280 V. N. Ghante et al.
Ankur Bt, Tulsi-144, VICH-32 and Pratika were
found to be moderately tolerant (Table 2 ).
Bt cotton hybrids are more prone to red leaf
symptoms. More than 500 Bt cotton hybrids
have been released for cultivation in India. The
expression of reddening depends on the interac-
tion of the hybrid and the environment. Cotton
varieties with hairy leaves are less susceptible to
leafhopper attacks than varieties with glabrous
leaves (Praharaj and Sankaranarayanan 2010 ).
The phenomenon of leaf reddening is genetically
controlled and some genome is responsible for
anthocyanin synthesis. A differential response
of different hybrids was observed with respect
to specific activity of phenylalanine ammonia
lyase, tyrosine ammonia lyase and phenol con-
tent of leaves, which play a major role in flavo-
noid biosynthesis (Koukol and Conn 1961 ). Bt
hybrids should have a strong photosynthetic sys-
tem and stay green so that the hybrid is capable to
withstand enhanced Bt gene-induced reproduc-
tive load (Patil et al. 2010 ).
Among the different nutrients tested through
foliar application during reproductive stage of Bt
cotton crop, multinutrient mixture (both major
and micro nutrients) proved best in managing
the reddening due to nutrient deficiencies and
recorded very less values for RLI (Table 3 ). The
mismatch in nutrient application and crop re-
moval resulted in multiple nutrient deficiencies
(Naidu et al. 2011 ). Foliar application/feeding is
one of the most efficient ways of supplying essen-
tial nutrients to the crop at the appropriate stage.
Through foliar nutrition, the nutrients are taken
into the foliage and distributed (transported) to
all parts of the plant within a short period to get
the needed effect. It is also effective in correcting
the mid-season discrepancies in crop growth that
may be due to either intensive growth or inap-
propriate supply of nutrients from the soil under
abiotic stress conditions (Rathinavel et al. 1999 ).
Based on the confirmation of the major factors
influencing reddening in Bt cotton (i.e., insect
pests, nutrients and Bt hybrid), multidisciplinary
crop management practices (MDCMP) involving
balanced and timely applications of macro- and
micro-fertilizers based on site-specific soil test
results, use of leaf reddening-tolerant cotton hy-
brid, effective management of sucking pests spe-
cially leafhoppers, effective management of dis-
eases and 2–3 foliar applications of water-soluble
multinutrient mixtures during reproductive stage
of the crop were evaluated for the management
of leaf reddening in Bt cotton and compared with
farmers’ practice. An integrated approach was
found (Table 4 ).Table 1 Severity of reddening in Bt cotton with and without sucking pest management
Treatment Reddening severity (RLI) Average LH/plant Yield/ha (qtl)
60 DAS 100 DAS
RCH 2 with sucking pest management 1.21 1.52 1.87 26.52
RCH 2 without sucking pest management 2.89 3.32 11.28 15.92
Fig. 4 a Differentiation of reddening due to cotton leaf-
hoppers, b nutrient deficiency