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Effect of Defoliation on Growth, Reproductive Characters and Yield in Mungbean

M. Monjurul Alam Mondal, PhD
Principal Scientific Officer
Crop Physiology Division, Bangladesh Institute of Nuclear Agriculture, BAU Campus, Mymensingh-2202, Bangladesh

Prof. Dr. MSA Fakir
Professor
Dept Crop Botany, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

Experiment were performed under sub-tropical condition with eight levels of defoliations (0, 25, 50 and 75% either from top or from base of the canopy, and 100%) at visible bud initiation stage were imposed to investigate the growth, reproductive characters, and yield attributes in two high and two low yielding mungbean genotypes during Kharif-I (February-May, 2006) and-II (September-December, 2007) seasons. Results revealed that degrees of defoliations parallely decreased leaf area and dry matter (DM) production irrespective of seasons and genotypes. Defoliation not only reduced source sizes but also decreased total sink (flower) production resulting in lower pod and seed yields. However, basal 25% defoliation did not significantly decrease total dry matter and seed yield plant^-1 indicating the fact that the mungbean plant, in general, can tolerate 25% basal leaf loss of the canopy. Furthermore, the high yielding genotypes showed higher compensatory mechanism of source loss than the low yielders. And exceeding this threshold limit (> 25%) either from the base or from the top of the canopy defoliation significantly reduced DM and seed yield. Reduction in yield was higher with top defoliation than basal one. Implication of the results in relation to pest management is also discussed.

Keywords: Vigna radiata; Defoliation; Canopy structure; Dry matter and Seed yield

Location: Experimental field of BINA, Mymensingh

Start Date: 03-03-2006

End Date: 15-05-2007

Program Area: Crop-Soil-Water Management

Commodity: Mungbean

Objectives:

To investigate the magnitude and positions of leaf removal during the beginning of reproductive phase affects growth, reproductive characters and seed yield under field condition in mungbean.

Methodology:

Experiments were conducted at the Field Laboratory, Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh in Kharif-II (September-December), 2007 and Kharif-I (February-May), 2006. Two high yielding (BMX 942-8 and VC 6173) and two low yielding (MB 300 and VC 3960) genotypes were used. The experimental design was split-split-plot with three replications i.e. the season was assigned in the main plot and four genotypes were in the sub-plot and eight defoliations were in the sub-sub-plot.

The eight levels of defoliation treatments were employed at the beginning of opening of flowering stage (35 and 45 days after sowing in Kharif-I and Kharif-II, respectively) were: i) control (no leaf removal), ii) 25 % leaves removed from bottom (basal 25%), iii) 25% leaves removed from top (top 25%), iv) similarly bottom 50%, v) top 50%, vi) bottom 75%, vii) top 75% and viii) 100% leaves removed. Total leaf area (LA) plant^-1 from ten randomly selected plants of each sub-sub-plot was determined by measuring leaf area at individual node in the mainstem using automatic leaf area meter (Model: LI 2000). Considering total LA plant^-1 as hundred per cent, contribution of LA at each nodal position in the mainstem was estimated. To defoliate leaf at different degrees, complete compound leaf and/ or leaves, and sometimes one or two leaflets or even a portion of a leaflet were clipped off.

The harvested plants of each sub-sub-sub plot was separately bundled and tagged. Daily flower count began from the date of opening of first flower of the randomly selected 15 plants, 5 from each replication and continued until flowering ceased in each treatment. Finally, at harvest leaf area, seed yield and yield components, dry matter production and it’s partitioning into plant parts were recorded. The collected data were analyzed statistically.

Source of Information: Australian Journal of Crop Science, 5(8):987-992 (2011)

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Loss of leaves through insect attack, disease and other environmental hazards reduces assimilatory surface. Such leaf loss at bud initiation stage up to 25% may not affect seed yield in mungbean as was investigated in the current experiment. Therefore, it may not advisable to spray pesticide for controlling pests in mungbean variety at one-fourth loss of leaf surface to make cost effective and to save environment from pollution.

Knowledge Management: Journal