In the current study, 50 ricegenotypes were evaluatedat Agricultural Research Station, Paramakudi and Rice Research Station, Tirur, Tamil Nadu, India, to find out Fe-rich genotypes for the development of bio-fortified,high yielding rice varieties. The resultsindicatedthat there is a significant genetic variation for Fe content among the studied rice genotypes. The statistical analyses (pooled ANOVA)of this investigation demonstrated a considerable and wide range of variance across all the traits (Genotypes and environments) linked with Fe content in both brown and polished rice.On other hand, mean sum squares of environment X Genotype exhibited significance association except for HP and HRR. Earlier researchers had also noted a significant level of variation in rice landraces (Nagamani et al., 2022; Kesh et al., 2022) for grain nutrients. The study of coefficient of variation for morpho-quality traits viz., HP, MP, HRR, KL, KB, LBR, FEB and FEP were recorded between the range of 2.47–15.87%. The coefficient of variation, a statistical tool used to quantify the degree of relationship or variation between two variables. It offers details regarding the direction and intensity of a linear relationship between two variables. It led to improvement of yield in the offspring, also predict the performance of certain traits based on other traits. Correlation analysis helps to validate the effectiveness of the markers by comparing the phenotypic correlations (Kiran et al., 2023).
Grain dimensions and seed coat color:
The genotypes under the study were divided into five categories based on grain dimension: long-slender (9), long-bold (5), medium-slender (22), short-slender (7) and short-bold (7).The seed coat (bran) colors of studied landraces (de-hulled grains) were classified in to white, light brown, brown, black and red as per rice descriptors IRRI, 1980 (Table 2). Out of 50 genotypes, twenty one genotypes possessed white kernel, ten were grouped as brown, two black (Kavuni and Kalabathi Black)and one (Kallundai) genotype was light brown in colour. Sixteen landraces were classified under red rice group. In domestication and advanced breeding programmes, long-grained rice is typically chosen mostly based on consumer demand. Grain dimensions, including length, width and shapewere considered crucially while domestication of rice(Anuradha et al., 2012; Zhang et al., 2021).
Thegenotypes Gandakasala, KalapathiBlack, AathurKichidiSamba, Chinnar and IllupoiPoo Sambawere exhibited high mean values for HP, MP and HRRcompare to other genotypes. These genotypes were exhibited medium slender, white; long slender, black; short slender, white; long slender, red and medium slender, white grain type and seed coat colors respectively. The Fe content of these genotypes recorded as 12.73/3.12, 10.98/4.85, 11.80/4.60, 12.33/4.77 and 10.98/4.28 mgkg− 1in brown rice andpolished rice respectively. The grain type and seed coat color demonstrated differences among the genotypes in caseofFe content in brown rice and polished rice.Majority of landraces possessed high FEB had medium slender grain type and red seed coat color compared to others. In general, red rice types have higher Fe content than white rice variants. The Fe content of rice landraces tends to vary significantly geographically, not only within India but also between countries for genetic causes (Anand and Prasad, 2020). Numerous studies have found that the traditional genotypes exhibited significantly highFe content levels (Anandan and Brar., 2011; Abera et al., 2019).A screening study among 50 landraces for Fe content in brown rice ranged from 9.28 to 14.45 mg kg− 1.The results also partially agree with Maganti et al. (2019) and Zhang et al. (2009) who found Fe content varied from 6.9 to 22.3 mg kg− 1among 33 landraces of Arunachal Pradesh landraces.Panels of 939 genotypes were evaluated for the variation in rice grain Fe content and which varies from 15.9 to 58.4 mgkg− 1in brown rice (Graham et al., 1999). Variation for Iron and zinc concentration was also documented by Nachimuthuet al., 2014 using 192 rice genotypes.
The Fe content of 50 genotypess in polished rice ranged from 1.88 to 4.87 mgkg− 1.The genotypes such as Kottara samba, KalapathiBalck, Jyothi, ChinnarandKalanamak noticed high FEP and it ranged from 4.68 to 4.87 mgkg− 1. The study also draws a weak correlation between Fe content in brown and polished rice. Which is highly possible due to intensive milling of the rice resulted in reduction of nutrients.Xiongsiyeeet al. (2018), Maganti et al. (2019), Majumder et al., (2019) and Sholehahet al. (2020) reported direct relationship between Fe content and Mp. Thus,brown rice is always considered nutritionally superior to milled white rice and is recommended as staple for human health benefits.
Correlation studies are useful in determining the relationship between various qualities, allowing plant breeders to select accessions with desirable traits. The highest associations were observed between HP and MP followed by FEB. Kernel breadth had negative association with FEP. Anuradha et al. (2012), Pippal et al. (2021) and Kiran et al. (2023)were reported negative correlation between grain dimension and Fe content in polished rice.The contribution of each component to the total variance is calculated using PCA. In the current study, four PCs explained 79.62% of the variation. Hemalatha et al., 2023 reported a similar percentage of cumulative variance. The contribution of each component to overall variance is calculated using principal component analysis. Selection of features that contribute to highest morphological variation via two primary PCs would be desirable.Thefourgenotypesviz., Chintamani,Kalanamak, Jai-Sri-Ram andKottaraSamba in PC1 had medium to long slender grain type and combination of red-white seed coat color. The three genotypes (Gandakasala, KalapathiBlack, AathurKichadi Samba) in PC2 observed different grain dimensions (long, medium and short slender) and white to black seed coat color were contributed to the maximum genetic diversity. Therefore, it would be beneficial to use these accessions as a donor parent in rice breeding programmes targeting nutritional improvements in rice.
Cluster analysis grouped 50 rice genotypes into five different clusters. Cluster III comprising 19 accessions accounting for medium slender to long slender grain type and the Fe content with in this group ranged from 9.47 to 12.6 and 1.88 to 3.58mgkg− 1 in brown and polished rice respectively. The red rice genotypes exhibited high amount of Fe contentthanbrown ricegenotypes.The genotype Kallundai (1.88 mgkg− 1), which exhibited light brown seed coatcolourand recorded lowest Fe content in polished rice. Thegenotypes having highest FEB viz., Jaya, KalanamakandKottaraSambabelongs to clusters IV and II, had medium to long slender grain type and red-white seed coat colors. These clusters (II and IV) represented lowest number of genotypes thus may be directly used as parents in further hybridization programmes to combine desirable characters. The similar results were drawn by Thuy et al., 2023.
This study found a positive correlation which indicating the selecting of most critical micronutrient (Fe) simultaneously. Fecontent in rice grains is significantly affected by environments, genotypes and genotype X environment interactions (Suwartoet al., 2011).A comparison of the grain Fecontent of 50 genotypes evaluatedin two different locations revealed significant variance, despite of that the overall trend for grain micronutrient content changed significantly between the locations (Fig. 6).The genotypes viz.,Jaya(14.45 mgkg− 1),Kalanamak (13.43 mgkg− 1), KottaraSamba(13.41mgkg− 1), Gandakasala(12.73) and Gopal Bhog(12.65 mgkg− 1) were top ranking with high pooled mean value for grain Fe content in brown rice. Interestingly among these five genotypes ‘Kalanamak’also had high pooled mean value (4.75 mgkg− 1) for Fe content in polished rice (Fig. 6).Micronutrient density in rice grains is determined by a number of interconnected metabolic pathways involved in soil uptake, transportation to source tissues, and mobilization as well as remobilization to developing grains, which likely explains the differences in content with previous reports(Chandel et al., 2011).