Morpho-anatomical and biochemical characterization of cotton in relation to whitefly tolerance
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation entitled “Morpho-anatomical and biochemical characterization of cotton in
relation to whitefly tolerance” was undertaken to evaluate the performance of backcross progeny
carrying genomic introgressions of wild cotton G. armourianum (D-genome) in G. hirsutum for
whitefly tolerance. Various leaf morphoanatomical characteristics such as stomatal frequency, gossypol
glands, trichome density, trichome length, trichome angle, mesophyll arrangement and leaf thickness
were studied in parents G. armourianum Acc. PAU 1, G. hirsutum cv. F 1861 and LH 1556, their F1,
BC1F1, BC2F1 derivatives to find out their relationship with B. tabaci infestation on host cotton. A
significant decline in stomatal frequency, gossypol glands and trichome density was observed in mature
leaves as compared to young leaves in the parents and their backcross derivatives. All the 69 individual
lines (genotypes) of BC2F1 progeny differed significantly in stomatal frequency, trichome density,
number of gossypol glands and lamina thickness; and hence their response to whitefly resistance.
Correlation studies revealed a positive association of trichome density with whitefly incidence on G.
hirsutum cultivars and developed backcross progeny. This relationship was observed in both young
(r=0.319) and mature leaves (r=0.340). Higher hair density might allow strong grip of insects during
oviposition and also their better retainment than on smooth leaves.This can be the reason of resistance
in G. armourianum which is trichome less. The interspecific F1 hybrid having about 50 % of G.
hirsutum genome exhibit short stellate trichomes but was highly resistant to whitefly. A positive
correlation of stomatal frequency with other morpho-anatomical trait such as gossypol gland (ry=0.251
and rm=0.296) and with trichome density (ry=0.360 and rm=0.305) was observed in both young and
mature leaves. Surprisingly, stomatal frequency on young leaves was positively correlated with
whitefly infestation (r=0.372). Trichome angle varied non-significantly between young and mature
leaves. No correlation of lamina thickness with whitefly incidence was observed in our study.Changes
in levels of various biochemicals such as gossypol, phenolic, sugars, starch, proteins, tannins and
chlorophyll content of leaf tissue were also determined in G. armourianum Acc. PAU1 along with G.
hirsutum parents and susceptible check LH 2107 at periodic intervals (0 hrs, 12 hrs, 24 hrs, 48 hrs and
72hrs) after whitefly infestation. Gossypol contents were significantly lower in resistant G.
armourianum than susceptible cultivar LH 1556 but was statistically at par to F1861 and LH 2107 on
pooled basis. However, total phenols varied significantly when observed at periodic time intervals after
B. tabaci infestation. The wild cotton G. armourianum had significantly higher tannin contents than G.
hirsutum cultivars before infestation. The magnitude of increase was about 9 -fold when compared with
susceptible check LH 2107. Further in response to whitefly infestation, leaf tannin levels declined
initially at 12hrs and 24 hrs but then increased significantly at 72hrs. But surprisingly in G.
armourianum, increase in tannin levels were observed much earlier i.e. after 24 hrs of infestation as
compared to G. hirsutum varieties. Such an early upregulation of chemical induced resistance would be
the reason for whitefly tolerance of this wild species.