News Update on Rice cultivar : Apr 2022

Rice cultivar evaluation for phosphorus use efficiency

Phosphorus deficiency is one of the most growth-limiting factors in acid soils in various parts of the world. The objective of this study was to screen 25 rice cultivars (Oryza sativa L.) at low, medium, and high levels of soil P. Number of tillers, root length, plant height, root dry weight and shoot dry weight were related to tissue P concentrations, P uptake and P-use efficiency. Shoot weight was found to be the plant parameter most sensitive to P deficiency. Significant cultivar differences in P use efficiency were found. Phosphorus use efficiency was higher in roots than shoots and decreased with increasing levels of soil P. Positive correlations were found among growth parameters such as plant height, tillers, root and shoot weight, and P content of roots and shoots. These results indicate selection of rice cultivars for satisfactory performance under low P availability can be carried out using shoot and root dry weight as criteria. [1]

RFLP mapping of genes conferring complete and partial resistance to blast in a durably resistant rice cultivar

Moroberekan, a japonica rice cultivar with durable resistance to blast disease in Asia, was crossed to the highly susceptible indica cultivar, CO39, and 281 F7 recombinant inbred (RI) lines were produced by single seed descent. The population was evaluated for blast resistance in the greenhouse and the field, and was analyzed with 127 restriction fragment length polymorphism (RFLP) markers. Two dominant loci associated with qualitative resistance to five isolates of the fungus were tentatively named Pi-5(t) and Pi-7(t). They were mapped on chromosomes 4 and 11, respectively. To identify quantitative trait loci (QTLs) affecting partial resistance, RI lines were inoculated with isolate PO6-6 of Pyricularia oryzae in polycyclic tests. Ten chromosomal segments were found to be associated with effects on lesion number (P < 0.0001 and LOD > 6.0). Three of the markers associated with QTLs for partial resistance had been reported to be linked to complete blast resistance in previous studies. QTLs identified in greenhouse tests were good predictors of blast resistance at two field sites. This study illustrates the usefulness of RI lines for mapping a complex trait such as blast resistance and suggests that durable resistance in the traditional variety, Moroberekan, involves a complex of genes associated with both partial and complete resistance. [2]

Pyramiding three bacterial blight resistance genes (xa5, xa13 and Xa21) using marker-assisted selection into indica rice cultivar PR106

Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major disease of rice in several countries. Three BB resistance genes, xa5, xa13 and Xa21, were pyramided into cv. PR106, which is widely grown in Punjab, India, using marker-assisted selection. Lines of PR106 with pyramided genes were evaluated after inoculation with 17 isolates of the pathogen from the Punjab and six races of Xoo from the Philippines. Genes in combinations were found to provide high levels of resistance to the predominant Xoo isolates from the Punjab and six races from the Philippines. Lines of PR106 with two and three BB resistance genes were also evaluated under natural conditions at 31 sites in commercial fields. The combination of genes provided a wider spectrum of resistance to the pathogen population prevalent in the region; Xa21 was the most effective, followed by xa5. Resistance gene xa13 was the least effective against Xoo. Only 1 of the BB isolates, PX04, was virulent on the line carrying Xa21 but avirulent on the lines having xa5 and xa13 genes in combination with Xa21. [3]

Relationship of Yield and Yield Related Traits of Some Traditional Rice Cultivars in Sri Lanka as Described by Correlation Analysis

Aims: To understand the relationship between individual trait and yield of one hundred rice cultivars according to Pearson’s correlation coefficient.

Study Design: Completely randomized block design with four replicates. Twenty plants were evaluated in each replicate and eighty plants were evaluated in each cultivar in four replicates.

Place and Duration of Study: Faculty of Agriculture, University of Ruhuna, Sri Lanka in 2011-2013.

Methodology: Data were collected in 80 plants of four replicates on: plant height (cm), number of tillers per plant, number of fertile tillers per plant panicle length (cm), panicle weight (g), number of spikelets per panicle, number of fertile spikelets per panicle, 100 grain weight (g), days to maturity and yield per plant (g). Pearson’s correlation coefficients were calculated using SPSS.

Results: According to statistical analysis grain yield was significantly and highly correlated with number of fertile spikelets/panicle (r = 0.765), panicle weight (r = 0.727), number of spikelets/panicle (r = 0.638), filled grain percentage (r = 0.620), number of fertile tillers/plant (r = 0.611), number of tillers/plant (r = 0.575). Hundred grain weight (r = 0.336) and plant height (r = 0.278) were also correlated with at 1% significant level. None of the studied trait was negatively correlated with the yield.

Conclusion: Fertile spikelets per panicle, panicle weight, number of spikelet per panicle and filled grain percentage can be considered as good criteria for selection of rice cultivars suitable for breeding programs. [4]

Rice Cultivar Production and Seed Overwinter Potential in Upstate Missouri

Climate change and opportunities for pharmaceutical rice (Oryza sativa L.) production in the U.S. may affect future production opportunities. Field research in 2005–2007 at Bethel (39º56’N, 92º3’W) and in 2005 at Novelty (40º01’N, 92º11’W) evaluated the production potential of rice cultivars (10 conventional or hybrid varieties), overwinter seed survival, and the effects of weeds on yield in upstate Missouri. Grain yields ranged from 3,880 kg ha-1 (Ilpumbyeo) to 10,540 kg ha-1 (Trenase). M103, M202 and XP723 yielded similarly to Trenase. Late-maturing cultivars had the greatest risk of yield loss due to frost damage. Weed interference [barnyard grass (Echinochloa crus-galli L.), fall panicum (Panicum dichotomiflorum Michx.), giant foxtail (Setaria faberi Herrm.), common cocklebur (Xanthium strumarium L.), and common waterhemp (Amaranthus rudis Sauer)] reduced grain yields of Cocodrie 35%, emergence by 4%, plant height by 21%, and head number by 21%. In fall 2005 and 2006, rice seed produced during the previous year was seeded on the soil surface, with vertebrate exclusion, and vertebrate plus invertebrate exclusion. Viable seed overwintered with 0.06 to more than 12% emergence the following spring. The yield potential of rice in upstate Missouri looks promising, but correct cultivar selection and weed control are essential for successful production.[5]

Reference

[1] Fageria, N.K., Wright, R.J. and Baligar, V.C., 1988. Rice cultivar evaluation for phosphorus use efficiency. Plant and Soil, 111(1), pp.105-109.

[2] Wang, G.L., Mackill, D.J., Bonman, J.M., McCouch, S.R., Champoux, M.C. and Nelson, R.J., 1994. RFLP mapping of genes conferring complete and partial resistance to blast in a durably resistant rice cultivar. Genetics, 136(4), pp.1421-1434.

[3] Singh, S., Sidhu, J.S., Huang, N., Vikal, Y., Li, Z., Brar, D.S., Dhaliwal, H.S. and Khush, G.S., 2001. Pyramiding three bacterial blight resistance genes (xa5, xa13 and Xa21) using marker-assisted selection into indica rice cultivar PR106. Theoretical and Applied Genetics, 102(6), pp.1011-1015.

[4] Ranawake, A.L. and Amarasinghe, U.G.S., 2014. Relationship of yield and yield related traits of some traditional rice cultivars in Sri Lanka as described by correlation analysis. Journal of Scientific Research and Reports, pp.2395-2403.

[5] Ranawake, A.L. and Amarasinghe, U.G.S., 2014. Relationship of yield and yield related traits of some traditional rice cultivars in Sri Lanka as described by correlation analysis. Journal of Scientific Research and Reports, pp.2395-2403.

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