Screening for Cold Tolerance in Tomatoes Using Some Promising Physiological and Metabolical Basis.

Abstract

Experiments were conducted during early summer seasons of 1996/97 and 1997/98 to screening for sold tolerance among different tomato genotypes, i.e. (MHX 668, MHX 4953, MHX 975, US, LX II, GR and Super Marmand) depending on some physiological and metabolical basis. The results could be summarized as follow:-All the studied genotypes were significantly varied in their morphological, physiological and metabolical behaviour under low temperature condition in open field. Genotypes arranged from the best to the worst in their dry matter, chlorophyll, total protein, soluble sugars and minerals as well as pollen grain weight and germination %, fruit setting and yield) and in reverse order dealing with I1 and I2 index of cold responses (tolerance or sensitive) as follows: MHX 668 -Lx 4 -MHX 4953 -US -Super marmand.  GR and at least MHX 975, respectively.Fruit setting % and yield were significantly and positively correlated with all the studied parameters and negatively with I1 and I2 index. It was found that MHX 668 and LX II were significantly the best genotypes in growth, fruit setting and yield under stress condition due to their superior physiological and metabolical behaviour and function during their different stages of development. Herein it could be concluded that, those must be utilized in breeding programs for producing new cold tolerant tomato cvs or to be directly cultivated in early summer seasons. The possibility of using one or more physiological or metabolical parameters in one or more development stage as a rapid and accurate technique for cold tolerance screening, i.e. I1 (Ch0/Ch1) index, I2 (EC1/EC2) index (their lower values indicated an cold tolerance case, whereas higher ones indicated cold injury case). Also, soluble sugars, total protein, minerals (N, P, K and Ca) as well as pollen grain weight and germination percentage, all in higher values associated with cold tolerance.