P. Jayamani

Bio: P. Jayamani is an academic researcher from Tamil Nadu Agricultural University. The author has contributed to research in topics: Biology & Cajanus. The author has an hindex of 2, co-authored 2 publications receiving 101 citations.

Genetic relatedness of Portuguese rice accessions from diverse origins as assessed by microsatellite markers

Abstract: Simple sequence repeat (SSR) markers detect a significantly high degree of polymorphism in rice (Oryza sativa L.) and are particularly suitable for evaluating genetic diversity among closely related cultivars. A total of 176 rice accessions originating from 19 countries in the Portuguese working germplasm collection and two standard rice varieties (IR36-indica and Nipponbare-japonica) were analyzed for DNA profile using 24 SSR loci covering two loci per chromosome. A total of 184 alleles were detected. The number of alleles per locus ranged from 3 to 16, with an average of 7.7, and the PIC value ranged from 0.179 to 0.894 with an average of 0.667. All the loci were polymorphic among the accessions and clearly distinguished the indica and japonica subspecies. At 20% similarity, cluster analysis of the 178 accessions revealed three major groups, japonica, basmati, and indica (Groups I, II, and III, respectively). The japonica group contained 87% of the accessions and showed a wide range of similarity values (0.21-0.92), revealing a high degree of diversity among the accessions. Many of the accessions included in this study are morphologically similar and lack pedigree information. Hence, identification of genetic distances among the accessions should improve their use in breeding programs. As a result of this study, genetically diverse parents can be identified, increasing the usefulness of germplasm collections by broadening the genetic base of rice varieties.

Host Plant Resistance and Analysis of Chemical Compounds Responsible for Bruchid Resistance in Greengram Vigna radiata (L.) Wilczek

Abstract: Background: Greengram Vigna radiata (L.) Wilczek, is an important legume crop that serves as a low-cost source of protein. The bruchid (Callosobruchus spp.) is a serious storage pest affecting greengram and other pulse crops. Thus, a study was designed to investigate bruchid resistance (Callosobruchus chinensis) in inter sub-specific derived lines of greengram and to identify chemical compounds responsible for resistance. Methods: The experimental material comprised of 200 inter sub-specific derived lines of F9 generation of VBN (Gg) 2 (susceptible to bruchid) × Vigna radiata var. sublobata/2 (resistant to bruchid) and a susceptible check variety. The bruchid screening experiment was carried out in completely randomized design and replicated twice with 50 seeds in each replication by adopting no choice test. Out of 200 lines evaluated for bruchid screening, seed damage due to bruchid was less than 20 per cent in 11 lines, identified as resistant. However, three resistant lines viz., GGISC 124, GGISC 140 and GGISC 150 were taken for further confirmation for bruchid resistance and GC-MS analysis to discover the chemical compounds conferring resistance (Clarus SQ 8C, Perkin Elmer). Result: In confirmation screening, seed damage due to bruchid (Callosobruchus chinensis) on 30th day was less than 20 per cent in three inter sub-specific lines viz., GGISC 124, GGISC 150 (17.00%) and GGISC 140 (18.00%), whereas the susceptible check [VBN (Gg) 2] reached 100 per cent adult emergence. The three inter sub-specific lines recorded susceptibility index of 0.046 (GGISC 124), 0.047 (GGISC 140) and 0.048 (GGISC 150) and classified as resistant. The susceptible check [VBN (Gg) 2] recorded the susceptibility index of 0.085. GC-MS study was carried out in resistant lines GGISC 124, GGISC 140, GGISC 150 and susceptible check VBN (Gg) 2. The results revealed that the existence of three compounds viz., 9,12-octadecadienoic acid, methyl ester; Hexadecanoic acid, 1-(hydroxymethyl)-1, 2-ethanediyl ester and Hexadecanoic acid, 2-oxiranyl methyl ester in resistant lines conferred resistance against C. chinensis in greengram.

Multivariate and Association Studies in Short Duration Pigeonpea [Cajanus cajan (L.) Millsp.] Genotypes

Abstract: Background: Absolute understanding of the relationship between yield and yield attributing traits contributing to variance is predominant in a breeding programme. To study the multivariate analysis and interrelationship among the yield and yield attributing traits in the pigeonpea, 68 genotypes were subjected to principal component analysis and association studies. Methods: The 68 pigeonpea genotypes were raised during two seasons viz., rabi, 2019-2020 and rabi, 2020-2021 in a randomized complete block design with two replications. The two-season data was pooled and utilized for multivariate and association studies. Result: The total variance was split into 12 principal components. Four principal components were found to have eigen values more than one and explained 78.75 per cent of the total variance. The correlation studies revealed that, the single plant yield was highly correlated with the traits viz., days to 50 per cent flowering (rg=0.213, P less than 0.05), days to maturity (rg=0.347, P less than 0.01), plant height (rg=0.536,P less than 0.01), number of branches per plant (rg=0.331,P less than 0.01), number of clusters per plant (rg=0.705,P less than 0.01), number of pods per plant (rg=0.805,P less than 0.01), pod length (rg=0.481, P less than 0.01), number of seeds per pod (rg=0.231, P less than 0.05) and hundred seed weight (rg=0.505, P less than 0.01). Selection for these traits will improve single plant yield. Path analysis showed that the traits viz., number of pods per plant (0.871), shelling percentage (0.391) and hundred seed weight (0.744) had high positive direct effect on single plant yield, whereas the high indirect effect on single plant yield possessed by number of pods per plant through traits viz., days to maturity (0.316), plant height (0.421), pod bearing length (0.454) and number of clusters per plant (0.706).

Molecular and environmental factors determining grain quality in rice

Abstract: Rice among other cereals is key to food security for at least half the world population. Since the 1960s, productivity of rice has largely been improved during the Green Revolution, which included development of new cultivars, irrigation infrastructure, new management techniques, and synthetic fertilizers and pesticides. Nowadays, scientists and breeders are more and more focused on improving the quality of rice for different purposes and markets. For instance, people in the Far East prefer sticky and soft rice, while in India, a non-sticky type is preferred. Consumers from developed countries ask mainly for grain with good cooking quality and eating characteristics, but in many developing regions, nutritional value is crucial as rice is the most consumed staple food. Grain quality is a general concept which covers many characteristics ranging from physical to biochemical and physiological properties. Starch and protein are the two main components of rice endosperm and therefore are key to quality. The knowledge of how starch and protein are synthesized, sorted, and stored in starch granules and protein bodies (PB) is important for rice breeding. Besides that, grain quality has been shown to be affected significantly by growing and environmental conditions, such as water availability, temperature, fertilizer application, drought, and salinity stresses. However, the signal transduction pathways controlling grain quality still remain largely unclear. In the following sections, we first briefly review the four main aspects of grain quality, followed by a discussion of the molecular and genetic basis of starch and seed-storage protein biosynthesis and the effects of environmental factors. Obviously, rice grain is also an important source of mineral micronutrients, as well as important vitamins. Storage of these also plays crucial roles in grain quality and nutritional value, but we will only discuss these aspects briefly in this review.

SSR marker-based molecular characterization and genetic diversity analysis of aromatic landreces of rice (Oryza sativa L.)

Abstract: Molecular characterization of the genotypes gives precise information about the extent of genetic diversity which helps in the development of an appropriate breeding program. In the present study, a total of 24 SSR markers were used across 12 elite aromatic rice genotypes for their characterization and discrimination. Among these 24 markers 9 microsatellite markers were showed polymorphism. The number of alleles per locus ranged from 2 alleles (RM510, RM244, and RM277) to 6 alleles (RM 163), with an average of 3.33 alleles across 9 loci obtained in the study. The polymorphic information content values ranged from 0.14 (RM510) to 0.71 (RM163) in all 9 loci with an average of 0.48. RM163 was found the best marker for the identification of 12 genotypes as revealed by PIC values. The frequency of most common allele at each locus ranged from 41% (RM163, RM590, and RM413) to 91% (RM510). The pairwise genetic dissimilarity co-efficient indicated that the highest genetic distance was obtained between Basmati PNR 346 and Deepa; Basmati PNR 346 and Patnai-23; Dolargura and Sugandha; Bhogganijia and Sugandha; and finally between Dolargura and Chinikani (88.89%). Opchaya, Basmati PNR 346 and Sugandha had close similarity among them but showed wide dissimilarity with other genotypes. Being grouped into distant clusters Dolargura and Opchaya could be utilized as potential parents for the improvement of fine grain aromatic rice varieties. Genotypes Deepa and Patnai-23 (having zero dissimilarity) might have possessed somewhat similar genetic background and more markers are needed to discriminate them. The microsatellite marker based molecular fingerprinting could serve as a sound basis in the identification of genetically distant accessions as well as in the duplicate sorting of the morphologically close accessions.

Identification and characterization of a novel Waxy allele from a Yunnan rice landrace.

Abstract: Low amylose content (AC) is a desirable trait for rice (Oryza sativa L.) cooking quality and is selected in soft rice breeding. To gain a better understanding of the molecular mechanism controlling AC formation, we screened 83 Yunnan rice landraces in China and identified a rice variety, Haopi, with low AC. Genetic analyses and transgenic experiments revealed that low AC in Haopi was controlled by a novel allele of the Wx locus, Wx hp , encoding a granule-bound starch synthase (GBSSI). Sequence com- parisons of Wx hp and Wx b alleles (from Nipponbare) showed several nucleotide changes in the upstream regu- latory regions (including the promoter, 5 0 -untranslated region, and first intron 5 0 splicing junction site). Interest- ingly, these changes had no obvious effect on the expression level and splicing efficiency of Wx transcripts. In addition, an examination of the coding region revealed that the Wx hp allele carries an A-to-G change at nucleotide position ?497 from the start codon, resulting in an Asp 165 /Gly 165 substi- tution. The amino acid substitution had no detectable effects on GBSSI activity in vitro; however, it notably reduced the binding of GBSSI to starch granules, resulting in a reduc- tion of AC in rice seeds. Moreover, three other Yunnan landraces with low AC also carry a nucleotide substitution identical to Haopi at the ?497 position of the Wx gene, suggesting common ancestry. Based on the single-nucleo- tide polymorphism, we have developed a new derived cleaved amplified polymorphic sequence marker for use in breeding practice to manipulate AC in rice endosperm.