The effect of spot blotch and heat stress on variation of canopy temperature depression,chlorophyll fluorescence and chlorophyll content of hexaploid wheat genotypes

Spot blotch, caused by Cochliobolus sativus (Ito and Kurib.) Drechsler ex Dastur, and heat stress are two important stresses of bread wheat (Triticum aestivum L.) causing substantial yield reduction in the warm areas of South Asia. These two stresses put pressure on at least 25 million hectares of wheat areas worldwide. This study was conducted to examine variation in physiological traits and its association with heat and spot blotch. Eleven diverse bread wheat genotypes were evaluated in replicated field trials under spot blotch epidemics and heat stress conditions in 2006 and 2007 at Rampur, Nepal. Canopy temperature depression (CTD), chlorophyll fluorescence (CF), chlorophyll content, percent disease leaf area, yield and yield components were recorded. Heat and spot blotch individually reduced CTD, CF, chlorophyll content, grain yield (GRY), and thousand kernel weight (TKW), with greater reductions recorded under combined stress. Genotypes showing lower GRY or TKW loss due to spot blotch also exhibited lower yield loss due to heat stress or combined heat and disease stress, suggesting an association between tolerance mechanisms to the stresses. The physiological traits chlorophyll content, CF and CTD showed higher correlations with GRY and TKW than with area under disease progress curve (AUDPC) suggesting their potential application in screening for heat and spot blotch tolerant genotypes. Genotypes with lower disease showed the highest values for chlorophyll content, CF and CTD. Our findings provide new information on the relationship of these physiological traits with spot blotch resistance and heat tolerance when examined in the same study. The physiological traits studied have potential application in integrative indirect selection criteria for improving spot botch and heat tolerance in wheat.     

An Awareness-Adoption Matrix for Strategic Decision Making in Agricultural Development Projects： A Case Study in Yunnan Province, China

Significant achievements have been made in generating sustainable agricultural technologies in developing countries. Usually, these new technologies have been more effective in increasing production and productivity than existing technologies. However, many new technologies considered ＇effective＇ have not been successful in alleviating the associated sustainability problems, due to poor adoption by targeted users. Success of any novel technical intervention should be judged on the basis of how widespread adoption is in the target area by targeted users. In this context, a case study identified the factors affecting farmers＇ adoption of improved technologies extended by an agricultural development project in a rural Village in Yunnan Province, China. Initial adoption/adaptation of project technologies was influenced by farmers＇ awareness of the technology. Farmers were more aware of polythene mulch, contour cultivation, intercropping and tree planting technologies than others. This led to a comparatively high initial uptake of polythene mulch, contour cultivation, sweet chestnut, and intercropping technologies. Farmers had inadequate knowledge about some Project technologies, the adoption of which was particularly low. This reveals the need for increasing farmers＇ awareness about the rationale for Project technologies to achieve greater adoption/adaptation of project technologies by farmers over wider areas. Farmers＇ testing of the technology leads to better adoption/adaptation compared to mere awareness. However, considerable time and resources are required for testing/trying technologies. This justifies the usefulness of comparatively quick and less resource demanding options for awareness creation. Development of effective cropping technologies is important for sustainable agricultural development. The success of any agricultural development project, especially in terms of improving sustainability, depends on how widely those improved technologies are adopted/adapted by farmers in the targeted region. Therefore, farmers＇ adoption of technologies should be a key criterion for judging the success of any project. The awareness-adoption matrix is a useful tool to guide research and development projects to achieve expected adoption/adaptation of technologies. Use of the matrix helps identification of weak and strong aspects of research and development projects and thus assists strategic decision-making.     

A new method to quantify how water repellency compromises soils' filtering function

Soil water repellency (SWR) is known to lead to preferential flow and to degrade the soil's filtering efficiency. However, no method is available to quantify directly how SWR affects the transport of reactive solutes. We propose a new method for conducting solute transport experiments in water‐repellent soils. It involves sequentially applying two liquids, one water, the other a reference fully wetting liquid, namely aqueous ethanol, to the same intact soil core with air‐drying between liquids. We applied this approach to quantify the impact of SWR on the filtering of the herbicide 2,4‐Dichlorophenoxyacetic acid (2,4‐D) in two Andosols. In batch experiments conducted prior to the transport experiments, 2,4‐D sorption was not influenced by aqueous ethanol for one soil. However, sorption in the second soil followed the co‐solvency theory, which predicts decreasing sorption with increasing solvent fractions. Thus, sorption experiments are necessary to complement our new method. Breakthrough curves were characterized by preferential flow with large initial concentrations, tailing and a long prevalence of solutes remaining in the soil. In the soil in which 2,4‐D sorption was unaffected by aqueous ethanol, SWR increased 2,4‐D losses by four and 50 times in the first 5‐mm outflow compared with the 2,4‐D losses with water. After 50‐mm outflow, the 2,4‐D losses were similar for one core, but in the other core they were still about four times greater with water than with aqueous ethanol. This method to quantify the reduction of the soil's filtering efficiency by SWR is needed for assessing the increased risk of groundwater contamination by solutes exogenously applied to water‐repellent soils.     

New method to estimate root biomass in soil through root-derived carbon

Quantification of root biomass through the conventional root excavation and washing method is inefficient. A pot experiment was conducted to estimate root-derived carbon (C) in soil. Spring wheat (Triticum aestivum L. cv. ‘Quantum’) was grown in plastic containers (6 L) filled with sterilized sandy soil in a greenhouse. Plants were enriched with ¹³CO₂ in a glass chamber twice at growth stages GS-37 and GS-59 for 70 min at each time. In one treatment, roots were separated from soil at crop maturity, washed and dried for the determination of biomass. Isotope ratios were then separately analyzed for roots and soil. In a second treatment, roots were thoroughly mixed with the whole soil and representative samples were analyzed for ¹³C abundance at crop maturity. Control plants were untreated with ¹³C, in which roots were separated from soil. The root biomass was calculated based on the root-derived C, which was measured through ¹³C abundance in the soil and root mixed samples. A substantial amount of root-derived C (24%) was unaccounted while separating the roots from soil. Similarly, about 36% of the root biomass was underestimated if conventional root excavation and washing method is used. It has been shown that root biomass can be estimated more accurately from the root-derived C using ¹³C tracer method than the estimates made by the conventional excavation and washing method. We propose this as an alternative method for the estimation of root-derived C in soil, based on which root biomass can be estimated.     

Fatty acid composition of yak (Bos grunniens) cheese including conjugated linoleic acid and trans-18:1 fatty acids

The esterified fatty acid composition of cheese (YC) from yak ( Bos grunniens), reared in the highlands of the Nepalese Himalayas, was studied using capillary gas-liquid chromatography and compared with that of dairy cow Cheddar cheese (DC) purchased in a local market. The YC was collected from Dolakha, Nepal. The YC had a lower (P<0.001) myristic acid (C14:0; 6.7 vs 10.3%, YC vs DC, respectively) and palmitic acid content (C16:0; 23.3 vs 29.2%, YC vs DC, respectively) compared to DC. The YC had a lower (P<0.01) total medium-chain saturated fatty acids (C10:0-C16:0) content compared to DC (36.7 vs 47.3%, YC vs DC, respectively). On the other hand, the YC had a 24.8% higher (P<0.01) level of total long-chain saturated fatty acids (C17:0-C26:0) and a 3.2 times higher (P<0.001) content of total n-3 PUFA than DC. The ratio of n-3 PUFA to n-6 PUFA in YC was 0.87 compared to 0.20 in DC. YC had a 2.8 times higher (P<0.001) total trans-18:1 (9.18 vs 3.31%, YC vs DC, respectively) content. The percentage of vaccenic acid ( trans-11-C18:1) in YC was 4.6 times higher (6.23 vs 1.35% of total fatty acids, YC vs DC, respectively) than in DC. Vaccenic acid constituted 67.9% of total trans-C18:1 in YC. The Delta9-desaturase index for YC was lower than that of DC. The total conjugated linoleic acid (CLA) content in YC was 2.3% of total fatty acids compared to 0.57% in DC. The cis-9, trans-11 CLA isomer in YC constituted 88.5% of the total CLA. The results suggest that cheese from yak, grazed on Himalayan alpine pastures, may have a more healthful fatty acid composition compared to cheese manufactured from dairy cattle fed grain-based diets.     

Diversity Analysis of Garlic (Allium sativum L.) Germplasms Available in Nepal Based on Morphological Characters

A total of 179 garlic (Allium sativum L.) accessions were collected from various parts of Nepal in 2000. Each accession was planted in each of a plot of 2.25 m² at the Institute of Agriculture and Animal Science (IAAS) Horticulture farm (225 m asl) and at the Agriculture Research Station, Dailekh (1400 m asl) of Nepal Agriculture Research Council (NARC) in the first week of November 2000. All accessions were characterized for leaf erectness, leaf color, leaf wax, leaf cross section, bulb regularity, bulb skin color, bulb outer scales number, days to emergence, bulbing period, number of green leaves at 135 days after planting, days to maturity, plant height, bulb weight, bulb diameter, number of cloves per bulb, clove diameter and bulb yield. Data were analyzed by using principal component and cluster analysis procedures to reveal three major clusters. Four principal components were identified explaining more than 86% of total variation. Major characters included in the principal components were bulb weight, diameter, yield, number of cloves per bulb, maturity, plant height, number of green leaves at 135 days after planting, and bulbing period. The level of variation found in the collection showed the great potentiality of improving agronomic characters in garlic.     

Collaborative breeding with farmers can be effective

Plant breeding efficiency is increased by better taking into account the needs of the clients. This can sometimes be helped by involving farmers in selection in the segregating generations. We describe a rice-breeding programme in Nepal where the use of simple breeding methods optimised the benefits from such collaboration. Farmers grew in their fields large populations that were bulks derived from the F₂ generations of single crosses. They selected within them starting in a generation where selfing was sufficiently advanced for the between-plant heritability to be high. Poorer bulks were soon rejected by farmers. A high proportion selected within the bulks and a significant proportion did so over several generations. An increasing number of farmers grew the best of the selected bulks because they spread from farmer to farmer without the need of intervention from scientists. Varieties selected from these bulks were preferred by farmers in on-farm trials and had a superior combination of yield and maturity compared with the later breeders’ selection from the same bulk. Levels of participation were higher with the better performing bulks and even when training was not provided, provided the germplasm performed acceptably well sufficient farmers selected in the bulks to make collaborative breeding cost effective. Collaborative breeding can be successful but demands different types of resources than those for on-station breeding so its cost effectiveness will vary with circumstances. It can be used to increase the probability of selecting segregants that perform well across environments by using methods that pool bulks selected by different farmers and it is also extremely useful for decentralising breeding programmes.