International Journal of Plant Production
Volume:3 Issue: 2, April 2009

Defoliation produced by abiotic factors and the subsequent re-growth can reduce sugar beet (Beta vulgaris L.) sucrose content and final sugar yield. Field experiments were conducted during 2003 and 2004 growing seasons in the farm of Hellenic Sugar Industry SA, Larissa factory, central Greece. Three sugar beet cultivars (Rival, Europa and Corsica) were ordinary irrigated till the beginning of July and then left without irrigation for a month. Three defoliation levels (control-C, moderate-MD and severe-SD) were performed at early August and irrigation was simultaneously started to promote re-growth. Four samplings were conducted (before defoliation, 15, 30 and 40 days after defoliation) to determine the changes in physiological and productive traits. Yields were lower in 2003 compared to 2004 because sugar beets were grown under more stressful conditions due to the delayed sowing, the higher temperatures and the lower rainfall. Both defoliation level and cultivar had significant effects on physiological and productive traits after re-growth only in 2003. The late-season cultivar, Corsica, showed better LAI maintenance compared to Europa and Corsica and had the greatest performance after re-growth in regard to fresh root weight and sugar yield. Also, this cultivar showed the least decrease of sucrose percentage in fresh root weight and juice purity mainly due to the stable potassium (K) concentration and limited increase of sodium (Na) accumulation in roots. Corsica consumed the least root α-amino N for its re-growth. Quantitative and qualitative traits were negatively affected only by the SD treatment. Plants suffered from MD treatment gradually recovered during growing season. This study demonstrates that under Mediterranean conditions, the adverse effects of re-growth on sugar beet yield and quality depend on the growing conditions and they can be restricted by the selection of an appropriate cultivar.

Twenty one F2 progenies derived from a 7×7 diallel crosses along with parents were evaluated for grain yield, flowering and maturity time. Due to significant genotypic effects for all traits, genetic analyses were performed on F2 progenies including analyses of combining ability and genetic components. The Analysis of variance revealed that both additive and non-additive genetic effects were involved in controlling these traits. GCA/SCA ratios were 0.91 for days to flowering, 0.95 for days to maturity and 0.83 for grain yield which indicated that the additive gene effects were more important than non-additive gene effects for all these traits. Narrow-sense heritability was high for days to flowering (73.12%) and days to maturity (81.99%) and low for grain yield (30.15%). Heterosis in hybrids seemed to be largely determined by complementary epistasis as well as genetic distance between the parents. The spring-type varieties Tower and Regent appeared as the best parents for earliness whereas winter-type varieties D.R. and Ceres were best parents for high grain yield. It could be concluded from the study that S1 recurrent selection would be effective to improve the performance of these genotypes for grain yield, flowering and maturity time. The selected S1 lines from each cycle can be used in a pedigree-breeding program to identify superior genotypes.

Carex divisa is a patrimonial rhizomatous species and acts as an important component of grazed wet permanent grassland on the French Atlantic coast. This study treated three storage regimes (wet-cold, dry-cold and dry-warm), burial in soil, fluctuating temperature and salinity on seed germination of C. divisa. The seeds were dormant at maturity. No seed germinated after 2 and 6 weeks of dry storage under laboratory conditions prior to the onset of the stratification treatment. Thus, the effect of after-ripening was not evident in C. divisa. Germination rate of 11.3% started only in the wet-cold stratification treatment after 2 months. Seeds that had been stored under wet-cold conditions for 8 months had a higher germination than seeds stored under dry-cold and dry-warm treatments for the same length of time. Seeds of C. divisa tested at 10-20 °C in light had no marked dormancy cycle, but in darkness under a fluctuating temperature regime (10-20 °C), C. divisa seems to exhibit annual dormancy cycles. There were no differences in germination between fluctuating temperatures 10-20 °C and 15-25 °C after 12 months in the wet-cold treatment. No germination occurred at fluctuating temperatures 0-10 °C. The highest percent germination was observed in distilled water, followed by 50 mM L-1 NaCl. The highest NaCl concentration (250 mM L-1) was found to inhibit seeds germination.

The effects of potassium fertilizer (K2SO4) levels K0, (0), K1,(150) and K2,(250 kg/ha) in two species of Brassica napus (Hyola 401 Hybrid) and Brassica juncea (landrace cultivar), under three irrigation regimes, control (irrigation after 50%,), moderate stress, (irrigation after 70%), and severe stress (irrigation after 90% soil water depletion) were studied in a factorial experiment laid out in a randomized complete block design with three replications. Grain yield and physiological indices, including relative water content (RWC), stomatal conductance (g), chlorophyll content (SPAD values); leaf temperature (TL), and the difference between canopy temperature and air temperature
(Tc-Ta) were measured at two stages (50% flowering and 100% siliques formation. Both species maintained, higher RWC, SPAD values and g, in non stress condition, but decreasing soil water supply caused a lower RWC, SPAD values, g, Δt and increased TL. Potassium application also improved above mentioned physiological traits. Grain yield was positively associated with RWC, g and SPAD values but showed a negative association with TL and Δt in both stages. Results showed that with increasing stress severity grain yield reduced significantly, but potassium application conferred great increase on rapeseed yield. Overall, grain yield showed significant association with RWC, g, SPAD values, Δt and TL under this experiment conditions. It is concluded that potassium application, could ameliorate negative effects of water stress on grain yield and physiological properties and consequently improved them. For selecting drought tolerant cultivars, due to easier measurement of g, SPAD values and TL, they could be recommended for screening large numbers of rapeseed cultivars in a short time at critical stages of crop growth.

A model has been used to simulate potassium (K) uptake by wheat in a pot culture experiment. Three soils from India, namely Alfisol, Inceptisol and Vertisol, were differentially K exhausted by Sudan grass (Surghum vulgare var. Sudanensis) for a period of 280 days and were used to simulate potassium uptake by wheat (Triticum aestivum) and also to predict the amounts of K released or fixed during cropping. Except in Alfisol all the predicted values of K uptake closely agreed with that of measured values. When predicted K uptake values were plotted against the observed values, r2 values were found to be 0.927, 0.828 and 0.721 in Inceptisol, Alfisol, and Vertisol, respectively. There is a close relationship between observed and predicted values of K uptake as evident from the high r2 values, but in case of Alfisol and Vertisol the model has over-predicted K uptake, which perhaps was due to over prediction of K release from non-exchangeable form. The model has been validated and has been applied to simulate response towards fertilizer application at different available K. It was showing that maximum response occurs at a particular value of available K, which shifts towards higher value as release threshold level (RTL) increases. Predicted K uptake was most sensitive to changes in root parameters such as root length density (RLD) and maximum influx rate (Vmax), since changes in the time at which maximum root length density was attained (RLD-B) and the decay constant of Vmax (Vmax-B) gave the greatest changes in K uptake in almost all the soils except highly exhausted Alfisol in which predicted potassium uptake was more sensitive to changes in RLD-B and intercept (c) than to root uptake kinetics, as described by Michaelis-Menten constant (Km) and Vmax. The predicted potassium uptake was least sensitive to changes in rate constants of release and fixation and fixation threshold level in Inceptisol and Vertisol, but was sensitive to release threshold level and rate constant of release in Alfisol

The expression pattern of TomPRO2 and LaPA1 genes in two tomato (Lycopersicon esculentum) cultivars named as Isfahani and Shirazi under in vitro salt stress were investigated. Four to six weeks old in vitro grown seedlings were transferred on MS medium containing 0, 80 and 160 mM NaCl and untreated plants were used as control. RNA was extracted from root and leaf and then cDNA was synthesized. Semi-quantitative analysis of TomPRO2 and LaPA1 expression using specific primers showed that with increasing of NaCl concentration from 0 to 160 mM, the expression level of TomPRO2 and LaPA1 genes in roots of both tomato cultivars did not change significantly. In leaf TomPR2 gene expression decreased significantly at 160 mM NaCl. At the same concentration of NaCl (160 mM) LaPA1 gene expression in leaf increased significantly. Based on the obtained results, TomPRO2 and LaPA1 genes have different expression patterns under in vitro salt stress in tomato root and leaf. However, both genes have a role in response to salt stress.

Search for an adapted forage species for feed production under existing marginal lands and harsh conditions is needed to overcome sever feed shortage in Egypt. Sesbania, Sesbania aegyptiaca (Sesbania sesban, L) has shown potential for forage production and being included in grazing systems, especially on marginal lands and salt–affected soils. An experiment was conducted in the summer of 2004 and 2005 under artesian irrigated water conditions where four cutting heights (10, 20, 30, and 40 cm above ground level) and three plant spacing (10, 20 and, 30 cm between plants) were investigated. The highest average accumulated fresh and dry forage yield obtained from cutting at 10 cm from ground surface whereas the 40 cm cutting level produced the lowest yield and no significant difference was observed between 20 and 30 cm cutting levels. Highest yield was obtained from second cutting. The CP% in forage harvested from 10 cm spacing was highest followed by 20 and 30 cm spacing, respectively. Forage from 1st cutting had the highest CP% followed by 2nd and 3rd cutting. The response of CF% in Sesbania aegyptiaca to cutting level and time was opposite to those of CP %.

In this study, nitrogen fertilizer was applied to corn (Zea mays L.) at conventional (excessive) and recommended levels, and the growth response was assessed by measuring plant height and stem perimeter. Corn plant maximum height was observed in recommended rates of N fertilizer treatment, and the height without N fertilizer was the same as that receiving excess N fertilizer. Stem perimeter was greatest in the treatment with recommended levels of N fertilizer, followed by the excess N fertilizer treatment. Greater increases in stem perimeter and plant height were observed after application of fertilizer at recommended rates, compared to control without N fertilizer and treatment with excessive N fertilizer, showing that application of N fertilizer at recommended rates results in better growth than that observed after application of fertilizer at excessive rates (i.e. those used in local farming practice). This study shows that soil testing to determine appropriate rates of fertilizer application can reduce fertilizer application rates by more than 50%, while retaining optimum growth in plant height and stem perimeter. Therefore, decreasing application of fertilizer is feasible to reduce environmental pollution and the cost of agriculture.

The critical period for weed control (CPWC) is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. Field studies were conducted in 2005 and 2006 in the University of Birjand at the south east of Iran to determine CPWC of corn using a randomized complete block design with 14 treatments and three replications. The treatments consisted of two different periods of weed interference, a critical weed-free period and a critical time of weed removal, were imposed at V3, V6, V9, V12, V15, and R1 (based on phonological stages of corn development) with a weedy check and a weed-free check. The CPWC was determined with the use of 2.5, 5, 10, 15 and 20% acceptable yield loss levels by non-linear regression method and fitting Logistic and Gompertz nonlinear equations to relative yield data. The CPWC of corn was from 5- to 15-leaf stage (19-55 DAE) to prevent yield losses of 5%. This period to prevent yield losses of 2.5, 10 and 20% was 4- to 17-leaf stage (14-59 DAE), 6- to 12-leaf stage (25-47 DAE) and 8- to 9-leaf stage (31-36 DAE) respectively.

A pot experiment was conducted in rabi season 2004-05 to study the effect of Kappaphycus alvarezii extract applied as a foliar spray at 0.25%, 0.50% and 1.0% on wheat. Compared to control the yield of grain increased by 80.44% when, the plants were sprayed with 1.0% K. alvarezii extract. The nutritional quality of grain such as carbohydrate, protein and minerals also improved under the influence of treatment.