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David W. Davis and Karl J. Sauter

Attention has been given in recent literature to crop breeding for heat tolerance, but, as with certain other physiological traits, such as photosynthetic efficiency, practical gain has lagged. The question remains as to whether heat tolerance can be improved, and, if so, if it can most efficiently be improved by a holistic approach, as in breeding for yield following timely high temperature levels in the field environment, or whether the breeding for heat (and drought) tolerance components in the laboratory would be feasible. At issue is the identification and repeatability of key plant responses, such as cell membrane damage, heat shock protein formation, increased ethylene output and other responses, and the relevance, effectiveness and cost of screening for such traits. Results from our laboratory, and the work of others, will be reviewed.

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B. Scully, R. Provvidenti, D. Benscher, D.E. Halseth, J.C. Miller Jr., and D.H. Wallace

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Phillip Griffiths, Molly Jahn, and Mike Dickson

1 To whom reprint requests should be addressed; e-mail pdg8@cornell.edu . 2 Department of Plant Breeding, Bradfield Hall, Cornell University, Ithaca NY14580. I thank Helene Dillard for the pathogen isolate used in this work, Jim Steadman

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Fredrick A. Bliss

41 ORAL SESSION (Abstr. 422-429) CROSS-COMMODITY: BREEDING I

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Benoît Bertrand, Hervé Etienne, and Albertus Eskes

In order to avoid nematode damage to roots of Coffea arabica L. in Latin America, a common practice is interspecific grafting on C. canephora var. Robusta (Pierre) rootstocks. The performance of two C. arabica cultivars, `Caturra' and `Catimor T5175', was evaluated on four rootstocks: C. canephora var. Robusta (`T3561' and `T3757') and C. liberica var. liberica (Hiern) and var. dewevrei (Lebrun), over 5 years in a trial at 1180 m elevation in Costa Rica. Nongrafted plants of the two Arabica cultivars were used as controls. Mortality of plants grafted on the two C. liberica cvs. was >20% vs. 6% to 13% for plants grafted on C. canephora, and 3% to 4% for the two controls. Analysis of accumulated yields over four harvests showed that the rootstocks limited stem girth and reduced yield 10% to 48%. Yield on the C. canephora rootstock was greater than that on the two C. liberica cultivars. However, grafting did not affect female fertility (peaberries, empty berries) or content of several chemicals, such as caffeine, fat, and sucrose. The two C. liberica rootstocks significantly reduced aroma and bean size. Histological studies revealed symptoms of incompatibility, characterized by more dilated and less distinct growth rings and appearance of plugged vascular connections. The poor performance of the rootstocks may therefore be explained by partial incompatibility. However, growth and productivity were also affected by poor adaptations of C. canephora, C. liberica, and C. dewevrei to the lower temperature at high altitudes and by morphological differences in the root systems. These results emphasize the need to develop better adapted rootstock cultivars from C. canephora var. Robusta.

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D.P. Coyne, J.R. Steadman, D.T. Lindgren, David Nuland, Durward Smith, J.R. Stavely, J. Reiser, and L. Sutton

101 POSTER SESSION 3A (Abstr. 127–158) Breeding & Genetics–Vegetables

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Sindynara Ferreira, Luiz Antonio A. Gomes, Wilson Roberto Maluf, Vicente Paulo Campos, José Luiz S. de Carvalho Filho, and Daniela Costa Santos

the use of resistant cultivars. Resistance sources to Meloidogyne spp. have been found in dry beans; however, they are not widely used by breeding programs ( Carneiro et al., 2003 ; Walber et al., 2003 ). Despite the great losses recorded on the dry

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Charles J. Wasonga, Marcial A. Pastor-Corrales, Timothy G. Porch, and Phillip D. Griffiths

were: 1) to develop and evaluate snap bean populations that combine the Ur-4 and Ur-11 rust resistance genes with heat tolerance; 2) to select from subsequent generations of these populations breeding lines that combine rust resistance (based on the

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Wesley Gartner, Paul C. Bethke, Theodore J. Kisha, and James Nienhuis

breeding objectives in dry beans to increase yield with either more or larger seeds. Fig. 1. Percent seed mass of P. vugaris fruit sampled over five day intervals after flowering for four edible podded cultivars (Champagne, Goldcrop, Hystyle and Morse