Pod Wall Research Articles

Artificial selection of mutations in two nearby genes gave rise to shattering resistance in soybean

Resistance to pod shattering is a key domestication-related trait selected for seed production in many crops. Here, we show that the transition from shattering in wild soybeans to shattering resistance in cultivated soybeans resulted from selection of mutations within the coding sequences of two nearby genes - Sh1 and Pdh1. Sh1 encodes a C2H2-like zinc finger transcription factor that promotes shattering by repressing SHAT1-5 expression, thereby reducing the secondary wall thickness of fiber cap cells in the abscission layers of pod sutures, while Pdh1 encodes a dirigent protein that orchestrates asymmetric lignin distribution in inner sclerenchyma, creating torsion in pod walls that facilitates shattering. Integration analyses of quantitative trait locus mapping, genome-wide association studies, and allele distribution in representative soybean germplasm suggest that these two genes are primary modulators underlying this domestication trait. Our study thus provides comprehensive understanding regarding the genetic, molecular, and cellular bases of shattering resistance in soybeans.

QTL mapping for pod quality and yield traits in snap bean (Phaseolus vulgaris L.).

Pod quality and yield traits in snap bean (Phaseolus vulgaris L.) influence consumer preferences, crop adoption by farmers, and the ability of the product to be commercially competitive locally and globally. The objective of the study was to identify the quantitative trait loci (QTL) for pod quality and yield traits in a snap × dry bean recombinant inbred line (RIL) population. A total of 184 F6 RILs derived from a cross between Vanilla (snap bean) and MCM5001 (dry bean) were grown in three field sites in Kenya and one greenhouse environment in Davis, CA, USA. They were genotyped at 5,951 single nucleotide polymorphisms (SNPs), and composite interval mapping was conducted to identify QTL for 16 pod quality and yield traits, including pod wall fiber, pod string, pod size, and harvest metrics. A combined total of 44 QTL were identified in field and greenhouse trials. The QTL for pod quality were identified on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv07, and for pod yield were identified on Pv08. Co-localization of QTL was observed for pod quality and yield traits. Some identified QTL overlapped with previously mapped QTL for pod quality and yield traits, with several others identified as novel. The identified QTL can be used in future marker-assisted selection in snap bean.

Morphological Basis of Resistance in Pigeonpea (Cajanus cajan (L.) Millsp.) against Pod Borer Complex

Field experiment was carried out to determine the morphological basis of resistance in pigeonpea against pod borer complex during kharif 2021-22, 2022-23 and 2023-24 at College of Agriculture, Navsari Agricultural University, Bharuch (Gujarat). Among the twelve pigeonpea genotypes/cultivars screened, BP-17-02 was found highly resistant and BP-16-182, BP-16-228, BP-16-261, ICPL-87119 and BP-16-166 were found resistant whereas, GNP-2 and Vaishali were found highly susceptible against pod borers. Genotypes/cultivars namely, BP-16-178, ICPL 87119, BP-16-182, BP-16-228 and BP-16-183 were found resistant to pod fly. Genotypes/cultivars having short pod length, narrow pod breadth, narrow seed breadth, more seeds/pod, more seed weight, more seed density, thick pod wall thickness and long trichome length recorded lower pod borers population. Pod length had a significant positive correlation with Maruca vitrata, Exelastis atomosa and Melanagromyza obtusa. Significant positive association was found between pod breadth and larval population of Helicoverpa armigera and Maruca vitrata. Significant negative correlation was found between Exelastis atomosa and pod wall thickness.

Low Light at Specific Growth Stage Affects Photoassimilates Transportation, Seed Quality and Yield in Brassica napus L.

ABSTRACTIn many parts of the world, solar radiation has decreased during the past 50 years due to industrialisation‐induced elevations in air aerosols which has negatively impacted crop productivity. Climate change threatens rapeseed (Brassica napus L.) production due to shade stress caused by reduced light radiation. However, studies on how shade affects photosynthetic mechanisms in rapeseed (leaves and pod wall) are not well documented. Understanding the mechanisms of shade on yield formation in rapeseed is important for breeding shade‐tolerant rapeseed varieties and optimising agricultural management practices in low‐light areas. Therefore, this study assesses the impacts of ‘global dimming’ simulated by shading at a specific period on rapeseed's photosynthetic behaviour, yield and seed quality. A two‐factor split‐plot design was arranged with three shading treatments (CK, FS and PS) and two hybrid genotypes (Chuannong and Zhongyouza) of rapeseed. We observed that shading at the flowering stage (FS) significantly inhibited the leaf area index, chlorophyll content, photosynthetic efficiency and enzymatic activities of both genotypes. Besides that, shading at pod development stage (PS) substantially declined the pod photosynthetic characteristics and transportation of carbohydrates towards economic organ (seeds) which directly decreased the yield of rapeseed. We found that PS treatment remarkably declined the oil content of both genotypes. According to the results, the photosynthetic capacity of rapeseed pod wall had a greater impact on yield and seed quality than leaves. Therefore, improving the photosynthetic capacity and material transport efficiency of the pod wall is a potential measure to increase the yield of rapeseed under shade stress. This study provides a new insight into the effects of shade on rapeseed production and provides a valuable reference for rapeseed breeding techniques to develop high‐yielding genotypes by enhancing the photosynthetic efficiency of rapeseed pod wall in low‐light conditions.

Registration of R18‐14147: A high‐protein conventional soybean germplasm line

AbstractR18‐14147 (Reg. no. GP‐528, PI 705143) is a high‐protein conventional soybean [Glycine max (L.) Merr.] germplasm of maturity group Mid‐IV developed and released by the University of Arkansas System – Division of Agriculture Research & Extension in 2023. The germplasm is an F3:4 selection from the cross LG10‐3671‐1 × R09‐430. Plants of R18‐14147 have an indeterminate growth habit with purple flowers, gray pubescence, brown pod wall, and imperfect black hilum. Across 28 environments in Arkansas (2019–2022), R18‐14147 yield averaged 4482 kg ha−1, with broad adaptability and yield stability. Seed of R18‐14147 contains on average 429 g kg−1 and 191 g kg−1 of protein and oil on a dry weight basis, respectively, and seed weight is 15.2 g 100 seeds−1. The average seed protein content of this line is 8%–27% higher than the average protein content of the check cultivars used in various trials to evaluate R18‐14147. Additionally, R18‐14147 has been identified as resistant to stem canker. R18‐14147 presents soybean growers in the mid‐southern United States with a promising germplasm alternative combining high yield potential and elevated seed protein content for alternative crop rotation in herbicide‐tolerant cultivar systems, offering potentially seed‐saving cost benefits and serving as a valuable germplasm for new cultivar development.

A DIRIGENT Gene GmDIR26 Regulates Pod Dehiscence in Soybean.

Pod dehiscence brings much loss for modern agricultural production, and multiple pod dehiscence components have been identified in many plant species. However, the pod dehiscence regulation factors in soybean are limited. In this study, we investigate the function of GmDIR26, a close homologues gene of pod dehiscence genes GmPdh1, PvPdh1, and CaPdh1, in the regulation of pod dehiscence in soybean. The secondary and tertiary structure analysis reveals that GmDIR26 protein has a similar structure with GmPdh1, PvPdh1, and CaPdh1 proteins. Synteny analysis of soybean and chickpea genomes shows that the genomic region surrounding GmDIR26 and CaPdh1 might be evolved from the same ancestor, and these two genes might have similar function. GmDIR26 shows an increased expression pattern during pod development and reaches a peak at beginning seed stage. Meanwhile, GmDIR26 exhibits high expression levels in dorsal suture and pod wall, but low expression pattern in ventral suture. In addition, GmDIR26 shows higher expression levels in pod dehiscence genotype than that in pod indehiscence accessions. Overexpression of GmDIR26 in soybean increases pod dehiscence in transgenic plants, of which the lignin layer in inner sclerenchyma pods is thicker and looser. The expression levels of several pod dehiscence genes are altered. Our study provides important information for further modification of pod dehiscence resistance soybean and characterization of soybean pod dehiscence regulation network.

Evaluation of different Kabuli chickpea genotypes against Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in relation to biotic and abiotic factors.

The chickpea pod borer Helicoverpa armigera (Hübner) is a significant insect pest of chickpea crops, causing substantial global losses. Field experiments were conducted in Central Punjab, Pakistan, to investigate the impact of biotic and abiotic factors on pod borer population dynamics and infestation in nine kabuli chickpea genotypes during two cropping seasons (2020-2021 and 2021-2022). The crops were sown in November in both years, with row-to-row and plant-to-plant distances of 30 and 15 cm, respectively, following a randomized complete block design (RCBD). Results showed a significant difference among the tested genotypes in trichome density, pod wall thickness, and leaf chlorophyll contents. Significantly lower larval population (0.85 and 1.10 larvae per plant) and percent damage (10.65% and 14.25%) were observed in genotype Noor-2019 during 2020-2021 and 2021-2022, respectively. Pod trichome density, pod wall thickness, and chlorophyll content of leaves also showed significant variation among the tested genotypes. Pod trichome density and pod wall thickness correlated negatively with larval infestation, while chlorophyll content in leaves showed a positive correlation. Additionally, the larval population positively correlated with minimum and maximum temperatures, while relative humidity negatively correlated with the larval population. Study results explore natural enemies as potential biological control agents and reduce reliance on chemical pesticides.

Pod-shattering characteristic differences between shattering-resistant and shattering-susceptible common vetch accessions are associated with lignin biosynthesis

The common vetch (Vicia sativa L.) is a self-pollinated annual forage legume that is widely distributed worldwide. It has wide adaptability and high nutritional value and is commonly used as an important protein source for livestock feed. However, pod shattering seriously limits the yield of common vetch. To clarify the mechanism of pod shattering in common vetch, the pod walls of three shattering-resistant (SR) accessions (B65, B135, and B392) and three shattering-susceptible (SS) accessions (L33, L170, and L461) were selected for transcriptome sequencing. A total of 17190 differentially expressed genes (DEGs) were identified in the pod wall of B135 and L461 common vetch at 5, 10, 15, 20, and 25 days after anthesis. KEGG analysis showed that “phenylpropanoid biosynthesis” was the most significantly enriched pathway, and 40 structural genes associated with lignin biosynthesis were identified and differentially expressed in B135 and L461 common vetch. We analysed the DEGs in the pod wall of three SR and three SS accessions at 15 days after anthesis, and most of the DEGs were consistent with the significant enrichment pathways identified in B135 and L461 common vetch. The total lignin content of SR accessions was significantly lower than the SS accessions. The present study lays a foundation for understanding the molecular regulatory mechanism of pod shattering related to lignin biosynthesis in common vetch and provides reference functional genes for breeders to further cultivate shattering-resistant common vetch varieties.

Ontogenetic Changes in the Feeding Behaviour of Helicoverpa armigera Larvae on Pigeonpea (Cajanus cajan) Flowers and Pods.

Despite substantial research examining caterpillar-plant interactions, changes in the feeding behaviour of lepidopteran larvae as they develop are poorly understood. In this study, we investigated ontogenetic changes in the behaviour of Helicoverpa armigera larvae feeding on reproductive structures of pigeonpea (Cajanus cajan). Specifically, we examined the preference for and avoidance of pigeonpea flowers and pods of first, second, third, and fourth instar H. armigera larvae. We also conducted a no-choice assay to compare the ability of third and fourth instar larvae to penetrate pigeonpea pod walls, which act as a physical defence against herbivory. When presented with a choice between pigeonpea pods and flowers, different instars behaved differently. First and second instar larvae largely avoided pigeonpea pods, instead feeding on flowers; third instar larvae initially avoided pods, but by 24 h, did not strongly discriminate between the structures; and fourth instars demonstrated a preference for pods. When initially placed on pods, first instars were slower than other instars to leave these structures, despite pods being suboptimal feeding sites for small caterpillars. We identified a clear instar-specific ability to penetrate through the pod wall to reach the seeds. Most third instar larvae were unable to penetrate the pod wall, whereas most fourth instars succeeded. Third instars suffered a physiological cost (measured by relative growth rate) when boring through the pod wall, which was not observed in fourth instars. Our study further illuminates the insect-plant interactions of the H. armigera-pigeonpea system and provides evidence for the significant changes in feeding behaviour that may occur during lepidopteran larval development.

Panoramic chemical imaging of opium alkaloids in Papaver somniferum by TOF-SIMS

Accurate mapping of opium alkaloids in Papaver somniferum (P. somniferum) is significant for comprehensively elucidating their biosynthetic pathways and metabolic regulations. Here we describe a panoramic chemical imaging strategy based on time-of-flight secondary ion mass spectrometry (TOF-SIMS) that enables a thorough and precise visualization of the spatial differentiation of five opium alkaloids (morphine, codeine, thebaine, papaverine and noscapine) in P. somniferum. Notably, the opium alkaloids exhibited enrichment in the capsule, pistil, receptacle and peduncle. Moreover, a series of cross sections of a capsule were imaged to reveal a three-dimensional horizon of internal distribution of opium alkaloids. Opium alkaloids were observed enriched within the pseudoseptum and the “tube-like” structure of the inner pod wall, witnessing a downward trend toward the stigmatic disk. Finally, in high spatial resolution mode of TOF-SIMS, direct single-cell level chemical mapping of opium alkaloids in the phloem of the vascular bundles of P. somniferum receptacle was achieved for the first time. The introduced imaging strategy can provide multi-dimensional insights into the spatial distribution of opium alkaloids in P. somniferum, and the findings are expected to facilitate shedding light on the biological activities of these pharmacologically valued alkaloids.

Dynamic Expressions of Yellow Stripe-Like (YSL) Genes During Pod Development Shed Light on Associations with Iron Distribution in Phaseolus vulgaris.

The global prevalence of iron deficiency-induced "hidden hunger" highlights a critical health concern, underscoring the pressing need to improve iron nutrition through safe and efficient means, such as increasing iron intake from plant-based foods. Yellow Stripe-Like (YSL) genes play a crucial role in long-distance iron transport between source and sink tissues in plants. Here, we report on the analysis of YSL family genes in the common bean (Phaseolus vulgaris L.), an iron-rich legume crop. We identified 9 YSL genes in the common bean genome using BLAST and HMM methods. Gene duplication analysis revealed that PvYSL7a and PvYSL7b originated through tandem duplication events. Structural analysis noted an absence of conservative motifs in PvYSL3b and PvYSL7a, which led to distinct predicted 3D protein structures. Leveraging publicly available RNA-seq data from developing bean pods, the expression patterns of PvYSL genes alongside pod and seed development were analyzed. Notably, PvYSL7a and PvYSL7b, as well as PvYSL1a and PvYSL1b, exhibited diverged expression patterns in seeds, signifying their functional divergence in this tissue. Moreover, PvYSL3a and PvYSL3b exhibited divergent expression patterns in both pod walls and seeds during pod development, underscoring their distinct roles in facilitating iron transportation between pods and seeds. This study provides valuable insights into the gene regulatory basis of iron accumulation in bean pods and seeds.

Trehalose-6-phosphate synthase 8 increases photosynthesis and seed yield in Brassica napus.

Trehalose-6-phosphate (T6P) functions as a vital proxy for assessing carbohydrate status in plants. While class II T6P synthases (TPS) do not exhibit TPS activity, they are believed to play pivotal regulatory roles in trehalose metabolism. However, their precise functions in carbon metabolism and crop yield have remained largely unknown. Here, BnaC02.TPS8, a class II TPS gene, is shown to be specifically expressed in mature leaves and the developing pod walls of Brassica napus. Overexpression of BnaC02.TPS8 increased photosynthesis and the accumulation of sugars, starch, and biomass compared to wild type. Metabolomic analysis of BnaC02.TPS8 overexpressing lines and CRISPR/Cas9 mutants indicated that BnaC02.TPS8 enhanced the partitioning of photoassimilate into starch and sucrose, as opposed to glycolytic intermediates and organic acids, which might be associated with TPS activity. Furthermore, the overexpression of BnaC02.TPS8 not only increased seed yield but also enhanced seed oil accumulation and improved the oil fatty acid composition in B. napus under both high nitrogen (N) and low N conditions in the field. These results highlight the role of class II TPS in impacting photosynthesis and seed yield of B. napus, and BnaC02.TPS8 emerges as a promising target for improving B. napus seed yield.

Registration of R16‐45 as a flood‐tolerant, high‐yielding soybean germplasm line

AbstractR16‐45 (Reg. no. GP‐526, PI 704118) is a high‐yielding soybean [Glycine max (L.) Merr.] breeding line with flood tolerance at early reproductive stages released as germplasm by the Arkansas Agricultural Experiment Station in 2023. It is an F2 selection from the cross between the flood‐tolerant breeding line R07‐6669 and the high‐yielding Arkansas cultivar ‘UA 5612’. R16‐45 is a conventional (non‐genetically modified) soybean with a relative maturity of 5.6. Plants have determinate growth habit, white flower color, and buff hilum color. It has gray pubescence, tan pod wall at maturity, and yellow cotyledons with a dull yellow seed coat. R16‐45 showed high yield potential and broad adaptability across 17 environments in Arkansas and other southern states, with an average of 4145 kg ha−1 (95.3% of the checks’ mean). Six years of field evaluations for flooding tolerance showed that R16‐45 is consistently tolerant to 8‐to‐10‐day flooding stress at the R1/R2 growth stages (average flood damage score of 3.6, compared with 6.0 from the reference checks). In addition, R16‐45 is resistant to stem canker. Given substantial yield losses associated with flooding stress and stem canker, R16‐45 is a valuable germplasm source for public and private soybean breeding programs attempting to incorporate novel genetic diversity into their breeding pipeline.

Development of Mungbean Genotypes for Shattering Tolerance and Correlation Analysis with Biochemical and Morphological Factors Governing Pre Harvest Sprouting

Background: Most of the mungbean genotypes are prone to shattering. The indeterminate flowering habit of this crop leads to a spread of flowering and pod maturity on a single plant over the entire reproductive phase. Consequently, pods which develop at the earliest flower may shatter prior to 100% pod maturity. Sometimes losses due to pre-harvest sprouting will be as high as 60-70%. High yielding varieties developed/identified in recent years, despite their high yield potential, could not increase/stabilize the yields of this crop due to lack of resistance to pre-harvest sprouting. Therefore, an attempt was essentially made to develop tolerant varieties to pre-harvest sprouting in the current investigation. Methods: The F2 (Healthy and well dried) seeds derived from the crosses DGGV-2 ´ Pant Moong-1 were irradiated with 60 kR gamma rays for the creation of desirable variability. The gamma rays irradiated seeds were sown in during kharif-2017 along with their respective checks to grow the F2M1 generation. Further advanced to F2M2. The individual plants were critically observed at maturity for morphological traits viz., small pod beak length and angle, thick pod wall and hard seededness that determine the tolerance to PHS. The mutant lines were compared with the parental lines viz., shattering tolerant variety Pant Moong-1 as well as susceptible variety DGGV2. The putative mutants selected and tagged in F2M2 and the seeds were harvested separately and forwarded to develop the F2M3 mutant population (1000 plants) in summer-2018. The seeds from F2M3 generation were harvested on individual plant basis and were sown. 806 progenies were sown in augmented design along with the checks in each block during kharif 2019. Thus from the population of 24812 such derived plants, genotypes with small pod beak and angle, thick pod wall, hard seededness and higher epicuticular wax and lignin content were isolated in F2M3 and F2M4. Further a total of 49 advanced breeding lines along with a known shattering susceptible check were studied for the morphometric and biochemical parameters governing the pre harvest sprouting. Result: Lower PHS was recorded in DGGV-79 (0.02%), DGGV-125 (0.02%) and DGGV 195 (0.91%). Higher phenol content was recorded in DGGV-125 (9.43 mg GA eq /g) and DGGV-79 (9.37 mg GA eq /g). Higher lignin content was recorded in DGGV-125 (6.42 mg/g) and DGGV-79 (6.10 mg GA eq /g). Further correlation analysis revealed that negative correlation of PHS was observed for epicuticular wax (r= -0.983), phenol (r= -0.892), lignin content (r= -0.981) and hard seed percentage (r= -0.942). Significant negative correlation was observed between PHS and pod wall thickness (r= -0.570). Pod beak length recorded highly significant positive correlation (r= 0.911) to PHS. Genotypes with inherent tolerance to seed shattering hold a promise to minimize yield losses due to viviparous germination.

Nitrogen supply alleviates seed yield reduction by improving the morphology and carbon metabolism of pod walls in shaded rapeseed.

Shading significantly affects rapeseed yield, while reasonable nitrogen (N) application has efficiency gains. However, the functions and mechanisms of N are not fully established for shaded rapeseed plants. Therefore, we conducted a 2-year field experiment to study the effect of N on pod wall morphology and carbon metabolism of shaded rapeseed. Two varieties, three N rates (120 [N1], 240 [N2], and 360 [N3] kg hm-2 ) and two light intensities (100 and 70% light transmission) from 10 to 35 days after the end of flowering were set as experimental parameters. Shading decreased the pod wall chlorophyll content, ribulose 1,5-bisphosphate carboxylase (Rubisco) activity and glucose content at 25 and 35 days after flowering (DAF). Decreased sucrose synthase (SuSy) and sucrose phosphate synthase activity caused by shading reduced sucrose and fructose content. They are responsible for the decline in the 1000-seed weight and a 22.1-37.6% decline in seed yield. More N under shading promoted pod elongation and pigment content, improved chloroplast ultrastructure, increased Rubisco and SuSy activity at 35 DAF, thus contributing to pod wall photosynthesis and fructose and glucose levels in shaded rapeseed plants. Similar trends were observed in pod number, pod weight, and seed weight, while the greatest increase in seed/wall ratio was observed under N2 for shaded rapeseed plants. The results indicated that N can reduce the yield difference between different light conditions and balance partitioning and conversion of photoassimilates in pod wall, but avoid applying an excessive amount of nitrogen.

Registration of soybean germplasm line R14‐1422 with high yield and moderate resistance to southern root knot nematode

AbstractR14‐1422 (Reg. no. GP‐523, PI 702562) is a mid‐maturity group (MG) V (relative maturity 5.4), determinate growth habit, high‐yielding, conventional soybean [Glycine max (L.) Merr.] germplasm line developed and released in 2021 by the Arkansas Agricultural Experiment Station. R14‐1422 is an F4 selection from the cross between ‘R06‐4433’, a cultivar released by Arkansas, and the Missouri cultivar ‘S05‐11482’. Trial results of over 74 environments in Arkansas and other southern states showed that R14‐1422 is well adapted and provides high‐yielding performance. R14‐1422 is a MG V (5.4), line with determinate growth habit, white flowers, gray pubescence, and a tan pod wall at maturity. Seed of R14‐1422 has yellow cotyledon, yellow seed coat, and buff hilum color. R14‐1422 has high yield potential and moderate resistance to southern root‐knot nematode and is a chloride excluder.

Microscopical Analysis of Autofluorescence as a Complementary and Useful Method to Assess Differences in Anatomy and Structural Distribution Underlying Evolutive Variation in Loss of Seed Dispersal in Common Bean.

The common bean has received attention as a model plant for legume studies, but little information is available about the morphology of its pods and the relation of this morphology to the loss of seed dispersal and/or the pod string, which are key agronomic traits of legume domestication. Dehiscence is related to the pod morphology and anatomy of pod tissues because of the weakening of the dorsal and ventral dehiscence zones and the tensions of the pod walls. These tensions are produced by the differential mechanical properties of lignified and non-lignified tissues and changes in turgor associated with fruit maturation. In this research, we histologically studied the dehiscence zone of the ventral and dorsal sutures of the pod in two contrasting genotypes for the dehiscence and string, by comparing different histochemical methods with autofluorescence. We found that the secondary cell wall modifications of the ventral suture of the pod were clearly different between the dehiscence-susceptible and stringy PHA1037 and the dehiscence-resistant and stringless PHA0595 genotypes. The susceptible genotype had cells of bundle caps arranged in a more easily breakable bowtie knot shape. The resistant genotype had a larger vascular bundle area and larger fibre cap cells (FCCs), and due to their thickness, the external valve margin cells were significantly stronger than those from PHA1037. Our findings suggest that the FCC area, and the cell arrangement in the bundle cap, might be partial structures involved in the pod dehiscence of the common bean. The autofluorescence pattern at the ventral suture allowed us to quickly identify the dehiscent phenotype and gain a better understanding of cell wall tissue modifications that took place along the bean's evolution, which had an impact on crop improvement. We report a simple autofluorescence protocol to reliably identify secondary cell wall organization and its relationship to the dehiscence and string in the common bean.

Morpho-physiological trait variation of pre-harvest sprouting tolerance to simulated rain in mungbean (Vigna radiata)

Preharvest sprouting (PHS) is one of the most important factors for lower productivity in mungbean [Vigna radiata(L.) R. Wilczek]. The morpho-physiological characters, ultra-structural variations in pods and seeds, changes andregulatory water absorption pathway of 30 mungbean genotypes in relation to pre-harvest sprouting behaviour wasstudied during kharif 2017–19 at Seed Research Technology Center, Indian Institute of Rice Research, Rajendranagar, Hyderabad, Telangana. Mungbean genotypes subjected to PHS imposed by simulated rainfall were evaluated. Rainfall simulator generates a rainfall spectrum that was similar to natural rainfall. Genotypes LGG 450 and K 851 with low score (%), while ML 267 and MGG 295 with high score (%) were screened as tolerant and susceptible to PHS. Accordingly, higher seed yield was recorded in LGG 450 (4.94 g/plant) followed by K 851 (4.20 g/plant) while lower seed yield was recorded in ML 267 (0.26 g/plant) followed by MGG 295 (0.79 g/plant). The findings were further corroborated with SEM studies by presence of sparse, wiry, short, twist or shriveled trichomes; thick cuticular pod wall, wide locular gap between seed coat (seed) and pod wall helping for the slow diffusion of moisture from endosperm to embryo. Further, the presence of lea-protein-insulated starch grains of endosperm merits lipophilic nature which might hindered dissipation of water to embryo via endosperm. The SEM studies have established ultrastructural features that determine the resistance to pre-harvest sprouting of mungbean and development of future resistant lines identification.

Earliness and Crop Morphological Traits Modulate Field Pest Infestation in Green Gram.

Breeding has significantly improved drought tolerance in green gram but marked yield losses continue due to damage by insect pests. Important pests of green gram are pod borers, Maruca vitrata (F.), aphids, Aphis gossypii Glover and whiteflies, Trialeurodes vaporariorum (Westwood). Management of these pests has partly been constrained by the limited understanding of crop traits that modulate their infestation. Field experiments were conducted in southeastern Kenya to evaluate a collection of old and new green gram varieties for tolerance to field pests, and to identify traits that confer resistance. The old varieties were KS20 and N26, both released in 1990s whereas the modern counterparts were Biashara, Karembo, and Ndengu-Tosha. Results showed significant differences among the varieties in maturity, leaf area, leaf hair density, leaf moisture content, and pod wall thickness. Earliness significantly reduced pest infestation, whereby KS20 matured early while N26 was late, and the new varieties were intermediate. On average, across the three environments, leaf area (R2 ≥ 0.32) and leaf moisture content (R2 ≥ 0.18) positively correlated with pest infestation while leaf hair density (R2 ≥ 0.30), and pod wall thickness (R2 ≥ 0.54) showed a negative association with pod borer and aphid counts. However, results did not reveal any particular traits that associated with the varieties, which implied that breeding of green gram in Kenya has not selected for tolerance to field pests. Nonetheless, green gram field pest management practices could select for varieties with early maturity, open plant canopy, pubescent leaves, and thicker pod walls.

Induced defense responses in cultivated and wild chickpea genotypes against Helicoverpa armigera infestation.

Five desi (GL 12,021, GL 29,095, GL 29,078, H11 22 and CSJ 515) and three wild (GLW 22, GLW 58 and GLW 187) chickpea cultivars showed induced defense response against Helicoverpa armigera infestation as a result of enhanced activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, glutathione reductase, polyphenol oxidase, phenylalanine ammonia lyase, tyrosine ammonia lyase in leaves, pod walls and seeds. Catalase activity increased in leaves of GL 12,021, H11 22, GL 29,095, CSJ 515, GLW 22, and GL 29,078 after infestation compared to resistant check; catalase and peroxidase activities in GL 29,095 and GL 29,078; ascorbate peroxidase and glutathione reductase activities in leaves of GLW 58. The increased activity of superoxide dismutase in pod wall of H1122; catalase in pod wall of 29,078, GL 29,095 and GL 22; ascorbate peroxidase and glutathione reductase in pod wall of GLW 58; phenylalanine ammonia lyase and tyrosine ammonia lyase in pod wall of GLW 187, H11 22, GL 20,978, GLW 22 and GLW 58 after infestation as compared to resistant check might be responsible for mitigating infestation induced oxidative stress. MDA content decreased in leaves, pod wall and seeds of GLW 187 and GL 12,021 after infestation. Lower percent pod damage (9.58-12.44%) in GL 12,021, GLW 187, GL 29,095, H11 22, GL 29,078, GLW 22 and GLW 58 as compared to resistant (16.18%) and susceptible (21.50) checks might be attributed to differential induced defense mechanism in them. The identified desi and wild genotypes might be used in breeding program to develop cultivars with improved resistance to herbivore.