Enhancing tolerance in horticultural crops to climatic stresses

At IIHR, phenotyping for drought and high temperature was carried out in a set of previously identified genotypes. The approach of inter-specific grafting was focussed upon for enhancing flood tolerance in tomato.

High temperature tolerance in tomato

Forty two tomato genotypes were screened for drought tolerance under both field and pot culture conditions. Under field conditions water stress was imposed at flowering and fruiting stages by withholding irrigation for 45 days. In pot culture water stress was imposed for 7 days at vegetative stage. Of these 42 genotypes, 12 genotypes were screened for drought tolerance based on morpho-physiological observations. Further, these 12 genotypes viz., 15-SB, IIHR 2195, IIHR 2201, IIHR 2327, IIHR 2336, IIHR 2338, IIHR 2777, Arka Meghali, Arka Vikas, Vybhav, Pusa Ruby, RF4A were evaluated for water stress. Water stress was imposed for 14 days under pot culture. Morphological observations like plant height, root length, number of branches, flowers and fruits were taken. Physiological observations such as gas exchange parameters, relative water content, electrolyte leakage and total
chlorophyll content were estimated. Observations on recovery were taken three days after release of stress. RF4A, IIHR 2195, IIHR 2201, Arka Meghali and Vybhav showed tolerance to water stress and recovered quickly. IIHR 2201 showed highest percentage of relative water content and leaf water potential. RF4A showed very less percentage of electrolyte leakage (better membrane stability index).

Incorporation of heat and drought tolerance in desirable genetic background

Hybrid of heat tolerant line (IIHR-2853) and drought tolerant line (RF4A) of tomato were raised during the period of report. F2 seeds were collected to develop mapping populations for marker identification. Backcrosses were also attempted with both the parents and seeds of both the back crosses were also collected to transfer heat and drought tolerance in to parental lines. In order to transfer heat tolerance in to desirable genetic back ground, hybrids (IIHR-2852 x 12-21, IIHR-2853 x 12-21, IIHR-2853 x 12-21, IIHR-2853 x 38-7 and IIHR-2853 x Arka Vikas) involving heat tolerant lines (IIHR-2852 & IIHR-2853) were also raised and back cross seeds with recurrent parents were collected. A field trial was taken up with tomato hybrid Arka Rakshak at three locations viz. Kolar, Chikkaballapur and Bellary during summer 2013 to evaluate for heat tolerance.

Screening for heat tolerance:

Six tomato F1 hybrids were evaluated for heat tolerance during early summer 2013. Three hybrids viz; H-329 (56 t ha-1), plate 1, H-363 (48 tha-1) & H-367 (53t/ha) out yielded commercial hybrids NS-501 (43 t ha-1) & To- 1389 (26 t ha-1). Preliminary studies revealed that an advanced breeding line BC1F126-9-33-4-4-3-3 (45 t ha-1) was also found to have drought tolerance. A set of seven lines viz. Arka Meghali, Vybhav, IIHR 2777, IIHR 2274, IIHR 2190, IIHR 2201, IIHR 2338 and two hybrids viz. Arka Rakshak and Arka Samrat were screened in polyhouse conditions, where temperature build up during the day was recorded in the range of 35-52°C. Based on percentage survival IIHR 2274 (93.33%) and IIHR 2201 (86.66%) turned out to be the best at elevated temperatures.

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