Pod Wall Research Articles

Defense system in chickpea genotypes differing in tolerance to Helicoverpa armigera infestation

Antioxidative enzymes, non enzymic antioxidants and signaling molecules were compared in leaves and podwall of ten chickpea genotypes namely ICC 506, ICCV 10, ICC 10393, 5282, RSG 963, GL 25016, GL 26054, ICCL 86111, ICC 3137 and L 550 after Helicoverpa armigera infestation. Two chickpea genotypes (ICC 3137 and L 550) were found to be susceptible and rest of eight genotypes were found to be resistant on the basis of leaf and pod damage due to to Helicoverpa armigera infestation. The activities of defensive enzymes like, peroxidase (POD), ascorbate peroxidase(APX) and glutathione reductase (GR); content of nitric oxide (NO), 2,2-diphenyl-1-picryl hydrazyl (DPPH), ferric reducing antioxidant power(FRAP), glycine betaine (GB), total phenols (TP) and proline were higher in leaves and pod wall of resistant genotypes than susceptible genotypes. Genotype 5282 was found to be the most resistant having lower leaf and pod damage and it had higher POD, nitric oxide, DPPH, FRAP, total phenols and proline content.

Expression of a Chimeric Gene Encoding Insecticidal Crystal Protein Cry1Aabc of Bacillus thuringiensis in Chickpea (Cicer arietinum L.) Confers Resistance to Gram Pod Borer (Helicoverpa armigera Hubner.).

Domain swapping and generation of chimeric insecticidal crystal protein is an emerging area of insect pest management. The lepidopteran insect pest, gram pod borer (Helicoverpa armigera H.) wreaks havoc to chickpea crop affecting production. Lepidopteran insects were reported to be controlled by Bt (cryI) genes. We designed a plant codon optimized chimeric Bt gene (cry1Aabc) using three domains from three different cry1A genes (domains I, II, and III from cry1Aa, cry1Ab, and cry1Ac, respectively) and expressed it under the control of a constitutive promoter in chickpea (cv. DCP92-3) to assess its effect on gram pod borer. A total of six transgenic chickpea shoots were established by grafting into mature fertile plants. The in vitro regenerated (organogenetic) shoots were selected based on antibiotic kanamycin monosulfate (100 mg/L) with transformation efficiency of 0.076%. Three transgenic events were extensively studied based on gene expression pattern and insect mortality across generations. Protein expression in pod walls, immature seeds and leaves (pre- and post-flowering) were estimated and expression in pre-flowering stage was found higher than that of post-flowering. Analysis for the stable integration, expression and insect mortality (detached leaf and whole plant bioassay) led to identification of efficacious transgenic chickpea lines. The chimeric cry1Aabc expressed in chickpea is effective against gram pod borer and generated events can be utilized in transgenic breeding program.

Evaluation and Analysis of Pod Dehiscence Factors in Shatter‐Susceptible and Shatter‐Resistant Common Vetch

Common vetch (Vicia sativa L.) is one of the most important annual forage legumes globally because of its multiple uses and high nutritional content. However, when it matures, the pod dehiscence can cause severe loss of seeds. In this research, we used eight shatter‐susceptible vetch accessions and 16 shatter‐resistant vetch accessions, which were evaluated and selected from 541 accessions, to compare and analyze the influencing factors related to pod dehiscence. We found that the shatter‐susceptible vetches all have abscission layers and that the shatter‐resistant vetches all lack abscission layers. External valve margin cells, which have not been reported in other plants to date, were located externally to the junction of the fruit valve where the valve margin exists, with the abscission layers below in the ventral suture. We found that shatter‐resistant vetches have significantly thicker external valve margin cell walls and obviously fewer pod wall torsion laps than shatter‐susceptible vetches, and there was no significant difference in the pod thickness to width ratio. In conclusion, abscission layers, external valve margin cells, and pod wall torsion laps are the main factors affecting pod dehiscence. Thus, this research lays the foundation for studying the mechanism of vetch pod dehiscence.

Development of ‘Ellis’ Soybean with High Soymeal Protein, Resistance to Stem Canker, Southern Root Knot Nematode, and Frogeye Leaf Spot

‘Ellis’ soybean [Glycine max (L.) Merr.] cultivar (Reg. No. CV‐523, PI 680630) was developed by the University of Tennessee Agricultural Experiment Station and was released as a late maturity group (MG) IV high‐yielding conventional (non‐genetically modified) cultivar in 2013. Ellis is an F5–derived single plant selection from the cross between two high‐yielding University of Tennessee cultivars, ‘5601T’ and ‘5002T’. In extensive field trials, Ellis has shown excellent adaptation and performance in Tennessee, the Mid‐South region, and the Southeast region of the United States. Ellis exhibits a relative maturity of 4.9, determinate growth habit, white flowers, gray pubescence, and tan pod wall. It is resistant to stem canker and southern root knot nematode and shows field tolerance to frogeye leaf spot. The protein and oil concentrations of Ellis seed enable it to produce high protein meal (>48% protein in the meal fraction). Ellis's excellent seed yield coupled with its ability to produce high protein meal gives this new cultivar high estimated processor values. It will be useful as a parent to soybean breeders, valuable as a new high‐yielding cultivar to producers, and profitable to processors.

Genetic control of viviparity in common bean

In common bean (Phaseolus vulgaris) harvesting is carried out in the field. It is therefore necessary that cultivars be tolerant to viviparity, i.e., germination of grains still in the pods. Study of the percentage of germination of beans in the pods under laboratory conditions, where humidity content is high, has been proposed. Furthermore, under question is whether the thickness of the pod wall affects water uptake by the pods and, consequently, viviparity. Thus, the aim of the present study was to verify if there is variance among progenies for viviparity and if it is influenced by pod thickness. We assessed the parents, Perola and ESAL 686, the F1, and a number of segregating generations in two crop seasons, in relation to the percentage of germination of seeds in the pods (PGSP) and pod wall thickness (PWT), and data on individual plants were obtained. The same traits were also assessed using the F2:3, F3:4 and F4:5 progenies. Taking into account the genetic and phenotypic parameters estimates, especially the level of high heritability, selection to less viviparity in common bean has to be carried out to evaluate PGSP in progenies.

Biomass remobilization in two common bean (Phaseolus vulgaris L.) cultivars under water restriction

Common bean (Phaseolus vulgaris L.) is one of the major sources of dietary protein for humans in Africa and Latin America. Efficient remobilization of storage materials accumulated in different tissues to seeds is one of the few alternatives that plants have to produce viable seeds under stress conditions. The aim of this study was to evaluate the biomass remobilization in two common bean (Phaseolus vulgaris L.) cultivars under water restriction. We hypothesize that under water restriction both cultivars exhibit a different pattern of remobilization of assimilates toward the seed. Plants of cv. V8025 and Canario-60 were irrigated to field capacity until starting seed filling stage under greenhouse conditions. At 63days after sowing, one group of plants was continued watering and another group was suspended watering. Five plants of each treatment were harvested starting watering halted (0days) and after 5, 10 and 20days. Dry mass of stem, branch, leaves, pod wall, seeds and yield components were evaluated; glucose, fructose, sucrose and starch in leaves and pods wall were calculated. In Canario-60 number of seeds and harvest index were not affected by water restriction; in contrast, in V8025 were strongly reduced. Both cultivars modified pattern of soluble sugars and starch accumulation in leaves in response to water restriction. Pods of both cultivars showed efficient degradation of starch. Canario-60 was also efficient for soluble sugars remobilization and contrasted with V8025. Results suggest that the capacity to translocate soluble sugars from pod wall or leaves to seeds filling could be an important adaptive response of common bean cultivars when stress for water restriction affects plants during grain filling periods.

Registration of ‘UA 5814HP’ Soybean with High Yield and High Seed‐Protein Content

‘UA 5814HP’ (Reg. No. CV‐522, PI 679957) soybean [Glycine max (L.) Merr.] was developed and released by the Arkansas Agricultural Experiment Station in 2014 as a high‐yielding and high‐protein late maturity group V conventional cultivar adapted to Arkansas and other southern states. UA 5814HP is an F4 selection from the cross of ‘R95‐1705’ and ‘S00‐9980‐22’. In the 2013–2014 Regional Quality Traits Tests for maturity group V, UA 5814HP was tested in 15 environments and yielded 4277 kg ha−1, which is comparable to the check (‘5601T’, ‘5002T’/‘Ellis’, and ‘Osage’) mean across 2 yr, 4374 kg ha−1. In the 2015 State Variety Tests conducted in Arkansas and other southern states (31 environments), UA 5814HP had an average yield (3723 kg ha−1) similar to that of ‘REV 57R21’ (Terral Seed) (3798 kg ha−1). In the Arkansas Soybean Breeding trials (12 environments; 2011–2015), UA 5814HP had higher seed‐protein content (455 g kg−1) than the check cultivars, ‘AG 5606’ (415 g kg−1, 2011–2013) and ‘AG 5831’ (395 g kg−1, 2014). UA 5814HP has a determinate growth habit, purple flowers, tawny pubescence, tan pod walls, and brown seed hilum. It is resistant to stem canker, frogeye leaf spot, and charcoal rot and is susceptible to races 2 and 5 of soybean cyst nematode, southern root‐knot nematode, and reniform nematode.

Photochemical activity changes accompanying the embryogenesis of pea (Pisum sativum) with yellow and green cotyledons.

The pea seeds are photosynthetically active until the end of the maturation phase, when the embryonic chlorophylls degrade. However, in some cultivars, the underlying mechanisms are compromised, and the mature seeds preserve green colour. The residual chlorophylls can enhance oxidative degradation of reserve biomolecules, and affect thereby the quality, shelf life and nutritive value of seeds. Despite this, the formation, degradation, and physical properties of the seed chlorophylls are still not completely characterised. So here we address the dynamics of seed photochemical activity in the yellow- and green-seeded pea cultivars by the pulse amplitude modulation (PAM) fluorometric analysis. The experiments revealed the maximal photochemical activity at the early- and mid-cotyledon stages. Thereby, the active centres of PSII were saturated at the light intensity of 15-20µmol photons m-2 s-1. Despite of their shielding from the light by the pod wall and seed coat, photochemical reactions can be registered in the seeds with green embryo. Importantly, even at the low light intensities, the photochemical activity in the coats and cotyledons could be detected. The fast transients of the chlorophyll a fluorescence revealed a higher photochemical activity in the coat of yellow-seeded cultivars in comparison to those with the green-seeded ones. However, it declined rapidly in all seeds at the late cotyledon stage, and was accompanied with the decrease of the seed water content. Thus, the termination of photosynthetic activity in seeds is triggered by their dehydration.

A Comprehensive Phenotypic Investigation of the "Pod-Shattering Syndrome" in Common Bean.

Seed shattering in crops is a key domestication trait due to its relevance for seed dispersal, yield, and fundamental questions in evolution (e.g., convergent evolution). Here, we focused on pod shattering in common bean (Phaseolus vulgaris L.), the most important legume crop for human consuption in the world. With this main aim, we developed a methodological pipeline that comprises a thorough characterization under field conditions, including also the chemical composition and histological analysis of the pod valves. The pipeline was developed based on the assumption that the shattering trait itself can be treated in principle as a “syndrome” (i.e., a set of correlated different traits) at the pod level. We characterized a population of 267 introgression lines that were developed ad-hoc to study shattering in common bean. Three main objectives were sought: (1) to dissect the shattering trait into its “components,” of level (percentage of shattering pods per plant) and mode (percentage of pods with twisting or non-twisting valves); (2) to test whether shattering is associated to the chemical composition and/or the histological characteristics of the pod valves; and (3) to test the associations between shattering and other plant traits. We can conclude the following: Very high shattering levels can be achieved in different modes; shattering resistance is mainly a qualitative trait; and high shattering levels is correlated with high carbon and lignin contents of the pod valves and with specific histological charaterstics of the ventral sheath and the inner fibrous layer of the pod wall. Our data also suggest that shattering comes with a “cost,” as it is associated with low pod size, low seed weight per pod, high pod weight, and low seed to pod-valves ratio; indeed, it can be more exaustively described as a syndrome at the pod level. Our work suggests that the valve chemical composition (i.e., carbon and lignin content) can be used for a high troughput phenotyping procedures for shattering phenotyping. Finally, we believe that the application of our pipeline will greatly facilitate comparative studies among legume crops, and gene tagging.

Optimal plant density and N fertilization to achieve higher seed yield and lower N surplus for winter oilseed rape (Brassica napus L.)

Greater synchrony between populations and individual plants is dependent on the interactions between plant density and nitrogen (N) fertilization and is crucial to achieve food and environment security. A two-factor designed experiment of transplanted winter oilseed rape was conducted in the 2012–2013 and 2013–2014 growing seasons in central China. Five transplanted plant densities and six N rates were used to study the influences of plant density and N fertilizer application rate on seed yield, N uptake and apparent N surplus. Optimal plant density was the prerequisite to obtain high seed yield and the contribution of plant density to seed yield was minor when it exceeded the optimal density. N fertilization offset the compensatory effect between plant density and pods per plant, enhance seed yield further. Seed yield increased linearly with the increase of seed N uptake, however, it did not increase as the non-seed parts (stem+pod wall) N uptake increased when seed yield exceeded the critical values in the high plant density treatments. Higher plant densities promoted shoot N uptake and reduced soil mineral N residues and apparent N surplus in root zone. Compared with the recommended transplanted density in this region (9.0×104 plant ha−1), the optimal N fertilizer application rate could be cut down with 10.3%–23.7% for the target yield (3000kgha−1) and apparent N surplus would be declined with 41.5%–92.1% when the density suitably increased to 10.0–12.0×104 plant ha−1; On the contrary, when the density was decreased to 7.0–8.0×104 plant ha−1, increasing N fertilization rate with 13.9%–34.8% also could gain the target yield, but the apparent N surplus would increase with 58.1%–148.0%. Consequently, varied combinations between plant densities and N fertilizer application rate are useful to fulfill high seed yield. Reducing N fertilizer rates under suitable higher plant densities are the optimal N management strategy to achieve high yield with lower environment risks.

Variability on morphological characters associated with pod shattering resistance in soybean

Abstract. Krisnawati A, Adie MM. 2016. Variability on morphological characters associated with pod shattering resistance in soybean. Biodiversitas 17: 73-77. Pod shattering is one of the major constraint associated with soybean production during dry season in Indonesia. The objectives of the study were to investigate varietal difference of pod shattering and to identify the morphological pod characters related to pod shattering. The field study was carried out in Blitar (East Java, Indonesia) during the dry season 2015. Morphological traits of pod were studied for their association with pod shattering trait in 30 soybean genotypes. The results showed significant differences between genotypes for all characters studied. The degree of shattering varied among genotypes with shattering percentage ranging from 2.5% (G511H/Argom//Argom-2-1) to 100% (Grobogan) with mean of 30%.However, among the 30 genotypes studied, 13 genotypes were relatively resistant, 11 genotypes moderate, 1 genotype susceptible, and 5 genotypes were very highly susceptible. Further path coefficient analysis indicated direct effects of the pod wall thickness and pod length on shattering percentage while other causal effects were small. These characters (pod wall thickness and pod length) may play role as determinant factors in pod shattering resistance. Therefore, soybean resistance to pod shattering could be enhanced by increasing thickness of the pod wall. 
 Keywords: Glycine max, pod characteristics, pod shattering, resistance

Free radical scavenging activities can mitigate the effect of water stress in chickpea

To get a comprehensive view of drought tolerance mechanisms, the influence of water deficit stress on antioxidative capacity due to scavenging of free radicals and ability to maintain reduced cell state was investigated in roots, nodules, leaves, pod wall and seeds of two chickpea cultivars differing in rooting behaviour. ICC4958 (deep rooted) possessed better ability to combat water deficit-induced oxidative stress relative to ILC3279 (shallow rooted) as revealed by increase in total phenol, reducing power, ferric reducing ability and capacity to scavenge 2,2-Diphenyl-1-picryl hydrazyl (DPPH) and OH free radicals. Effect of water deficit stress on photosynthetic pigments of these cultivars was also studied. The investigation revealed that the influence of water stress in enhancing antioxidative capacity was most prominent in roots of ICC4958 among all other tissues as revealed by increased total phenols, DPPH and OH free radical scavenging activity and total reducing power under stress. However, roots of ILC3279 suffered a decrease in total phenolic content, total reducing power and DPPH free radical scavenging activity under prolonged stress, which was reflected in reduced antioxidative defence in reproductive tissues like decreased reducing power in pod wall and ferric-reducing antioxidant power ability in seeds.

Screening of Short Duration Pigeonpea [Cajanus cajan (L.) Millsp.] Genotypes against Major Insect Pests

Ten promising short duration genotypes of pigeonpea were screened under field conditions for two years (2013-15) to identify sources of resistance against pod borers. On the basis of per cent pod damage and Pest Susceptibility Rating (PSR) index, genotypes PUSA-2012-1, PA 409, PA 406, AL1747 were found to be least susceptible (PSR= 4 to 5) while two genotypes, AL 1790 and AL 1770 were ascertained highly susceptible against pod borers having damage rating of 8 over the susceptible check cultivar (Manak). Phenol and flavonoid content present in the pod wall of all the test genotypes/cultivars were also estimated. Highest phenol and flavonoid content was recorded from PUSA-2012-1 while the lowest content was obtained from the genotype AL 1790. Correlation studies made with these biochemical constituents revealed a significant and negative association of pod damage (%) with phenol (r = -0.896**) and flavonoid (r = -0.872**) content in pod walls. Thus the genotypes having higher content of phenols and flavonoids in their pod walls offered resistance against pod borer complex.

Differential proline metabolism in vegetative and reproductive tissues determine drought tolerance in chickpea

Proline is emerging as a critical component of drought tolerance and fine tuning of its metabolism under stress affects the plants sensitivity and response to stress. Thus the study was carried out to analyse the effect of water deficit on the proline content and principal enzymes involved in its synthesis (Δ1-pyrolline-carboxylate synthetase) and catabolism (proline dehydrogenase) at different developmental stages and in different organs (roots, nodules, leaves, pod wall, and seeds) of two chickpea (Cicer arietinum L.) cultivars differing in drought tolerance (drought tolerant ICC4958 and drought sensitive ILC3279). It was observed that increased Δ1-pyrolline-carboxylate synthetase activity under moderate stress in roots and nodules of ICC4958 caused an increase in proline content during initiation of reproductive development whereas increased proline dehydrogenase activity in nodules and leaves at this period helped to maintain reducing power and energy supply in tissues and proper seed development as seed biomass increased consistently up to maturity. On the other hand, roots and nodules of ILC3279 responded to stress by increasing proline content after the developmental phase of reproductive organs was over (near maturity) which negatively affected the response of pod wall to stress. Concurrent increase in activities of Δ1-pyrolline-carboxylate synthetase and proline dehydrogenase in pod wall of ILC3279 aggravated the oxidative stress and affected seed development as seed biomass initially increased rapidly under stress but was unaffected near maturity.

Expression of chimeric Bt gene, Cry1Aabc in transgenic pigeonpea (cv. Asha) confers resistance to gram pod borer (Helicoverpa armigera Hubner.)

The gram pod borer (Helicoverpa armigera Hubner) is the most serious insect pest of pigeonpea. It is highly susceptible to the insecticidal proteins of Bacillus thuringiensis (Bt). A codon-optimized chimeric Cry1Aabc gene of Bt driven by a constitutive promoter was introduced in pigeonpea (cv. Asha) to confer resistance against the insect. A total of eight transgenic plants could be established with transformation frequency of 0.06%. Two transgenic events were selected for advancement based on high insect mortality, single locus integration, protein expression and fertility status. Quantitative ELISA indicated high protein expression in different plant parts viz., leaves (pre and post flowering), flowers, pod walls and immature seeds. Analysis for the stable integration, expression and insect mortality (detached leaf and pod bioassay) led to identification of lines with high efficacy. These events were further advanced for the identification of a viable event by selfing to create homozygosity. The chimeric Cry1Aabc expressed in pigeonpea is effective against gram pod borer and can be utilized in transgenic variety development programme.

Deciphering Transcriptional Programming during Pod and Seed Development Using RNA-Seq in Pigeonpea (Cajanus cajan)

Seed development is an important event in plant life cycle that has interested humankind since ages, especially in crops of economic importance. Pigeonpea is an important grain legume of the semi-arid tropics, used mainly for its protein rich seeds. In order to understand the transcriptional programming during the pod and seed development, RNA-seq data was generated from embryo sac from the day of anthesis (0 DAA), seed and pod wall (5, 10, 20 and 30 DAA) of pigeonpea variety “Asha” (ICPL 87119) using Illumina HiSeq 2500. About 684 million sequencing reads have been generated from nine samples, which resulted in the identification of 27,441 expressed genes after sequence analysis. These genes have been studied for their differentially expression, co-expression, temporal and spatial gene expression. We have also used the RNA-seq data to identify important seed-specific transcription factors, biological processes and associated pathways during seed development process in pigeonpea. The comprehensive gene expression study from flowering to mature pod development in pigeonpea would be crucial in identifying candidate genes involved in seed traits directly or indirectly related to yield and quality. The dataset will serve as an important resource for gene discovery and deciphering the molecular mechanisms underlying various seed related traits.

GmSALT3, Which Confers Improved Soybean Salt Tolerance in the Field, Increases Leaf Cl- Exclusion Prior to Na+ Exclusion But Does Not Improve Early Vigor under Salinity.

Soil salinity reduces soybean growth and yield. The recently identified GmSALT3 (Glycine max salt Tolerance-associated gene on chromosome 3) has the potential to improve soybean yields in salinized conditions. Here we evaluate the impact of GmSALT3 on soybean performance under saline or non-saline conditions. Three sets of near isogenic lines (NILs), with genetic similarity of 95.6–99.3% between each pair of NIL-T and NIL-S, were generated from a cross between two varieties 85–140 (salt-sensitive, S) and Tiefeng 8 (salt-tolerant, T) by using marker-assisted selection. Each NIL-T; 782-T, 820-T and 860-T, contained a common ~1000 kb fragment on chromosome 3 where GmSALT3 was located. We show that GmSALT3 does not contribute to an improvement in seedling emergence rate or early vigor under salt stress. However, when 12-day-old seedlings were exposed to NaCl stress, the NIL-T lines accumulated significantly less leaf Na+ compared with their corresponding NIL-S, while no significant difference of K+ concentration was observed between NIL-T and NIL-S; the magnitude of Na+ accumulation within each NIL-T set was influenced by the different genetic backgrounds. In addition, NIL-T lines accumulated less Cl- in the leaf and more in the root prior to any difference in Na+; in the field they accumulated less pod wall Cl- than the corresponding NIL-S lines. Under non-saline field conditions, no significant differences were observed for yield related traits within each pair of NIL-T and NIL-S lines, indicating there was no yield penalty for having the GmSALT3 gene. In contrast, under saline field conditions the NIL-T lines had significantly greater plant seed weight and 100-seed weight than the corresponding NIL-S lines, meaning GmSALT3 conferred a yield advantage to soybean plants in salinized fields. Our results indicated that GmSALT3 mediated regulation of both Na+ and Cl- accumulation in soybean, and contributes to improved soybean yield through maintaining a higher seed weight under saline stress.

Selective Phenotyping Traits Related to Multiple Stress and Drought Response in Dry Bean

Abiotic stress tolerance in dry bean (Phaseolus vulgaris L.) is complex. Increased population sizes are contributing to finding QTL conditioning stress response but phenotyping has not kept pace with high throughput genotyping for such studies. Our objectives were to determine effectiveness of 20 most tolerant and 20 most susceptible lines representing phenotypic extremes from a RIL population (‘Buster’ × ‘Roza’ [BR]) to facilitate examination of 19 traits for relevance to stress response and to validate existing QTL conditioning stress response. Using phenotypic extremes tested across multiple trials, eight of the 19 traits were clearly associated with drought stress. Pod wall ratio (PW), plant biomass by weight or a visual rating, and greenness index (NDVI) were most associated with seed yield (SY) under stress followed by phenology traits. The phenotypic extreme lines were also useful for validating QTL previously identified in the whole RIL population conditioning SY, seed weight (SW) and days to flower (DF), harvest maturity (HM), and seed fill (DSF). New QTL were identified for biomass, PW, and NDVI which co‐segregated with major QTL for seed yield SY1.1BR and SY2.1BR. The preliminary finding of NDVI 1.1BR supports aerial imaging in larger genetic populations geared toward QTL analysis of stress response. In summary, phenotypic extremes helped sort through traits relevant to stress response in the Buster × Roza RIL population and verified the effect of two major QTL in response to terminal drought.

Genotypic variation in the accumulation of water-soluble carbohydrate in canola and its potential contribution to seed yield in different environments

Water-soluble carbohydrates (WSC) stored in the stems and pod wall in canola (Brassica napus L.) can be an important source of assimilates contributing to yield. However, genotypic variation in WSC and its contribution to yield have not been investigated. The aims of this work were to quantify genotypic variation of WSC and the extent to which WSC contributes to seed yield. We measured the concentration and content of WSC in a number of hybrid and open pollinated triazine tolerant (TT) and non-TT canola genotypes at flowering, podding and maturity from 2009 to 2011. There were significant repeatable differences in WSC concentration among genotypes (28–108mgg−1 at podding) and WSC content (12–113gm−2 at podding). The major difference in WSC content occurred between the TT and non-TT canola while the difference between hybrid and open-pollinated canola was small. On average, non-TT canola produced higher amount of WSC (68gm−2) than TT canola (47gm−2). Seed yield increased with the increased amount of remobilized WSC in the limited water-stressed conditions (2009 and 2011). Despite the high amount of WSC in drought (2010) year, no significant relationship was found between yield and the remobilized WSC because the higher WSC was offset by yield penalty from delay in flowering in these varieties. The contribution of WSC to yield was higher in drought (10–22%, 2010) year than in the average (3–9%, 2009) and above-average (7–12%, 2011) rainfall year. Genotype and environment interaction was relatively small compared to genotype effect. The difference in the amount of WSC between the herbicide tolerant groups and among genotypes was repeatable and the rankings of genotypes for WSC remained similar across the years. Both the WSC content and the ratio of remobilized WSC to yield had large broad-sense heritability (H=0.68–0.85). The high heritability, the positive relationships between seed yield and WSC under limited water stress conditions, and the high contribution of WSC to yield under drought conditions suggest that WSC could be used as a breeding trait to augment yield in the limited water-stress condition and maintain yield under drought conditions by reducing the effect of water stress on yield.

Physiological Mechanisms behind Differences in Pod Shattering Resistance in Rapeseed (Brassica napus L.) Varieties.

Pod shattering resistance index (SRI) is a key factor affecting the mechanical harvesting of rapeseed. Research on the differences in pod shattering resistance levels of various rapeseed varieties can provide a theoretical basis for varietal breeding and application in mechanical harvesting. The indicators on pod shattering resistance including pod morphology and wall components were evaluated on eight hybrids and open pollinators, respectively, during 2012–2014. The results showed the following: (1) From the current study, SRI varied greatly with variety, and conventional varieties had stronger resistance than hybrid according to the physiological indexes. and (2) Under the experimental conditions, the SRI was linearly related to pod wall weight and the water content in pod walls, and the goodness-of-fit measurements for the regression model of the SRI based on pod wall weight and water content were 0.584** and 0.377*, respectively, reaching the significant level. This illustrated that pod wall weight and the water content in pod walls determined the SRI. (3) Compared with the relative contents of biochemical components in pod walls, the contents of particular biochemical components in pod walls had closer correlations with SRI. Among the biochemical components, the hemicellulose content was the decisive factor for the SRI.