In order to develop a method to measure resistance to Alternaria brassicicola (cause of dark leaf spot disease) in Brassica rapa, the effects of inoculum concentration, leaf stage, leaf age and incubation temperature of inoculation on infection were studied under controlled conditions using several B. rapa genotypes. Three inoculation methods (cotyledon, detached leaf and seedling inoculation) were evaluated for this purpose. The detached leaf inoculation test was the most suitable for screening B. rapa genotypes because clear symptoms were observed on the leaves in less than 24 h, and there was a significant positive correlation between the results from the detached leaf inoculation test and the seedling inoculation test, an established method considered to yield reliable results. In addition, it was very easy to screen plants for resistance on a large scale and to maintain standard physical conditions using detached leaves. For successful infection, inoculum concentration should be adjusted to 5 Â 10 4 conidia ml )1 , and incubation temperature should be between 20°C and 25°C. The 3rd/4th true leaves from 30 day-old plants were optimal for inoculation. In a screening test using 52 cultivars of B. rapa, the detached leaf test effectively discriminated between various levels of partial resistance among cultivars. As a result, we identified two cultivars, viz Saori and Edononatsu, as highly resistant and five cultivars, viz Tokinashi Taisai, Yajima Kabu, Purara, Norin-F 1 -Bekana and Tateiwa Kabu, as having borderline resistance.

A survey was carried out in some selected potato growing districts of Bangladesh during December to February 2011 to know the status of bacterial wilt of potato caused by Ralstonia solanacearum in terms of its incidence and severity. The results showed that the highest wilt incidence was recorded in Munshigonj (22.65%), followed by Nilphamari (19.98%) and the lowest incidence was recorded in Jamalpur (9.07%). The highest bacterial wilt severity was recorded in Munshigonj (3.80), while the lowest wilt severity was recorded in Jamalpur (2.90). A total of 44 isolates (R. solanacearum) were obtained from the wilted potato plant samples i.e. 20 from Munshigonj, 17 from Nilphamari and 7 from Jamalpur and the isolates were divided into three groups. The production of pink or light red colour with whitish margin on TZC medium by the bacterial isolates indicated all groups of R. solanacearum isolates were virulent. The results of pathogenicity test revealed that all groups of R. solanacearum isolates were able to cause wilt symptoms in potato plants and brown rot symptoms in potato tuber. On the other hand, all biochemical tests were used for the identification of R. solanacearum isolates. The biovar test using the oxidization of disaccharides (sucrose, lactose, maltose) and sugar alcohols (manitol, sorbitol and dulcitol) by R. solanacearum isolates confirmed that all groups of R. solanacearum isolates belong to biovar III. The race identification of R. solanacearum isolates by pathogenicity test on brinjal, tomato, tobacco and chilli indicating a narrow host range (only in potato) and were categorized in race 3. Therefore, the R. solanacearum isolates causing bacterial wilt of potato in Bangladesh were belonging to Biovar III and Race 3.

Ralstonia solanacearum causes bacterial wilt of solanaceous crop plants including brinjal, a most devastating disease in humid tropic. A survey was conducted on the status of bacterial wilt incidence and severity in major brinjal growing areas and to characterize the isolates of R. solanacearum causing bacterial wilt of brinjal in Bangladesh. The wilt incidence was recorded maximum (22.52) in Rangpur followed by Jessore (20.56) and Panchagarh (20.0) while the lowest wilt incidence was recorded in Jamalpur (6.12). On the contrary, the wilt severity was recorded highest (4.00) in Jhinaidah and the lowest (2.80) was recorded in Jamalpur followed by Jessore (2.93) at the time of survey. The isolates of R. solanacearum were obtained from different locations surveyed were arranged in seven groups based on the location. Gram's staining and Potassium hydroxide solubility test revealed that all groups of R. solanacearum isolates are gram negative. The isolates of R. solanacearum fermented four basic sugars (Dextrose, sucrose, manitol and lactose). These results of all biochemical tests in combination with the pathogenicity test confirmed the isolates were R. solanacearum causing bacterial wilt of brinjal. All groups of R. solanacearum isolates were found virulent producing pink or light red color or characteristic red center and whitish margin on TZC medium after 24 hours of incubation. On the biovar test clearly revealed that all groups of R. solanacearum isolates oxidized disaccharides (Sucrose, lactose, and maltose) and sugar alcohols (manitol, sorbitol and dulcitol) within 3-5days and confirmed biovar as III. Pathogencity test on tomato and chilli indicating wide host range of R. solanacearum isolates and categorized them in race 1. Therefore, it may be confirmed that R. solanacearum causing bacterial wilt of brinjal in Bangladesh belong to Biovar III and Race 1.

Brassica napus is a leading oilseed crop throughout many parts of the world. It is well adapted to long day photoperiods, however, it does not adapt well to short day subtropical regions. Short duration B. napus plants were resynthesized through ovary culture from interspecific crosses in which B. rapa cultivars were reciprocally crossed with B. oleracea. From five different combinations, 17 hybrid plants were obtained in both directions. By self-pollinating the F1 hybrids or introgressing them with cultivated B. napus, resynthesized (RS) F3 and semi-resynthesized (SRS) F2 generations were produced, respectively. In field trial in Bangladesh, the RS B. napus plants demonstrated variation in days to first flowering ranging from 29 to 73 days; some of which were similar to cultivated short duration B. napus, but not cultivated short duration B. rapa. The RS and SRS B. napus lines produced 2–4.6 and 1.6–3.7 times higher yields, respectively, as compared to cultivated short duration B. napus. Our developed RS lines may be useful for rapeseed breeding not only for subtropical regions, but also for areas such as Canada and Europe where spring rapeseed production can suffer from late spring frosts. Yield and earliness in RS lines are discussed.

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease of many economically important crop species. A significant variation in wilt incidence and severity in eggplant and potato was observed among the growing areas surveyed. R. solanacearum isolates obtained both from eggplant and potato belong to biovar III, while isolates from eggplant belong to race 1 and isolates obtained from potato belong to race 3. Random amplified polymorphic DNA (RAPD) technique was used as a tool for assessing genetic variation and relationship among seven isolate groups of R. solanacearum viz., RsB-1, RsB-2, RsB-3, RsP-1, RsP-2, RsP-3 and RsP-4, consisting in a total of 28 isolates. Out of the RAPD markers used, amplification with four decamer primers produced 70 bands with sizes ranging from 100 to 1400 bp. Out of 70 bands, 68 bands (97.06%) were polymorphic and two bands (2.94%) were monomorphic amongst the seven R. solanacearum isolates group. The Unweighted Pair Group Method of Arithmetic Means (UPGMA) dendrogram constructed from Nei's genetic distance produced two main clusters of the seven isolates of R. solanacearum. The isolates RsB-1, RsB-2, RsB-3 and R-4 grouped in cluster І, while RsP-2, RsP-3 and RsP-4 grouped in cluster ІІ. The highest intra-variety similarity index (Si) was found in RsB-1 isolate (86.35%) and the lowest one in RsP-2 (56.59%). The results indicated that relatively higher and lower levels of genetic variation were found in RsP-3 and RsB-3, respectively. The coefficient of gene differentiation (G(st)) was 0.5487, reflecting the existence of a high level of genetic variations among seven isolates of R. solanacearum. Comparatively higher genetic distance (0.4293) and lower genetic identity (0.6510) were observed between RsB-2 and RsP-4 combinations. The lowest genetic distance (0.0357) and highest genetic identity (0.9650) were found in RsB-1 vs. RsB-2 pair. Thus, RAPD offers a potentially simple, rapid and reliable method to evaluate genetic diversity analysis in R. solanacearum.

Incidence of Phomopsis vexans on farmers' eggplant seeds collected from different areas of Bangladesh varied from 0.0 to 7.5%. The highest incidence of P. vexans (7.50 %) was recorded in cultivar Dohazari and Rupgonj L collected from Chandanish and Rupgonj, respectively. No incidence of P. vexans was observed in the cultivar Katabegun and Jessore-L collected from Pabna and Monirampur, respectively. Very low seed infection was recorded in the cultivar Shingnath, Bijoy, Ishurdi-Land Longla-long collected respectively from Chandina, Modhukhali, Ishurdi and Kulaura. Seeds collected from HRC of BARI had higher seed infection by P. vexans. Seed selection had a significant impact on the incidence of P. vexans. Use of apparently healthy seed was found effective in controlling damping off, tipover and seedling blight of eggplant. The least incidence of P. vexans (1.25%) and the highest germination (86.75%) were recorded in apparently healthy seed as against 6.5% seed infection and 60% seed germination recorded in farmer's seed. In the net house, the least incidence of damping off, tipover and seedling blight were recorded in case of apparently healthy seed. Seed treatment with hot water (56 0 C for 15 minutes), garlic (Allium cepa L) bulb extract and Allamanda (Allamanda cathertica L) leaf extract, Trichoderma harzianum CP, Trichoderma harzianum T 22 and Bavistin were found promising in controlling seedling diseases in the nursery and in increasing the seed germination. Combinations of apparently healthy seed (T 2 ), treated with garlic bulb extract (T 3 ) and soil treated with T. harzianum CP (T 11 ) completely controlled damping off, tipover and seedling blight in the nursery bed and increased seed germination by 48.83% over control.

An experiment was conducted in the field laboratory, Department of Plant pathology, Bangladesh Agricultural University, Mymensingh to know the efficacy of compost tea and poultry litter extract in controlling stem canker of potato under natural infection condition. Significant effect of different treatments was observed on the incidence of stem canker of potato as compared to control. The results evidently showed the lowest stem canker incidence recorded in plots when IPM Lab Biopesticde was applied followed by foliar spray of Ridomil, compost tea, and BAU-Biofungicide while the highest stem canker incidence was recorded in untreated control plot. However, the soil drenching of compost tea and poultry litter extract also performed better as compared to control in reducing the incidence of stem canker. Significant effect of the treatments was observed on the plant height and yield except number of plant raised per tuber. Foliar and soil application of compost tea, poultry litter and mustard oil cake showed better performance in increasing the plant height and yield as compared to all other treatments. Benefit cost analyses of the treatments revealed that foliar application of compost tea showed highest BCR (65.20) followed by Soil application of IPM Lab Biopesticide with BCR 54.38. The treatments viz. foliar spray of Ridomil and BAU-Biofungicide resulted 35.31 and 38.88 BCR, respectively which were the second best treatments as compared to untreated control. The results indicated that an investment of Tk. 1.00 may lead to a profit up to Tk. 65.20 by foliar application of compost tea which shows the maximum profit in the present study. Therefore, compost tea as foliar spray may be used as an alternative environment-friendly approach to control stem canker of potato along with other biological means with maximum economic return.

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