Rice, generally classified as a typical glycophyte, often faces abiotic stresses such as excessive drought, high salinity, prolonged submergence, cold, and temperature, which significantly affects growth, development, and ultimately, grain yield. Among these negative impacts of abiotic factors in rice production, salinity stress is a major constraint, followed by drought. There is considerable research on the use of marker-assisted selection (MAS), genome editing techniques, and transgenic studies that have profoundly improved the present-day rice breeders’ toolboxes for developing salt-tolerant varieties. Salinity stresses significantly affect rice plants during seedling and reproductive stages. Hence, greater understanding and manipulation of genetic architecture in developing salt-tolerant rice varieties will significantly impact sustainable rice production. Rice plants’ susceptibility or tolerance to high salinity has been reported to be the result of coordinated actions of multiple stress-responsive quantitative trait loci (QTLs)/genes. This paper reviews recent literature, updating the effects of salinity stress on rice plants and germplasm collections and screening for salinity tolerance by different breeding techniques. Mapping and identification of QTLs salt tolerance genes are illuminated. The present review updates recent breeding for improvement in rice tolerance to salinity stress and how state-of-the-art tools such as MAS or genetic engineering and genome editing techniques, including mutagenesis and conventional breeding techniques, can assist in transferring salt-tolerant QTLs genes into elite rice genotypes, accelerating breeding of salt-resistant rice cultivars.

Abiotic and biotic stresses adversely affect rice growth, development and grain yield. Traditional rice breeding techniques are insufficient in modern agriculture to meet the growing population’s food needs on a long-term basis. The development of DNA markers closely linked to target genes or QTLs on rice chromosomes, and advanced molecular techniques, such as marker-assisted selection (MAS), have encouraged the evolution of contemporary techniques in rice genetics and breeding, such as gene pyramiding. Gene pyramiding refers to the act of combining two or more genes from multiple parents into a single genotype, which allows the overexpression of more than one gene for broad-spectrum abiotic and biotic stress resistance. Marker-assisted pedigree, backcrossing and pseudo-backcrossing methods can increase the conventional breeding speed by reducing the number of breeding generations in order to enhance the pyramiding process. Pyramiding is affected by several factors: the number of transferred genes; the range within gene and flanking markers; the number of chosen populations in every breeding generation; the features of genes and germplasms; and the potentiality of breeders to identify the target genes. Modern breeding methods, such as the marker-assisted backcrossing approach, have made gene pyramiding more precise and reliable for the development of stress-tolerant rice varieties in the coming decades. This review presents up-to-date knowledge on gene pyramiding schemes, marker-assisted gene pyramiding techniques, the efficiency of marker-assisted gene pyramiding and the advantages and limitations of gene pyramiding methods. This review also reports on the potential application of marker-assisted selection breeding to develop stress-tolerant rice varieties that stabilize abiotic and biotic stresses. This review will help rice breeders to improve yields by increasing rice productivity under abiotic and biotic stress conditions.

In the establishment of oil palm seedlings, apart from the application of adequate amount of fertilizers, other sustainable plant nutrient sources are known to have the potential in enhancing vegetative growth and improve plants’ resistance against pests and diseases. The application of plant growth promoters is known to contribute towards sustaining healthy plant growth leading to strong plant defense mechanisms. The present study was conducted to determine plant growth promotion potentials of bacterium, Bacillus cereus (UPM15) and fungus Trichoderma asperellum (UPM16). Isolates B. cereus and T. asperellum were assessed on their effectiveness as plant growth promoters for oil palm seedlings. Plant growth-promoting potentials were evaluated in terms of their ability to produce indole acetic acid (IAA), a naturally occurring plant hormone of the auxin class, iron-chelating compounds or siderophores, and phosphate solubilisation, considered to be one of the most important traits associated with plant phosphate nutrition. A series of treatments was applied to establish the potential of B. cereus and T. asperellum as microbial inoculants in singles and mixed applications in an in vivo nursery study. The ability to solubilize precipitated phosphate and to produce siderophores was positively demonstrated by T. asperellum. Both B. cereus and T. asperellum were capable of producing IAA. The results showed that the former significantly contributed towards growth enhancement of roots and the later in growth promotion of aerial parts of oil palm seedlings. Mixture of these isolates yielded good vegetative growth. The study revealed the benefits of microbial inoculants that extended beyond their capacity as biofertilizers.