Screening Of Tomato Germplasm For Drought Tolerance And Its Index Evaluation

This investigation was carried out to screen the response of45tomatoes inbred-lines todrought stress at germination and seedling stages. Out of these the effect of water stresscondition in physiological growth parameters of35tomato inbred lines was studied. After this,hybridization was made among the four most tolerant inbred lines. Then, comparison of theinbred lines and their hybrids for drought tolerance and assessment of the most importantselection criteria for drought tolerance was made. These inbred-lines which were collectedfrom different countries were screened with osmotic concentration of12.5%polyethyleneglycol6000while their respective control treatments were treated using distilled water fortwelve days at germination stage. Relative germination energy (RGE), relative germinationrate (RGR), relative germination index (RGI), relative vitality index (RVI) and the relativePEG injury rate were computed to identify the most tolerant inbred-lines on germination stage.Inbred-lines TTI1103B-2, A0911, Roma, L12, and TTD210B were found to be the mosttolerant. While inbred-lines L9, TTI1109B-1-2-1, A4, B6and A7were the most sensitive todrought. Moreover, analysis of variance revealed significant differences among the inbred-lines studied. The experiment was repeated for confirmation and the result was similar.An additional study was conducted on30days old seedlings to observe their water stressresponse at their seedling stage. A total of30inbred-lines,10inbred-lines each from tolerant,moderate and sensitive; were selected based on the results found at germination stage. Afterproper watering for30days, watering was stopped for the following10days. After that, thedead and alive was counted. The seedlings were then re-watered for the following one weekand those recovered from dead were counted again. Finally, the dead and recoverypercentages were computed as an indicator of water stress tolerance. And the result was verysimilar to the experiment done on germination stage. The relative percentages of shoot length,root length, shoot weight; root weight and relative germination rate of35tomato inbred lineswere computed to determine the effect of water stress on the growth parameters. Accordingthe experiment’s result, drought tolerant inbred lines have longer root length and higher rootweight than the susceptible inbred lines. Shoot length and weight were not much affected bythe drought situation at the germination stage. The most drought tolerant inbred lines have thehighest relative germination rate and the drought susceptible inbred lines have a lower relative germination rate. The highest germination percentage was recorded at control treatments thanin the PEG treatments.12hybridizations were made among4drought tolerant tomato inbred lines; the seeds of theparents and their hybrids were treated with osmotic concentration of13%polyethylene glycol6000while their respective control treated with distilled water for12days at germinationstage. Based on their scores of relative germination energy (RGE), relative germination rate(RGR), relative germination index (RGI), relative vitality index (RVI) and relative PEGinjury rate TTD210B*TTI1103B-2, TTI1103B-2*TTD210B, TTD210B*Roma, TTI1103B-2*Roma, TTI1103B-2*A0911, TTD210B*A0911, Roma and TTI1103B-2are the mosttolerant materials at germination stage and were used in the seedling stage experiment.Fresh shoot weight (FSW), dry shoot weight (DSW), fresh root weight (FRW), dry rootweight (DRW), turgid shoot weight (TSW), turgid root weight (TRW), shoot lenght (SL), rootlength (RL), root surface area (SA) and root volume (RV) were computed in drought inducedtreatments and their respective control. Using principle component analysis method, rootlength, root surface area and root volume are identified as the best drought stress screeningparameters among the ten assessed parameters at seedling stage. Based on these outstandingparameters, TTD210B*TTI1103B-2, TTD210B*Roma, and TTI1103B-2*TTD210B andTTI1103B-2*A0911are the most drought tolerant hybrids at seedling stage.