ABSTRACT
The incidence of leaf spot of mustard (cv. BARI sharisha 13) grown in different orientations and distances under around twelve years old Akashmoni (Acacia auriculiformis) tree was studied in the field laboratory of the Department of Agroforestry, BAU, Mymensingh during 2004-05. The assessment result showed that the disease incidence was higher near the tree base in every side (1 m from the tree base) and higher in North side in all distances at different date of sowing. The lowest disease incidences were found in South orientations 3 m from the tree base and highest in North 1 m from the tree base. The siliqua infection significantly influenced on crop yield. The highest seed yield was observed in South orientation 3 m from the tree base and lowest in North 1 m from the tree base plot. The distance and orientation showed marked effect in disease development at different date after sowing. In open field condition (control) disease incidence also affect on yield and statistically different from tree-crop combination.
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DOI: 10.3923/ajps.2006.193.196
URL: https://scialert.net/abstract/?doi=ajps.2006.193.196
INTRODUCTION
Bangladesh has the lowest per capita land due to its high population density. This limited land resources are engaged in producing minimum food require for the people. Official records reveal that 12.8% of the hand area of Bangladesh is under forest. However, actual tree coverage is only 5 to 6% (FMP, 1992). In Agroforestry system interaction between trees and crops (or animals) is important because of sharing of the common resources. However, these interaction should take place with respected to how the component of Agroforestry utilizes and shares the resources of the environment and how the growth and development of the compost will influenced the other (Torquesiau, 1994).
Rape-seed mustard suffers from at least 10 disease in Bangladesh (Meah et al., 1985; Bari, 1985). Alternaria blight has been recognized as the most serious and devastating disease of rapeseed- mustard in the country (Meah et al., 1985; Bari, 1985) Alternaria bight or leaf spot of mustard is caused by Alternaria brassica (Berk) zacc. The disease caused blight of leaf, Pod and stem (Meah et al., 1988) and seed abnormalities (Howlider et al., 1991). It is endemic in Bangladesh and all cultivated varieties are susceptible. The disease caused an average yield loss 30-60% in Bangladesh (Meah et al., 1988; Fakir, 1980).
In this study, if we practice the simultaneous cultivation of mustard along with intercropping of suitable tree-species, the overall production may be increased under such production system and for this the incidence of leaf spot of mustard need to be determined. Therefore, the present research work was designed to determine the incidence of leaf spot of mustard under Akashmoni (Acaciq auriculiformis), so that the Akashmoni-Mustard Agroforestry system can introduced in our farming system after harvesting T. aman rice in rabi season successfully.
MATERIALS AND METHODS
The study was conducted during Rabi season of 2004-2005 in the Agroforestry field laboratory, Bangladesh Agricultural University, Mymensingh. The cultivar BARI Sharisha 13 (Brassica napus) of mustard was used in the study. The experiment was carried out under 12-years old plantation of Akashmoni established by the Village Farm Forest Project (VFFP) area in the Agroforestry field laboratory. The experiment area covered 1500 m2 including the borders and the open area for control plots. The experiment was used one row of trees involving trees of the Akashmoni species. The experiment was carried out by RCBD design with three replications. The two factors i.e., orientations and distances from the tree species involved in the study.
The Orientations were O1 = South, O2 = West, O3 = North and O4 = East, and Distances from the tree base were D1 = 1 m distance from the tree base, D2 = 2 m distance from the tree base, D3 = 3 m distance from the tree base and D0 = (Open field) means-outside the tree canopy. The distance 1 m from the tree base was selected because farmers usually do not want to waste any land. So they cultivate all areas having about 1m around each tree (for 12-years-old tree). The size of each plot were 1x1m. The crown diameter of each of the three trees was measured along North-South and East-West axis using measuring tape. The dose of fertilizers and manures were applied in the field as recommended by BARI according to cultivation manual (Anonymous, 2004). Seed rate was 8 kg ha-1. The seeds were sown in line. The line to line distance were 30 cm and placed at a depth of 2.5-3 cm. After sowing, the seeds were covered with soil. When germination was completed 50-60 plants were kept in each plot. Intercultural operations were done as needed. Data were recorded on % Plant infection,% Leaf infection,% Leaf Area Diseased (LAD),% Total siliqua infection,% Siliqua infection, No. of spots per siliqua, Plant height, No. of branches per plant, Weight of seeds per plant and Weight of seeds per plot.
RESULTS AND DISCUSSION
The effect of different orientation and distance showed significant influence on disease incidence at different days after sowing (Table 1). At 30 DAS disease incidence ranged from 2.58 to 9.20%, where the highest disease incidence was found in O3D1 and the lowest disease incidence was found in the plot 3 m from the tree base at south orientation (O1D3). In open field (control) the disease incidence was 5.45%. Disease incidence was more in D1 distance (1 m from the tree base) and gradually decreases in respect to increase in distance. The results are statistically significant. Disease incidence was significantly differing among the treatments in different days after sowing. Disease incidence ranged from 12.70 to 39.95% at 45 DAS, where the highest disease incidence range from 68.94 to 97.89% at 90 DAS. Similar trends were observed in 60 DAS and 75 DAS. Open field (control) showed lower disease incidence.
Percent leaf infection under different condition showed significant difference in different DAS. Significantly the higher percent leaf infection 105.96% at O1D3 plot at 75 DAS. The range of leaf infection were 0.00 to 105.96%, where the control plot in open condition showed lower leaf infection ranged 12.50 to 88.89% at 30 DAS to 75 DAS. The infection range gradually increased in different plots in order to decrease of distance and increase in DAS (Table 2).
Leaf infection first appeared at 30 DAS both in control plot and under trees. The leaf area diseased varied from 2.53 to 67.97%, where the lowest were found in O2D3 at 30 DAS and the highest in O3D1 at 75 DAS.
Table 1: | Influence of orientations and distances on disease incidence (%) of rapeseed mustard (var. BARI sharisha 13) under Akashmoni tree |
Figure in a column having the same letter (s) do not differ significantly as per DMRT at 1% level of provability |
Table 2: | Influence of orientations and distances on percent leaf infection of rape-seed mustard (var. BARI sharisha 13) under Akashmoni tree |
Figure in a column having the same letter (s) do not differ significantly as per DMRT at 1% level of provability |
Table 3: | Influence of orientations and distances on%leaf area diseased of rape-seed mustard (var. BARI sharisha 13) under Akashmoni tree |
Figure in a column having the same letter (s) do not differ significantly as per DMRT at 1% level of provability |
Percent leaf area diseased ranged from 10.0 to 36.65% in control plot (open field) at 30 to 75 DAS (Table 3).
The plot result were significantly differs on percent siliqua infection in the main rachis at different DAS. Lowest infection was observed at O1D2 (15.52%) at 45 DAS and highest at O4D1 at 90 DAS (69.90%).
Table 4: | Effect of orientation and distance on percent siliqua infection 30 cm from the top of the plant of rape-seed mustard variety BARI sharisha 13 at different days after sowing |
Figure in a column having the same letter (s) do not differ significantly as per DMRT at 1% level of provability |
Table 5: | Effect of different orientations and distance on yield and yield contributing characters of mustard (vir. BARI sharisha 13) as influenced by leaf spot of mustard disease |
Figure in a column having the same letter (s) do not differ significantly as per DMRT at 1% level of provability |
Control plot showed moderate siliqua infection ranged 12.41% to 20.69% at 45 DAS to 90 DAS (Table 4).
The plant grown under O0-orientation (outside the tree canopy) produced the tallest plant (126.8 cm) from other orientations. The smallest plant (64.20 cm) was produced in O3D1 north-1 m from tree base In all orientations plant heights were gradually increased in different distance from the tree base and gradually reduced near in 1 m distance from the tree base. The variation in number of branches was distinct in O0 (open field) compared to other orientations. The highest number of branches was obtained from O1D3 orientation (5.81) and the lowest was in O3D1 orientation (2.14). The number of branches/plant varied from 2.14 to 6.85. A significant different was showed in total number of siliqua/plant by different orientation and distance. The maximum number of siliqua per plant (67.93) was found in O2D2, which was statistically similar to O1D3 (67.03), the minimum number of siliqua per plant (31.70) found in O3D1 combination. The effect of orientation and distance was statistically significant on seed weight per plant. The highest seed weight (3.6 g) was recorded from O0 (open field) and the lowest (1.76 g) was recorded from O3D3 (North-1 meter from tree base) orientation that was gradually increased in different orientations. Weight of seeds/plot under different treatment combinations ranged from 158.3g to 270.0 g, while the maximum weight of seeds/plot was obtained from the plants of control (O0) (Table 5). Seed weight/plot was found to vary significantly from one orientation to another.
Alternaria blight of mustard an endemic disease caused by Alternaria brassicae and Alternari brassicicola is a most devastating disease in Bangladesh. It also reported that Alternaria causes infection on almost all above ground parts of mustard plant and eventually becomes transmitted from plant to seed and seed to seedling (Meah et al., 1988; Fakir, 1976). Symptoms of the disease as observed in the present study confirm to those describe by Kimber and McGregor (1995). Acaci auriculiformis (Akashmoni) is a leguminous plant and mycorhizal association of the species have been carried out in Bangladesh Mridha et al. (1999) and the rhizosphere zone favoured fungi for much multiplication. Soil properties and microorganism might be influenced by root after the associate plants and their disease infection. Degree of infection of Alternaria brassicase largely depends on factor like wetness of both soil and sir temperature (<20°C) and also leaf wetness. These might be the cause for variation in infection of the pathogen in different distance form the tree base. Result obtained by Singh et al. (1992) reported that low temperature (10-15°C min, 24-27°C max) and high RH 80-90% increase the disease intensity and the development of disease highly significant on crop growth stages. The critical stage of disease development is important progressive growing stage of plant and developing pods at 30 DAS. It might be considered as the critical stage of disease development. Disease symptom first appears at 30 DAS and gradually increased. Siliqua are important components of yield of mustard. It is fact that infection of siliqua greatly affects yield. Siliqua infection and siliqua spotting in different orientation and distance from the tree base were statistically significant. As there was no direct report on leaf spot of mustard disease incidence in tree-mustard Agroforestry system but the downey mildew and white rust is directly influence by shade and the other disease such as angular leaf spot, anthracnose of bean, powdery mildew of milon, blast of rice disease incidence are also enhance by shade in tree crop Agroforestry system. Yield reduction due to Alternaria blight of mustard different orientation and distance observe in the present study. No similar result was found.
Results of the study reveal that Akashmoni trees had significant influence on Alternaria blight disease incidence as well as decreases yield in different distances and orientations.