Soybean Aphid Infestation Induces Changes in Fatty Acid Metabolism in Soybean

The soybean aphid (Aphis glycines Matsumura) is one of the most important insect pests of soybeans in the North-central region of the US. It has been hypothesized that aphids avoid effective defenses by inhibition of jasmonate-regulated plant responses. Given the role fatty acids play in jasmonate-induced plant defenses, we analyzed the fatty acid profile of soybean leaves and seeds from aphid-infested plants. Aphid infestation reduced levels of polyunsaturated fatty acids in leaves with a concomitant increase in palmitic acid. In seeds, a reduction in polyunsaturated fatty acids was associated with an increase in stearic acid and oleic acid. Soybean plants challenged with the brown stem rot fungus or with soybean cyst nematodes did not present changes in fatty acid levels in leaves or seeds, indicating that the changes induced by aphids are not a general response to pests. One of the polyunsaturated fatty acids, linolenic acid, is the precursor of jasmonate; thus, these changes in fatty acid metabolism may be examples of “metabolic hijacking” by the aphid to avoid the induction of effective defenses. Based on the changes in fatty acid levels observed in seeds and leaves, we hypothesize that aphids potentially induce interference in the fatty acid desaturation pathway, likely reducing FAD2 and FAD6 activity that leads to a reduction in polyunsaturated fatty acids. Our data support the idea that aphids block jasmonate-dependent defenses by reduction of the hormone precursor

Adoption of improved cassava varieties in Uganda: implications for agricultural research and technology dissemination

Improved germplasm from the cassava-breeding program has generated new varieties that are increasingly being grown by farmers in Uganda.In this study, the socio-economic and demographic characteristics of cassava farmers in different regions of Uganda, adopted cassava varieties, their adoption rates, desirable and undesirable attributes, and factors that have influenced the speed of adoption of the most adopted variety were determined. The negative binomial model was used to analyze the determinants of the speed of adoption of the most widely adopted cassava variety. NASE 1, NASE 2, NASE 3, NASE 4, NASE 10 and NASE 12 are the varieties so far adopted. NASE 3 is the most widely adopted, to adoption levels as high as 77% in central Uganda. Farmers consider disease resistance, maturity period, taste, dry matter content, cyanide content, inground storability and diversity in forms of utilization in their decision to adopt new cassava varieties. From the Negative Binomial model, speed of adoption of NASE 3 was positively and significantly influenced by age of household head, household size and access to extension services. However, it was negatively and significantly influenced by number of hoes owned by a household. The considerable variability within the crop can be exploited to ensure that each variety has a fair blend of all desirable quality attributes. There is need to continue breeding for adaptability to biotic stresses such as diseases while improving on attributes that influence palatability and nutritive value of the crop. With respect to technology dissemination, strengthening the link between farmers and agricultural extension agents/service providers and improving the targeting of extension services will enhance the adoption of new cassava varieties

Evaluation of advanced cassava genotypes in Uganda

In a bid to increase the number of genotypes reaching farmers, on-farm trials were conducted in 2001/2002 with the aim of increasing the number of genotypes available to farmers to be evaluated for performance, adaptation and acceptability. Twenty improved genotypes were planted in Lira, Nakasongola, Gulu, Kumi and Katakwi districts using augmented design. The results indicated that cassava mosaic disease (CMD) varied from location to location but was more influenced by the genotype than the environment. The highest CMD severity (>4) was recorded among the farmers' local varieties across all environments, followed by Alice local (3.8±O.4) in Nakasongola and Lira (2.8±O.2) districts and 160142 (3.0±0.0) in Kumi and Lira (2.8±O.2) districts. Six clones (MM96/0245, MM96/056 I , 192/2324, MM96/3585, MM96/4589 and MM96/0264) showed resistance (score I for CMD) while the rest had severity scores below the average (2.5). At harvest, the highest yield (60.8±3.7 t ha-') was obtained from Alice local followed by clone MM 96/0561 (59.5±6.6 t ha-') in Nakasongola district and clone MM 96/4614 (52.5±13.2 t ha-') in Lira district. The lowest yield was from clone MM 96/3585 (l0.3±4.2 t ha-') followed by Oko Iyawo (I) 99 (l4.2±4.2 t ha-') in Kumi district. All the varieties tested were either sweet or slightly bitter with the scores of I or 2, respectively. Genotype MH97/296I was the most preferred in Kumi and Lira districts, while it was third in Nakasongoladistrict. All these genotypes also had a sweet taste for cooking. The most preferred genotypes in N akasongola were TME 5 and MM96/53 12 and had a sweet taste for cooking. The genotype by environment analysis indicated that genotypes TME 5, MM961 1419, 19210427, and MH97/044 (2) UG were the most stable and adapted across all environments while MM96/4614 and Alice local were more specific for Lira and Nakasongola, respectively. These findings provide a basis for recommendations with regard to cultivation and preference of cassava genotypes in different environments

Evaluation of Advanced Cassava Genotypes in Uganda

In a bid to increase the number of genotypes reaching farmers, on-farm trails were conducted in 2001/2002 with the aim of increasing the number of genotypes available to farmers to be evaluated for performance, adaptation and acceptability. Twenty improved genotypes were planted in Lira, Nakasongola, Gulu, Kumi and Katakwi districts using augmented design. The results indicated that cassava mosaic disease (CMD) varied from location to location but was more influenced by the genotype than the environment. The highest SMD severity (>4) was recorded among the farmers" local varieties across all environments, followed by Alice local (3.8 ±0.4) in Nakasongola and Lira (2.8 ±0.2) districts and I 60142 (3.0 ±0.0) in Kumi and Lira (2.8 ±0.2) districts. Six clones (MM96/0245, MM96/0561,I92/2324, MM96/3585, MM96/4589 and MM96/0264) showed resistance (score 1 for CMD) while the rest had severity scores below the average (2.5). At harvest, the highest yield (60.8 ±3.7 t ha-1) was obtained from Alice local followed by clone MM96/0561 (59.5 ±6.6 t ha-1) in Nakasongola district and clone MM96/4614 (52.5 ±13.2 t ha-1) in Lira district. The lowest yield was from clone MM96/3585 (10.3 ±4.2 t ha-1) followed by Oko Iyawo (1) 99(14.2 ±4.2 t ha-1) in Kumi district. All the varieties tested were either sweet or slightly bitter with the scores of 1 or 2, respectively. Genotype MH97/2961 was the most preferred in Kumi and Lira districts, while it was third in Nakasongola district. All these genotypes also had a sweet taste for cooking. The most preferred genotypes in Nakasongola were TME 5 and MM96/5312 and had a sweet taste for cooking. The genotype by environment analysis indicated that genotypes TME 5, MM96/1419, I92/0427, and MH97/044 (2) UG were the most stable and adapted across all environments while MM96/4614 and Alice local were more specific for Lira and Nakasongola, respectively. These findings provide a basis for recommendations with regard to cultivation and preference of cassava genotypes in different environments

Evaluation of advanced cassava genotypes in Uganda

In a bid to increase the number of genotypes reaching farmers, on-farm trials were conducted in 2001/2002 with the aim of increasing the number of genotypes available to farmers to be evaluated for performance, adaptation and acceptability. Twenty improved genotypes were planted in Lira, Nakasongola, Gulu, Kumi and Katakwi districts using augmented design. The results indicated that cassava mosaic disease (CMD) varied from location to location but was more influenced by the genotype than the environment. The highest CMD severity (>4) was recorded among the farmers' local varieties across all environments, followed by Alice local (3.8±O.4) in Nakasongola and Lira (2.8±O.2) districts and 160142 (3.0±0.0) in Kumi and Lira (2.8±O.2) districts. Six clones (MM96/0245, MM96/056 I , 192/2324, MM96/3585, MM96/4589 and MM96/0264) showed resistance (score I for CMD) while the rest had severity scores below the average (2.5). At harvest, the highest yield (60.8±3.7 t ha-') was obtained from Alice local followed by clone MM 96/0561 (59.5±6.6 t ha-') in Nakasongola district and clone MM 96/4614 (52.5±13.2 t ha-') in Lira district. The lowest yield was from clone MM 96/3585 (l0.3±4.2 t ha-') followed by Oko Iyawo (I) 99 (l4.2±4.2 t ha-') in Kumi district. All the varieties tested were either sweet or slightly bitter with the scores of I or 2, respectively. Genotype MH97/296I was the most preferred in Kumi and Lira districts, while it was third in Nakasongoladistrict. All these genotypes also had a sweet taste for cooking. The most preferred genotypes in N akasongola were TME 5 and MM96/53 12 and had a sweet taste for cooking. The genotype by environment analysis indicated that genotypes TME 5, MM961 1419, 19210427, and MH97/044 (2) UG were the most stable and adapted across all environments while MM96/4614 and Alice local were more specific for Lira and Nakasongola, respectively. These findings provide a basis for recommendations with regard to cultivation and preference of cassava genotypes in different environments

Effect of SCN and BSR fungus infections on fatty acid levels in soybean seeds.

<p>For two seasons (2008 and 2009), soybean plants were challenged with soybean cyst nematode (SCN), the brown stem rot (BSR) fungus, or the two in combination with soybean aphid (SBA). Seeds were then collected at harvest and fatty acid analysis was carried out. Statistical analysis indicated a significant treatment*year*variety interaction only for stearic acid levels. Thus, for 18:0 (C-D), results are shown for both years and varieties separately; for other fatty acids (A, 16:0; B, 18:1; E, 18:2; F, 18:3) the results from both years and varieties were combined. Different letters indicate statistically significant differences (p< 0.05) among treatments.</p

Effect of SCN and BSR fungus infections on soybean leaf fatty acid levels.

<p>For two seasons (2008 and 2009), soybean plants were infested with soybean cyst nematode (SCN), the brown stem rot (BSR) fungus or the two in combination with soybean aphid (SBA). At 6 weeks after SBA infestation, leaf samples were picked and fatty acid composition was analyzed. Control plants were kept free of aphids throughout the whole experiment. Different letters indicate statistically significant differences (p< 0.05) among treatments.</p