Genetic Control and High Temperature Effects on Starch Biosynthesis and Grain Quality in Rice

Grain quality is one of the key targets to be improved for rice breeders and covers cooking, eating, nutritional, appearance, milling, and sensory properties. Cooking and eating quality are mostly of concern to consumers and mainly determined by starch structure and composition. Although many starch synthesis enzymes have been identified and starch synthesis system has been established for a long time, novel functions of some starch synthesis genes have continually been found, and many important regulatory factors for seed development and grain quality control have recently been identified. Here, we summarize the progress in this field as comprehensively as possible and hopefully reveal some underlying molecular mechanisms controlling eating quality in rice. The regulatory network of amylose content (AC) determination is emphasized, as AC is the most important index for rice eating quality (REQ). Moreover, the regulatory mechanism of REQ, especially AC influenced by high temperature which is concerned as a most harmful environmental factor during grain filling is highlighted in this review.

Study of Parental Polymorphism and Allelic Variation for Grain Quality and Yield Traits in Rice (Oryza sativa L.) Using SSR Markers

Aim: Identification of polymorphic markers is prerequisite for conducting any QTL mapping experiment because if the parents are polymorphic for the traits of interest, then further selection of plants in the progenies becomes easy. Hence, the objective of the present study was to identify polymorphic markers for grain quality and yield traits among the parental lines Improved Samba Mahsuri and Badshabhog. Place and Duration of Study: It was carried out at Molecular Breeding Lab, Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi - 221 005, India, during 2019. Methodology: Two parents Improved Samba Mahsuri and Badshabhog were used for the present study. The DNA extraction was done as per the CTAB method suggested by Murray and Thompson. Standard PCR protocol was followed. Results: For parental polymorphism survey, a total of 576 randomly selected SSR markers including 26 gene specific markers related to aroma, cooking and eating quality, grain dimension and yield related traits distributed across the 12 chromosomes of rice were used. Overall, 96 markers including 4 gene specific markers were found to be polymorphic between the two genotypes indicating a total polymorphism percentage of 16.67%. The highest polymorphism percentage was recorded on chromosome 6 (26.67%) followed by chromosome 4 (21.43%) and the lowest polymorphism percentage was observed on chromosome 10 (8.93%). The gene specific markers nksbad2, ARO7, BADEX7_5 and SSI were found to be polymorphic. Conclusion: Based on the present study it may be concluded that the polymorphic markers identified will further be utilized in genotyping of F2:3 population, linkage analysis and mapping QTL’s for grain quality and yield traits.

Genotype × Environment Interaction and Stability Analysis in Basmati Rice (Oryza sativa L.) Genotypes

Background: Basmati rice is an important cereal crop occupying a unique position in Indian agriculture. More than 90% of global rice is produced and consumed in Asia and plays a crucial role in the entry of mineral nutrients into the food chain. Identification of stable genotypes is of great significance because the environmental conditions vary from season to season and year to year. Methods: Thirty six Basmati rice genotypes were evaluated in four production environments during kharif 2016 and kharif 2017 at two locations Kaul and Uchani to study the G × E interaction for milling, appearance, cooking and eating quality parameters. The genotypes were grown in randomized block design with three replications. Result: Based on the stability analysis of Eberhart and Russell model, genotypes viz., Haryana Mahak 1, Pusa 1826-12-271-4 and HKR 06-434 were found stable across the environments for milling%, grain length before cooking and length breadth ratio before cooking, respectively.

The Potential of Silicon in Improving Rice Yield, Grain Quality, and Minimising Chalkiness: A Review

Silicon (Si) is a micronutrient that can increase the resistance of certain plants against multiple biotic or abiotic stresses. It is known that Si has a beneficial effect on plant growth, beginning in the soil, which could lead to a good crop yield. Despite its benefits, Si is not listed among the generally essential elements or nutrients for rice production in many countries such as Malaysia. This review discusses the ability to uptake Si and its benefits on rice. Environmental factors affect rice production, and among the factors, high temperature has been shown to disrupt the physiological development of rice grain, which contributes to chalkiness. Chalkiness is an undesirable trait that decreases grain’s value, milling, cooking, and eating quality. The application of Si could ameliorate rice grain quality, thus providing a valuable reference for Si fertiliser use in high-quality rice production. This review also presents an update on the potentials of Si in improving the rice yield and grain quality, including Si’s ability to minimise grain chalkiness. Therefore, it is anticipated that Si applications will increase rice yield and grain quality and help to reduce chalkiness.

Breeding of High Cooking and Eating Quality in Rice by Marker-Assisted Backcrossing (MABc) Using KASP Markers

The primary goals of rice breeding programs are grain quality and yield potential improvement. With the high demand for rice varieties of premium cooking and eating quality, we developed low-amylose content breeding lines crossed with Samgwang and Milkyqueen through the marker-assisted backcross (MABc) breeding program. Trait markers of the SSIIIa gene referring to low-amylose content were identified through an SNP mapping activity, and the markers were applied to select favorable lines for a foreground selection. To rapidly recover the genetic background of Samgwang (recurrent parent genome, RPG), 386 genome-wide markers were used to select BC1F1 and BC2F1 individuals. Seven BC2F1 lines with targeted traits were selected, and the genetic background recovery range varied within 97.4–99.1% of RPG. The amylose content of the selected BC2F2 grains ranged from 12.4–16.8%. We demonstrated the MABc using a trait and genome-wide markers, allowing us to efficiently select lines of a target trait and reduce the breeding cycle effectively. In addition, the BC2F2 lines confirmed by molecular markers in this study can be utilized as parental lines for subsequent breeding programs of high-quality rice for cooking and eating.

Breeding for Grain Quality Improvement in Rice

Oryza sativa holds a unique position among domesticated crop species as it is one of the most important staple foods globally. Without rice, the day will not be fulfilled in most of the Asian countries. Requirement of rice for consumption is anticipated from 450 million tons in 2011 to about 490 million tons in 2020 and to around 650 million tons by 2050 globally. To meet the food demands, it has been estimated that 40 per cent more rice is needed to be produced by 2050 for the ever increasing population. Increasing incidences of both biotic and abiotic stresses under changing climate are the major constraints in rice production to meet the rapidly escalating population. Crop improvement in rice will not be completed lacking of grain quality analysis. Rice grain quality embraces storage, milling, market quality, cooking and eating quality and nutritive quality of grain. Demand for high quality rice has increased globally in recent years and continues to trend upward due to the taste preferences. Since, consumer demand in Asia and all over the world are diverse due to varied demographics and culture, defining uniform attributes to grain quality becomes more challenging. The Middle Eastern consumers highly prefer long grain, well milled rice with strong aroma while European consumers prefer long grain non aromatic rices. In Asia, Chinese consumers prefer semi-aromatic rice to pure aromatic rice. Cooked kernel elongation is the most important quality traits, which differentiate the highly valued basmati rice from other rice types. Kernel elongation after cooking is an important character of fine rice and the most rice consumers prefer lengthwise elongation.