Study on Maize Stalk Lodging Resistance in Cyclic Cross Selection

Stalk lodging resistance is a particularly important trait on maize, especially in terms of mechanized harvesting of the crop. Stalk lodging represents a major problem of corn with yield losses. Because of this reason, it takes a special attention on the breeding process. The purpose of this research was the study of maize stalk lodging resistance before the harvest time and finding the best breeding lines for this type of resistance. We used 7 breeding lines (TE 229, TE 202B, TA 452, TE 330A, TD 364, TE 317 and TE 335) as maternal lines and another 3 (TD 268, TC 385A and TC 399) as testers. Lines were tested in 2011 and 2012, in compared cultures with 24 variants, where 21 of them were the experimental hybrids between tested lines and testers and the other 3 werethe control hybrids Turda 201, Turda Favorit and PR39D81. Variance analysis was performed according to the classical model of a two-factor system. Genic effects were calculated after 2nd North Carolina model. Regarding the results, the highest percentage of unbroken plants was on TD 268 tester (80.7%) and the lowest on TD 364 tested line (70.2%). Tested lines that was noted for the general combining ability of lodging resistance were TA 452 and TE 335. Crossings that marked high values for non-additive effects were TA 452 x TC 385A, TE 202B x TC 399 and TE 202B x TD 268. Effects values for general combining ability were between -4.72% and +4.49% on tested lines, -1.68% and +5.78% on testers; effects values for specific combining ability were between -11.25% and +7.58%. Regarding the tested lines was noted TA 452 inbred line and regarding the testers was noted TD 268 inbred line. On this issue, we can state that in the selection process of maize hybrids must be chosen only those hybrid combinations with stalk-lodging resistance because of the similar contribution of additive and non-additive genic effects to resistant genotypes

Combining Ability for Yield of Single-Cross Hybrids Derived from Maize Composites (Zea mays L.)

Development of high-yielding hybrids of maize depends on good understanding of combining ability and inheritance of yield trait. To achieve this goal, synthetic populations of lines are developed and improved upon by recurrent selection to be utilized as initial material for the creation of inbred lines. Therefore, the aims of the present paper were: to determine the combining ability among some inbred lines developed from composites and commercial hybrids by recurrent selection method and to choose the most promising inbreds for maize yield improvement and the most suitable hybrid combinations. The highest value of the general combining ability (GCA) was obtain from inbred line TA 447 (1,655 kg ha-1) followed by tester TC 399 (233 kg ha-1). For the specific combining ability (SCA), TA 447 × TC 385 A, TA 427 × TC 399, TA 428 × TC 399 and CO 305 × TD 268 had good compatibility. The research concluded that GCA was more important that SCA, indicating that the additive genetic effects are mainly involved in the heredity of yield potential of maize. For the non-additive effects to increase, the next selection cycles must focus on plants’ pairs with more pronounced heterosis for the yield trait