gris × rootstock interaction and a series of desirable traits under WS induced by several rootstocks; (iii) the potential benefit for the use a series of affordable methods (e.g., RGB imaging) to easily detect dynamic changes in biomass in grapevine and quickly phenotype genotypes with superior responses under WS. In conclusion, the near-isohydric and conservative behavior observed for G28 and G121 coupled with their low vigor suggest them as potential Pinot gris rootstock candidates for sustaining grapevine productivity in shallow soils likely to develop terminal stress conditions.

Genetic resources of chickpea and the efficiency of their use in breeding

The results of more than 20 years of studying a large set of chickpea accessions from many countries of the world are summarized. The sources and donors of early maturity, drought resistance, seed size, a number of economically valuable traits, increased protein content, improved technological indicators of seeds, tolerance to fusarium and ascochita diseases have been identified.The purpose and objectives of the study. In the conditions of the arid Steppe, identify sources and donors of economically valuable traits among the large volume of collection material, the best of which can be used in the breeding program.Materials and methods. During 1995–2020. in the arid conditions of the steppe zone of Ukraine, about 3 thousand chickpea genotypes were evaluated, which were obtained from the National Center for Genetic Resources of Ukraine (Kharkiv) and the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT, Patancheru, India). The experiments were carried out on the experimental fields of the Breeding and Genetic Institute (Odesa) and the Odesa State Agricultural Experimental Station of the National Academy of Agrarian Sciences of Ukraine. In the field the collection forms were sown like a breeding nursery in two-meter rows with a row spacing of 45 cm. The standard variety was placed in 20 numbers. The protein content in seeds was determined by the Kjeldahl method, fat ‒ by the Ruszkowski method.Fusarium resistance was assessed at the early stages of seedling growth in laboratory conditions under artificially created infectious background.Results and discussion. The data obtained in the field indicate that the largest group of genotypes characterized by growing season of 81–100 days. The smallest group consisted of ultra-early maturing forms that matured in less than 75 days. Although in this group of ripeness, the maximum number of early flowering samples was revealed. Our observations did not establish a clear dependence of plant productivity on the duration of the "seedling – flowering" and "flowering – ripening" phases, although the group of highly productive forms is distinguished by a more extended "flowering – ripening" period. Samples were identified in which the weight of seeds per plant for a number of years exceeds 10 g per plant, which corresponds to a yield of about 3 t/ha. The genotypes characterized by an increased number of beans and seeds per plant, a more significant value of the weight of seeds per plant are described. 4 genotypes have been identified, in which two beans are formed in most of the nodes. Genetic analysis showed that this trait is determined by one recessive gene. A number of genotypes have been identified, the weight of 1000 seeds of which exceeded 600 g. Collection forms of chickpea are important for breeding, combining a high level of seed productivity with a weight of 1000 seeds over 400 g. High-protein samples are recommended for use in hybridization to create varieties with increased protein amount per unit area. Significant genotypic variability of water absorption by chickpea seeds was established at different temperature conditions. This process was more intensive in the genotypes NEC 1838 (Chile) and the sample from Italy. In laboratory conditions 27 forms revealed a high level of tolerance against the fusarium, while possessing a valuable complex of economically valuable traits. The drought-resistant genotypes described in India turned out to be ultra-early maturing and undersized under our conditions, although they formed large seeds. A brief description of 12 varieties of chickpea obtained during the period of these studies is given.Conclusions. As a result of the research carried out, donors and sources of the main economically valuable traits of chickpea have been identified and characterized, and those have been identified that have especially valuable complexes.The presence of genotypes from different geographic zones and genetic centers will allow more targeted breeding, especially in the creation of disease-resistant forms. The forms of chickpea described by us can be used in breeding by other scientific institutions in our country and abroad

Limited effects of the soluble organic phosphorus fraction on the root phosphorus uptake efficiency of upland rice genotypes grown in acid soil

ABSTRACT The root phosphorus (P) uptake efficiency (RE), defined as plant P uptake per unit root mass or root area, may contribute to the P efficiency of upland rice grown in acid, P-deficient soils. The identification of root traits conferring RE of rice has been compromised by the lack of attention given to P speciation when evaluating P-mining mechanisms. Here we disentangled the effect of soluble organic P (PO) from that of total soluble P (PT) on the RE in rice seedlings in acid soil. Six rice genotypes were grown for 21 days in P-deficient substrates, i.e. a sample of an acid mineral soil, an acid peat and a mixture thereof. Each of the three substrates were amended with different P doses, partially limed and incubated, yielding substrates with significant differences in total soluble P (0.005–0.41 mg P/L) and in the percentage of organic P in that pool (PO/PT, 0–55%). Plants showed a large growth response to the P addition. There was a significant genotypic variation in P uptake (0.9–1.5mg P/plant) and RE (4.4–8.3 mg P/g root mass) under moderate P deficiency but these traits were unaffected by the PO/PT in the soluble fraction of the substrates. Along the same lines, phosphatase activity in the rhizosphere soil was unaffected by genotypes and did not explain the RE among all data (R2 = 0.17, ns). A multiple regression model showed that the RE of rice seedlings was mainly affected by the inherent genotypic effects, the PO/PT and the total soluble P concentration in soil (R2 = 0.73), while the genotype-PO/PT interaction only marginally improved the RE model (R2 = 0.78). This suggests limited genotypic effects due to the better use of organic P. A root elongation test in the acid mineral soil that was either or not limed suggests that the differences in acid soil tolerance may play a larger role in the genotypic performance of RE than organic P utilization potential.

Agronomical and Physiological Behavior of Durum Wheat (Triticum durum Desf.) Genotypes Under Semi-Arid Conditions

In the semi-arid high plains of Algeria, water stress is one of the most significant factors restricting wheat production. This study aims at analyzing water stress effect on durum wheat behavior with a particular focus on relationships between some agronomical and physiological traits. Ten genotypes were tested under rain-fed and full-irrigated conditions in semi-arid climate of Eastern Algeria. The experiment was led down in a randomized complete block design at the experimental field of Natural and Life Sciences Faculty of Sétif1 University. Yield and its components, leaf relative water content, leaf specific weight, grain-filling rate and duration and leaf chlorophyll content were measured. Significant genotypic and environmental variations were observed for major measured traits. Water stress significantly decreased the potential yield by 28%. A significant and strong correlation was observed between agronomical and physiological characteristics. In both stress and non stress conditions, grain yield was positively and significantly associated with: Chlorophyll content (r = 0.893), relative water content (r = 0.956) and grain filling duration (r = 0.853). Wheat productivity was highly associated with high photosynthetic activities, good water status and long grain filling duration. This finding suggests using these traits as tools for screening durum wheat tolerance to water stress.

Trait Association, Genetic Analyses and Fatty Acid Profiles in Oilseed Producing Rapeseed-Mustard (Brassicaspp.) Genotypes

Short duration oilseed Brassica varieties are important to increase cropping intensity as well as total oilseed production. In this research, genetic and multivariate analyses were conducted for 19 morphological characters of 48 rapeseed and mustard genotypes. Evaluation of oil content and fatty acid profiles were done for ten selected rapeseed and mustard genotypes. Significant genotypic variations were observed for all morphological characters except 1000 seeds weight. Days to 50% flowering, plant height, total number of siliqua per plant, number of seeds per siliqua, length of siliqua and days to maturity exhibited high broad sense heritability along with high genetic advance. Length of primary branches, number of primary branches, number of secondary branches, total number of siliqua per plant, number of siliqua per main axis and number of siliqua per primary branches had a significant and positive correlation with yield per plant. According to principal component analysis and cluster analysis, BARI Sarisha-9, BD-110455, BD-7113, BD-6954 and BD-6953 were the earliest genotypes and BD-10112, M-395 and M-119-5 were comparatively high yielding genotypes. The genotypes BD-6953, BD-6954, BD-10455, BD-10112 and BD-7113 had comparatively lower erucic acid and saturated fatty acid profiles that are regarded as better edible oil characteristics. The selected genotypes and associated traits could be utilized for developing short duration, high yielding and edible quality rapeseed-mustard varieties.

Variability and selection among mutant families of wheat for biomass allocation, yield and yield‐related traits under drought‐stressed and non‐stressed conditions

AbstractGenetic variation is fundamental for plant breeding programmes. Exploiting the genetic variation of wheat for biomass allocation, yield and yield‐related traits enhances breeding for drought tolerance. The aim of this study was to evaluate genetic variation and to select best individuals among 180 M3 mutant families of wheat developed through EMS mutagenesis based on better biomass allocation to root systems, desirable agronomic traits and high yield potential under greenhouse and field environment evaluations with drought‐stressed and non‐stressed conditions. Experiments were conducted using a randomized complete block design with two replications. Days to 50% heading (DTH), days to 90% maturity (DTM), plant height (PH), number of productive tillers (PTN), shoot biomass (SB), root biomass (RB), total biomass (TB), root–shoot ratio (RSR), spike length (SL), spikelet per spike (SPS), one thousand seed weight (TSW) and grain yield (GY) were collected. Mutant families showed significant genotypic (p < .05) variation for yield and biomass traits, whereas genotype × environment × water regime interaction effects were significant (p < .05) for DTM, SB, TB, TSW and GY. Superior families designated as 52, 159, 103, 126 and 145 were selected for improved drought tolerance and high biomass allocation to roots.

Genetic Dissection of Resistance to Gray Leaf Spot by Combining Genome-Wide Association, Linkage Mapping, and Genomic Prediction in Tropical Maize Germplasm.

Gray leaf spot (GLS) is one of the major maize foliar diseases in sub-Saharan Africa. Resistance to GLS is controlled by multiple genes with additive effect and is influenced by both genotype and environment. The objectives of the study were to dissect the genetic architecture of GLS resistance through linkage mapping and genome-wide association study (GWAS) and assessing the potential of genomic prediction (GP). We used both biparental populations and an association mapping panel of 410 diverse tropical/subtropical inbred lines that were genotyped using genotype by sequencing. Phenotypic evaluation in two to four environments revealed significant genotypic variation and moderate to high heritability estimates ranging from 0.43 to 0.69. GLS was negatively and significantly correlated with grain yield, anthesis date, and plant height. Linkage mapping in five populations revealed 22 quantitative trait loci (QTLs) for GLS resistance. A QTL on chromosome 7 (qGLS7-105) is a major-effect QTL that explained 28.2% of phenotypic variance. Together, all the detected QTLs explained 10.50, 49.70, 23.67, 18.05, and 28.71% of phenotypic variance in doubled haploid (DH) populations 1, 2, 3, and F3 populations 4 and 5, respectively. Joint linkage association mapping across three DH populations detected 14 QTLs that individually explained 0.10–15.7% of phenotypic variance. GWAS revealed 10 significantly (p < 9.5 × 10–6) associated SNPs distributed on chromosomes 1, 2, 6, 7, and 8, which individually explained 6–8% of phenotypic variance. A set of nine candidate genes co-located or in physical proximity to the significant SNPs with roles in plant defense against pathogens were identified. GP revealed low to moderate prediction correlations of 0.39, 0.37, 0.56, 0.30, 0.29, and 0.38 for within IMAS association panel, DH pop1, DH pop2, DH pop3, F3 pop4, and F3 po5, respectively, and accuracy was increased substantially to 0.84 for prediction across three DH populations. When the diversity panel was used as training set to predict the accuracy of GLS resistance in biparental population, there was 20–50% reduction compared to prediction within populations. Overall, the study revealed that resistance to GLS is quantitative in nature and is controlled by many loci with a few major and many minor effects. The SNPs/QTLs identified by GWAS and linkage mapping can be potential targets in improving GLS resistance in breeding programs, while GP further consolidates the development of high GLS-resistant lines by incorporating most of the major- and minor-effect genes.

Phenotypic Divergence Analysis in Pigeonpea [Cajanus cajan (L.) Millspaugh] Germplasm Accessions

Pigeonpea (Cajanus cajan (L.) Millspaugh) is an important source of grain protein for low-income countries such as Malawi. Knowledge of the genetic diversity in pigeonpea is essential for an effective breeding program. The study objective was to assess the genetic diversity among diverse pigeonpea accessions to select complementary and unique genotypes for breeding. Eighty-one pigeonpea accessions were evaluated in six environments in Malawi using a 9 × 9 alpha-lattice design with two replications. The cross-tabulation analysis revealed a significant genotype variation on plant growth, flower, and seed traits. The combined analysis of variance identified genotypes MWPLR 14, ICEAP 01170, ICEAP 871091, and ICEAP 01285 as early maturing varieties, while Kachangu, MWPLR 16, TZA 5582, No. 40, and MWPLR 14 were identified as high-yielding genotypes. The correlation analysis revealed a significant positive correlation between grain yield and a hundred seed weight (HSWT) (r = 0.50, p &lt; 0.01), suggesting the usefulness of this trait for selection. The nonlinear principal component analysis identified grain yield (GDY), days to 50% flowering (DTF), days to 75% maturity (DTM), number of pods per plant (NPP), number of racemes per plant (NRP), 100 seed weight (HSWT), leaf hairiness (LH), and number of seeds per pod (NSP) as the most discriminated traits among the test genotypes. The cluster analysis using morphological traits delineated the accessions into three clusters. The selected high-yielding and early-maturing genotypes may be recommended as parental lines for breeding and grain yield improvement in Malawi or similar agro-ecologies.

Genotypic variation in intrinsic transpiration efficiency correlates with sugarcane yield under rainfed and irrigated field conditions.

Intrinsic transpiration efficiency (i TE), the ratio of photosynthesis (A) to stomatal conductance (g s), is considered a useful trait for improving productivity; however, higher i TE with high A is more desirable than that with low g s. This study dissects i TE of 20 sugarcane genotypes to understand its relationship with total dry matter (TDM) and cane yield (TCH) under irrigated and rainfed conditions. Water stress reduced mean A and g s by 56 and 61%, and mean TDM and TCH by 55 and 59%, respectively; however, genotype × irrigation treatment interaction was smaller than genotype variance. Mean i TE increased from 117.4 μmol mol−1 in the irrigated treatment to 130.6 μmol mol−1 in the rainfed treatment. In irrigated conditions, i TE had high heritability (H 2 b = 0.67) and significant genetic correlation with TDM (r g = 0.58) and TCH (r g = 0.72). Under water stress, at g s below 0.1 mol m−2 s−1, non‐stomatal limitation to A was evident and i TE had low heritability (H 2 b = 0.2). Whereas in the g s range of 0.1–0.4 mol m−2 s−1, heritability of i TE (H 2 b = 0.63) and its genetic correlation with TDM (r g = 0.78) and TCH (r g = 0.75) were maximised. There was significant genotypic variation in photosynthetic capacity (A c), and the differences were related to TDM and i TE. Selecting genotypes with higher i TE and A c could offer potential for improving productivity without the unfavourable effect of low g s.

Selection for bean fly (Ophiomyia spp) resistance and agronomic performance in selected common bean (Phaseolus vulgaris L.) accessions

The bean fly (Ophiomyia spp) is one of several yield limiting insect pests of common bean (Phaseolus vulgaris L.) in eastern and southern Africa. High performing common bean cultivars with the bean fly resistance, good agronomic traits and market-preferred attributes are yet to be developed in the region. The objective of this study was to evaluate the bean fly resistance and agronomic performance of common bean accessions adapted to the eastern and southern African regions and to select parental lines for breeding. Ninety-nine common bean accessions were evaluated in bean fly hotspot areas in two locations in Malawi during the 2018 and 2019 growing seasons. Damage severity (BDS), plant mortality rate (PMR) and pupa count (PC) were measured to evaluate resistance to the bean fly. The following agro-morphological traits were assessed: the length between first internode and fifth internode at first flowering (FIL), number of nodes at the first flower (NFF), stem diameter (SD) at 50% flowering stage, days to 50% flowering (DTF), days to 90% physiological maturity (DTM), number of pods per plant (NPP), number of seed per pod (NSP) and grain yield in kg ha−1 (GYD). The analysis of variance revealed significant genotypic variation (p < 0.05) for both bean fly resistance and agro-morphological traits for common bean improvement. About 67.13% variation was explained by the first three principal components associated with BDS, PMR, DTF, SD, NPP, NSP and GYD. Phenotypic correlations between bean-fly resistance traits and grain yield were significant (p < 0.05) and negative, implying that direct selection for bean fly resistant genotypes could improve GYD. Twelve genotypes, namely, A55, A222, A429, Sinoni, ALB 196, MW3954, SIN526, CZ114-50, SCR63, MW3917, ALB133 and A344 showed high grain yield and exhibited resistance to the bean fly. These genotypes will be useful as parental lines for resistance breeding programs in the region.

Diallelic Analysis of Tropical Maize Germplasm Response to Spontaneous Chromosomal Doubling.

Chromosome doubling is an important step in the production of maize doubled haploid (DH) lines to induce fertility in the male and female reproductive organs of haploid plants. Chromosomal doubling is routinely accomplished by treating haploid seedlings with mitosis-inhibiting chemicals. However, chromosomal doubling involves several labor-intensive steps and toxic chemicals. Spontaneous chromosomal doubling without any chemical treatments occurs at high frequency in haploids from a few maize genotypes. This study focused on elucidating the genetic components of two traits important for using spontaneous doubling in maize-breeding programs, namely, haploid male fertility (HMF) and haploid fertility (HF). In two different sets of diallel crosses, haploids were derived and assessed for HMF and HF in two environments in replicated trials. The results revealed significant genotypic variations for both traits. The general combining ability (GCA) and specific combining (SCA) were significant for both traits. Significant and positive GCA effects of up to 14% and 9% were found for HMF and HF, respectively. No significant reciprocal effects and genotype-by-environment (G×E) interactions were found for HF in both experiments, but HMF showed significant effects for both in one of the experiments. The GCA effects were more important than the SCA effects for HMF and HF across environments, implying that selection could facilitate their improvement. The high correlations between F1-hybrid performance and mid-parent values, as well as that between F1-hybrid performance and GCA effects, also supports the assumption that these traits are controlled by a few genes. SCA effects also played a role, especially when lines with low spontaneous doubling were used as parents. Overall, spontaneous doubling can be introgressed and improved in elite germplasm with selection, and it has the potential to be employed in DH pipelines.

Causal shoot and root system traits to variability and plasticity in juvenile cassava (Manihot esculenta Crantz) plants in response to reduced soil moisture.

Cassava is an important source of food security and livelihoods for millions of consumers daily. Water deficit conditions are one of the major factors that affect the development of root system architecture (RSA) and consequently, crop productivity, and yet, due to its long maturity periods and bulky storage root systems, RSA studies in cassava are uncommon. The objective of this study was to identify traits that are responsible for the variability and plastic responses of cassava in response to drought at the juvenile stage of growth. Eight cassava genotypes were grown in soil-filled pots under well-watered and droughted conditions for up to 45days and multivariate analyses employed to determine the major contributory traits to variability and the relative distance plasticity index (RDPI) was computed to evaluate plasticity. There were significant genotypic variations for most of the traits measured. Drought generally inhibited root production and development and the degree of inhibition was between 2 and 22%. Regardless of the soil moisture condition, traits which differentiated the RSA included root biomass, root numbers, root branching density, and total root length, and these were also the important contributory traits to variability under well-watered soil conditions. Important contributory traits to variability traits under drought were shoot-related traits such as leaf area and shoot biomass, and also root system traits such as nodal root number, root biomass, diameter and branching density. Phenotypic plasticity was found in most traits where the number, branching density and diameter of upper nodal roots presented the highest RDPI. These traits corresponded with the traits contributing greatly to variation. Plastic responses of cassava to drought were dependent on trait and genotype. It is concluded that upper nodal roots-related traits could have importance in breeding cassava to better tolerate water deficit conditions. The secondary growth and ability to maintain or increase the upper nodal root count or density under limited soil moisture may be related to good growth and yield performance of cassava under drought conditions. Upper nodal roots could be used to screen and select cassava genotypes adapted to drought at the juvenile stage but as a potential indirect selection strategy, the persistence and pertinence of these traits and their relationship with yield and yield components under drought conditions in the field must be confirmed.

Effects of Lentil Genotype on the Colonization of Beneficial Trichoderma Species and Biocontrol of Aphanomyces Root Rot.

Trichoderma species are opportunistic plant symbionts that are common in the root and rhizosphere ecosystems. Many Trichoderma species may enhance plant growth, nutrient acquisition, and disease resistance, and for these reasons, they are widely used in agriculture as biofertilizers or biocontrol agents. Host plant genotype and other microorganisms, such as root pathogens, may influence the efficacy of Trichoderma inoculants. Aphanomyces euteiches is an important soil-borne oomycete in western Canada that causes root rot in legume crops such as lentil and pea, and there is not yet any significantly resistant varieties or effective treatments available to control the disease. In this study, the composition of root-associated fungal communities and the abundance of Trichoderma species, T. harzianum strain T-22 and T. virens strain G41, was determined in the roots of eight Lens genotypes based on internal transcribed spacer (ITS) Illumina MiSeq paired-end sequencing, both in the presence and the absence of the root rot pathogen Aphanomyces euteiches. Biocontrol effects of T. harzianum on A. euteiches was also examined. Significant genotypic variations were observed in the composition of root-associated fungal communities and the abundance of the different Trichoderma species in the lentil roots. The presence of A. euteiches altered the composition of Trichoderma found associated to the lentil genotypes. Biocontrol of A. euteiches by T. harzianum T22 species was observed in vitro and positive correlations between the abundance of Trichoderma and plant root and shoot biomass were observed in vivo. These findings revealed that lentil genotype and infection by the phytopathogen A. euteiches greatly influenced the colonization of root-associated fungi and the abundance of the Trichoderma species, as well as the effect on plant growth promotion. The multipartite interactions observed among lentil genotypes, Trichoderma species and A. euteiches suggest possibilities to select compatible host-beneficial microbe combinations in lentil breeding programs and to develop application strategies to harness the beneficial effects of Trichoderma inoculants in sustainable crop production systems.

Screening the FIGS Set of Lentil (Lens culinaris Medikus) Germplasm for Tolerance to Terminal Heat and Combined Drought-Heat Stress

Lentil (Lens culinaris Medikus) is one of the most important cool season food legume crops grown in many countries. Seeds are typically rich in protein, fiber, prebiotic carbohydrates and minerals, such as iron and zinc. With changing climate and variability, the lentil crop faces frequent droughts and heat stress of varying intensity in its major production zones. In the present study, a set of 162 lentil accessions selected through the Focused Identification of Germplasm Strategy (FIGS) were screened for tolerance to heat stress and combined heat-drought stresses under field conditions at two contrasting locations, namely Marchouch and Tessaout in Morocco. The results showed a significant genotypic variation for heat tolerance and combined heat-drought tolerance among the accessions at both locations. Based on the heat tolerance index (HTI), accessions, namely ILL 7833, ILL 6338 and ILL 6104, were selected as potential sources of heat tolerance at Marchouch, and ILL 7814 and ILL 8029 at Tessaout. Using the stress tolerance index (STI), ILL 7835, ILL 6075 and ILL 6362 were identified as the most tolerant lines (STI &gt; 1) at Marchouch, and ILL 7814, ILL 7835 and ILL 7804 (STI &gt; 1) at Tessaout, under the combined heat-drought stress conditions. Accession ILL 7835 was identified as a good source of stable tolerance to heat stress and combined heat-drought stress at both locations.

A Study on the Biodiversity of Pigmented Andean Potatoes: Nutritional Profile and Phenolic Composition.

The characterization of six varieties of native Andean potatoes with a wide biodiversity in tuber shape, flesh, and skin color was performed, through the determination of their proximate composition, mineral content, and phenolic profile. Minerals concentration revealed significant genotypic variation. Potassium was the most abundant element in all varieties, ranging from 7272.9 to 13,059.9 µg/g and from 12,418 to 17,388.6 µg/g dried weight for the flesh and skin samples, respectively. Iron content was relevant, ranging from 20.5 to 39.9 µg/g and from 112.2 to 288.8 µg/g dried weight in flesh and skin samples, respectively. Phenolic compounds were consistently higher in the skin than in the flesh. The total content varied greatly from 19.5 to 2015.3 µg/g and from 1592.3 to 14807.3 µg/g dried weight for flesh and skin tissues, respectively. 5-caffeoylquinic acid was 74% of the total phenolic acids. Different pattern of anthocyanins was found, depending on the color of the variety; the red genotypes contained predominantly pelargonidin derivatives, while the purple samples had petunidin as a major anthocyanidin. This study increases the knowledge of the composition of the local Andean varieties (which are only scarcely studied so far), helping to enhance these genotypes and the conservation of biodiversity.

Spike photosynthesis measured at high throughput indicates genetic variation independent of flag leaf photosynthesis

Future increases in yield potential will rely largely on improved photosynthesis. Whereas emphasis has traditionally been given to measuring leaf photosynthesis, wheat spikes have an important role in filling grains since they can intercept up to a third of incident light. In the present study, 196 genetically diverse spring wheat lines were evaluated for spike photosynthesis (SP) under temperate (yield potential) and heat stressed, irrigated conditions. Two different methods to estimate SP were used: (i) gas exchange measurements of SP rate and (ii) integrative measurements using a SP inhibition treatment (consisting of a permeable textile covering the spikes). Rate of SP was measured directly in 45 selected genotypes under yield potential conditions using a custom-made illuminating chamber. In these lines, a variation of 2.8-fold for spike photosynthetic rate is reported for the first time with good heritability estimates. Correlations between SP rate and yield, thousand grain weight, number of grains per spike and radiation use efficiency are reported across different panels. Genotypic variation in SP was independent from flag leaf photosynthesis suggesting that any strategy aiming to increase canopy photosynthesis should also consider SP. The SP inhibition treatments were applied on the 196 lines in both environments to estimate SP contribution to grain weight per spike, which was 30–40 % under both heat stressed and yield potential conditions averaged across lines. Positive correlations with grain yield were observed for spike photosynthesis contribution across all of the panels under heat stress and when combining heat and yield potential environments (P < 0.001, r = 0.401). These results indicate a highly significant genotypic variation of spike photosynthetic rate and spike photosynthesis contribution to grain yield among wheat lines and highlight its importance under irrigated and heat stressed conditions.

Assessing genetic variation for Fusarium wilt race 4 resistance in tetraploid cotton by screening over three thousand germplasm lines under greenhouse or controlled conditions

Cotton (Gossypium spp.) is the most widely-grown natural fiber crop used by the textile industry. Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum (FOV) comprised of eight nominal pathogenic races, is one of the most destructive diseases in cotton. FOV race 4 (FOV4) is an emerging threat to cotton production in the US. In this study, a total of 3258 lines including 3080 Upland (G. hirsutum) and 178 Pima (G. barbadense) germplasm lines were evaluated in 21 tests under greenhouse or temperature-controlled conditions for resistance to FOV4. A total of 2224 lines from 13 tests were screened in a commercial potting soil in the greenhouse under higher temperature (HT) conditions (24–32 °C), while 1204 lines from 8 tests were screened in a naturally FOV4-infected farm soil at a lower temperature (LT) setting (20–21 °C), both with artificial inoculations. The 170 Pima lines were evaluated in both temperature regimes. The results showed that, at 30 days post inoculation, both temperature regimes produced similar disease incidence (81.2% for HT vs. 86.8% for LT), but LT caused significantly higher disease severity ratings (DSR, 3.86 vs. 1.94) and plant mortality (81.7% vs. 7.5%) than did HT. DSR and morality rate were highly significantly correlated (r = 0.849–0.941) at LT. Significant genotypic variations in DSR were detected in all studies except two, and the broad-sense heritability estimates for DSR were 0.59–0.83 with an average of 0.70 at HT and 0.61–0.72 with an average of 0.69 at LT, indicating that 70% the phenotypic variation in FOV4 resistance was determined by genetic variation. Using the naturally FOV4-infected farm soil and LT to screen 1034 Upland and 170 Pima germplasm lines (with 20–40 plants for each line) with artificial inoculations, 48% showed 100% mortality; 22% had a mortality rate between 70 and 99%; 5% had mortality below 30%; and 0.5% (6 lines) did not display any apparent FOV4 symptoms. The results indicated that many existing available germplasm lines may be heterogeneous for FOV4 resistance and pedigree selection within germplasm may increase frequencies of resistant plants. This study represents one of the first publicly reported large-scale screenings of cotton for FOV4 resistance in the US and provides useful information for breeding cotton with resistance to FOV4.

The search for yield predictors for mature field-grown plants from juvenile pot-grown cassava (Manihot esculenta Crantz).

Cassava is the 6th most important source of dietary energy in the world but its root system architecture (RSA) had seldom been quantified. Ability to select superior genotypes at juvenile stages can significantly reduce the cost and time for breeding to bridge the large yield gap. This study adopted a simple approach to phenotyping RSA traits of juvenile and mature cassava plants to identify genotypic differences and the relationships between juvenile traits and harvest index of mature plants. Root classes were categorised and root and shoot traits of eight (8) juvenile pot-grown cassava genotypes, were measured at 30 and 45 days after planting (DAP). The same or related traits were measured at 7 months after planting of the same genotypes grown in the field while yield and yield components were measured in 12-months old field-grown plants. The field experiment was done in 2017 and repeated in 2018. Differences between genotypes for the measured traits were explored using analysis of variance (ANOVA) while traits in juvenile plants were correlated or regressed onto traits measured in 7- and 12-months old plants. The results show significant genotypic variations for most of the traits measured in both juvenile and 7-months old plants. In the 12-months old plants, differences between genotypes were consistent for both 2017 and 2018. Broad-sense heritability was highest for the number of commercial roots (0.87) and shoot fresh weight (0.78) and intermediate for the total number of roots (0.60), harvest index (0.58), fresh weight of roots (0.45). For all the sampling time points or growth stages, there were greater correlations between traits measured at a particular growth stage than between the same traits at different growth stages. However, some juvenile-mature plant trait relationships were significant, positive and consistent for both 2017 and 2018. For example, total root length and the total number of roots in 30 DAP, and branching density of upper nodal roots in 45 DAP, positively correlated with harvest index of 12-months old plants in both 2017 and 2018. Similarly, the diameter of nodal roots, for example, had a negative, significant correlation with fresh shoot biomass of mature plants in both 2017 and 2018. Regression of traits measured in 30 DAP explained up to 22% and 36% of the variation in HI of mature plants in 2017 and 2018, respectively. It is concluded that the simple, rapid, inexpensive phenotyping approach adopted in this study is robust for identifying genotypic variations in juvenile cassava using root system traits. Also, the results provide seminal evidence for the existence of useful relationships between traits of juvenile and mature cassava plants that can be explored to predict yield and yield components.