Mature Plant Stage Research Articles

Rice A20/AN1 protein, OsSAP10, confers water-deficit stress tolerance via proteasome pathway and positive regulation of ABA signaling in Arabidopsis.

Overexpression of rice A20/AN1 zinc-finger protein, OsSAP10, improves water-deficit stress tolerance in Arabidopsis via interactionwith multiple proteins. Stress-associated proteins (SAPs) constitute a class of A20/AN1 zinc-finger domain containing proteins and their genes are induced in response to multiple abiotic stresses. The role of certain SAP genes in conferring abiotic stress tolerance is well established, but their mechanism of action is poorly understood. To improve our understanding of SAP gene functions, OsSAP10, a stress-inducible rice gene, was chosen for the functional and molecular characterization. To elucidate its role in water-deficit stress (WDS) response, we aimed to functionally characterize its roles in transgenic Arabidopsis, overexpressing OsSAP10. OsSAP10 transgenics showed improved tolerance to water-deficit stress at seed germination, seedling and mature plant stages. At physiological and biochemical levels, OsSAP10 transgenics exhibited a higher survival rate, increased relative water content, high osmolyte accumulation (proline and soluble sugar), reduced water loss, low ROS production, low MDA content and protected yield loss under WDS relative to wild type (WT). Moreover, transgenics were hypersensitive to ABA treatment with enhanced ABA signaling and stress-responsive genes expression. The protein-protein interaction studies revealed that OsSAP10 interacts with proteins involved in proteasomal pathway, such as OsRAD23, polyubiquitin and with negative and positive regulators of stress signaling, i.e., OsMBP1.2, OsDRIP2, OsSCP and OsAMTR1. The A20 domain was found to be crucial for most interactions but insufficient for all interactions tested. Overall, our investigations suggest that OsSAP10 is an important candidate for improving water-deficit stress tolerance in plants, and positively regulates ABA and WDS signaling via protein-protein interactions and modulation of endogenous genes expression in ABA-dependent manner.

Screening and identification of heat tolerance in Indian wheat genotypes using generalized regression neural network (GRNN) model

The present study using a generalized regression neural network (GRNN) model was carried out to check the effect of high temperature on five Indian bread wheat genotypes, namely, C306, K7903, CBW12, HD2329, and HD2428, and to develop an algorithm for the screening and identification of heat tolerance in wheat. A highly significant differential survivability in response to the temperature induction response technique with germinating seeds was observed for the five wheat genotypes. Maximum survivability was observed for C306 and K7903, whereas HD2329 and HD2428 showed minimum survival in response to lethal temperature stress. Similarly, at the mature plant stage, in response to heat treatment of 34°C/26°C (day/night), all five wheat genotypes showed a significant difference in chlorophyll a fluorescence, total chlorophyll content, and the reduction of 1,1- diphenyl-2-picryl-hydrazyl (DPPH) in response to heat treatment. The genotypes, C306, K7903, and CBW12 showed better performance for all the chlorophyll a fluorescence parameters under study including Fo, Fv/Fm, qL, qP, NPQ, θPSII, ETR, along with the total chlorophyll content and DPPH reduction, in contrast, the genotypes, HD2329 and HD2428 performed poorly for all parameters including chlorophyll a fluorescence parameters, total chlorophyll, and DPPH reduction. Higher inflection temperature and peak temperature were observed in C306 and K7903, in contrast, HD2329 and HD2428 showed significantly lower inflection temperature and peak temperature. Higher expression of the selected genes involved in photosynthesis and ROS scavenging was observed in C306 and K7903 relative to HD2329 and HD2428. On the basis of the different chlorophyll a fluorescence parameters, the algorithm was developed for the calculation of the heat susceptibility index. The algorithm was independently checked for the identification and segregation of all the five wheat genotypes taken in this study as tolerant, moderate, and susceptible. For all the genotypes, the algorithm was able to predict the heat susceptibility of the genotypes with high accuracy. Hence, the algorithm in combination with chlorophyll a fluorescence can be used for the screening of wheat and other plant species in response to abiotic stress, especially heat stress.

Transgenic sugarcane expressing Bacillus thuringiensis Cry1Ac protein offers new possibilities for controlling the giant borer, Telchin licus (Drury), a pest difficult to control

The giant borer, Telchin licus (Drury), is an important insect pest of sugarcane in Central and South America. This pest is difficult to control with chemical or biological control approaches due to the larvae behavior of hiding in the deepest parts of the plants. Manual scavenging and skewer killing have been the main approaches for monitoring and control of T. licus in Brazil, the world's largest sugarcane producer. Recently, Brazil launched the first commercial use of transgenic sugarcane expressing Bacillus thuringiensis (Bt) proteins to control the sugarcane borer, Diatraea saccharalis (F.), a primary insect pest of sugarcane in the Americas. In this study, five independent field/greenhouse tests were conducted to evaluate the larval survival of and plant injury by T. licus on five non-Bt and five Bt sugarcane varieties containing a single cry1Ac gene. The multiple field/greenhouse tests showed that Cry1Ac sugarcane was highly effective to control T. licus; and the high control efficiency was consistent across varieties, from immature to mature plant stages, as well as for F0 generation plants and F1 ratoons. In addition, diet-incorporated bioassays were performed to determine the susceptibility of three field-collected T. licus populations in Brazil to diet treated with purified Cry1Ac protein or with a 25-fold dilution of Cry1Ac sugarcane stalk tissue. The diet bioassays exhibited that the field T. licus populations were also susceptible to the purified Cry1Ac protein, as well as to diet treated with the 25-fold dilution of stalk tissue. The results of this study provide compelling evidence that the single-protein Cry1Ac sugarcane varieties offer new possibilities for managing the T. licus, a pest that is difficult to control with other current available technologies.

Phenolic compounds of sorghum [Sorghum bicolor (L.) Moench] and their allelopathic effect

Purpose. To establish the quantitative composition of phytochemicals containing in vegetative and generative organs of sugar sorghum hybrids with high and medium sugar content ‘Sugargraze ARG’ (Argentina), ‘Sioux’ and ‘Mohawk’ (USA) and ‘Ananas’ and ‘Medovyi’ (Ukraine) and their allelopathic effect
 Methods. Allelopathic, physiological-biochemical, agrochemical and statistical methods were used. The content of phytochemicals in the vegetative and generative organs of the studied sugar sorghum hybrids was determined by the extraction method.
 Results. A high concentration of sorghum phenolic substances in the seeds at the mature plant stage was found. However, their concentration was species specific and depended on their quantitative component in the process of morphogenesis of vegetative and generative organs of sorghum of different genetic origin. The analysis of the total content of phytochemical compounds in the studied hybrids showed an increase in their number at the end of the vegetation season. The research was conducted in vitro. The manifestation of phenolic compounds was observed through manifestation of the allelopathic effect of cultivated sorghum plants. It was found that on the 7th day of cultivation, the plants actively secreted phenolic compounds; the increase in the number of leaves and the height of plants in hybrids did not change and amounted to 3–5 and 1.6–2.0 cm, respectively. On the 14th day of the experiment, the phenolic spots grew significantly, and yellowing of the lower leaves appeared. In the process of morphogenesis of sorghum plants (during 21 days), a more intense release of phenolic compounds led to suppression and slowing down of growth and subsequently to the death of the clone, regardless of the genetic origin of the hybrids. Phenolic compositions also influenced the formation of the root system of cultivated sorghum plants. A significant decrease in the number of lateral roots and the length of the root system was noted in all studied hybrids.
 Conclusions. The highest content of phenolic compounds was found in the seeds (grain) and stems of the studied sorghum hybrids. Thus, the quantitative composition of glycosides and tannins was 34–39 and 5.5–6.9 %, respectively, in the seeds and 25–29 and 0.3–1.4 %, respectively, in the stems of the studied hybrids. The highest content of hydroxycinnamic acids (from 7 % to 14 %) was found in the leaves of the studied sorghum hybrids. Phenolic compositions under in vitro conditions cause stress, which slows down the growth and development of cultivated plants, and subsequently lead to the death of clones.

Soil bacterial community structure at different plant maturity stages in an annual grass–legume production system

IntroductionTo infer changes in soil function and thus determine appropriate agronomic management practices, this study evaluated the effects of plant maturity stage on root characteristics, soil chemical and enzymatic properties, and soil bacterial community composition in an annual grass–legume production system.MethodsAnnual ryegrass or rye was sown in combination with one of three legume species at a legume ratio of 50%. Eighteen plots (six plant combinations, three replicates per combination, 20 m × 25 m plots) were tilled to a depth of 20 cm after mowing. Soil samples from each plot were collected on four dates as the plants matured: January 4 (H1), March 14 (H2), April 21 (H3), and May 19 (H4). Bacterial community structures were characterized via 16S rRNA high-throught sequencing and the bio-informatics methods were used to evaluate the structural characteristics of soil bacteria.ResultsThe most abundant root growth was observed at the H3 stage. No significant differences in organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium contents (p > 0.05) were observed on any sampling date. Soil collected at the H3 stage exhibited lower acid protease and urease activities (p < 0.05) and higher nitrate reductase activity (p < 0.05). The structure of the microbial community at stage H3 differed markedly from that at other stages, as evidenced by a higher abundance of Proteobacteria, Bacteroidetes, Acidobacteria, and Verrucomicrobia (p < 0.05) and a lower abundance of Actinobacteria, Cyanobacteria, and Planctomycetes (p < 0.05). At the class level, the relative abundances of Sphingobacteria, Betaproteobacteria, and Gammaproteobacteria in soil was higher at H3 stage than those of other stages (p < 0.05). The order level for Sphingomonadales, Sphingobacteriales, and Burkholderiales and at the family level for Chitinophagaceae and Sphingomonadaceae showed the same trend toward higher.ConclusionNutrient cycling in the soil was slowed at the H3 stage, and the loss of nitrogen would also be greater. Measures may need to be taken to improve the nitrogen fertilizer utilization efficiency to reduce denitrification and nitrous oxide production at this stage (the booting stage of grasses and budding stage of legumes).

Improvement of Growth and Development of Sweet Basil (Ocimum basilicum L.) Through the Application of Chitosan at Different Plant Maturity Stages

Sweet basil is one of the most popular culinary, medicinal, and fragrance herbs in Mediterranean, Asian, and Western countries. This study aims to increase the growth performance of sweet basil via different concentrations of chitosan, which is applied at three growth stages. The study was arranged in a factorial randomized complete block design with four replications. The plants were divided into three growth stages, which were the vegetative stage (S1), the reproductive stage (S2), and both the vegetative and reproductive stages (S1 + S2). Those plants were then treated with four different concentrations of chitosan (0, 2, 4, and 6 ml/L) either on S1, S2, or S1 + S2. The results indicated that plants treated with chitosan at S1 showed greater performance. Chitosan concentration of 4 ml/L produced greater plant height (55.09 ± 1.75 cm/plant), stem diameter (11.08 ± 0.89 mm/plant), and a number of leaves (296.57 ± 11.61 leaves/plant). It is also interesting to observe that the lowest chitosan concentration was non-significantly different, with 4 ml/L at S1 in some parameters. Plants in those treatments showed the highest average length of internode, number of branches, total root length, average root diameter, total root volume, and total root surface area. Besides, correlation analysis proved that all the parameters significantly correlated positively. As the concentration of 4 ml/L showed a superior effect, especially on the number of yields, thus it is recommended for growers to apply chitosan at 4 ml/L during S1.

Evaluation of Rumen Degradation Kinetics of Low-Lignin Alfalfa 'Hi-Gest® 360' in Saskatchewan Canada.

The objective of this study was to determine rumen degradation kinetics of new low-lignin alfalfa (Medicago sativa L.) cv. Hi-Gest®360 (HiGest) in comparison with conventional alfalfa cv. AC Grazeland (Grazeland) in monoculture and binary mixtures at different maturity stages. Two cultivars of alfalfa (HiGest, and AC Grazeland) and their binary mixtures with hybrid bromegrass (HBG; cv. AC Success), grown in 2019 at two locations (Saskatoon and Lanigan), were cut at three maturity stages of alfalfa (1 = 10% bloom; 2 = 40% bloom; and 3 = 100% bloom). Rumen degradation characteristics, including rapidly degradable fraction (S), potentially degradable fraction (D), undegradable fraction (U), degradation rate (Kd), lag time (T0), and effective degradability (ED) of each component were determined using in situ technique and were analyzed by a first-order kinetic equation described by Ørskov and McDonald with lag time. Generally, in alfalfa monoculture, S or D were decreased and U was increased without affecting Kd and T0, resulting in decreased ED fraction with increasing stage of maturity. In binary mixtures, plant maturity stages have negligible effects on rumen degradation characteristics of CP. HiGest had higher effective degradability of DM (EDDM) as well as of NDF (EDNDF) than Grazeland. In conclusion, HiGest had greater DM and NDF rumen degradation potential relative to Grazeland. HiGest and Grazeland were different in DM and CP degradation patterns, with HiGest having higher EDDM and EDCP than Grazeland.

Variation in potential feeding value of triticale forage among plant fraction, maturity stage, growing season and genotype

Cereal forages, such as triticale forage, progressively gain interest as alternative crop for maize. The main study objective was to investigate the variation in potential feeding value of triticale forage among maturity stage, growing season and genotype, using total plant and stem fractions. Therefore, near infrared spectroscopy (NIRS) was evaluated as fast screening tool. The prediction ability was good (ratio of prediction to deviation, RPD ≥3.0) for total plant residual moisture, starch, sugars and for stem crude ash (CAsh) and neutral detergent fibre (aNDFom); suitable for screening (2.0 ≤ RPD <3.0) for total plant CAsh, acid detergent fibre (ADFom), in vitro digestibility of organic matter (IVOMD), in vitro digestibility of neutral detergent fibre (IVNDFD) and for stem total lignin (TL) and IVNDFD; poor (1.5 ≤ RPD <2.0) for total plant crude protein, crude fat, aNDFom, lignin (sa) and for stem Klason lignin (KL); unreliable (RPD <1.5) for stem residual moisture and acid soluble lignin (ASL). The evolution in potential feeding value of 36 genotypes harvested at the medium and late milk to the early, soft and hard dough stage was followed. The most important changes occurred between the late milk and early dough stage, with little variation in quality after the soft dough stage. During 2 growing seasons, variation in feeding value of 120 genotypes harvested at the soft dough stage was demonstrated. Interestingly, variation in stem IVNDFD is almost twice as high as for the total plant (CV 12.4% versus 6.6%). Furthermore, Spearman correlations show no link between dry matter yield and digestibility of genotypes harvested at the soft dough stage. Based on linear regression models ADFom appears as main predictor of both plant IVOMD and plant IVNDFD. Stem IVNDFD is particularly determined by KL.

Novel Functions of Arabidopsis Pumilio RNA-Binding Protein 6 in Salt Stress

To control gene expression, plants use the post-transcriptional/translational regulation system, which plays important roles in development and biotic and abiotic responses. Some RNA-binding proteins (RBPs) are known to regulate target genes via direct binding of specific RNA motifs. Pumilio and fem-3 binding factor (Puf) proteins exhibit a specific capacity for binding of the 3’ untranslational region (3’ UTR) of target mRNA and work as a post-transcriptional regulator in the mammalian system. Recently, it was reported that Arabidopsis Pumilio RNA-binding protein (APUM), a plant Puf homologue, is involved in biotic and abiotic stress and development. However, the function of plant Puf proteins has not yet been fully recovered. In the current study, APUM6 gene expression was reduced by salt stress. APUM6 localized in the cytoplasmic foci of the mRNA decay sites and ER membrane. Purified APUM6-pumilio homologue domain (HD) protein showed ‘UGUANAUA’ binding activity in vitro. APUM6-RNAi transgenic plants displayed reduced tolerance to salt stress during the germination and mature plant stages. In APUM6-RNAi transgenic plants under salt stress, abiotic stress-responsive gene expression levels showed no significant difference compared with Col-0. Collectively, these results indicate that APUM6 might play important roles in responses to salt stress via translational modification.

The effect of ripening on the capsaicinoids composition of Jeromin pepper (Capsicum annuum L.) at two different stages of plant maturity

The changes of capsaicinoids in the pericarp and placenta of Jeromin pepper fruits, collected at two different stages of plant's maturity (young and adult), has been studied throughout the ripening process. This variety is used in the production of “Pimentón de La Vera” and recognized under a Protected Designation of Origin, so it is of great importance to determine their optimum harvesting time to get the most of its beneficial health effects. Capsaicinoids reached the maximum concentration on the 30th days post-anthesis (dpa) for the young plant, while in the adult plant it was later, specifically on 40th and 60th dpa for the placenta and pericarp, respectively. From this moment on, a sharp decrease in their content is observed. In addition, higher amounts of total capsaicinoids have been found in the second stage of plant maturity with respect to the first one, both in the placenta and in the pericarp.

RLM1, Encoding an R2R3 MYB Transcription Factor, Regulates the Development of Secondary Cell Wall in Rice.

Leaf morphology is an important component of rice ideal plant type. To date, many regulatory genes influencing leaf morphology in rice have been cloned, and their underlying molecular regulatory mechanism has been preliminarily clarified. However, the fine regulation relationship of leaf morphogenesis and plant type remains largely elusive. In this study, a rolling-leaf mutant, named rlm1-D, was obtained and controlled by a pair of dominant nuclear genes. Cytological observations revealed that the rlm1 was mainly caused by abnormal deposition of secondary cell walls. Molecular evidence showed ectopic expression of a MYB-type transcription factor LOC_Os05g46610 was responsible for the phenotype of rlm1-D. A series of experiments, including the transcription factor-centered technology, DNA-binding assay, and electrophoretic mobility shift assay, verified that RLM1 can bind to the promoter of OsCAD2, a key gene responsible for lignin biosynthesis in rice. An interacting partner of RLM1, OsMAPK10, was identified. Multiple biochemical assays confirmed that OsMAPK10 interacted with RLM1. OsMAPK10 positively regulated the lignin content in the leaves and stems of rice. Moreover, OsMAPK10 contributes to RLM1 activation of downstream target genes. In particular, RLM1 is exclusively expressed in the stems at the mature plant stage. The yield of RLM1 knockdown lines increased by over 11% without other adverse agricultural trait penalties, indicating great practical application value. A MAPK-MYB-OsCAD2 genetic regulatory network controlling SCW was proposed, providing a theoretical significance and practical value for shaping the ideal plant type and improving rice yield.

Nutrients, Fiber Fraction, and In Vitro Fiber Digestibility of Brown-Midrib Sorghum Mutant Lines Affected by The Maturity Stages

The mutant line of Brown-midrib sorghum has lower lignin content than conventional sorghum. The objectives of this research were to investigate the effects of plant maturity stages at harvest times on nutrient, fiber fraction, tannin content, volatile fatty acids (VFA) production, and in vitro fiber digestibility of mutant lines of Brown Midrib (BMR) sorghum. This research was arranged into a complete block design with a factorial arrangement in three replications. The first factor was a line of BMR sorghum consisted of 3 levels, i.e., Patir 3.1 (non-BMR line/control), Patir 3.2 (BMR line), and Patir 3.7 (BMR line). The second factor was the generative stages of sorghum consisted of 3 levels, i.e., flowering stage, soft-dough stage, and hard-dough stage. The observed variables were nutrient, fiber fraction, tannin content, in vitro rumen fluid characteristics, VFA proportion, acetate: propionate (A:P) ratio, and in vitro fiber-fraction digestibility (IVFFD). Data were analyzed by Analysis of Variance (ANOVA) and Duncan’s Multiple Range Test (DMRT). No interaction between sorghum-mutant lines and harvest time on nutrient contents, except on total digestible nutrients (TDN), tannin, and VFA. The factor of sorghum-mutant line affected (p&lt;0.01) crude protein (CP), crude fiber (CF), acid detergent fiber (ADF), lignin, neutral detergent fiber digestibility (NDFD), NH3, butyrate, isovalerate, and valerate. Maturity stages affected dry matter (DM), CF, ash, crude fat, fiber, and fraction, except hemicellulose, acid detergent fiber digestibility (ADFD), and NDFD, NH3, isovalerate, and valerate. Patir 3.7 at the hard-dough stage produced the highest TDN, but the highest VFA was produced by Patir 3.1 at flowering stages. BMR sorghum-mutant lines produced higher ADF digestibility than non-BMR sorghum-mutant lines. The increasing NDF digestibility was significantly influenced by both sorghum-mutant lines and maturity stages (p&lt;0.01). It is concluded that BMR sorghum-mutant lines at the hard-dough stage produce better nutrient and in vitro digestibility, but the butyric acid is higher in non-BMR sorghum-mutant lines.

Responses and screening of white jute (Corchorus capsularis L.) genotypes against salinity stresses

Soil salinity, a serious threat to jute cultivation in saline areas (southern parts) of Bangladesh. Bangladesh Jute Research Institute (BJRI) has developed a moderately salt tolerant White Jute variety (BJRI Deshi pat-8; BJC 2197) in 2013 which can’t grow well in saline areas having more than 8.0 dSm-1 salinity stress. Hence, 23 whitejute accessions and one control variety (BJC 2197) were tested to isolate the salt tolerant accession(s) for hybridization purpose followed by augmented design in farmers’ field having nearly 8.0-9.0 dSm-1 salinity at Patuakhali district during mid-March to mid-August 2019. The experimental plot size was 3.0 m2 (3 m × 1 m) for each genotype having 3 lines of 1.0 m length, plant-plant: 10-15 cm and line- line: 30 cm distance. Soil salinity was recorded during sowing, vegetative and plant maturity stages. In this study, the highest plant height 2.84 m was recorded in Acc. 2750 followed by Acc. 2589 (2.76 m) and Acc. 1779 (2.69 m). The highest fiber yield (9.0 g plant-1) was observed in Acc. 1779 followed by Acc. 2589 (8.40 g plant-1) and Acc. 2750 (8.0 g plant-1). The lowest plant mortality rate (2.5%) was found in Acc.2750 followed by Acc.1779 (6.24%), Acc. 1780 (7.50), Acc. 3556 (11.10%), Acc. 2589 (11.20%) and BJC 2197 (16.5%). Few seeds were germinated in Acc. 3020 and Acc. 3658 but plants were died after 20 days of sowing. Six genotypes of cluster I showed higher diversity in Euclidean cluster analysis. The Acc. 2750, Acc. 1779, Acc. 2589 of cluster I having relative salinity tolerance and good fiber yield capacity would be grown in next year for confirmation as well as hybridization with the existing salinity susceptible variety to develop high yielding white jute variety for saline areas.

Integration of early disease-resistance phenotyping, histological characterization, and transcriptome sequencing reveals insights into downy mildew resistance in impatiens

Downy mildew (DM), caused by obligate parasitic oomycetes, is a destructive disease for a wide range of crops worldwide. Recent outbreaks of impatiens downy mildew (IDM) in many countries have caused huge economic losses. A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired. In this study, we established an early and rapid system to achieve these goals using impatiens as a model. Thirty-two cultivars of Impatiens walleriana and I. hawkeri were evaluated for their responses to IDM at cotyledon, first/second pair of true leaf, and mature plant stages. All I. walleriana cultivars were highly susceptible to IDM. While all I. hawkeri cultivars were resistant to IDM starting at the first true leaf stage, many (14/16) were susceptible to IDM at the cotyledon stage. Two cultivars showed resistance even at the cotyledon stage. Histological characterization showed that the resistance mechanism of the I. hawkeri cultivars resembles that in grapevine and type II resistance in sunflower. By integrating full-length transcriptome sequencing (Iso-Seq) and RNA-Seq, we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp. Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance, including three resistance genes orthologous to the sunflower gene RGC203, a potential candidate associated with DM resistance. Our approach of integrating early disease-resistance phenotyping, histological characterization, and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.

Quantifying Solanum chacoense root morphology responses to limited nitrogen supply using in vitro, hydroponic, and field monolith methods

Solanum chacoense Bitt. (chc) is a short-day adapted wild diploid (2n = 2x = 24) species, relative of the commercial potato S. tuberosum L. (tbr), that has demonstrated higher below-ground biomass when cultivated under limited nitrogen (N) supply, suggesting it possesses greater potential for N recovery by increasing root length density (RLD). The objectives of this study were to compare screening methodologies for evaluating RLD responses of chc genotypes and tbr cultivars under limited N supply for the identification of superior rooting chc genotypes. Seventeen genotypes of chc and three commercial tbr varieties were exposed to 0.5 and 1.0 N rates across three root screening methodologies: in vitro, hydroponic, and field evaluated at tuber initiation and plant maturity stages. Although the development of a reliable high throughput root screening system was unachievable due to differences in environment and root sampling protocols across methodologies, there were significant positive correlations amongst RLD for a majority of methods in both chc and tbr. This suggests that RLD can be utilized for evaluating both Solanum species and genotypes within species and environments. RLD for chc 0048-34 and 0053-7 genotypes were significantly higher than tbr cultivars in all tested methods indicating that chc possesses the potential for increasing N recovery in future breeding with tbr.

Agronomic characteristics and nutritive value of pigeon pea [Cajanus cajan (L.) Millsp.] harvested at different stages of maturity.

This study was divided into three parts. The first evaluated the effects of five stages of plant maturity (60, 75, 90,120 and 180 d) on the agronomic characteristics, chemical composition and in vitro degradability (IVDMD) of pigeon pea [Cajanus cajan (L.) Millsp.] 'Kaki' and its anatomical fractions, leaves and stems. In the second part, the selective consumption of this legume was studied. In the third part, the effects of the inclusion of pigeon pea in diets based on tropical grass hay for goats on voluntary intake, and digestibility of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) were determined. Plant height increased and leaf :stem ratio decreased, as the plants grew. In the whole plant, DM and NDF content increased (P &lt; 0.05) by 13.9 and 19.2 percentage units, but CP content numerically decreased by 4.8 units as plant maturity progressed from 60 to 120 d. At the five successive stages evaluated, CP content in the leaves exceeded that of the stems, whereas NDF content showed the opposite trend. The IVDMD values were 69.6% in the whole plant, 73.9% in the leaves, and 50.4% in the stems. Whole plant IVDMD decreased (P &lt; 0.05), with advancing plant maturity, from 71.2% at 60 d to 55.8% at 180 d. In the selective consumption trial, intake of fresh pigeon pea was compared with that of fresh native tropical grass (NTG) or NTG hay. A high selection of pigeon pea was observed for the first 10 minutes, but during the following 20 minutes this selection decreased. In the voluntary intake and digestibility trial that utilized six goats (26.4 kg live weight) to evaluate the inclusion of 25% of pigeon pea in a NTG-based diet, CP intake was markedly higher (P &lt; 0.05) with legume supplementation. Dietary inclusion of the legume also tended to improve the digestibility of DM and CP but not at the P &lt; 0.05 level of significance (56.7% vs. 51.4% and 58.7 vs. 51.2%); however, it did not affect NDF digestibility. As the pigeon pea plant increased in height, changes occurred in leafistem proportions and chemical composition. The IVDMD results suggest that the interval from 75 to 120 d of growth is favorable for possible utilization of pigeon pea as fresh forage in diets for small ruminants.

Yield Response of Determinate Chipping Potato to Artificial Defoliation.

The relationship between canopy defoliation by insects and yield loss in potato (Solanum tuberosum L.) has been extensively researched. However, detailed analysis of varieties with different properties and examination of methods of defoliation are still lacking. Absence of research results has led many producers to use a very conservative economic threshold (ET) of 10% defoliation in the management of insect defoliators. A series of leaf removal experiments was conducted on a determinate chipping variety of potato at different plant stages. In 2002, the highest levels of defoliation induced upon the plant canopy were 50, 30, and 75% for tuber initiation, full bloom, and plant maturity stages, respectively. In 2003, defoliation levels were increased to 70, 80, and 90% for tuber initiation, full bloom, and plant maturity, respectively. Total yield was unaffected, and no significant changes in market sized yield, or number of marketable tubers were observed at any growth stage in either year. Because the determinate variety showed remarkable ability to recover from substantial defoliation, two different methods of defoliation: hand cut (cutting the edge of leaves with scissors while avoiding the midrib) and hole punching (hole-punching leaf tissue [15.08-mm diameter] while avoiding midrib) were tested. Although total yield was unaffected, marketable yield and small potato yield were reduced, Thus, although defoliation methods must be considered, a 10% defoliation ET is exceedingly conservative and an ET of 60% for all stages of determinate chipping potato could be adopted by growers.

Decoding Wheat Endosphere-Rhizosphere Microbiomes in Rhizoctonia solani-Infested Soils Challenged by Streptomyces Biocontrol Agents.

The endosphere and the rhizosphere are pertinent milieus with microbial communities that perturb the agronomic traits of crop plants through beneficial or detrimental interactions. In this study, we challenged these communities by adding Streptomyces biocontrol strains to wheat seeds in soils with severe Rhizoctonia solani infestation. Wheat plants were grown in a glasshouse standardized system, and the bacterial and fungal microbiomes of 233 samples of wheat roots (endosphere) and rhizosphere soils were monitored for 20 weeks, from seed to mature plant stage. The results showed highly dynamic and diverse microbial communities that changed over time, with Sphingomonas bacteria and Aspergillus, Dipodascus, and Trichoderma fungi increasing over time. Application of biocontrol Streptomyces strains promoted plant growth and maturation of wheat heads and modulated the root microbiome, decreasing Paenibacillus and increasing other bacterial and fungal OTUs. The soils with the highest levels of R. solani had increased reads of Thanatephorus (Rhizoctonia anamorph) and increased root disease levels and increased Balneimonas, Massilia, Pseudomonas, and unclassified Micrococcaceae. As we enter the era of biologically sustainable agriculture, it may be possible to reduce and limit the effects of serious fungal infestations by promoting a beneficial microbiome through the application of biocontrol agents during different periods of plant development.

Contrasting Patterns of Colonization with Verticillium longisporum in Winter- and Spring-Type Oilseed Rape (Brassica napus) in the Field and Greenhouse and the Role of Soil Temperature

Oilseed rape, an important source of vegetable plant oil, is threatened by Verticillium longisporum, a soil-borne vascular fungal pathogen so far occurring in oilseed rape growing regions in Europe and Canada. Despite intensive research into V. longisporum in the last decades in controlled conditions, basic knowledge is still lacking about the time course of infection, temporal pattern of colonization, and disease development on field-grown plants. In this study, colonization of roots, stem bases, and stems with V. longisporum was followed by real-time PCR from the seedling until mature plant stages in 2-year field experiments with microsclerotia-infested plots and either spring-type or autumn-sown (winter-type) oilseed rape cultivars. The temporal pattern of plant colonization differed between greenhouse and field-grown oilseed rape and between spring- and winter-type plants in the field. Within 28 to 35 days, a continuous systemic colonization with V. longisporum was detected in roots and shoots of young plants in the greenhouse associated with significant stunting. In contrast, real-time PCR analysis of V. longisporum in field-grown winter oilseed rape plants displayed a strongly discontinuous colonization pattern with low fungal growth in roots during juvenile growth stages until flowering, whereas in spring oilseed rape, no root colonization was observed until early flowering stages. Hence, stem colonization with the pathogen required 6 months in winter oilseed rape and 1 month in spring oilseed rape from the time of initial root infection. The different patterns of stem colonization were related to soil temperature. Average soil temperatures in 5-cm depth during 7 days before sampling time points from 2 years of field experiments displayed a significant relationship with fungal colonization in the root. A climate chamber inoculation trial with soil temperature levels that varied from 6 to 18°C revealed a threshold temperature of >12°C in the soil to enable root invasion. This soil condition is reached in winter-type oilseed rape in the field in Germany either until the eight-leaf stage in early autumn or after pod stage in spring, whereas in spring-sown oilseed rape early root infection is delayed owing to the cool conditions during juvenile growth stages. The delay of stem colonization in field-grown oilseed rape may explain the lack of stunting as observed in the greenhouse and the previously reported inconsistent effects of V. longisporum on yield levels and seed quality, which were confirmed in this study.

Registration of R.LBK1 and R.LBK2 Sorghum Germplasm with Resistance to the Sugarcane Aphid [Melanaphis sacchari (Zehntner)

The sorghum [Sorghum bicolor (L.) Moench] germplasm lines R.LBK1 (Reg. No. GP‐865, PI 687244) and R.LBK2 (Reg. No. GP‐866, PI 687245) were developed and released by the USDA in Lubbock, TX, in 2017 because of their high degree of resistance to the sugarcane aphid (SCA) [Melanaphis sachari (Zehntner) (Hempitera: Aphidae)]. Both lines were developed using the pedigree method of plant breeding and are confirmed to be restorer lines. The breeding crosses for both lines were made in Lubbock, TX, and selections were made in Lubbock and Corpus Christi, TX. Evaluation for SCA resistance was conducted in two field locations in Texas in 2016, as well as a greenhouse experiment at the USDA‐ARS laboratory in Lubbock. Both lines express strong resistance to SCA pressures at both seedling and mature plant stages. Preliminary hybrids using highly susceptible seed parents have also shown strong resistance to SCA, indicating that the resistance is dominantly expressed in F1 hybrids using these two lines. R.LBK1 and R.LBK2 are not completely immune to the SCA, but damage is greatly reduced and resistance is extremely apparent when compared to other susceptible sorghum lines and hybrids. These lines provide much needed resistance to the SCA and are suitable as germplasm in a plant breeding program or as parental lines for hybrid development.