Shorter Plant Height Research Articles

Elevated CO2 improves lodging resistance of rice by changing physicochemical properties of the basal internodes

Elevated atmospheric CO2 concentration has been shown to increase rice yield but its effect on plant lodging resistance is still under debate. In this study, we examined lodging incidence in the field and lodging-related traits of two rice cultivars with contrasting lodging susceptibility under ambient and elevated CO2 (ca. 200 μmol mol−1 above ambient) concentrations by using a free-air CO2 enrichment (FACE) system. Elevated CO2 (E-CO2) increased lodging resistance as shown by reduced visual lodging incidence in the field at the late grain filling stage in E-CO2 plots. This coincided with enhanced in situ pushing resistance of intact plants one week before lodging occurred. The positive CO2 effect was more pronounced in the lodging-susceptible cultivar LY084. In contrast, the cultivar WYJ23 displayed greater pushing resistance in the field, and no lodging occurred at either ambient or elevated CO2 conditions throughout the cropping season. The field observations were consistent with the physicochemical characterization of basal internodes of rice plants at the grain filling stage. Greater lodging-resistance of WYJ23 was mainly attributed to its shorter plant height and thicker culm wall of basal internodes. The improvement of lodging resistance by E-CO2 for the lodging-susceptible cultivar LY084 was mainly related to enhanced culm density, which was explained by elevated starch deposition in the stem. Less lodging incidence under elevated CO2 contributed to an increase in grain yield by 36% for LY084. In conclusion, rice production could benefit from elevated CO2 in a changing climate because of an increase in lodging resistance as a result of CO2-induced improvements in mechanical strength of basal internodes.

Identification of superior high yielding sunflower (Helianthus annuus L.) hybrids for rabi-summer season in West Bengal

An experiment was carried out during 2012-13 to 2014-15 at Nimpith Centre of Ramkrishna Ashram Krishi Vigyan Kendra Research Farm, West Bengal to identify suitable sunflower hybrids for rabi-summer season. A total of 150 sunflower hybrids were tested including two National check hybrids (KBSH-44 and DRSH-1). The field observation revealed that the hybrid PSCHT-12-38 (2260 kg/ha, 36.0% oil content), PSCHT-12-42 (2250 kg/ha, 37.5% oil), PSCHT-12-26 (2217 kg/ha, 37.7%) and PSCHT-12-36 (2151 kg/ha, 37.9% oil content) recorded higher seed yield as well as high oil content in comparison to the national check hybrids. The new experimental hybrids viz.,PSCHT-12-42,SAHT-12-09,PSCHT-12-26, PSCHT-12-36, PSCHT-12-38, PSCHT-12-66,PSCHT-12-76 and PSCHT-12-29 were tolerant to sunflower wilt (PDI score 10-12.5%) in comparison to the checks (PDI score 20-25%). Considering the other yield attributing parameters like plant height, days to 50% flowering or days to maturity, hull content and volume weight, hybrids like PSCHT-12-38, PSCHT-12-42 , PSCHT-12-26 and PSCHT-12-36 were promising due to their 7-10 days earliness and 30-50 cm shorter plant height at harvest coupled with good seed yield and oil yield as well as high degree of tolerance to sunflower wilt.

Molecular and comparative mapping for heading date and plant height in oat

Selection of oat genotypes combining earliness and short plant height could stimulate oat cultivation worldwide. However, the mechanisms involved with the genetic control of heading date and plant height traits are not fully understood to date. This study aimed to identify genomic regions controlling heading date and plant height in two hulled by naked oat populations and to compare these genomic regions with that of other grass species. Recombinant inbred lines of each population and their parents were genotyped by a 6 K BeadChip Illumina Infinium array and assessed for heading date and plant height in two sowing dates. The quantitative trait loci (QTL) affecting these traits were detected by simple interval mapping. The two oat populations showed different genetic mechanisms controlling heading date. A major QTL was identified in one of the populations, mapped into the ‘Mrg33’ consensus linkage group from the current oat map. Two other QTL were detected into the ‘Mrg02’ and ‘Mrg24’ groups, in the second population. On the other hand, both populations presented the same genomic region controlling plant height. Six SNP markers, mapping on the same linkage group within each population, were associated with the trait, regardless the sowing date, explaining more than 20% of the phenotypic variation. Five of these six markers were mapped into three different linkage groups on the oat consensus map. Genomic regions associated with heading date and plant height in oat seem to be conserved in Oryza sativa L. and Brachypodium distachyon. Our results provide valuable information for marker-assisted selection in oats, allowing selection for earliness and plant height on early segregating generations.

Phosphorous Fertilization Influenced Weeds Attributes and Phenological Characteristics of Mungbean Cultivars (Vigna radiata L.)

Weeds are abundant in nature having supreme growth characters over the other economic crop. Weeds show aggressive behavior in term of growth, development, reproduction and for water and nutrients uptake through which dominantly spread over the ground and reduced yield of the economic crop. Weeds frequency and density responded positively to phosphorous application and may retard the production potential of the economic crop. Therefore present study was established in a randomized complete block design with three replications at Agriculture Extension Demonstration plot Matta Circle Swat Pakistan, in summer 2014. Five levels of phosphorous (20, 40, 60, 80 and 100 kg ha–1) with one control in the form of single super phosphate (SSP) and three cultivars of mungbean (SWAT-I, SWAT-II and NM-54) were used during the experiment. Results revealed that weeds density and phenological traits of mungbean varied with P2O5 application. A linear increase in weeds density was observed with increase in P2O5 levels. Fewer days to flowering (40 days) were observed in plots received P at the rate of 80 and 100 kg ha–1 followed by 60, 40, 20 and 0 kg P ha–1, while more (44 days) were recorded in control plots. In case of varieties late flowering (42 days) was observed in variety SWAT I followed by SWAT-II, while early flowering (41 days) was recorded in cultivar NM-54. Minimum days (48 days) to pods formation was noticed in P2O5 at the rate of 80 and 100 kg ha–1, while more days (52 days) to pod formation were recorded in control plots. In case of varieties NM-54 took less days (49 days) while SWAT-I were statistically at par. Highest plant height (73.9 cm) was recorded with 60 kg P ha–1 while at par plant height was noted at the rate of 80 and 100 kg P2O5 ha–1. Shorter plant height (57.3 cm) was recorded in control plots. Maximum leaves plant–1 (23) were noted at the rate of 80 kg ha–1, while control plots produced minimum number of leaves plant–1 (16). In case of mungbean varieties SWAT-I produce maximum leaves plant–1 (21) followed by SWAT-II (20), while NM-54 produced minimum leaves plant–1 (19). Biological yield (3978 kg ha–1) was obtained in the plots treated with 80 kg P ha–1 while the minimum biological yield (2668 kg ha–1) was recorded in control plots. Among the varieties SWAT-I produced maximum biological yield (3551 kg ha–1) followed by SWAT-II (3440 kg ha–1) and NM-54 (3317 kg ha–1) respectively.

Combining ability of new pistillate lines for plant growth attributes, seed yield and its components in castor (Ricinus communis L.)

Combining ability of four newly developed pistillate lines were tested using Line x Tester analysis. Sixteen hybrids generated using four pistillate lines and four testers were studied along with parents and three checks to estimate combining ability for nine characters in castor. Non-additive gene action was preponderant in all the characters studied except for seed yield, which indicated a negative estimate. Among the female parents, IPC-15 (DPC-15) was a good general combiner for earliness and short plant height while IPC-19 (IPC-19) for late duration and tall plant height. Three pistillate lines, DPC-15 (IPC-15), DPC-19 (IPC-19) and DPC-21 (IPC-21) were identified as good general combiners for total and effective primary spike length. Among the eight parents studied, DCS-107 was a good general combiner for seed yield and other traits like total primary spike length, effective primary spike length and 100-seed weight. None of the hybrids were good specific combiners for seed yield and several other yield contributing characters while three hybrids viz., DPC-16 x DCS-107 (1800 kg/ha), DPC-15 x DCS-107 (1646 kg/ha) and DPC-21 x DCS-107 (1595 kg/ha) were identified as the top three performing hybrids. Among them, DPC-21 x DCS-107 (DCH-1720), has been tested in the All India Coordinated multi location trials for three years while DPC-15 x DCS-107 (PHT-12-2) wastested in three locations (2014-15) and found promising.

Lack of the α1,3-Fucosyltransferase Gene (Osfuct) Affects Anther Development and Pollen Viability in Rice.

N-linked glycosylation is one of the key post-translational modifications. α1,3-Fucosyltransferase (OsFucT) is responsible for transferring α1,3-linked fucose residues to the glycoprotein N-glycan in plants. We characterized an Osfuct mutant that displayed pleiotropic developmental defects, such as impaired anther and pollen development, diminished growth, shorter plant height, fewer tillers, and shorter panicle length and internodes under field conditions. In addition, the anthers were curved, the pollen grains were shriveled, and pollen viability and pollen number per anther decreased dramatically in the mutant. Matrix-assisted laser desorption/ionization time-of-flight analyses of the N-glycans revealed that α1,3-fucose was lacking in the N-glycan structure of the mutant. Mutant complementation revealed that the phenotype was caused by loss of Osfuct function. Transcriptome profiling also showed that several genes essential for plant developmental processes were significantly altered in the mutant, including protein kinases, transcription factors, genes involved in metabolism, genes related to protein synthesis, and hypothetical proteins. Moreover, the mutant exhibited sensitivity to an increased concentration of salt. This study facilitates a further understanding of the function of genes mediating N-glycan modification and anther and pollen development in rice.

Alteration of Crop Yield and Quality of Wheat upon Exposure to Silver Nanoparticles in a Life Cycle Study.

As a result of the rapid development of nanotechnology, metal-based nanoparticles (NPs) are inadvertently released into the environment and may pose a potential threat to the ecosystem. However, information for food quality and safety in NP-treated crops is limited. In the present study, wheat ( Triticum aestivum L.) was grown in different concentrations of Ag-NP-amended soil (20, 200, and 2000 mg kg-1) for 4 months. At harvest, physiological parameters, Ag and micronutrient (Fe, Cu, and Zn) contents, and amino acid and total protein contents were measured. Results showed that, with increasing the exposure doses, Ag NPs exhibited severe phytotoxicity, including lower biomass, shorter plant height, and lower grain weight. Ag accumulation in roots was significantly higher than that in shoots and grains. Decreases in the content of micronutrients (Fe, Cu, and Zn) in Ag-NP-treated grains suggested low crop quality. The results of amino acid and protein contents in Ag-NP-treated wheat grains indicated that Ag NPs indeed altered the nutrient contents in the edible portion. In the amino acid profile, the presence of Ag NPs significantly decreased the contents of arginine and histidine by 13.0 and 11.8%, respectively. In summary, the effects of metal-based NPs on the edible portion of crops should be taken into account in the evaluation of nanotoxicity to terrestrial plants. Moreover, investigation of the potential impacts of NP-caused nutrient alterations on human health could further our understandings on NP-induced phytotoxicity.

A dCAPS marker developed from a stress associated protein gene TaSAP7-B governing grain size and plant height in wheat

Stress associated proteins (SAPs) are the A20/AN1 zinc-finger proteins which confer to abiotic stresses in plants. In this study, TaSAP7-B, including two AN1 domains, was isolated from B genome of wheat (Triticum aestivum L.). Sequencing analysis on TaSAP7-B illustrated one InDel (insertion-deletion) and one SNP (single nucleotide polymorphism) in the promoter region while no diversity was observed in the coding region. On the basis of SNP in the promoter region (–260 bp), a dCAPS (derived cleaved amplified polymorphic sequences) marker SNP-260 was developed for TaSAP7-B. Using a natural population consisting of 262 wheat accessions, significant associations were detected between the marker SNP-260 and agronomic traits, such as plant height (PH), peduncle length (PL), length of penultimate internode (LPI), number of spike per plant (NSP), and 1 000-grain weight (TGW). Two genotypes were identified using marker SNP-260 in the natural population. Among them, the genotypes possessing C allele exhibited a higher TGW and shorter PH than the T genotypes. Hence, base C was considered as the superior allele. The dCAPS marker of TaSAP7-B can be instrumental for marker-assisted selection for high grain size and short plant height.

Evaluation of Agronomic Traits and Inorganic Nutritional Composition of Rice Seed from IRSSTN Genotypes in Iraq

The study aimed to determine the agronomic traits of two rice modules (IRSSTN 1 for a coastal salinity-wet season, and IRSSTN 2 for an inland salinity-coastal salinity-dry season) to select promising genotypes that have highest grain yields, early maturity, and stable under Al-mishkhab, Iraq environmental conditions by using inorganic and organic nutrition. The results showed that genotype IR72049-B-R-22-3-1-1 performed the best agronomic traits with late flowering (>130 days), shorter plant height, the highest ratio of seeds/panicle and grain yield compared to control, while genotype IR70023-4B-R-12-3-1 gave the highest panicle length and the highest number of panicle/m2. Significant differences were found at macronutrient (N, P, K, Na, Mg, and Ca) and micronutrient (Zn, Mn, Fe, and Cu). ‘IRSSTN module 1’ genotypes showed superiority in P, Mg, and Cu and IRSSTN module 2 genotypes had superiority in N, Ca, and Cu. The simple correlation analysis shows that 6 genotypes of 2 sets of IRSSTN genotypes improved the nutritional quality of whole grain may be having a stable medium. It can be recommended to improve the new cultivars at a research station and producing good seed quality.

Statistical Analysis of Foreign Rice Phenotypes under Different Seasons of the Philippines

Korean rice is a foreign genetic resources in the Philippines that has to be characterized for its proper germplasm utility. Ten Korean phenotypes were analyzed using correlation, clustering and principal component analyses (PCA) based on the 13 traits viz., culm length (CL), days to 50% flowering (D50F), days to maturity (DM), filled grains per panicle (FGP), flag leaf length (FLL), flag leaf width (FLW), grain length (GL), grain width (GW), grain yield (GY), plant height (PH), productive tillers (PT), spikelet fertility SF) and thousand grain weight (TGW) under different seasons of the Philippines. It was found out that Korean phenotypes had earlier D50F and DM, shorter PH and CL, more PT, FGP and SF, and higher GY under dry than wet season. Each season had three groups based on the clustering analysis with a pattern of group 1 having phenotypes with heavy TGW, early D50F and DM, short PH and FLL; and more FGP, SF and GY; group 2 having long CL, wide FLW, light TGW; and late D50F and DM; and group 3 having short CL, narrow FLW and low PT. Correlation in FGP, PT and SF to GY was consistently high positive (r≥0.68) in two seasons. Also, PCA consistently showed that GY, PH and PT were the highest contributor of variation with an average of 21.42% in two seasons. Korean GY therefore was highly variable but attaining higher GY can be possible by utilizing grain-filling (FGP and SF) and productive tillering (PT) traits as selection indices in the breeding program.

Irrigated soft white spring wheat is largely unresponsive to conservation management in rotations with dry bean, potato and sugar beet

Historically, soft white spring (SWS) wheat (Triticum aestivum L.) has been a crop choice in southern Alberta’s irrigation districts. A 12-yr (2000–2011) study compared conservation (CONS) and conventional (CONV) management for SWS wheat in 3–5-yr rotations with dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), and sugar beet (Beta vulgaris L.). Conservation management incorporated reduced tillage, compost, cover crops, and narrow-row dry bean. Wheat was largely unresponsive to CONS management, with only 2 of 13 parameters showing significant positive effects: greater grain Ca (605 vs. 576 μg g−1 on CONV) and S concentrations (1137 vs. 1105 μg g−1 on CONV). Two parameters showed significant negative responses to CONS management: shorter plant height (82.8 vs. 84.8 cm on CONV) and higher take-all [Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker] severity (1.34 vs. 1.27 rating on CONV). The remaining nine parameters were unresponsive: plant density, days to maturity, grain y...

Field Performance of Five Soybean Mutants Under Drought Stress Conditions and Molecular Analysis Using SSR Markers

The objective s of this research w ere to evaluate (1) the performance of soybean mutant lines under drought stress condition s, and (2) the genetic diversity and relationship among the mutant lines using SSR markers. The field evaluation was conducted during the dry season of 2011 and 2012 at the experimental F arm of Mataram University, West Nusa Tenggara, Indonesia. The field experiment was set up in a randomized block design . Ten mutant lines and two control varieties were evaluated in four replications. Genetic distance among evaluated lines were determined based on allelic diversity analysis using 40 s imple sequence repeat (SSR) loci. Under drought stress conditions, two mutant lines , K dl 3 and K dl 8 , showed a better performance compared to the other ones. The h igh yielding mutant lines were K dl 3 and K dl 8, which yielded 1.75 t ha -1 and 1.69 t ha -1 , respectively, compared to the parent and national control , Panderman 1.43 t ha -1 and Muria 1.32 t ha -1 . These mutant lines required 30.75 to 32 days to flower and 79.75 to 83.75 day to harvest with relatively short plant height 28.25 and 23.35 cm respectively. T hose mutant characters were better than those of the other three mutants, the original parents, and the control soybean species. Since the evaluated soybean mutant lines yielded more under drought stress conditions than the standard varieties, t he y can be used and registered as drought-tolerant soybean mutant s . Moreover, the evaluated soybean accessions showed a wide genetic distance. The accessions were clustered into two groups according to their genetic background, namely group I (the Panderman with three mutant lines) and group II (the Muria with two mutant lines). Twenty-three out of 40 evaluated SSR loci, including AW31, BE806, CMAC7L, S080, S126, S57, S171, S224, S285 , S 294 , S 393 , S294 , S 383, S511 , S 511, S 5 20 , S 5 40, S547, S551, S571, S577, and S578, provided polymorphic alleles between the parents and their mutants and could be used to differentiate mutants from their parents. Therefore, these loci are informative and may be use ful for further analysis of soybean mutant lines in relation to breeding program.

Evaluation of Agronomic Traits and Drought Tolerance of Winter Wheat Accessions from the USDA-ARS National Small Grains Collection

Wheat accessions from the USDA-ARS National Small Grains Collection (NSGC) are a potential genetic resource for variety improvement. This study assessed the agronomic performance and drought tolerance in 198 winter wheat accessions under irrigated and terminal drought environments in the 2012–2013 season, and repeated the test under terminal drought only during the 2013–2014 season. The 198 accessions were classified into three maturity groups, early, intermediate, and late based on heading data. In all three environments, the early accessions had the best agronomic performance, produced higher grain yield, thousand-kernel weight and grain volume weight, and had earlier heading date and shorter plant height. The intermediate accessions had similar grain yield and thousand-kernel weight as the early accessions in the irrigated environment, but had lower thousand-kernel weight in the terminal drought environments. Terminal drought had significant effects on grain yield, plant height, thousand-kernel weight, and grain volume weight. The positive correlation between GY and HD suggests that the ‘late early’ types in the early maturity were the most successful. Out of 198 accessions evaluated, twenty-three had high yield stability and drought tolerance according to the drought susceptibility index and membership function value of drought tolerance. The eight of twenty-three accessions identified (four early and four intermediate) had high grain yield in three environments. Some of these accessions have been further used in bi-parental mapping studies and by breeders for grain yield and drought tolerance improvement.

Interspecific hybrid between silver leaf sunflower (Helianthus argophyllus T. and G.) and cultivated sunflower: Cytomorphological characterization of F1 hybrid

Hybrid plants were obtained by crossing cultivated sunflower (Helianthus annuus L., 2n=2x=34) lineARM-243B and a wild Helianthus species [H. argophyllus; 2n=2x=34; HEL-153/83 (PI-649865)], using the latter as pollen parent. The wild Helianthus accession was selected for this study because of its short duration and short plant height compared to other accessions of H. argophyllus. Morphological and cytological analyses were carried out to confirm the hybrid nature of the F1 plants. The hybrids exhibited morphological features intermediate to both the parents for few attributes and more related to wild Helianthus species like leaf and stem pubescence, stem hairiness, flower colour, stem size, branching, disc floret pigmentation, plant height, seed size and seed shape etc. A reduction in pollen fertility (87.5%) was recorded in F1 plants as compared to both the parents. Meiotic analysis revealed a mixture of univalents, bivalents, trivalents and quadrivalents in all the pollen mother cells (PMCs) analysed. In addition to bivalents and univalents, a trivalent was also observed in few PMCs, indicating segmental homology between chromosomes. Frequently observed chromosome configurations in diakinensis were 15 II + 1 IV and 13 II + 2 IV. The results suggested that the species H. argophyllus and H. annuus differ by 1-2 translocations and 1-2 inversions. Results show that the wild species is compatible with cultivated sunflower and using H. argophyllus cultivated sunflower can be improved for biotic (downy mildew) and abiotic stresses (drought and salinity).

Ectopic expression of a novel OsExtensin-like gene consistently enhances plant lodging resistance by regulating cell elongation and cell wall thickening in rice.

SummaryPlant lodging resistance is an important integrative agronomic trait of grain yield and quality in crops. Although extensin proteins are tightly associated with plant cell growth and cell wall construction, little has yet been reported about their impacts on plant lodging resistance. In this study, we isolated a novel extensin‐like (OsEXTL) gene in rice, and selected transgenic rice plants that expressed OsEXTL under driven with two distinct promoters. Despite different OsEXTL expression levels, two‐promoter‐driven OsEXTL‐transgenic plants, compared to a rice cultivar and an empty vector, exhibited significantly reduced cell elongation in stem internodes, leading to relatively shorter plant heights by 7%–10%. Meanwhile, the OsEXTL‐transgenic plants showed remarkably thickened secondary cell walls with higher cellulose levels in the mature plants, resulting in significantly increased detectable mechanical strength (extension and pushing forces) in the mature transgenic plants. Due to reduced plant height and increased plant mechanical strength, the OsEXTL‐transgenic plants were detected with largely enhanced lodging resistances in 3 years field experiments, compared to those of the rice cultivar ZH11. In addition, despite relatively short plant heights, the OsEXTL‐transgenic plants maintain normal grain yields and biomass production, owing to their increased cellulose levels and thickened cell walls. Hence, this study demonstrates a largely improved lodging resistance in the OsEXTL‐transgenic rice plants, and provides insights into novel extensin functions in plant cell growth and development, cell wall network construction and wall structural remodelling.

Registration of ‘Silver’ Durum Wheat

‘Silver’ (Reg. No. CV‐1128, PI 668100) durum spring wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.] was developed and released by the Montana Agricultural Experiment Station in 2013. Silver durum was initially selected in 2000 as a single F2 head from a male sterile facilitated recurrent selection durum population maintained at the Montana State University, Eastern Agricultural Research Center near Sidney, MT. Final selection came from an F6 head row and was subsequently tested under the experimental name MT03012 in Montana and North Dakota from 2006 to 2012. Quality was evaluated in multilocation trials beginning in 2006. Silver is a day‐length insensitive, high‐yielding durum line with medium to high test weight, early heading date, short plant height, medium to high grain protein content, and acceptable semolina quality. Silver was released for its day‐length insensitivity, short stature and early heading date.

English

A field experiment was conducted during the 2006 cropping season in Ofla district in southern Tigray to assess the response of bread wheat (Triticum aestivum L.) varieties to nitrogen and phosphorus fertilizer rates. Factorial combinations of two wheat varieties (HAR1685 and Shehan), four N rates (0, 23, 46 and 69 kg N/ha), and four P rates (0, 10, 20 and 30 kg P/ha) were laid out in split plot design (varieties in the main plot and N-P fertilizer rates to the sub plots) with three replications. The variety HAR1685 exhibited significantly higher values for  grain yield, harvest index, total N uptake, grain P uptake, N apparent recovery, and agronomic efficiency but had shorter plant height and maturity period. Shehan on the other hand, exhibited higher values for tiller number per plant, plant height, shoot dry weight at 50% flowering and at physiological maturity, biomass yield, straw yield. Application of N and P fertilizers significantly (P<0.01) influenced plant height, shoot dry weight at physiological maturity, and tiller number per plant. The variety-P-N interactions were highly significant for grain yield, biomass yield, harvest index, and straw yield. The increase and decrease in shoot dry weight at 50% flowering, grain yield, biomass yield harvest index, straw yield and available soil phosphorus at harvesting did not show a consistent trend. However, an increasing trend was observed when the rate of N increased from 0 to 69 kg N/ha. Non-significance difference due to the interaction of P and N with respect to plant height, number of tillers per plant, initial plant stand, 1000 kernels weight ,days to 50% flowering and total soil nitrogen at harvest was observed. The grain and straw N and P contents and uptakes, increased with N and P levels but the apparent recovery and agronomic efficiency of N and P fertilizers decreased with increasing N and P rates in both varieties. Grain and biomass yields were significantly and positively correlated with most of the agronomic parameters, grain N and P contents, grain N and P uptakes, and total N and P uptakes. Moreover, grain and straw N and P contents and their uptakes were strongly and positively correlated with applied N and P respectively.  Even though it is one year in one location study, it can be concluded that the released variety HAR1685 had high grain yield potential, strong stems, medium plant height, heavier kernel weight, higher harvest index, and shorter maturing period and responsive  to higher N and P rates. The shortcoming of the experiment was it was conducted in a single location. It should be repeated in more than one location.   Key words: Bread wheat, nitrogen, phosphorous, soil, physical, chemical.

English

Field experiments were conducted in two seasons at the farm of Sokoine University of Agriculture in Morogoro, Tanzania (6.85°S; 37.64°E and 568 m.a.s.l.) during the short rain (November 2014 to January 2015) and the long rain (March to June 2015). The experiment was a split plot in randomized complete block design (RCBD) with 4 replicates. Weed management practices (herbicides, hoe weeding (3x) and weedy) were the main plot treatments; four rice genotypes (NERICA-1, NERICA-4, NERICA-7 and Mwangaza) were the subplots. Significant differences (P<0.05) were recorded on weed counts. Dominant weed groups as determined by Summed Dominance Ratio (SDR) in both experiments were broadleaf species (50.8%), sedges (25.2%) and grasses (24.0%). Post-emergence (8.6%) and hoe weeding (12.3%) significantly reduced weed dry biomass as compared to pre-emergence (17.8%) and weedy (61.3%) treatments in both experiments, respectively. Significant differences (P<0.05) were recorded among the rice variables. Data showed that Mwangaza and NERICA-1 had the tallest and shortest plant height (129.8 and 39.1 cm), respectively in both experiments. The highest and lowest tiller (35.3 and 7.5 m2) count was recorded for both these genotypes, respectively. The lowest and highest LAI (2.5 and 4.5) were recorded on Mwangaza and NERICA-7 respectively; and NERICA-7 had the highest and lowest straw biomass (1603 and 305.1 g/m2) in both experiments. The highest rice grain yield were recorded for NERICA-1 on hoe weeded plots and plots applied with post-emergence herbicide (2187.5 and 1562.5; 4176.1 and 4630.6 kg/ha) as compared to plots applied pre-emergence herbicide and weedy plots (965.9 and 0.0; 3323.8 and 0.78 kg/ha) in 2014/2015 and 2015 experiments, respectively. The highest return on investment, 3 352 846 Tanzanian shillings (Tshs) was obtained on NERICA-1 in post-emergence herbicide plots, and this was also similar (P<0.05) to hoe weeded plots. Post-emergence herbicide was also effective in weed control and had significant effect on profit analysis. This treatment/practice should be used in combination with hoe weeding under integrated weed management for better weed control. Key words: Weeds, management, upland rice, yields, growth, profitability.

Maturity groups and growing seasons as key sources of variation to consider within breeding programs for high yielding rice in the tropics

Differences in crop performance between seasons has raised concerns on whether or not contrasting rice varieties should be grown in each season in the tropics. Solving this question requires evaluation if key plant traits subtending grain yield are expressed similarly across seasons. Within each dry season (DS) and wet season (WS), one approach to address the issue was to group 32 high-yielding and contrasted cultivars with respect to crop duration, and to consider the crop cycle as two distinct phases: the first one from early vegetative to flowering (pre-flowering) and the second one from flowering to maturity (post-flowering). For each of these two phases, one key descriptive parameter was identified, the potential sink size (PSS) at flowering for the pre-flowering phase, and the grain filling rate (FR) for the post-flowering phase. Significant correlations were observed for grain yield with both PSS and FR within maturity groups in both seasons, indicating the strong effect of both phases in grain yield establishment. Finally, relevant traits in the DS were those favoring light capture along the whole crop cycle in both maturity groups. Traits for the WS differed among maturity groups. Traits for the early maturity group were also those favoring light capture, while the same traits were non desirable for the medium and late maturity groups, for which delayed leaf senescence and short plant height were identified. The difference between relevant traits highlights the need of developing distinct breeding programs respective of the growing seasons and maturity groups.

BRS Kurumi and BRS Capiaçu - New elephant grass cultivars for grazing and cut-and-carry system

Abstract Cultivar BRS Kurumi is characterized by short plant height, short internodes, high dry matter production (29.25 t ha-1yr-1), has a high nutritional value and is recommended for the cut-and-carry system or grazing. Cultivar BRS Capiacu, indicated for silage and the cut-and-carry system, has tall upright growth, high dry matter production (49.75 t ha-1yr-1), good forage quality, is lodging-resistant and suitable for mechanical harvesting. Both cultivars are vegetatively propagated by stem cuttings.