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Water availability is a major limiting factor for wheat (Triticum aestivum L.) production in rain-fed agricultural systems worldwide. Root architecture is important for water and nutrition acquisition for all crops, including wheat. A set of 158 diverse wheat genotypes of Australian (72) and Indian (86) origin were studied for morpho-agronomical traits in field under irrigated and drought stress conditions during 2010-11 and 2011-12.Out of these 31 Indian wheat genotypes comprising 28 hexaploid (Triticum aestivum L.) and 3 tetraploid (T. durum) were characterized for root traits at reproductive stage in polyvinyl chloride (PVC) pipes. Roots of drought tolerant genotypes grew upto137cm (C306) as compared to sensitive one of 63cm with a mean value of 94.8cm. Root architecture traits of four drought tolerant (C306, HW2004, HD2888 and NI5439) and drought sensitive (HD2877, HD2012, HD2851 and MACS2496) genotypes were also observed at 6 and 9 days old seedling stage. The genotypes did not show any significant variation for root traits except for longer coleoptiles and shoot and higher absorptive surface area in drought tolerant genotypes. The visible evaluation of root images using WinRhizo Tron root scanner of drought tolerant genotype HW2004 indicated compact root system with longer depth while drought sensitive genotype HD2877 exhibited higher horizontal root spread and less depth at reproductive stage. Thirty SSR markers were used to study genetic variation which ranged from 0.12 to 0.77 with an average value of 0.57. The genotypes were categorized into three subgroups as highly tolerant, sensitive, moderately sensitive and tolerant as intermediate group based on UPGMA cluster, STRUCTURE and principal coordinate analyses. The genotypic clustering was positively correlated to grouping based on root and morpho-agronomical traits. The genetic variability identified in current study demonstrated these traits can be used to improve drought tolerance and association mapping.

Key messageA novel leaf rust resistance gene, LrM, introgressed from Aegilops markgrafii and mapped on chromosome 2AS using SSR- and SNP-based PCR markers will aid in broadening the genetic base of rust resistance in wheat.A new leaf rust resistance gene tentatively named LrM was introgressed from the diploid non-progenitor species Ae. markgrafii (2n = 2x = 14, genome CC) into common wheat using the nulli-5B mechanism. The introgression line ER9-700 showed a high degree of resistance against a wide spectrum of Puccinia triticina pathotypes. Genetic analysis was performed using the F1, F2, F2:3 and BC1F1 generations derived from the cross ER9-700/Agra Local. The results showed a single dominant gene for leaf rust resistance. The resistance gene LrM was mapped on chromosome arm 2AS using SSR- and SNP-based PCR markers. Preliminary mapping with SSR markers in the F2:3 population from the cross ER9-700/Agra Local identified two SSR markers flanking the LrM. SNPs were identified in the genomic region flanked by SSR markers, and SNP-based PCR markers were developed to construct the final map. Three SNP-based PCR markers co-segregated and mapped closest to the resistance gene at a distance of 2 cM. The gene LrM was distinguished from all the other genes designated and mapped on chromosome arm 2AS by molecular markers and rust reaction. All five markers used in the mapping amplified identical alleles in the donor Ae. markgrafii accession and introgression line ER9-700. The chromosomal location and rust reaction suggest that LrM is a novel leaf rust resistance gene that may be useful in broadening the genetic base of leaf rust resistance in wheat.

The mode of inheritance of wheat leaf rust resistance gene Lr45 was studied at seedling stage under greenhouse conditions against leaf rust race 77-5 in two F₂populations derived from the crosses between Thatcher (Tc)+Lr45 and two susceptible cultivars Agra Local and NI5439. The genetic analysis in F₂:₃progeny validated the F₂results which unambiguously showed segregation for a single dominant gene. Genetic analysis in F₂and BC₁F₁generations against five other leaf rust races confirmed the single dominant gene inheritance of Lr45. Mapping was carried out with 92 microsatellite markers specific to chromosome 2A on the F₂population of the cross Agra Local × Tc+Lr45. Out of seven markers linked to the gene, four (gwm372, gwm275, gpw3167 and gwm122) were co-dominant and the other three (cfd168, cfd6 and gwm249) showed dominance, amplifying the allele only in the susceptible parent. The genetic map of 13.1 cM was constructed based on the results in 140 homozygous resistant and homozygous susceptible plants. cfd168 was the closest marker linked to Lr45, followed by gwm372. These markers were validated on the NI5439 × Tc+Lr45 F₂population, 12 different backcross lines carrying Lr45 and near-isogenic lines, mostly in Tc background isogenic for 46 different Lr genes belonging to both native and alien species. The marker gwm122 was found to be monomorphic. The closest co-dominant marker gwm372 showed reduced polymorphism. Two sequence-based primer pairs, G372 ₉₄ and G372 ₁₈₅ , were designed and validated. Hence, the markers G372 ₉₄ and G372 ₁₈₅ closely linked to the gene can serve as robust co-dominant markers for utilization of Lr45 in wheat improvement.

Due to extensive root system, connected rhizome bamboos are considered suitable for improving soil properties within a short period, though most of the claims are anecdotal and need to be supported with quantified data. The study evaluates seven bamboo species viz., Bambusa balcooa, Bambusa bambos, Bambusa vulgaris, Bambusa nutans, Dendrocalamus hamiltonii, Dendrocalamus stocksii and Dendrocalamus strictus for their rooting pattern and impact on soil health properties. Coarse and fine root intensity was maximum in B. vulgaris . Coarse root biomass ranged from 0.6 kg m −3 in B. nutans to 2.0 kg m −3 in B. vulgaris and B. bambos . Fine root biomass ranged from 1.1 kg m −3 in B. nutans to 4.5 kg m −3 in D. hamiltonii . Contribution of fine roots in terms of intensity and biomass was much higher than coarse roots. Fine root biomass showed declining trend with increase in soil depth in all the species. During sixth year, the litter fall ranged from 8.1 Mg ha −1 in D. stocksii to 12.4 Mg ha −1 in D. hamiltonii . Among soil physical properties significant improvement were recorded in hydraulic conductivity, water stable aggregates and mean weight diameter. Soil pH, organic carbon and available phosphorus under different species did not reveal any significant changes, while significant reduction was observed in total nitrogen and potassium. Significant positive correlation was observed between WSA and iron content. Soil microbial population and enzyme activities were higher in control plot. Considering root distribution, biomass, soil hydraulic conductivity and water stable aggregates, B. bambos , B. vulgaris and D. hamiltonii are recommended for rehabilitation of degraded lands prone to soil erosion.

The rapid growth rate, high biomass production, and annual harvesting make bamboo a suitable species for commercial production. Allometric equations for many broadleaf and conifer tree species are available. However, knowledge of biomass production and allometric equations of bamboos is limited. This study aims to develop species- specific allometric models for predicting biomass and synthetic height values as a proxy variable for seven bamboo species in Himalayan foothills. Two power form-based allometric models were used to predict aboveground and culm biomass using diameter at breast height (D) alone and D combined with culm height (H) as an independent variable. This study also extended to establishing an H–D allometric model that can be used to generate synthetic H values as a proxy to missing H. In the seven bamboo species studied, among three major biomass components (culm, branch and foliage), culm is the most important component with the highest share (69.56–78.71%). The distribution of percentage (%) share of culm, branch and foliage to above-ground fresh weight varies significantly between different bamboo species. D. hamiltonii has the highest productivity for above-ground biomass components. Ratio of dry to fresh weight of seven bamboo species was estimated for culm, branch, foliage and above-ground biomass to convert fresh weight to dry weight.

Grewia optiva Drummond is one of important agroforestry tree species grown by the farmers in the lower and mid-hills of western Himalaya. Different models viz., monomolicular, logistic, gompetz, allometric, rechards, chapman and linear were fitted to the relationship between total biomass and diameter at breast height (DBH) as independent variable. The adjusted R² values were more than 0.924 for all the seven models implying that all models are apparently equally efficient. Out of the six non-linear models, allometric model (Y = a × DBH ᵇ ) fulfils the validation criterion to the best possible extent and is thus considered as best performing. Biomass in different tree components was fitted to allometric models using DBH as explanatory variable, the adjusted R² for fitted functions varied from 0.872 to 0.965 for different biomass components. The t values for all the components were found non-significant (p > 0.05), thereby indicating that model is valid. Using the developed model, the estimated total biomass varied from 6.62 Mg ha⁻¹ in 4 year to 46.64 Mg ha⁻¹ in 23 year old plantation. MAI in biomass varied from 1.66–2.05 Mg ha⁻¹ yr⁻¹. The total biomass carbon stocks varied from 1.99 Mg ha⁻¹ in 4 year to 15.27 Mg ha⁻¹ in 23 year old plantation. Rate of carbon sequestration varied from 0.63–0.81 Mg ha⁻¹ yr⁻¹. Carbon storage in the soil up to 30 cm soil depth varied from 25.4 to 33.6 Mg ha⁻¹.

One hundred and four released varieties of bread wheat ( Triticum aestivum L ssp. aestivum ) in India were crossed to two T. aestivum L ssp. aestivum testers, namely, C306 (Ne 1 Ne 1 ne 2 ne 2 ) and HD2329 ( ne 1 ne 1 Ne 2 Ne 2 ) to determine the frequency and distribution of genes for hybrid necrosis present in them. Sixty-seven varieties (65.4 %) showed the presence of Ne 2 gene and only eight varieties (7.7 %) had Ne 1 gene in their background. Twenty-nine varieties (27.9 %) were non carrier ( ne 1 ne 1 ne 2 ne 2 ) for both the genes. Most of the Ne 1 -carriers are of Indian origin and their pedigree revealed the involvement of landraces and old varieties as parents. Predominance of Ne 2 gene in Indian varieties happened after the introduction of semi-dwarf Mexican wheat varieties, which are mostly Ne 2 carriers and also due to the extensive and continuous use of germplasm from Mexican and European origin in the hybridization programme. Moreover varieties with Ne 2 gene is selected for their linked beneficial traits mainly rust resistance genes. The phenomenon of hybrid necrosis is one among the post zygotic barrier speciation process which acts as a barrier for either intra or inter specific gene flow. The genetic architecture of hybrid necrosis in wheat is simple following the minimal predictions of the Bateson–Dobzhansky–Muller model. Widespread occurrence of dominant genes for hybrid necrosis in Indian varieties is of great concern to wheat breeders as it often interferes in the choice of elite parents and imposes restrictions on the productivity of crosses.

A study on mode of inheritance and mapping of fertility restorer (Rf) gene(s) using simple sequence repeat (SSR) markers was conducted in a cross of male sterile line 2041A having Triticum timopheevi cytoplasm and a restorer line PWR4099 of common wheat (Triticum aestivum L.). The F1 hybrid was completely fertile indicating that fertility restoration is a dominant trait. Based on the pollen fertility and seed set of bagged spikes in F2 generation, the individual plants were classified into fertile and sterile groups. Out of 120 F2 plants, 97 were fertile and 23 sterile (based on pollen fertility) while 98 plants set ≥5 seeds/spike and 22 produced ≤4 or no seed. The observed frequency fits well into Mendelian ratio of 3 fertile: 1 sterile with χ2 value of 2.84 for pollen fertility and 2.17 for seed setting indicating that the fertility restoration is governed by a single dominant gene in PWR4099. The three linked SSR markers, Xwmc503, Xgwm296 and Xwmc112 located on the chromosome 2DS were placed at a distance of 3.3, 5.8 and 6.7 cM, respectively, from the Rf gene. Since, no known Rf gene is located on the chromosome arm 2DS, the Rf gene in PWR4099 is a new gene and proposed as Rf8. The closest SSR marker, Xwmc503, linked to the Rf8 was validated in a set of Rf, maintainer and cytoplasmic male sterile lines. The closely linked SSR marker Xwmc503 may be used in marker-assisted backcross breeding facilitating the transfer of fertility restoration gene Rf8 into elite backgrounds with ease.

A 26 years old agroforestry plantation consisting of four multipurpose tree species (MPTs) ( Michelia oblonga Wall, Parkia roxburghii G. Don, Alnus nepalensis D. Don, and Pinus kesiya Royle ex-Gordon) maintained at ICAR Research Complex, Umiam, Meghalaya, India were compared with a control plot (without tree plantation) for soil fertility status and CO 2 efflux. The presence of trees improved all the physico-chemical and microbial biomass parameters studied in this experiment. Relative to control, soils under MPTs showed significant increases of 17 % soil organic carbon, 26 % available nitrogen (AN), 28 % phosphorus (AP), 50 % potassium (AK), 65 % mean weight diameter (MWD) of aggregates, 21 % moisture and 34 % soil microbial biomass carbon (MBC) while reducing the mean bulk density (7 %). However, these parameters significantly differed among the tree species i.e., soils under A. nepalensis and M. oblonga had higher values of these attributes except bulk density, than under other species. Irrespective of treatments, the values of all these attributes were higher in surface soils while bulk density was highest in subsurface (60–75 cm). Cumulative CO 2 efflux under MPTs was significantly higher (15 %) and ranged from 1.71 g 100 g −1 ( M. oblonga ) to 2.01 g 100 g −1 ( A. nepalensis ) compared to control at 150 days of incubation. In all the treatments, increment in temperature increased the oxidation of soil organic matter, thereby increased the cumulative CO 2 efflux from soils. Of the tree species, with increment in temperature, A. nepalensis recorded more CO 2 efflux (2.50 g 100 g −1 ) than other MPTs but the per cent increase was more in control plot. P. kesiya and A. nepalensis recorded highest activation energy (59.1 and 39 kJ mol −1 , respectively). Net organic carbon sequestered in soil was highest under A. nepalensis (25.7 g kg −1 ) followed by M. oblonga (19.3 g kg −1 ), whereas control showed the lowest values. Amount of net carbon stored in the soil had significant and positive correlation with MBC ( r  = 0.706**), MWD ( r  = 0.636*), and AN ( r  = 0.825**).

Agroforestry offers a huge potential for carbon sequestration, contributing to climate change mitigation and carbon trading. This study focuses on Bauhinia variegata and Celtis australis , two important agroforestry tree species in the Western Himalayas aiming to develop allometric models and biomass prediction ratios using empirical data collected through selective sampling and minimally destructive methods. Biomass components were categorized and weighed, and allometric equations were developed using diameter at breast height and height as independent variables. Model stability was validated using cross-validation techniques, and their predictive accuracy was assessed. Models, particularly based on diameter, has significant predictive ability for predicting the biomass components for both the species. B. variegata demonstrated a higher capacity for CO 2 absorption and carbon credit generation. The biomass expansion factor and root-to-shoot ratio for C. australis and B. variegata was estimated to be 1.39 and 1.40; and 0.24 and 0.17, respectively. The annual biomass of B. variegata and C. australis was 5.97 and 4.67 Mg ha −1  yr −1 , respectively. The total carbon stock for both species varied from 23.80 to 30.47 Mg C ha −1 . In B. variegata and C. australis , carbon sequestration was 105.93 and 82.11 Mg ha −1 , respectively, and net oxygen release ranged from 59.72 to 77.04 Mg ha −1 . The carbon sequestration by B. variegata translates into generating US$ 2119 in total carbon credits, with an annual credit of US$ 193, while C. australis yields US$ 1642 in total credits and US$ 149 annually. These findings highlight the utility of B. variegata and C. australis for carbon sequestration and provide valuable allometric equations for carbon credit estimation. The study emphasizes the importance of agroforestry in meeting India’s Nationally Determined Contributions and addressing climate policy goals.