Influence of Long-term Use of Organic and Inorganic Nutrients on HLB Disease of Wheat under Rice-Wheat Cropping Pattern

Helminthosporium leaf blight (HLB) is one of the most destructive diseases of wheat in terai (plain) region of Nepal. This study was conducted to determine the effect of long-term application of various levels of nitrogen (N), phosphorus (P), potassium (K) and organic nutrients on HLB disease of wheat. The experiment was superimposed on long-term fertility experiment conducted in RCB design with three replications under rice-wheat cropping pattern at National wheat research program (NWRP), Bhairahawa, Nepal. The treatments include various combinations of nitrogen 100 kg ha-1, phosphorus 0 and 60 kg ha-1, and potash 0, 50 and 100 kg ha-1 with or without Sesbania (Sesbania cannabina) and farm yard manure (FYM). Area under disease progress curve (AUDPC) was calculated using the disease scores and yield parameters were recorded. Among the inorganic nutrients, long-term deficiency of potash in the field markedly enhances the HLB disease. Application of phosphorus in various doses increased the HLB severity in absence of potash. Regular application of at least potash 50 kg ha- 1 in wheat noticeably reduced the HLB disease. Regular use of FYM 10 ton ha-1 for long-term considerably reduced the HLB disease but long-term use of Sesbania as green manure did not show any impact on HLB severity. Inclusion of potash in nutrients considerably increased the yield and thousand grain weight (TGW) of wheat. In long term, balanced use of inorganic and organic nutrients with special attention on regular inclusion of potash and FYM in the nutrient combinations is vital in suppression of HLB disease under rice-wheat cropping pattern.Nepal Agric. Res. J. Vol. 9, 2009, pp. 76-84DOI: http://dx.doi.org/10.3126/narj.v9i0.11644

Morpho-physiology of wheat genotypes under different sowing dates as affected by Helminthosporium leaf blight and leaf rust in Chiwan, Nepal

An experiment was conducted at the Agronomy farm of the Institute of Agriculture and Animal Science (IAAS), Rampur, Nepal in 2008/09. The experiment was laid out in factorial design in spit plot arrangement consisting of date of sowing as main factor and wheat genotypes as sub factor. Wheat genotypes were sown in 22 November for normal sowing and 29 December for late sowing condition. These were assessed against Helminthosporium leaf blight and leaf rust severity in a naturally inoculated environment. Result showed that wheat genotypes differed significantly with respect to flag leaf area, flag leaf duration and plant height. Genotype BL-3064 showed the lower decline (624.9 to 615.1) in chlorophyll content whereas RR-21 showed highest decline (471.2 to 360.4) in chlorophyll content from normal to late sowing, possibly contributing to resistant to the disease. The AUDPC value revealed that genotypes BL-3625 and BL-3623 had increased level of resistance due to lower AUDPC value and higher flag leaf duration. The results of this study suggest that genotypes BL-3623, BL-3625, BL-3063 and BL-3064 could be the option in warm and humid regions of Terai condition so far as resistant to Helminthosporium leaf blight and leaf rust are concerned. Agronomy Journal of Nepal (Agron JN) Vol. 3. 2013, Page 109-116 DOI: http://dx.doi.org/10.3126/ajn.v3i0.9012

Yield and Yield Components Response to Defoliation of Spring Wheat Genotypes with Different Level of Resistance to Helminthosporium Leaf Blight

Breeding for resistance to Helminthosporium leaf blight (HLB) caused by a complex of spot blotch (Cochliobolus sativus) and tan spot (Pyerenophora tritici-repentis Died) of wheat (Triticum aestivum L.) is difficult due to complex nature of resistance, and high influence of environment. This study was conducted to examine whether genotypes having variation in level of resistance and tolerance differ in compensation to loss of leaves. Five spring wheat genotypes with different levels of resistance and tolerance to HLB were grown under irrigated field conditions in randomized complete block design during 2001-2002 and 2002- 2003 wheat-growing season at Rampur, Chitwan, Nepal. Defoliation treatments consist of removal of flag (F), penultimate (F-1), and both F and F-1 leaves were done one day after anthesis. Results showed that defoliation had significant effects on grain yield, biomass yield, thousand-kernel weight (TKW) but not on harvest index, number of grains per spike, kernel per spikelet, and spikelets per spike. All genotypes included in this study showed some degree of compensation for loss of F, F-1, and both F and F-1 leaves, which was found to be variable between years. Removal of flag leaf was compensated by the resistant genotype NL750 for both grain yield and TKW but not for both F and F-1 leaves. Loss of both F and F-1 leaves was better compensated by BL 1473, a stably tolerant genotype in both years. For other genotypes sensitivity to defoliation was found as variable as tolerance to HLB. Key words: Spot blotch, tan spot, defoliation, compensation, flag leaf removal, penultimate leaf removal J. Inst. Agric. Anim. Sci. 26:43-50 (2005)