VASO is a Portuguese participatory maize breeding project (1984), where several maize landraces such as Pigarro have been selected both by a farmer's (phenotypic recurrent selection) and a breeder's approach (S2 lines recurrent selection). The objectives of this study were to determine the phenotypic and genotypic responses to participatory selection using these two different approaches, to clarify to which extent both selection methods preserve genetic diversity, and conclude what is the preferred method to apply in sustainable farming systems. The results, obtained via ANOVA, regression analyses and molecular markers, indicate that for both selection methods, genetic diversity was not significantly reduced, even with the most intensive breeder's selection. Although there were some common outputs, such as the determinated versus indeterminated ears, cob and ear weight ratio per ear and rachis 2, specific phenotypic traits evolved in opposite directions between the two selection approaches. Yield increase was only detected during farmer selection, indicating its interest on PPB. Candidate genes were identified for a few of the traits under selection as potential functional markers in participatory plant breeding.

MAIZE EAR FASCIATION:Knowledge of the genes affecting maize ear inflorescence may lead to better grain yield modeling. Maize ear fasciation, defined as abnormal flattened ears with high kernel row number, is a quantitative trait widely present in Portuguese maize landraces.MATERIAL AND METHODS:Using a segregating population derived from an ear fasciation contrasting cross (consisting of 149 F2:3 families) we established a two location field trial using a complete randomized block design. Correlations and heritabilities for several ear fasciation-related traits and yield were determined. Quantitative Trait Loci (QTL) involved in the inheritance of those traits were identified and candidate genes for these QTL proposed.RESULTS AND DISCUSSION:Ear fasciation broad-sense heritability was 0.73. Highly significant correlations were found between ear fasciation and some ear and cob diameters and row number traits. For the 23 yield and ear fasciation-related traits, 65 QTL were identified, out of which 11 were detected in both environments, while for the three principal components, five to six QTL were detected per environment. Detected QTL were distributed across 17 genomic regions and explained individually, 8.7% to 22.4% of the individual traits or principal components phenotypic variance. Several candidate genes for these QTL regions were proposed, such as bearded-ear1, branched silkless1, compact plant1, ramosa2, ramosa3, tasselseed4 and terminal ear1. However, many QTL mapped to regions without known candidate genes, indicating potential chromosomal regions not yet targeted for maize ear traits selection.CONCLUSIONS:Portuguese maize germplasm represents a valuable source of genes or allelic variants for yield improvement and elucidation of the genetic basis of ear fasciation traits. Future studies should focus on fine mapping of the identified genomic regions with the aim of map-based cloning.

Under the scope of a Portuguese regional maize ear competition (the "Sousa Valley Best Ear Competition"), an ear value (EV) formula was developed in 1993 based on published maize trait correlations. This formula had two main purposes, ears evaluation for the ear competition and maize improvement selection. The EV formula included only ear length, kernel weight at 15% moisture, number of rows and number of kernels/ear, with no direct inputs from farmers maize yield.In order to add a more scientific dimension to this popular maize evaluation approach, four main goals were defined: (1) to test alternative interpretable regression methods to provide new ear value formulas that better estimates the yield potential using ear traits; (2) to develop a new instance ranking method, allowing to select the best new ear value formula to be used on the ear competition; (3) to identify a set of traits that will help farmers on selection toward better yield; and (4) to compare the ranking results obtained by the original EV formula and the newly one developed, using data from the "Sousa Valley Best Ear" competition.To achieve these goals we analyzed some of the competition winning maize populations, on a multilocation field trial, collecting not only ear, but also field traits and yield. This data was analyzed using multiple linear regression (MLR) and multiple adaptive regression splines (MARS).A new ranking evaluation measure (PR.NDCG measure) was developed to rank the eleven interpretable regression methods obtained, and our results indicated that the most appropriate formula for yield potendal estimation included the original EV traits, but with different coefficients and was entitled adjusted EV (EVA). Ear weight, kernel depth and rachis 2, followed by cob and ear diameters and number of kernels per row were also considered traits of major importance to define potential EV formulas, i.e., contributing to yield increase. Plant stand was the most important field variable for yield potential estimation. We also observed, from comparing EV and EVA ranking, that four of the top ranks maize ears using EV were included on the EVA top ten ranks.From all the above and due to its simplicity, we conclude that the new EVA formula is a valid starting point for a long term engagement of farmers with maize germplasm development and improvement and an open door to their better understanding of maize quantitative genetics. (C) 2014 Els6vier B.V. All rights reserved.

Since the first domestications of wild plants about 12.000 years ago, farmers have been re‐ sponsible for the development and conservation of thousands of crop landraces in hundreds of species [1]. Farmers put aside, for the next generation, a part of the harvested seed. De‐ pending on the crop and the farmer, selection is carried out to obtain a crop answering bet‐ ter to the wishes of the growers and communities [2].

In 1984, Pêgo started, with the CIMMYT support, an on-farm participatory maize breeding (PMB) project at the Portuguese Sousa Valley region (VASO). VASO was intended to answer the needs of small farmers (e.g., yield, bread making quality, ability for polycropping systems). During 20 years of PMB at VASO, mass (MS) and S2 recurrent selection (S2RS) were applied on the maize landrace ‘Pigarro’. Morphological (e.g., ear length and fasciation level) and yield evaluations were conducted in Portugal (2–3 locations in 2 years) and in USA (4 locations in one year) using samples from original population, six MS cycles and three S2RS cycles. North American Populations (BS21, BS22, TEPR-EC6) were also included as checks. ANOVA comparisons and regression analyses on the rate of direct response to selection were performed. Response to MS for Iowa showed significant decrease in stalk lodging, while in Portugal ear length significantly decreased, whereas ear diameter, kernel-row number, and fasciation level significantly increased. Selection also significantly increased days-to-silk and anthesis in Portugal. Response to S2RS in Portugal significantly increased days-to-silk, uniformity, and cob/ear weight ratio. These results showed that the methods used by farmer and breeder were not effective for significant yield increase, but the ear size increased significantly for MS and showed a positive tendency for S2RS. Adaptation to farmer needs was maintained for the last cycles of selection.

Natural, and in particular, artificial (human) selection may pose a danger to the existing crop genetic diversity. Nevertheless, on-farm breeding systems seem to achieve phenotypic improvements even though preserving variability. Using SSR markers, we analysed several selection cycles, over a 20 years period, of a Portuguese on-farm participatory maize OPV- Pigarro' breeding project. No significant differences in allelic richness (N-ar), observed heterozygosity (H-O), expected heterozygosity (or gene diversity; H-E) or inbreeding coefficient (f) were detected among the selection cycles. 58 out of 107 alleles were common to all the selection cycles studied. The analysis of molecular variance showed that the variation among selection cycles represented only 7% of the total molecular variation. However, the number of private alleles varied among the selection cycles, being the highest detected at the beginning of the selection project. These findings demonstrate that an allele flow took place during the on-farm selection process of 'Pigarro' but the level of genetic diversity was not significantly influenced. Since interesting phenotypic improvements were also achieved, on-farm breeding projects, like this one, should be valued as a way to preserve unique Portuguese maize landraces in risk of disappearing.