Identification of bacterial blight resistance genes in rice landraces from Yunnan Province, China

Bacterial blight (BB), a serious bacterial disease caused by pathogen Xanthomonas oryzae pv. oryzae (Xoo) affects rice growth and yield. Yunnan Province is regarded as a center of rice diversity in China and indeed the world, and has abundant rice landrace resources, which may offer prospective candidate donors in rice improvement and breeding. In this study, a set of 200 rice landraces were evaluated to determine their resistance to 10 pathogenic Xoo strains resistance by the leaf-clipping method. The results indicated that the tested rice landraces had different resistance levels against different Xoo strains. Multiple comparisons showed that the Xoo strain PXO99 was virulent to the tested rice landraces. Sixty-six rice landraces conferred resistance against at least one Xoo strain. These resistant rice landraces screened were then performed the presence of 14 cloned BB resistance genes by closely linked molecular markers and designed specific primers. The results showed that none of these resistant accessions contained xa13, Xa21, Xa27, and Xa45(t) homologous fragments, while 9, 24, 4, 7, 9, 15, 1, 5, 4 and 27 accessions contained Xa1, Xa2/Xa31(t), Xa14, Xa3/Xa26, Xa4, xa5, Xa7, Xa10, Xa23 and xa25 homologous fragments, respectively. Sequence analysis further revealed that nucleotide variations around functional nucleotide polymorphisms region were observed within these accessions containing the Xa1, Xa2/Xa31(t), Xa14, Xa3/Xa26, Xa4, xa5, Xa10, Xa23 and xa25 homologous fragments. These results along with phenotypic resistance spectrum supported that these accessions carried nine resistance homologous genes. Only one accession (Qishanggu_Wenshan) carried the Xa7 resistance gene. We also found that some resistant rice landraces, especially Xilandigu_Baoshan, and Laoyaling_Lincang without the above resistance genes, which mediated broad spectrum resistance to multiple Xoo strains, were identified as potential sources for breeding rice lines resistance to BB.

Genetic diversity analysis in indigenous rice (Oryza sativa L.) germplasm for Bacterial Leaf Blight (Xanthomonas oryzae pv. Oryzae) using resistance genes linked markers

Among rice ( Oryza sativa L.) diseases, bacterial blight (BB), caused by Xanthomonas oryza pv. Oryzae , plays a pivotal role in decreasing rice yield. BB is reported to be the most serious constraint to improving rice yield. The present investigation assessed the potentiality of bacterial blight resistance and molecular characterization of 100 rice accessions for four major BB resistance genes, viz., Xa4, xa5, xa13 and Xa21 . Disease screening was carried out under glasshouse conditions using a BB culture isolated from BB-infected rice fields through the leaf clipping method. Analyses of 13 BB resistance genes linked with polymorphic microsatellites markers indicated the presence of single-, two-, three- and four-gene combinations of xa5, xa13, Xa4 and Xa21 . We found four accessions to be resistant; 34 accessions to be moderately resistant; 49 accessions to be moderately susceptible and 13 accessions to be susceptible. Among the resistant lines, IR12L110, Namcheonbyeo, Dhalaheera and SahbhagiDhan recorded a minimum lesion length of 3.7cm, 4.2cm, 4.67cm and 8.3 cm, respectively. Phylogenetic tree, constructed using molecular data, grouped the rice germplasm into four major clusters. R genes xa 5 and Xa4 contributed 14 positive compatible R genes, each belonging to 28 germplasm for BB resistance. The potential genetic resources identified as resistant to BB can be used as donors for the improvement of rice BB resistance in rice breeding programs.

Effect of Nitrogen Rates and Leaf Clipping on Forage and Grain Yield, and Seed Quality of Transplant Aman Rice

Sustainable fodder production is difficult from limited cultivable land occupied for food grain production. This paper presents the results of the experiment designed to test the hypothesis that forage could be produced along rice grain from the same rice field. The aim of the present study was to investigate the influence of N-rates and leaf clipping on forage and grain yield; and seed quality of transplant Aman (wet season) rice. Four nitrogen (N) rates (N1=46, N2=69, N3=92 and N4=115 kg N ha-1) and four times of leaf clipping viz, C0=No leaf clipping, C1=leaf clipping at 25 DAT (Days after transplanting), C2=40 and C3=55 DAT were evaluated following split-plot design with three replications. BRRI dhan41 was used in the experiment. N rates, leaf clipping times and its interaction had significant effects on forage and grain yield, yield components and seed quality except thousand grain weight. The results revealed that forage yield increased with increasing N rates and leaf clipping times. Grain yield was higher in higher N rates and early leaf clippings, however, it was decreased in the late clipping (55 DAT). The highest mean grain yield (5.25 t ha-1) was obtained from the treatment combination of 115 kg N ha-1 (N4) and no leaf clipping (N4C0) which was statistically similar (5.18 t ha-1) to N3C0 (5.18 t ha-1), N3C1 (5.10 t ha-1) and N4C1 (5.06 t ha-1). The lowest mean grain yield (3.17 t ha-1) was obtained from N1C3. Grain yield was reduced by 3, 6 and 24% in C1, C2 and C3, respectively compared to C0 (No leaf clipping). Qualitative characters (germination and vigour index) of seed increased with increased N rates, however it decreased in the delayed leaf cuttings. Application of 92 to 115 kg N ha-1 with early leaf clipping (25 to 40 DAT) might be allowed to attain moderate forage yield, higher grain yield, and quality seed of transplant Aman rice. Bangladesh Rice j. 2019, 23(2): 49-57

Palm Date Leaf Clipping: A New Method to Reduce PAPR in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is the key technology used in high-speed communication systems. One of the major drawbacks of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signal. The transmitted signal with a high PAPR requires a very large linear range of the Power Amplifier (PA) on the transmitter side. In this paper, we propose and study a new clipping method named Palm Clipping (Palm date leaf) based on hyperbolic cosine. To evaluate and analyze its performance in terms of the PAPR and Bit Error Rate (BER), we performed some computer simulations by varying the Clipping Ratio (CR) and modulation schemes. The obtained results show that it is possible to achieve a gain of between 7 and 9 dB in terms of PAPR reduction depending on the type of modulation. In addition, comparison with several techniques in terms of PAPR and BER shows that our method is a strong alternative that can be adopted as a PAPR reduction technique for OFDM-based communication systems.

Leaf Clipping and Population Density Effects on Green Fodder and Grain Yield for Hybrid Maize (Zea mays) in Bangladesh

Smallholder farmers having fragmented lands need fodder and grains simultaneously for earning food security for their families. A study was conducted in Crop Physiology and Ecology Research Field and Laboratory at Hajee Mohammad Danesh Science and Technology University, Bangladesh during the period of March to July-2013 to investigate the effect of leaf clipping and population density on fodder and grain yield in maize. Three population densities (D1= 75 cm × 25 cm, D2= 60 cm × 20 cm and D3= 50 cm × 20 cm) and three clipping treatments (C1 = no clipping, C2 = removal of all leaf blades below the lowermost cob and C3 = removal of all leaf blades above the uppermost cob) at the silking stage were included as experimental treatments. The experiment was laid out in a two factors Randomized Complete Block Design (RCBD) with three replications. Results revealed that D1 required the maximum days to attain most of the phenological stages of maize. Higher population density (D3) with C3 clipping treatment gave the highest plant height, whereas D1 with non-clipping treatment gave the lowest. Highest total dry matter (TDM) was found in D2 with C1 and the lowest was found in D1 with C1 treatment. The highest yield (8.88 t ha-1) and harvest index (36.2%) were found in D3 treatment whereas the lowest yield (5.92 t ha-1) in D1 population density but harvest index (32.6 %) was lowest in D2. The highest yield (8.33 t ha-1) and harvest index (35.5 %) were obtained from C1 treatment and the lowest yield (6.55 t ha-1) and harvest index (33.5 %) were obtained from C3 treatment. The highest fodder yield (3.33 t ha-1) was obtained from D3 treatment and the lowest (2.11 t ha-1) in D1 treatment. In C2 treatment, the highest amount of fodder (4.67 t ha-1) was obtained. The interaction between population density and leaf clipping treatment showed a significant variation among the yield and yield attributes in maize. It is indicated that D3 and C1 combination showed the best performance in respect of grain yield (9.67 t ha-1) and harvest index (38.3 %) of maize. But for both grain and fodder yield, D3 with C2 showed the best performance.

Two Wheat Cultivars with Contrasting Post-Embryonic Root Biomass Differ in Shoot Re-Growth after Defoliation: Implications for Breeding Grazing Resilient Forages

The ability of forages to quickly resume aboveground growth after grazing is a trait that enables farmers to better manage their livestock for maximum profitability. Leaf removal impairs root growth. As a consequence of a deficient root system, shoot re-growth is inhibited leading to poor pasture performance. Despite the importance of roots for forage productivity, they have not been considered as breeding targets for improving grazing resilience due in large part to the lack of knowledge on the relationship between roots and aboveground biomass re-growth. Winter wheat (Triticum aestivum) is extensively used as forage source in temperate climates worldwide. Here, we investigated the impact of leaf clipping on specific root traits, and how these influence shoot re-growth in two winter wheat cultivars (i.e., Duster and Cheyenne) with contrasting root and shoot biomass. We found that root growth angle and post-embryonic root growth in both cultivars are strongly influenced by defoliation. We discovered that Duster, which had less post-embryonic roots before defoliation, reestablished its root system faster after leaf cutting compared with Cheyenne, which had a more extensive pre-defoliation post-embryonic root system. Rapid resumption of root growth in Duster after leaf clipping was associated with faster aboveground biomass re-growth even after shoot overcutting. Taken together, our results suggest that lower investments in the production of post-embryonic roots presents an important ideotype to consider when breeding for shoot re-growth vigor in dual purpose wheat.