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Pak. J. Bot., 48(4): 1665-1671, 2016.

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IS REDUCTION IN YIELD POTENTIAL OF SOME BRASSICACEOUS SPECIES

DUE TO APHID INFESTATION ASSOCIATED WITH THE CHANGES

IN STOMATAL FACTORS OF PHOTOSYNTHESIS?

MUHAMMAD RAZAQ^1*, MUZAMMIL FAROOQ¹, GUL ABBASS¹, MUHAMMAD ASLAM²_,

MUHAMMAD AFZAL³ HAFIZ MAHMOOD UR REHMAN⁴_, MUHAMMAD IQBAL⁵

AND HABIB-UR-REHMAN ATHAR⁶

¹Department of Entomology, Faculty of Agricultural Sciences and Technology,

Bahauddin Zakariya University, Multan 60800, Pakistan

²South Punjab Institute of Science & Technology 6-KM, Jampur Road, Dera Ghazi Khan, Pakistan.

³University College of Agriculture, University of Sargodha, Sargodha, Pakistan

⁴Department of Entomology, University Collage of Agricultural and Environmental Sciences, the

Islamia University of Bahawalpur, Bahawalpur-Pakistan

⁵Department of Botany, University of Education, Okara Campus, Okara, Pakistan

⁶Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan 60800, Pakistan

^*Corresponding author’s email: muhammadrazaq@bzu.edu.pk, mrazaq_2000@yahoo.com

Abstract

Aphids cause heavy yield losses to Brassicaceous species by affecting various physiological and biochemical processes including photosynthesis. In the present study, seasonal activity of aphid population and its impact on some brassicaceous species was assessed. Three brassicaceous species (Brassica campestris, Brassica carinata, Eruca sativa) were grown in field following standard agricultural practices. Plants of control plots retained aphid free by insecticide spray, whereas treatment plots were freely allowed for aphid infestation. There was also intermediate treatment of partial aphid infestation where insecticidal spray was applied two times. Peak populations of both aphid species were observed in the 2^nd week of March during which plant photosynthetic attributes were recorded. At the time of maturity, yield attributes were also recorded. From the results, it is obvious that application of insecticide significantly reduced the aphid populations on the three brassicaceous species and enhanced the crop yield. Yield losses due to aphid infestation were maximal in Brassica campestris followed by B. carinata whereas it was minimal in Eruca sativa. Yield losses in Brassica campestris and B. carinata were due to reduction in number of pods per plant, number of seeds per pod and size of seeds, whereas yield losses due to aphid infestation in Eruca sativa was mainly attributed to reduction in number of pods per plant. Although insecticidal spray reduced the aphid population and increased growth and productivity of all brassicaceous species, it did not change photosynthetic capacity of all plants except in Eruca sativa. Moreover, growth and yield reduction was not associated with stomatal factors of photosynthesis. Chlorophyll contents measured as SPAD values were reduced due to aphid infestation which is positively associated with yield reduction. Insecticidal spray increased chlorophyll contents in these three brassicaceous species by reducing aphid population. Application of insecticidal spray two times caused lower aphid infestation in brassicaceous species but it could not recover total yield losses. From these results, it is suggested that aphid infestation induced growth and yield reduction in the three brassicaceous species was due to some non-stomatal factors or due to alteration in metabolism of chloroplast. To affirm this, further research is needed.

Key words: Crop productivity, Canola, Tara mira, Chlorophyll, Losses, Pest population dynamics