FIELD EVALUATION OF PROMISING MUTANTS OF MUNGBEAN AGAINST FLEA BEETLE, APHID AND POD BORER

Experiment was conducted at the Agricultural Farm of Patuakhali Science and Technology University to know the morphological characteristics of different mutants of mungbean and to find out tolerant/least susceptible mutant(s) against flea beetle, aphid and pod borer based on the reaction of insect pests to promising mutants of mungbean during the period from April to June, 2015. The mutant MBM-07(S)-2 was found to be the tallest (32.57 cm) with highest number of branches/plant (5.03), highest number of leaves/plant (11.06) among all mutants and check variety while MBM-07-Y-2 (23.4 cm) was the shortest plant height, MBM-656-51-2 had the lowest number of branches/plant (3.73), MBM-347-13 (7.03) had the lowest number of leaves/plant. The mutant MBM-427-87-3 had the highest number of pods (5) compared to other mutants but MBM-656-51-2 had the lowest number of pods/plant (3.09). Mutant MBM-347-13 had the lowest population of flea beetle (18) and pod borer (2) compared to all other mutants while the lowest number of aphid/plant was observed in mutant MBM-07-Y-1 (1). In case of infestation, the mutant MBM-347-13 had the lowest percentage of infestation (20.69%) by flea beetle, (3.18%) by pod borer but the lowest infestation by aphid (3.33%) was recorded in the mutant MBM-390-94-Y while the mutant MBM-427-87-3 had the highest percentage of plant infestation (37.8%) by flea beetle, pod damage (9.69%) by pod borer and variety BARI moog-6 had the highest percentage (34.45%) of plant infestation by aphid. Mutant MBM-347-13 was least susceptible to flea beetle and pod borer while mutant MBM-427-87-3 was highly susceptible to flea beetle and pod borer. However, mutant MBM-390-94-Yand MBM-07-Y-2 were less susceptible to aphid while BARI moog-6 and mutant MBM-427-87-3 were highly susceptible to aphid. 30 DAS total number of and healthy plants was recorded from 15 randomly selected plants of each plot to determine the level of infestation by flea beetle and aphid.


INTRODUCTION
Mungbean (Vigna radiata L. Wilczek) belonging to the family Leguminosae is an important pulse crop having a rich source of protein (22-24%) according to Nazir (1994). It is a native to Indian subcontinent and mainly grown in China, India, Philippines, Burma, Bangladesh, and Pakistan. It is a short duration crop and is widely cultivated in the southern part of Bangladesh immediately after harvesting rabi crops. It is cultivated for seed, edible purpose and fits well in any cropping system. As mungbean is an important legume crops, fix the atmospheric nitrogen, which becomes the source of fertilizer in the soil (Hafeez et al., 1988). After chickpea, mungbean is called as poor people diet due to its protein content and is meeting the major protein demand of the people (Shafique et al., 2009). Biomass of mungbean is a good source of fodder for animals and also used as green manuring to produce good quality organic matter in soil. It is grown on all types of soils in both rain fed and irrigated conditions of the country twice a year i.e., both in rabi and kharif seasons.
Mungbean crop is vulnerable to different species of insect pests which occurs at any stage from seedling to harvest. There are 64 species of insects attacking on mungbean crop (Lal, 1985). A total of 16 species have been reported to attack on mungbean in Bangladesh (Hossain et al., 2004). Several insect pests have been reported to infest mungbean damaging the crops during seedlings, leaves, stems, flowers, buds and pods causing considerable losses (Sehgal and Ujagir, 1988;Rahman and Miah, 1988). Among them aphid, whitefly, hairy caterpillar (Rahman et al., 1981), pod borer, thrips (Rahman et al., 1981;Hossain et al., 2004), jassid (Hossain et al., 2009) stem fly (Lal, 1985) are considered major ones. Both nymphs and adults of Aphis craccivora suck sap from young leaves and stems at the seeding stage, vegetative stage and continue to flowering stage while spotted pod borer, Maruca vitrata damage flower buds, flowers and pods of mungbean (Rahman, 1991). The flea beetle, Phyllotreta nigripes feeds on the cotyledons and leaves of young plants making innumerable round holes (Prodhan et al., 2008;Hossain et al., 2012). The population of flea beetle remained lower throughout the vegetative stage (Echezona et al., 2010). The incident and development of flea beetle is much dependent upon the prevailing weather conditions (Khan et al., 2018). Different control strategies are in practice in the field for the control of insect pests of mungbean. Among the insect control strategies, host plant resistance using resistant varieties is an effective and safe strategy in pest management with no additional cost to the growers by the plantation of resistant cultivars. Chhabara and Kooner (1994) have evaluated mungbean cultivars against their resistance to insect pests. Naqvi et al. (1995) has tested 10 genotypes of mungbean against insects and found only two cultivars, M-8-20 and M-1030 resistant against insects compared to others. Khattak et al. (2004) has screened five mungbean varieties viz., NM 92, NM-98, NM-121-125, M-1 and NCM-2009 against sucking pests, whiteflies, jassid and thrips and found that whitefly, jassid and thrips population was comparatively lower on NM-92 and NM-98 which enables to get higher yield compared to other tested varieties. Now many promising lines or mutants of mungbean are available in Bangladesh which is not evaluated to screen against insect pests. All varieties or mutants are not equally infested by insects. Therefore, it is urgent need to find out suitable tolerant mutants to withstand the attack of insect pests. BARI and BINA have developed some varieties of summer mungbean, which are high yielding, insect pest resistant, but farmers are reluctant to mungbean cultivars for asynchronous pod maturity. Recently, BINA has developed some summer mungbean mutants, which are high yielding. These mutants need to be assessed for their resistance to insect pest among the existing summer mungbean varieties. The use of resistant varieties in the pest management is economical and safer as compared to the chemical control method. In view of this requirement, the present research programme was undertaken to observe the morphological characteristics of different mutants of mungbean, to know the reaction of insect pests to promising mutants of mungbean and to find out tolerant/least susceptible mutant(s) against major insect pests attacking mungbean.

MATERIALS AND METHODS
The experiment was conducted at the Agricultural Farm of Patuakhali Science and Technology University, Dumki, Patuakhali during the period from April to June, 2015. Geographically the experiment field was located at N latitude and E longitude at a height of 3.5 m above the mean sea level. Nine mutants viz., MBM-07-Y-1, MBM-07-Y-2, MBM-656-51-2, MBM-527-114, MBM-07-(S)-2, MBM-347-13, MBM-390-94-Y, MBM-427-87-3, MBM-80 (Local) and a check variety BARI moog-6 were used as study materials. The seeds were collected from Plant Breeding Division, Bangladesh Institute of Nuclear Agriculture, Mymensingh. The seeds were sown on the 02 nd April, 2015 at the rate of 11 kg/ha under natural field conditions. Experiment was planned in Randomized Complete Block Design with three replications. Unit plot size was 3 m ×2 m. The distance between two-unit plots was 0.75 m and between block to block was 1 m. Standard agronomic practices including weeding, irrigations and fertilizers were carried out according to the crop requirements. Weeding was done twice. First weeding was done at 22 days after sowing (DAS) and second weeding was done at 35 DAS. Irrigation was done once at 30 days after sowing. The fertilizers were applied as per fertilizers recommendation guide (BARI, 2011). Urea, TSP and MP were applied @ 50, 85 and 35 kg ha -1 , respectively during final land preparation. No plant protection measures were adopted throughout the crop growing period. All plants from each unit plot were observed individually and the number of flea beetle, aphid and pod borer per plant were recorded at different days after sowing (DAS) in case of flea beetle at 14, 21 and 30 DAS, aphid at 37 and 47 DAS and for pod borer at 50, 57 and 65 DAS from podding to harvesting stages. The total number of infested and healthy plants was recorded from 15 randomly selected plants of each plot to determine the level of infestation by flea beetle and aphid.
Data on the percentage of pod borer infested pods; the number of damaged and total pods from 10 randomly selected plants from each plot was counted. The data were collected three times (50, 57 and 65) from pod development to harvest.

Statistical analysis
Data were analyzed in the computer by using MSTAT program following RCBD. Means of different significant parameters were separated by using Duncan's Multiple Range Test (DMRT).
The findings of the present study agree with the results of Islam et al. (2021) where they stated that varieties did not show complete resistance against major insect pests of mungbean. Our results are also in comparison to work of the previous researchers (Sahoo and Hota, 1991;Naqvi et al. 1995;Yadav and Dahiya, 2000;Singh and Singh, 2014) who reported that the findings regarding screening of mungbean cultivars against sucking pets are in the line of the results that we have attained in our study. Our present findings are in accordance to the results reported by Khattak et al. (2004) who have screened five mungbean varieties viz., NM-92, NM-98, NM-121-125, M-1 and NCM-2009 against sucking pests viz., whiteflies, jassids and thrips. They observed that whitefly, jassid and thrips population was comparatively lower on Nm-92 and NM-98 which enables to get higher yield compared to other tested varieties. Several insect pests viz., chrysomelids, pod borer and aphids have been reported to infest mungbean damaging the seedlings stage and leaves, stems, flowers, buds and pods causing considerable losses (Sehgal and Ujagir, 1988). Rani et al. (2014) screened ten green gram cultivars against Maruca and reported LGG-450 was highly susceptible while LGG 497 was highly tolerant. They also reported that the differences in pod length among different cultivars were also found to influence pod damage by M. vitrata. The correlation between pod length and incidence was positive and significant. Swarnalatha (2007)   Within columns means followed by same letter (s) are not significantly different at 5% level by DMRT CONCLUSION Mutants did not show complete resistance against flea beetle, aphid and pod borer. Among all the tested mutants, MBM-347-13 was found less susceptible to flea beetle and pod borer and mutant MBM-390-94-Y to aphid.