Muhammad Rashid Shaheen

Citrus canker is an economically devastating disease that causes millions of dollars in losses worldwide. The onset and progression of the disease are strongly influenced by favorable environmental conditions. In this study, correlation analysis was employed to determine the relationship between environmental factors and the severity of citrus canker. This approach enabled an assessment of disease epidemic development from its initiation to the appearance of symptoms. Fifteen commercial citrus cultivars were evaluated to determine their level of resistance to canker. Among them, Tangerine, Succari, Jaffa, Pineapple, Mungal Singh, and Kinnow exhibited moderate resistance, whereas Chinese lime, Blood red, Mayer lime, Grapefruit, and Musambi were highly susceptible. The cultivars sweet lime, Feutral’s early, Valencia late, and Malta showed moderate susceptibility to the disease. Environmental variables, including wind speed (km/h), relative humidity (%), and temperature (maximum and minimum), were significantly correlated with disease incidence and severity. Rainfall also exhibited a significant positive correlation with canker development. The disease initiated in July and reached peak intensity during August and October. Understanding the linkage between epidemiological parameters and pathogen behavior provides valuable insights for developing integrated management strategies to minimize fruit losses and ensure sustainable citrus production. Keywords: Xanthomonas axonopodis pv. citri, bacterial disease, pathogen, dieback, leaf miner.

Strigolactones, a new group of phytohormones, are reported to improve plant tolerance to multiple abiotic stresses. A pot experiment was conducted to investigate the impact of synthetic strigolactone (GR24 at 0.001, 0.01 and 0.1 mg L⁻¹) application on ornamental sunflowers (Helianthus annuus cv. Vincent’s Choice) grown under salt stress (150 mM NaCl). Salt stress was applied after 14 days, and SL was applied 25 days seed sowing. The results showed that amongst various GR24 concentrations, 0.01 mg L⁻¹ proved to be superior, as it enhanced the photosynthetic rate (9.29%), transpiration rate (0.76%), stomatal conductance (77.5%), total soluble protein (0.55%) and K⁺ (14.63% in roots; 14.87% in shoots) and Ca²⁺ (12.63% in roots; 11.48% in shoots) contents under control conditions. Similarly, the leaf turgor potential (Ψ_p), osmotic potential (Ψ_s) and free proline, glycinebetaine (GB), superoxide dismutase (SOD), catalase (CAT) and peroxide (POD) contents increased by 58.17, 89.95, 159.04, 101.54, 74.42, 175.68 and 53.62%, respectively, under salt stress conditions. The leaf water potential (Ψ_w) decreased (−0.14%) and the malondialdehyde (MDA) content increased (16.65%) when treated with the 0.001 mg L⁻¹ GR24 level. Meanwhile, hydrogen peroxide (H₂O₂) and Na⁺ concentrations in roots and shoots increased by 62.53%, 74.66% and 38.55% under saline conditions with a GR24 level of 0 mg L⁻¹. Regarding the plant biomass, a GR24 level of 0.01 mg L⁻¹ with salt stress greatly decreased the root (−47.27% and −50.45%) and shoot (−44.79% and −59.42%) fresh and dry weights, respectively, compared to control conditions. These results reveal that exogenously applied GR24 might be an effective way to mitigate the perilous impacts of salt stress in ornamental sunflower production. It is suggested that the use of molecular techniques to study different processes in which GR24 could play a vital part in various commercial floricultural crops is extremely imperative and can open novel horizons for future investigations in this exhilarating field of plant hormones.

Gene silencing is the epigenetic regulation of any gene in order to prevent gene expression at the transcription or translation levels. Among various gene silencing techniques, RNA silencing (RNAi) is notable gene regulation technique that involves sequence-specific targeting and RNA degradation. However, the effectiveness of transgene-induced RNAi in F₁ generation of chrysanthemum has not been studied yet. In the current study, we used RNAi-constructed CmTFL1 (white-flowered) and CmSVP overexpressed (yellow flowered) transgenic plants of previously conducted two studies for our experiment. Cross hybridization was performed between these intergeneric transgenic and non-transgenic plants of the winter-growing chrysanthemum selection “37” (light pink flowered). The transgene CmSVP was confirmed in F₁ hybrids by RT-PCR analysis, whereas hybrids of CmTFL1 parental plants were non-transgenic. Besides this, quantitative real-time PCR (qPCR) was used to explain the molecular mechanism of flower development using reference genes. Intergeneric and interspecific hybrids produced different colored flowers unlike their respective parents. These results suggest that generic traits of CmSVP overexpressed plants can be transferred into F₁ generations when crossed with mutant plants. This study will aid in understanding the breeding phenomenon among intergeneric hybrids of chrysanthemum plants at an in vivo level, and such transgenics will also be more suitable for sustainable flower yield under a low-light production system.

Keeping in view the yield losses instigated by heat stress in several crops, we carried out an experiment to explore the curative effect of exogenous applications of proline on the morpho-physiological, biochemical, and water-related attributes of okra genotypes under high-temperature stress (controlled conditions). Four contrasting genotypes C1, C2, C3, and C4 heat tolerant and heat sensitive genotypes were selected from a diverse panel of okra genotypes (n = 100) to examine plant responses to high-temperature stress and exogenous application of proline. Four-week-old seedlings were subjected to heat stress by gradually increasing the temperature of a growth chamber from 28/22 °C to 45/35 °C (day/night) and sprayed with an optimized proline concentration 2.5 mM. The experiment consisted of a factorial arrangement of treatments in a completely randomized design. The results showed that there were maximum increases in shoot length (32.7%), root length (58.9%), and shoot fresh (85.7%). The quantities of leaves per plant were increased by 52.9%, 123.6%, 82.5%, and 62.2% in C1, C2, C3, and C4 after proline application. On the other hand, only root fresh weight decreased in all genotypes after proline application by 23.1%, 20%, 266.7%, and 280.8% (C1, C2, C3, C4). A lower leaf temperature of 27.72 °C, minimum transpiration of 3.29 mmol m⁻² s⁻¹, maximum photosynthesis of 3.91 μmol m⁻² s⁻¹, and a maximum water use efficiency of 1.20 μmol CO₂ mmol H₂O were recorded in the genotypes C2, C1, C3, and C4, respectively. The highest enzymatic activity of superoxide dismutase, peroxidase and catalase were 14.88, 0.31, and 0.15 U mg-protein in C2, C1, and C3, respectively. Maximum leaf proline, glycinebetaine, total free amino acids, and chlorophyll content 3.46 mg g⁻¹, 4.02 mg g⁻¹, 3.46 mg g⁻¹, and 46.89 (in C2), respectively, due to foliar applications of proline. Another important finding was that heat tolerance in okra was highly linked highly linked to genotypes’ genetic potential, having more water use efficiency, enzymatic activities, and physio-biochemical attributes under the foliar applications of proline.