Indian Institute of Horticultural Research

Delivery of biomolecules into plant vascular tissues remains a barrier to managing diseases caused by insect vector-borne pathogens and to modifying phenotypes of established perennial crops. Inspired by the vascularized growth of crown galls induced by Agrobacterium tumefaciens, we repurposed the bacterium’s plant growth regulator (PGR) genes to engineer autonomously dividing, transgene-expressing plant cell structures termed symbionts. A plant transformation vector (pSYM) incorporating the IaaM, IaaH, Ipt and gene5 cassette from A. tumefaciens strain C58 together with a gene of interest on the same transfer DNA was delivered to stems of herbaceous and woody dicots using disarmed A. tumefaciens strain EHA105. Symbiont morphology, vascular differentiation, transgene expression, molecular mobility and protein secretion were evaluated using microscopy, fluorescent reporters, dye tracing, RNA silencing assays and mass spectrometry-based proteomics. pSym inoculation reproducibly generated symbionts across diverse host plant species that were vascularly integrated into their host plants and transgene expression ranging from heterogeneous niches to more uniform patterns. Small molecules moved between symbionts and host vascular tissues, whereas larger proteins exhibited more restricted mobility. Post-transcriptional gene silencing signals moved freely throughout the symbiont and slightly into adjacent stem tissue. Under tested field and greenhouse conditions in potato and tomato, respectively, gall or symbiont formation had no negative impacts on plant growth or tuber and fruit yield. In vitro, symbiont cultures abundantly secreted recombinant protein into surrounding media. Together, these results establish symbionts as a modular, plant bioengineering platform capable of producing and potentially delivering biomolecules without modifying the host plant genome, providing a foundation for vascular-targeted therapeutics and phenotype modulation in crops.

Salinity stress hinders the production and productivity of sweet potato worldwide. Stringent selection under in vitro salinity conditions would be a nebulous approach to developing stress-tolerant lines. Eight pre-breeding sweet potato genotypes, SP-12, SP-13, SP-23, SP-27, SP-33, SP-42, SP-44, and SP-45, selected from a broad genetic base of 380 germplasms, were evaluated under NaCl-mediated salinity stress conditions using nodal cultures in vitro. Sweet potato nodal cultures were raised in Murashige and Skoog (MS) medium with different levels of salinity (0, 50, and 100 mM). The morphological, physiological, and antioxidative enzyme activities under control conditions and salinity stress were assessed. Shoot and root organogenesis under the NaCl-induced MS medium (100 mM) were consistent in genotype SP-13. The antioxidative enzymes increased significantly [0.1-fold in catalase (CAT) to 2.7-fold in ascorbate peroxidase (APX) and guaiacol peroxidase (GPX)] with increasing salinity stress conditions compared to the control across the genotypes. Genotypes SP-13, SP-12, and SP-42 exhibited a higher stress tolerance index (STI) for antioxidative enzymes (AOEs). Pearson’s correlation coefficient (r) matrix revealed a strong integration among the growth parameters and AOEs. Among the antioxidative enzymes, APX (r = 0.74) and dehydroascorbate reductase (DHAR; r = 0.60) showed strong and positive correlations with glutathione reductase (GR). Polyphenol oxidase (PPO) exhibited a strong negative correlation with shoot parameters, including shoot length (r = −0.74) and shoot number (r = −0.71), indicating its association with shoot retardation. Principal component analysis (PCA) and hierarchical clustering indicated that genotype SP-13, followed by genotypes SP-12 and SP-42, is closely related to higher growth performances and better antioxidative enzyme mechanisms. Overall, SP-13, SP-12, and SP-42 performed well, maintaining plantlet growth and AOE properties. The results encourage the rapid screening of the more extensive pre-breeding populations to streamline breeding strategies and develop salinity-tolerant plants.

Chrysanthemums hold a prominent place in global floriculture, valued as both cut flowers and potted plants. However, their cultivation practices differ significantly across regions. Unlike in the Western world, where chrysanthemums are primarily cultivated in controlled environments for ornamental purposes, in India, they are widely grown in open fields for loose flower production. These flowers are predominantly used in making garlands for various festivals and religious celebrations, reflecting their cultural and economic importance in the Asian subcontinent, particularly in India. This chapter focuses on the cultivation of chrysanthemums in open fields for loose flower production, highlighting the traditional and modern practices that have evolved to meet the demands of garland-making and religious festivities. Furthermore, it delves into the advancements made by Indian research institutes in improving chrysanthemum varieties, addressing challenges, and optimizing cultivation techniques under India’s favorable agroclimatic conditions.

Sitophilus oryzaeis a significant and devastating pest of stored cereal grains such as rice, wheat, barley and maize, causes damage to about 10-80 % under prolonged suitable conditions. The research investigation on host preferences of Sitophilus oryzae in unhusked rice, husked rice, barley, wheat, maize, and eight basmati rice varieties. Parameters such as adult emergence (AE), median development period (MDP), growth index (GI), susceptibility index (SI), grain weight loss (%), and grain damage (%) were evaluated. Experiment revealed that the rate of adult emergence was higher in unhusked rice signifying the suitability of the host over maize followed by barley, wheat, and husked rice. Among all basmati rice varieties tested PB-1509 (SI=4.81) showed moderate resistance compared to other varieties. Positive significant correlations were observed among SI and adult emergence (r = 0.967), growth index (r = 0.968), grain weight loss (r = 0.945), and grain damage (r=0.841) but it showed a negative significant correlation with median developmental time (r = − 0.696) indicating that resistance mechanisms can prolong developmental periods, reduce pest generations, and limit damage. These findings emphasize the importance of incorporating resistance traits into breeding programs to enhance storage stability and minimize post-harvest losses in Basmati rice-growing regions.

Guava, an important nutritionally rich fruit crop, exhibits a wide range of variations for peel and pulp colour. The present investigation was carried out during 2022-24 at ICAR-Indian Institute of Horticultural Research (IIHR), Bengaluru, in intervarietal progenies of guava derived from Purple Local × Arka Poorna to know the extent of genetic variability present in various fruit traits and the inheritance of peel and pulp colour based on intervarietal progenies that fruited consistently over two seasons. The result revealed high to low Genotypic Coefficient of Variance (GCV) and Phenotypic Coefficient of Variance (PCV) for the measured traits. The highest PCV and GCV were exhibited for fruit weight (FW) (37.44 % and 21.56 %), number of seeds/100 g of fruit (NS) (42.69 % and 25.58 %) and seed weight/100 g of fruit (SW) (26.08 % and 37.53 %). The high heritability value with high genetic advance was recorded for all the peel and pulp colour traits viz. Peel L* (0.83 % and 50.55 %), Peel a* (0.73 % and 100.77 %), Peel hº (0.89 % and 68.36 %) and Pulp L* (0.67 % and 26.79 %), Pulp a* (0.79 % and 84.54 %), Pulp b* (0.63 % and 44.30 %), Pulp C* (0.67 % and 41.32 %) and Pulp hº (0.80 % and 88.29 %). Whereas, the moderate heritability with high genetic advance was recorded for FW (0.33 % and 25.56 %), diameter of calyx cavity (DCC) (0.56 % and 23.19 %), NS (0.36 % and 31.57 %) and SW (0.48 % and 37.34 %). Further, the segregation analysis for peel and pulp colour in intervarietal progenies of guava demonstrated that there is an epistatic interaction between genes and two genes governing the colour characters and the peel colour was inherited with a segregation ratio of 9:7, indicated there is a complimentary gene action whereas, the pulp colour was inherited with 9:3:4 ratio indicated that there is a supplementary gene action. Thus, based on the high heritability with high genetic advance, it can be inferred that fruit peel and pulp colour, along with the fruit weight, could form a selection criterion in the guava improvement program.

The soybean–wheat rotation system forms a crucial component of Central India’s rainfed agriculture. Although historically productive and profitable, the system’s sustainability is increasingly threatened by suboptimal nutrient management, and soil degradation under changing climate. This three-year study, conducted on small and semi-medium farms in Central India using a Participatory Technology Development (PTD) approach, aimed to evaluate how diverse nutrient management strategies influence yield, profitability, and resource use efficiency. Four nutrient management strategies were tested on small to semi-medium farms: (T1) Integrated Nutrient Management (INM) using chemical fertilizers, farmyard manure and biofertilizers, (T2) Integrated Nutrient Management using chemical fertilizers, enriched compost and biofertilizers, (T3) Soil test crop response-based fertilization, and (T4) Farmers’ conventional practice. Among the four treatments T2 achieved the highest system productivity (6.63 t ha ⁻ ¹ wheat equivalent), net returns (67,680 INR ha ⁻ ¹), and superior yield stability, under climatic variability. T3 offered moderate productivity while promoting balanced nutrient use and lower input costs. Both T2 and T3 enhanced microbial activity and soil health, while T4 led to nutrient depletion, (especially potassium), and low returns. Furthermore, the timing and distribution of monsoon rainfall significantly impacted performance and yield stability of soybean. This study highlights the critical need for integrated, site-specific, and farmer-centric nutrient management strategies to ensure sustainable productivity, profitability, and soil health under changing climatic conditions.

• Organic amendments and microbial inoculants improved dragon fruit cutting survival. • Vermicompost + Bacillus amyloliquefaciens gave 100 % sprouting in red pulp type. • Neem cake + AM fungi/Actino Plus enhanced rooting and enzyme activity in white pulp. Dragon fruit ( Selenicereus spp.) is an emerging high-value crop known for its nutritional benefits, adaptability to marginal environments, and growing global demand. To enhance its sustainable propagation, an experiment was conducted in 2023–2024 to evaluate the effects of soil microbial inoculants and organic amendments. Five organic amendments (T1-T5) and four microbial inoculants (S2-S5) were tested in a factorial completely randomized design on red and white pulp cultivars of dragon fruit. The results revealed significant cultivar-specific responses in shoot and root growth traits. In red pulp type, the highest number of shoots and fresh shoot biomass were observed in T2S5 (Vermicompost + Bacillus amyloliquefaciens strain P-72 ) and T2S3 (Vermicompost + Arka Actino Plus ) respectively . In white pulp type, the highest number of shoots and fresh shoot biomass were recorded in T1S5 (Conventional practice + Bacillus amyloliquefaciens strain P-72 ) and T5S3 (Pongamia cake + Arka Actino Plus) respectively. The highest number of roots were recorded in T4S4 (Neem cake + AM fungi) and T1S5 (Conventional practice + Bacillus amyloliquefaciens strain P-72 ) in red and white pulped type respectively. The treatment T2S4 (Vermicompost + AM fungi) achieved 100 % sprouting in both cultivars. Multivariate analyses (heatmap, PCA, and correlation) confirmed these trends. In the red pulped cultivar treatments T2S5, T2S4, and T2S3 clustered with favourable traits including shoot length, soil microbial populations and enzyme activities. In the white pulped cultivar, neem cake-based treatments (T4S1, T4S2, T4S4) were more effective, particularly for soil microbial and β-glucosidase activities. Correlation analysis highlighted strong positive associations between propagation success and root traits, microbial activity, and enzyme levels in both cultivars, while mortality was negatively correlated with all traits ( r = -0.6 to -1.0). The results underscore the genotype-specific requirement of organic-microbial inputs. These findings offer a sustainable and bio-intensive nursery management strategy to enhance rooting, sprouting success, and early vigor in dragon fruit.