Symbiotic effectiveness of acid-tolerant Bradyrhizobium strains with soybean in low pH soil

Eight acid tolerant strains of Bradyrhizobium isolated from soybean plants grown on acid soils in Madhya Pradesh, India, were examined for their ability to survive in soil and YEMB at low pH levels. All the tested isolates survived in acidic (pH 4 -6) conditions and their survival capacity was higher in soilthan in nutrient medium at same levels of low pH. Variation among different strains showed that there is potential to improve strain performance under stress conditions. Further, symbiotic effectiveness of these strains was determined under the polyhouse conditions in sterilized soil (pH 4.5). Highest and lowest symbiotic characters, dry matter production and nitrogen improvement per plant were observed in PSR001 and NSR008 inoculated plants, respectively. All the examined isolates showed considerablevariability in their symbiotic performance. The strain found to be more tolerant to stress were more effective N2 fixers in symbiosis with soybean in acid-soil condition

Low cost high throughput image based root phenotyping pipeline for evaluation of sugarcane root system architecture under drought stress

Root System Architecture (RSA) plays an important role in the agronomic performance of a crop. Incorporation of these root traits in breeding program is hampered by the complexity in accessing the roots and its phenotyping. Lack of high throughput root phenotyping platforms for sugarcane is one of the major constraints in sugarcane root studies. In the present study an attempt was made to develop high throughput sugarcane root phenotyping pipeline comprising of a low cost plant cultivation platform and customized root image acquisition platform and image analyses using already available automated software. PVC tube system of specified dimension were used for plant growth and customized optical correction tank were used for imaging RSA. The acquired root images were fed into automated software GIAroots and about twenty quantitative root phenotype data were extracted and analysed. The working of the whole pipeline from plant growth to image analyses is demonstrated through comparative root phenotyping under drought using five genotypes of sugarcane wild relative Erianthus arundinaceus and three commercial sugarcane varieties.The relationships between the different root variables and genotypes in PCA biplots indicated high correlation among the different root traits. The study shows the low cost high throughput image based root phenotyping pipeline can be used to extract quantifiable root traits and analysed within a short span of time

Prospecting in Western Ghats of Karnataka for indigenous Bacillus thuringiensis isolates harbouring novel crystal toxin genes for sugarcane pest management

Prospecting for potential novel Bacillus thuringiensis with new holotype crystal toxins was carried out in the Western ghats hill range of Karnataka state, India. From the soil samples collected three Bt isolates SBIKWG 12, SBIKWG 24 and SBIKWG 70 were isolated. Of these while the two isolates, namely SBIKWG 12 and SBIKWG 24 produced bipyramidal crystal toxins, the third isolate produced spherical crystal. PCR screening of the isolates revealed the presence of lepidopteran and coleopteran active cry genes. Partial sequences obtained from these isolates revealed the presence of multiple crystal toxin genes. BlastX analysis of the partial gene sequences indicated the potential for the occurrence of new holotype crystal toxin genes in SBIKWG 24 and SBIKWG 70

Studies on association of coefficient of coancestry with progeny performance in sugarcane

The utilization of superior parental lines and identification of superior families enhance the genetic gain in sugarcane. To identify the superior parental lines and superior progenies, 1889 progenies derived from twenty crosses involving genetically diverse historical parents were evaluated for juice quality and yield attributing traits.The historical parental lines were selected based on coefficient of coancestry from the tropical and subtropical parents maintained at National Hybridization Garden. Based on progeny performance, families of Co 99006 × CoSe 92423 and Co 86032 × 85R186 were found superior for number of millable canes, , Co 86032 × 85R186 and Co 8371 × CoT 8201 for cane thickness and CoSe 95422 × Co 775 and Co 8371 × CoV 92102 for sucrose content. Parental lines such as Co 86002, Co 99006 and CoLk 98184, Co 775, 85R186 and BO 130 were identified for HR Brix; Co 419 and Co 89010, CoS 510, CoV 92102 and CoSe 92423 for cane thickness; and CoLk 94184, BO 91 and BO 32 for number of millable canes. The estimates of coefficient of coancestry was negatively correlated with HR Brix and cane thickness suggesting that parental cross combination with lesser value of coefficient of coancestry or inbreeding coefficient resulted in produce the heterotic progenies. This study based on the historic parental lines selected based on the coefficient of coancestry and inference limited to only to this experimental material. The evaluation of families derived from the population parental cross combination and parental lines in replication family block design permits the estimation of BLUP based breeding values and helpful in selection of superior parental lines and superior progenies

Variability and molecular diversity of wild sugarcane germplasm collected from low temperature regions Lohit and Changlang of Arunachal Pradesh

159-168Saccharum spontaneum L. is a perennial grass representing the most genetically diversified species in Saccharum genus. It has the potential to withstand severe biotic/abiotic stresses and frequently used as donor of stress tolerant genes in sugarcane improvement program through gene introgression. In this study, the phenotypic variation and molecular diversity of forty nine S. spontaneum accessions collected from Lohit and Changlang regions of Arunachal Pradesh, North Eastern India were investigated for morphometric traits and polymorphic STMS marker. The phenotypic coefficient of variation showed ample variability for the traits viz., plant height (27.19%), stalk diameter (28.21%), single cane weight (48.97%), internode number (22.60%) and internode length (29.15%). Further, twenty nine sequence-tagged microsatellite site (STMS) markers generated 495 bands with an average of 14.06 polymorphic bands. The accessions specific bands in respect to specific marker combinations were identified. The Jaccard’s similarity coefficients among these accessions ranged from 0.42 to 0.78 with an average of 0.58 and clustering using unweighted pair group method of arithmetic-average (UPGMA) showed two major clusters with subclusters. Similarly polulation structure analysis based Bayesian approach grouped the individuals into two subpopulations, with alpha value of 0.112. The study shows that S. spontaneum accessions collected from Arunachal Pradesh is highly diverse, most of them will be harbouring the genes for cold tolerance and biomass. The set of markers which produced specific bands for the specific accessions identified in the study will help in identification of the particular accessions. The accessions studied are potential source for cold tolerance and high biomass, the results obtained in the present study will definitely help in planning and utilising them in sugarcane improvement programme

Whole genome analysis and functional characterization of a novel Bacillus thuringiensis (Bt 62) isolate against sugarcane white grub Holotrichia serrata (F)

In this study, we report the whole genome assembly of Bt 62, a novel isolate harbouring cry8 holotype gene identified by us earlier. Sequencing was carried out using a combination of Illumina NextSeq 500 and Oxford Nanopore sequencing Technologies (ONT). The final assembled genome was 6.13 Mb comprising a circular chromosome and four plasmids. The bioassay studies against Holotrichia serrata (F.) (Coleoptera: Scarabaeidae), a polyphagous pest infesting sugarcane and other crops, indicated significant toxicity to first instar grubs over untreated larvae achieving a highest mean mortality of 91.11% for various doses tested. In vitro proteolytic assay and histopathological studies of the midgut of infected white grubs revealed proteolytic processing of the protoxin and extensive degeneration of larval midgut epithelial cells. The results demonstrate that this novel isolate could be used as a biopesticide or its crystal toxin genes could be expressed in sugarcane and other crops for resistance against H. serrata

Phage typing of indigenous soybean-rhizobia and relationship of a phage group strains for their asymbiotic and symbiotic nitrogen fixation

1006-1011A total of 354 indigenous bradyrhizobia were isolated from soybean nodules collected from five major crop grown regions. Host-specific 12 phages, each active on particular strains were selected. Factors, which influence the interaction between the host and phage, were examined. Four different types of plaques were detected. Nearly 17% of isolates were found resistant to all phages. Phage sensitivity patterns revealed a total of 32 distinct phage genotype groups. Different set of phage combinations expressed variation in specificity for parasitizing against particular group of rhizobia. Distributions of isolates in each phage types differed markedly between regions. Interestingly, nine strains belonging to phage group 16 exhibited high ex planta nitrogenase activity in culture. However, no correlation could be established between high ex planta nitrogenase activity and their symbiotic effectiveness with soybean cultivars. Soybean cv. JS335 showed relatively superior performance than Bragg and Lee with indigenous bradyrhizobial strains. Phage typing revealed the existence of large genetic diversity among native rhizobia and selection of the superior bradyrhizobial strains can also be possible for a given soil-climate-cultivar complex

Regulation of urease in <i style="">Bradyrhizobium</i> colonizing green gram (<i style="">Vigna radiata</i> (L.) Wilczek)

846-851In the present study attempts have been made to characterize urease expression in slow growing Bradyrhizobium strains TAL442 and MO5 which are endosymbionts of green gram (Vigna radiata (L.)Wilczek). It was found that urease activity in vegetative cells of both the strains was inducible unlike their fast growing counterparts. Mode of regulation in TAL442 was governed by presence of ammonia. Urease expression was also detectable in bacteroids of both the strains which was not influenced by presence of external nickel chloride in high concentration, a situation detrimental to the vegetative cells

Analysis of genetic diversity in high biomass producing sugarcane hybrids (<i>Saccharum</i> spp. complex) using RAPD and STMS markers

214-220RAPD and STMS primers (15 of each) were employed to reveal genetic diversity among 23 high biomass producing sugarcane hybrids (Saccharum spp. complex). These high biomass hybrids were derived from Saccharum gene pool that consist of commercial hybrids (Co canes), genetic stocks with special characters, interspecific and intergeneric hybrids, and multi species hybrids. RAPD primers generated 221 amplicons, of which 162 amplicons (~73.3%) were polymorphic and 3 amplicons were specific to genotype. STMS polymorphic primer pairs generated 214 amplicons with an average of 11.9 polymorphic amplicons per primer pair. Six hybrids were identified by 12 unique STMS markers. Polymorphic information content (PIC) varied from 0.121 to 0.631, with an average of 0.447, and 0.195 to 0.663, with an average of 0.526, for RAPD and STMS markers, respectively. The genetic similarity between cultivars varied from 0.542 to 0.844 for RAPD and 0.478 to 0.874 for STMS markers. <span style="color:#131313;mso-fareast-language: EN-IN;mso-bidi-language:TE" lang="EN-GB">The average genetic similarity among the hybrids was 72% for RAPD and 73% for STMS. Dendrogram generated based on RAPD and STMS markers data grouped all the clones into three and six clusters, respectively. This study shows STMS markers as a good tool to discriminate genotypes of high biomass sugarcane hybrids with unique DNA fingerprints. </span