Selection index and molecular markers in reciprocal recurrent selection in maize

Reciprocal recurrent selection among full-sib families is one of the outstanding methodologies of maizeimprovement, since gains are possible in the per se and/or in cross populations. Here the selection index proposed by Smithand Hazel was used in the cited methodology; besides, an additional phase involving RAPD markers was introduced topreserve the genetic variability of the selected genotypes and identify contaminants before their recombination. Multivariatetechniques of grouping and discriminant analyses were used for this purpose, to assure the continuance of the improvementprogram and amplify the genetic distance between the populations Cimmyt and Piranão, which were used for an intervarietalhybrid. The molecular technique proved useful to identify contaminants and helpful in the choice of the genotypes to berecombined to maximize heterosis among populations. The technique can be included in recurrent selection programs, mainlythose that target the development of hybrids

Inferências genéticas na produção e qualidade de tomateiro sob cruzamento dialélico

Genetic inferences on the performance of five tomato cultivars (Ângela I.5100, Floradade, IPA-05, Jumbo AG-592 and Santa Clara) and their p(p - 1)/2 hybrids for production characteristics and fruit quality were obtained through Hayman's methodology (1954). The results showed a favorable situation for breeding to production characteristics, but not for content of soluble solids, total carotenoids, and content of betacarotene. The data evidenced low variability in the cultivars studied.Inferências genéticas sobre o desempenho de cinco cultivares de tomateiro (Ângela I.5100, Floradade, IPA-05, Jumbo AG-592 e Santa Clara) e seus p(p -1)/2 híbridos dialélicos foram obtidas com base em três características de produção e quatro características relacionadas à qualidade dos frutos, empregando-se a metodologia de Hayman (1954). Os resultados evidenciaram a possibilidade de ganhos genéticos relativos às características de produção. O mesmo não ocorreu com os teores de sólidos solúveis, carotenóides totais e betacaroteno. Isto denota a reduzida variabilidade nas características da qualidade dos frutos avaliados

COMPARISON OF TESTERS IN THE EVALUATION OF COMBINING ABILITY OF S2 FAMILIES IN POPCORN

The aim of the present study was to compare three testers (three-way hybrid Zélia, single cross hybrid IAC 112 and composite CMS 43) for evaluating general and specific combining ability of thirty six S2 popcorn families obtained from CMS 43. Families were evaluated considering per se and topcrosses performances, in four 6X6 lattices, with three replications. Trials were carried out in the experimental field at Universidade Estadual de Maringá, in Iguatemi, Paraná, in the years 2001 and 2002. General and specific combining ability were estimated following the partial diallel model. Heterosis of topcrosses in relation to the mean of each tester as well as the correlation between families performances and respective topcrosses were estimated. Correlation estimates were obtained among four sets of means: the S2 families and the three topcrosses sets. Results showed that the more appropriate testers for grain yield and popping expansion were Zélia in 2001 and CMS 43 in 2002

Combining abilities in green corn genotypes for yield and industrial quality traits

The general and specificcombining abilities and the reciprocal effects of seven hybrids and two open pollination varieties of green corn were evaluated, aiming the formation of base populations to be used as a source of superior inbred lines. For the purpose of this study, two experiments were carried out in Maringá/PR and Sabáudia/PR, during the crop season of 2014/15. The experiments were evaluated in incomplete block design alpha lattice, with three replications. The parents AM811, HTMV1, Cativerde 02 and AL Piratininga were selected based on their ĝi and the following hybrid combinations AM811 x CD316, AM811 x AG1051, AM811 x HTMV1, AM606 x Cativerde 02 and Al Piratininga x AG4051 presented the most desirable ŝij effects. Regarding the reciprocal effects, the genotype AM811 is recommended to be used as male parent in further hybrid combination

Comparison of selection traits for effective popcorn (Zea mays L. var. Everta) breeding under water limiting conditions

Climate change is expected to intensify water restriction to crops, impacting on the yield potential of crops such as popcorn. This work aimed to evaluate the performance of 10 field cultivated popcorn inbred lines during two growing seasons, under well-watered (WW) and water stressed (WS) (ψsoil≥ -1.5 MPa) conditions. Water stress was applied by withholding irrigation in the phenological phase of male pre-anthesis. Additionally, two contrasting inbred lines, P7 (superior line) and L75 (low performer) were compared for grain yield (GY) and expanded popcorn volume (EPV), selected from previous studies, were tested under greenhouse conditions. In the field, no genotype x water condition x crop season (G×WC×CS) interaction was observed, whereas GY (-51%), EPV (-55%) and leaf greenness (SPAD index) measured 17 days after anthesis (DAA) (> -10%) were highly affected by water limitation. In general, root traits (angles, number, and density) presented G×WC×CS interaction, which did not support their use as selection parameters. In relation to leaf senescence, for both WS and WW conditions, the superior inbred lines maintained a stay-green condition (higher SPAD index) until physiological maturity, but maximum SPAD index values were observed later in WW (48.7 by 14 DAA) than in WS (43.9 by 7 DAA). Under both water conditions, negative associations were observed between SPAD index values 15 and 8 days before anthesis DBA), and GY and EPV (r ≥ -0.69), as well as between SPAD index 7, 17, and 22 DAA, and angles of brace root (AB), number of crown roots (NC) and crown root density (CD), in WS (r ≥ -0.69), and AB and CD, in WW (r ≥ -0.70). Lower NC and CD values may allow further root deepening in WS conditions. Under WS P7 maintained higher net photosynthesis values, stomatal conductance, and transpiration, than L75. Additionally, L75 exhibited a lower (i.e., more negative) carbon isotope composition value than P7 under WS, confirming a lower stomatal aperture in L75. In summary, besides leaf greenness, traits related to leaf photosynthetic status, and stomatal conductance were shown to be good indicators of the agronomic performance of popcorn under water constraint