Marker-assisted selection of low erucic acid quantity in short duration Brassica rapa

Low erucic acid (LEA) rapeseed, which has accumulated mutant fatty acid elongase genes at the BnFAE1.1 and BnFAE1.2 loci of the A- and C-genome, respectively, is an important oilseed crop. Short growing turnip rape (B. rapa) is also important as a catch crop in the continuous cropping of rice in Asia but there is no LEA B. rapa cultivar for cultivation in South Asia. In order to develop LEA turnip rape cultivars, high erucic acid turnip rape cultivars were interspecifically crossed as recurrent parents to a canola quality rapeseed. In the meantime, we monitored incorporation of the mutant bnfae1.1 (e1) gene into A-genome of turnip rape, using a dCAPS primer pair, which can amplify PCR fragment only for the mutant e1 gene from A-genome. The early backcross progenies showed poor seed set, but which was improved in advanced progenies. Finally, homozygous e1e1 genotypes were established in the selfed progenies of BC₂–BC₃, and their LEA content was confirmed by gas-chromatography analysis. Our results and promising lines will contribute to LEA-trait selection in turnip rape and rapeseed breeding.     

The locus for resistance to Asian soybean rust in PI 587855

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi is one of the most serious soybean (Glycine max) diseases in tropical and subtropical areas. A soybean line, PI 587855, showed a resistance phenotype against ASR pathogens in Japan and South America at high frequency; however, little is known of the genetic control of this resistance and chromosomal location of the corresponding locus. Therefore, the aim of this study was to study the inheritance of PI 587855 resistance and map the corresponding locus with SSR markers aiming to use the linked markers in marker‐assisted selection. In the segregating population, resistance to ASR appeared to be controlled by a single dominant gene. The ASR resistance locus was mapped near to the chromosomal region where the resistant loci, Rpp1 and Rpp1‐b, were previously mapped. Comparative genetic mapping and disease reaction profiles of other seven lines carrying Rpp1 or Rpp1‐b to four Brazilian ASR isolates revealed that the resistance reaction exhibited by PI 587855 was similar to that of Rpp1‐b‐carrying varieties which have useful resistance to South American ASR strains.     

Salinity tolerance of earthworms and effects of salinity and vermi amendments on growth of Sorghum bicolor

Salinity is a major factor limiting irrigated agriculture in arid regions. Vermi amendments can be used for improving the fertility of salt-affected soils. Current study was aimed to find out the response of different earthworm species to soil salinity and to check the effects of salinity and different vermi amendments on growth of Sorghum bicolor under salt stress. Eight earthworm species were subjected to different salinity levels for 4 weeks. Various vermi amendments and salinity treatments were provided in a factorial combination to S. bicolor plants to see their effect on growth and biomass parameters. L. mauritii, E. incommodus and P. posthuma were found to be the most salt-tolerant species showing good survival and growth till soil EC_e value of 10.48 mS cm^?1. Results showed that salinity significantly decreased plant growth that was enhanced by the application of different vermi amendments. Maximum growth of S. bicolor was recorded when vermicompost and vermiwash were used together under both saline and non-saline conditions. The results showed that the application of vermi amendments improved nutritional balance of the soil, delayed salt-induced damage to the plants and supported their growth so can be helpful in increasing crop production on saline soils.     

Optimizing fertilizers doses and their effects on photosynthesis and biomass yield of Hibiscus cannabinus cultivated on BRIS soil

In tropical climate, huge amount of fertilizer need to be used for the cultivation of kenaf (Hibiscus cannabinus L.) in Beach Ridges Interspersed with Swales (BRIS) soil, however this approach is not cost effective and environmental friendly. Therefore, the optimizing of fertilizer rate for BRIS soils and selection of suitable soil amendments are crucial to get a higher yield. In this study, the effects of different combinations of urea, chicken manure and biochar on soil properties, growth performance and physiological characteristics of kenaf cultivated on the BRIS soil were investigated. Eight treatments were conducted namely: control (T1), biochar (T2), chicken manure (T3), urea (T4), chicken manure + urea (T5), biochar + chicken manure (T6), urea + biochar (T7) and biochar + chicken manure + urea (T8). The biomass and physiological characteristics of kenaf were recorded every month, while the soil was analyzed following a standard laboratory procedure. The application of organic and inorganic fertilizer (urea) significantly increased the nutrient content of the soil compared to the T1, whereas T3 showed the highest pH, cation exchange capacity, and exchangeable bases (Na, Mg, Ca). However, the mixing of biochar with organic and inorganic fertilizers showed the highest plant height, diameter of stem and number of leaves as well as dry biomass compared to other treatments. Furthermore, the application of nitrogen fertilizer significantly increased the photosynthesis rate and stomatal conductivity. The results suggest that the mixing of biochar with organic and inorganic fertilizers represents an effective approach for the cultivation of kenaf in tropical climate.     

Effect of replacing fishmeal with canola meal on growth and nutrient utilization in kuruma shrimp Marsupenaeus japonicus (Bate)

A feeding trial was conducted to assess the nutritional values of canola meal as a substitute for fishmeal in diets for kuruma shrimp using five isocaloric diets (190 kJ kg^?1) prepared by replacing 0%, 10%, 20%, 30% and 40% of fishmeal protein with canola meal protein in CM0, CM10, CM20, CM30 and CM40 diets respectively. Triplicate groups of juveniles (0.19 g) were fed the respective diets for 60 days in tanks. At the end of trial, weight gain (%) and specific growth rate (% day^?1) were not significantly (P > 0.05) different among shrimp fed CM0, CM10 and CM20 diets. However, growth was significantly (P < 0.05) decreased in shrimp fed CM30 and CM40 diets. As with growth performance, feed intake, feed conversion ratio and protein efficiency ratio were also decreased (P < 0.05) in CM30 and CM40 groups. Whole body dry matter, methionine and proline were significantly decreased with canola meal substitution levels. In general, retention efficiency of protein and indispensible amino acids were decreased as canola meal increased in diets. It may be concluded that 20% fishmeal protein can be successfully replaced with canola meal, while supplementation of amino acids or blending with complementary proteins could facilitate higher fishmeal replacements in kuruma shrimp diets.     

Dietary calcium requirement in fishes

The dietary requirement of calcium (Ca) has been well established in terrestrial animals. However, investigations for dietary Ca requirement in fish are complicated and reports limited as fish can use waterborne Ca in addition to dietary Ca. Ca absorption in fishes from environmental water is species specific and depends on concentration of Ca in rearing environment and availability of dietary Ca. Ca and phosphorus are generally combined together in fish body therefore maintaining a dietary calcium: phosphorus ratio is important. Ca exists in a complex form in fish meal, which is not available to fishes; hence, although fish meal contains an appreciable amount of calcium, dietary Ca supplementation in fish meal‐based diets for some species is necessary. This review article summarizes and discusses pertinent information on absorption of Ca from water, essentiality of dietary Ca, bioavailability of Ca from different sources, optimum calcium:phosphorus ratio and dietary Ca requirement in fishes.