Agrobacterium-mediated transformation is one of the most commonly used genetic transformation method that involves transfer of foreign genes into target plants. Agroinfiltration, an Agrobacterium-based transient approach and the breakthrough discovery of CRISPR/Cas9 holds trending stature to perform targeted and efficient genome editing (GE). The predominant feature of agroinfiltration is the abolishment of Transfer-DNA (T-DNA) integration event to ensure fewer biosafety and regulatory issues besides showcasing the capability to perform transcription and translation efficiently, hence providing a large picture through pilot-scale experiment via transient approach. The direct delivery of recombinant agrobacteria through this approach carrying CRISPR/Cas cassette to knockout the expression of the target gene in the intercellular tissue spaces by physical or vacuum infiltration can simplify the targeted site modification. This review aims to provide information on Agrobacterium-mediated transformation and implementation of agroinfiltration with GE to widen the horizon of targeted genome editing before a stable genome editing approach. This will ease the screening of numerous functions of genes in different plant species with wider applicability in future.

Cucumber (Cucumis sativus L.), a major horticultural crop, in the family Cucurbitaceae is grown and consumed globally. Parthenocarpy is an ideal trait for many fruit and vegetables which produces seedless fruit desired by consumers. The seedlessness occurs when fruit develops without fertilization which can be either natural or induced. So far, a limited number of genes regulating parthenocarpic fruit set have been reported in several fruit or vegetable crops, most of which are involved in hormone biosynthesis or signalling. Although parthenocarpic cucumber has been widely used in commercial production for a long time; its genetic basis is not well understood. In this study, we retrieved thirty five parthenocarpy fruit-set related genes (PRGs) from bibliomic data in various plants. Thirty-five PRG homologs were identified in the cucumber genome via homology-based search. An in silico analysis was performed on phylogenetic tree, exon–intron structure, cis-regulatory elements in the promoter region, and conserved domains of their deduced proteins, which provided insights into the genetic make-up of parthenocarpy-related genes in cucumber. Simple sequence repeat (SSR) sequences were mined in these PRGs, and 31 SSR markers were designed. SSR genotyping identified three SSRs in two polymorphic genes. Quantitative real-time PCR of selected genes was conducted in five cucumber lines with varying degrees of parthenocarpic fruit set capacities, which revealed possible association of their expression with parthenocarpy. The results revealed that homologs CsWD40 and CsPIN-4 could be considered potential genes for determination of parthenocarpy as these genes showed parental polymorphism and differential gene expression in case of parthenocarpic and non-parthenocarpic parents.

Citrus is the prime fruit crop cultivated worldwide, and well known for nutritional, organoleptic and nutraceutical related properties. Citrus fruits are rich source of several secondary metabolites (SM), like flavonoids, ascorbic acid, polyphenols, carotenoids, terpenoids, and limonoids. Citrus have evolved a multitude of defense mechanisms to enhance their resilience against biotic and abiotic stresses, with SM playing a critically significant role in plant survival, defence, adaptability, and reproduction. Among all biotic stresses, Huanglongbing (HLB, citrus greening) is the major constraint to limits citrus production. HLB is a destructive disease caused by Candidatus Liberibacter spp. HLB has been found in nearly all cultivated varieties which causes the losses by affecting fruit development, quality, tree vigor, and production. This review gives brief highlights on these compounds and discussed their function in citrus defence mechanism, role in fruit maturation, metabolic responses against Huanglongbing (HLB), and hormone signalling pathways. Majority of the amino acids, flavanone, terpenes, flavone, flavonoids, aldehyde, volatile compounds, and monoterpenes in HLB-tolerant cultivars were much higher than susceptible. Various metabolic studies indicated that specific metabolites play a crucial role in limiting the spread and multiplication of the pathogens. Additionally, these metabolic signatures have the potential to be developed as markers for tolerance against HLB. Advanced tools like CRISPR/Cas9, metabolomics, and synthetic biology should be employed to validate the candidate genes involved in enhancing the production of compounds associated with HLB tolerance. The identified genes or SM could serve as valuable targets for citrus breeding, providing long-term solutions to combat HLB disease.

During shoot apex development, the plants undergo a very complex transition phase of flowering for successful reproduction, seed/cone setting and fruit development. The conversion of vegetative shoot meristems to floral meristems depends upon numerous endogenous, exogenous factors and flowering genes for the development of floral parts. The perennial crops suffer from the limitation of the innate ability to keep some meristems in the vegetative state for the polycarpic growth habit leading to the long juvenile phase. Conventional breeding approaches viz. selection of early flowering parental lines, flower thinning and grafting are time-consuming requiring more time for the release of a new cultivar which is undesirable for rapid crop improvement. The best way to accelerate the perennial plant breeding improvement programs and to reduce the long juvenile phase is the induction of early flowering through the utilization of biotechnological approaches. The ability to allow the transmission of an early flowering gene to the progeny in a Mendelian fashion is the major advantage of biotechnological interventions. The introgression of early flowering traits from non-commercial germplasm or sexually compatible species to perennial species through the biotechnological aspects will act as a boon for crop improvement in future studies. The present review gives an overview of various flowering genes in perennial crops accompanying the implementation of biotechnological approaches including overexpression studies, RNA interference, Virus-induced flowering and CRISPR-Cas approaches that will help in reducing the period for induction of flowering in perennial crops.