Agriculture Reference
In-Depth Information
VC11-3-1-8, VC 11-2-5, Divisoria-2) and the United States (e.g., Tamu
Chico III, PI289309) (Opena et al.,
1992). However, lower yields in the
heat tolerant lines are still a concern. More heat tolerant varieties are re-
quired to meet the needs of a changing climate, and these must be able to
match the yields of conventional, nonheat tolerant varieties under non-
stress conditions. A wider range of genotypic variation must be explored
to identify additional sources of heat tolerance, for example AVRDC's
breeding line, CL5915, has demonstrated high levels of heat ranges from
15%-30% while there is complete absence of fruit set in heat-sensitive
lines in mean field temperatures of 35 °C. Now, new breeding lines have
been developed from CL5915 and other sources that exhibit increased heat
tolerance. A CL5915 line is considered best combiners for percentage fruit
set and total yield in hybrids developed for heat-tolerance (Metwally et
al.,
1996). Similarly for cold tolerance several genotypes have shown very
good tolerance like, PI-120256, a primitive tomato from Turkey; LA-1777
(
Solanum habrochaites
) from AVRDC, Taiwan and
Lycopersicon hirsu-
tum
. LA3921 and LA3925 both
Solanum habrochaites
from AVRDC, Tai-
wan has also shown chilling tolerance. Similarly EC-520061 (
Solanum
habrochaites
) can set fruits both under high (40±2 °C) and low (10±2 °C)
temperature. These lines can be used for development of cold tolerance in
various backgrounds.
Presently Division of Vegetable Science, Indian Agricultural Research
Institute has developed some varieties of vegetables to mitigate the harm-
ful effect of heat. Tomato varieties Pusa Sadabahar and Pusa Sheetal and
one hybrid Pusa Hybrid-1 have been developed. They are tolerant to high
and low temperature. Radish variety, Pusa Chetaki has been developed
having better root formation under high temperature regime i.e. April-Au-
gust. Similarly carrot variety, Pusa Vrishti can form root at high tempera-
ture and high humidity i.e. March-August. Early cauliflower variety, Pusa
Meghna has been developed which can form root at high temperature.
These varieties can be used directly for mitigating effect of high tempera-
ture as well as for future breeding program. There is need to transfer toma-
to leaf curl virus (TYLCV), early and late blight resistance in heat tolerant
lines through gene pyramiding using wild relatives, that is,
S. habrochiates
and
S. pimpinellifolium
for their wide adaptability.
