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Effect of different temperature regimes on vegetative growth of melon plants Amuyunzu, P.A.; Chweya, J.A.; Rosengartner, Y. & Mendlinger, S. Abstract Experiments were conducted at the Institutes for Applied Research in Beer-Sheva, Israel between November 1992 and April 1993 to study the effects of different temperature regimes on vegetative growth of thirteen melon (Cucumis melo L.) cultigens and to identify rapid and reliable selection criteria for breeding for cold resistance. The cultigens were grown in greenhouses at two temperature regimes: high and low with mean minimum and maximum temperatures of 13 and 34 C, and 8 and 33 C, respectively. The cultigens were examined for the rate and amount of vegetative growth which included lengths of mainstems, number of nodes, internode lengths and leaf chlorophyll content. Variation among the cultigens both between and within temperature regimes was significant for most of the traits. The best six cultigens for tolerance to suboptimal growing temperatures were Cinco, Midget, BsFDHK, Tal Dvash, H17 and H19. These cultigens were found to perform better, but not necessarily to the same degree in the low temperature regime for all the traits considered than the other cultigens examined. Relative growth rate (RGR) was found to be superior over the rest of the traits in distinguishing between cold sensitive and cold tolerant lines. It could, therefore, serve as a rapid and reliable selection criterion for breeding for cold tolerance in melons. Keywords Cucumis melo, cold tolerance, cultigen, suboptimal cold temperature

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Amuyunzu, P.A.; Chweya, J.A.; Rosengartner, Y. & Mendlinger, S. Résumé Des experiences sur la croissance de "cultivars" de treize melons (Cucumis melo L.) ont ete menees a l'institut de recherces appliquees de Beer Sheva (Israel) entre novembre 1992 et Avril 1993. Ces experiences ont etudie l'incidence de differents regimes de temperature sur la croissance des cultivars, et cherche a identifier des criteres de selection rapides et fiables pour l'aquisition de la resistance au froid. Les cultigens ont pousse dans des serres a des regimes de temperatures differents; respectivement 1) 13 a 34 C et 2) 8 a 33 C. Ces cultivars ont ete examines en fonction de taux de croisssance vegetative (longueur de la branche centrale, nombre de noeuds, espace entre les noeuds et teneur en chlorophylle). La variation parmi les cultivars entre differents regimes et dans les memes regimes de temperature s'est averee significative pour la plupart des plants. Les six meilleurs cultivars resistants a une temperature suboptimale sont Cinco Midget, BsFDHK, Tal Dvash, H17 et H19. Ces cultivars se sont montres plus performants mais pas necessairement a la meme temperature dans les bas regimes, que les autres plants si l'on distingue la sensation au froid et les lignes de tolerance au froid. Des lors, cela pourrait constituer des criteres de selection rapides et fiables pour acquerir la tolerance au froid. Mots Clés Cucumis melo, tolerance au froid, cultivars, temperature froide suboptimale, criteres de selection

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