Abstract Spike fertility index (SF) is a trait easily measured at maturity and strongly associated with the number of grains per unit area. In order to identify genomic regions involved in SF control, a biparental (Baguette 10 × Klein Chajá) population of 80 recombinant inbred lines (RIL) was used. Seven field trails were conducted to determine the SF BLUP value per RIL. RILs were genotyped using a commercial chip (Axiom® 35K SNP Wheat Breeder's Array, Affimetrix). A linkage map was constructed with 857 SNP markers, and SF QTL mapping was performed. The narrow-sense heritability of SF was 0.89. Three genomic regions (QTL) associated with SF were found on chromosomes 2D, 4A, and 7A. The proportion of genetic variation explained by these three QTL was 32%, with no significant epistatic interaction between QTL.

Leaf rust, caused by Puccinia triticina Eriks. is a common and widespread disease of bread wheat (Triticum aestivum L.), in Argentina. Host resistance is the most economical, effective and ecologically sustainable method of controlling the disease. Gene postulation helps to determine leaf rust resistance genes (Lr genes) that may be present in a large group of wheat germplasm. Additionally presence of Lr genes can be determined using associated molecular markers. The objective of this study was to identify Lr genes that condition leaf rust resistance in 66 wheat cultivars from Argentina. Twenty four differential lines with individual known leaf rust resistance genes were tested with 17 different pathotypes of leaf rust collected from Argentina. Leaf rust infection types produced on seedling plants of the 66 local cultivars were compared with the infection types produced by the same pathotypes on Lr differentials to postulate which seedling leaf rust genes were present. Presence of Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, Lr25, Lr26, Lr29, Lr34, Lr35, Lr37, Lr47 and Lr51 was also determined using molecular markers. Eleven different Lr genes were postulated in the material: Lr1, Lr3a, Lr3ka, Lr9, Lr10, Lr16, Lr17, Lr19, Lr24, Lr26, Lr41. Presence of Lr21, Lr25, Lr29, and Lr47 could not be determined with the seventeen pathotypes used in the study because all were avirulent to these genes. Eleven cultivars (16.7%) were resistant to all pathotypes used in the study and the remaining 55 (83.3%) showed virulent reaction against one or more local pathotypes. Cultivars with seedling resistance gene combinations including Lr16 or single genes Lr47 (detected with molecular marker), Lr19 and Lr41, showed high levels of resistance against all pathotypes or most of them. On the opposite side, cultivars with seedling resistance genes Lr1, Lr3a, Lr3a + Lr24, Lr10, Lr3a + Lr10, Lr3a + Lr10 + Lr24 showed the highest number of virulent reactions against local pathotypes. Occurrence of adult plant resistance genes Lr34, Lr35 and Lr37 in local germplasm was evaluated using specific molecular markers confirming presence of Lr34 and Lr37. Our data suggest that combinations including seedling resistance genes like Lr16, Lr47, Lr19, Lr41, Lr21, Lr25 and Lr29, with adult plant resistance genes like Lr34, SV2, Lr46 will probably provide durable and effective resistance to leaf rust in the region.

Amylose and amylopectin are the two polysaccharides that constitute starch in bread wheat and the enzyme GBSSI (Granule-bound starch synthase I), also known as waxy protein, is responsible for amylose synthesis in storage tissues. Decrease of the amylose content in starch has been associated with the lack of waxy protein(s). In this work, different sets of PCR markers were used to characterize the genetic variability of waxy loci from 103 Argentinean bread wheat cultivars. For the Wx-A1 locus, Wx-A1a and a novel molecular allele designed Wx-A1g were detected. Wx-B1 locus showed three alleles (Wx-B1a, Wx-B1b, Wx-B1e), and Wx-D1 locus showed only the Wx-D1a allele. Novel single-locus allele specific markers for Wx-A1b, Wx-B1b and Wx-D1b null alleles were also described. To our best knowledge this is the first study focused to characterize the genetic variability for waxy genes in bread wheat cultivars from South America.

Leaf rust resistance gene Lr47 is located within a interstitial segment of Triticum speltoides Taush. 7S chromosome translocated to the short arm of chromosome 7A of bread wheat. This gene is resistant against currently predominant races of leaf rust from Argentina. The objectives of this study were to identify microsatellites linked to this source of resistance as a potential tool to introgress this source of resistance. Isogenic lines with and without Lr47 developed from 10 cultivars/breeding lines as well as 10 microsatellites previously mapped in 7AS chromosome were used in this study. Microsatellite gwm 60 was the only marker that co-segregated completely linked to Lr47. These data indicate that gwm 60 could be a valuable marker to introgress Lr47 in wheat germplasm.