Evaluation In Lodging-resistance Characters And Early Generation Selection In Wheat

Twenty wheat varieties (lines) with different lodging resistance as materials were studied on the tendency features of the fresh and dry density of the second bottom elongate stem during the stages of heading to maturation, and the relationship between stem density and yield characteristics, other morphological and physiological parameters. The heritability and general combining ability (GCA) of six parents in lodging-resistance characters were determined, as well as the specific combining ability (SCA) and reciprocal effect (REC) of the 6×6 complete diallel crosses combination. On the populations of F2 and F3 of two hybridized combination of SN3068×JN4072(A) and SN3068×JM20(B), we also analyzed the directly selecting effects of lodging-resistance characters and the indirect effects of selecting single lodging-resistance trait on other major lodging traits, morphology and yield characters. We probed into the feasibility of using directly the fresh and dry density of the bottom elongate stem to evaluate the lodging resistance of wheat varieties, the combining ability and heritability of major lodging-resistance characters, and providing references for the evaluation and early generation selection in lodging-resistance of wheat hybrids. The main results are as follows:1. The stem density of the second bottom elongate can be effectively used to evaluate the relative strength degree of the lodging-resistance of stem. The results indicated that the lodging-resistance of wheat stem was closely related to the values of density of the bottom elongate stem. The fresh density declined following the process of grouting, with the lowest values in dough stage; the dry density showed higher values, but in some less lodging-resistance varieties varied greater in the middle stage of grouting. Significantly positive correlation at the level of 0.01 existed between the fresh and dry stem density and the morphological and physiological parameters e.g. mechanical strength of stem (r=0.500**, 0.650**), fresh weight of individual plant, 2 cm fresh and dry weight and walk sickness of the first and second bottom elongate stem. Moreover, the fresh and dry density of the second bottom elongate stem had a significantly negative correlation at the level of 0.01 with index of lodging (r=-0.561**, -0.478**), and yield characteristics, such as the numbers of sterile spikelets (r=-0.370**, -0.550**), and ears per acre (r=-0.426**, -0.507**), and a significantly positive correlation with the number of seed-setting spikelets at the level of 0.05. Therefore, it is achievable to evaluate the relative effects of lodging-resistance of wheat according to the direct utilization of the fresh and dry density of the second bottom elongate stem.2. The results of narrow heritability analysis showed that the internal and external diameters of the first bottom elongate, large vascular bundle number, and the dry weight of the second bottom elongate stem have the high heritability; the dry weight of the first bottom elongate stem, the dry density of the first and second bottom elongate stem, fresh stem weight, large and small vascular bundle width, mechanical strength, length of the sclerenchyma, barycenter height, index of lodging have the medium heritability; the length of the first and second bottom elongate stem, small vascular bundle number, length of the parenchyma and the breastwork thick of the first and second bottom elongate stem have the low heritability.3. Taking the filial generation of 6×6 complete diallel crosses combination in wheat as materials, we analyzed the genetic effects of 21 traits of height of center of gravity, mechanical strength, and lodging of index, et al.. The results indicated that there were significant differences at the probability of 0.01 level among GCA, SCA, and REC in height of center of gravity, lodging index, mechanical strength, dry weight and density of the first and second bottom elongate stem, length, and internal and external diameters of the second bottom elongate stem, the number of small vascular bundles, the width of large vascular bundle, and the length of sclerenchyma and parenchyma, respectively; therefore, A1×A3,A1×A4,A3×A2,A5×A2,A2×A6,A4×A5 are superior cross combinations according to the effects of GCA and SCA and A1,A2 and A4 are superior parents.4. By the direct selection of the barycenter height, mechanical strength, index of lodging, the dry weight per unit length and density of the stem of the second elongate in the two combination of A and B, the average trend of the two combinations showed that, the genetic advance of all the indicators had a in line with the needs of genetic breeding (direction), the stem density has a higher relative genetic progress, and index of lodging has the lower relative genetic progress. The order of the five indicators is stem density, mechanical strength, dry weight per unit length, barycenter height, index of lodging.5. There were different impacts of selecting single lodging-resistance character on other lodging resistance characters; and the results were as follows: (1) The mechanical strength(11.291% , 5.100%), index of lodging(-11.979%,-8.622%), dry weight per unit length (18.877%,2.389%) and length in the bottom stem were the positive synergies with the barycenter height, the genetic advance of the dry density and wall thickness in the bottom stem was inconsistent between the two combinations. (2) The dry density (9.298%,6.428%) of the bottom elongate stem was the positive synergies with the mechanical strength, the genetic advance of the barycenter height, index of lodging, and the dry weight per unit length in the bottom elongate stem was inconsistent between the two combinations. (3) The barycenter height was negative synergies, and the dry weight of the bottom elongate stem was the positive synergies with the lodging index, and other lodging resistance characters were inconsistent between the two combinations. (4) The barycenter height, mechanical strength (9.943%,66.089%), the dry weight per unit length of the bottom elongate stem (4.490%,43.345%) were conducive to breeding selection with the stem density, the genetic advance of other lodging resistance characters was inconsistent between the two combinations. (5) The barycenter height and the dry density of the bottom elongate stem were conducive to breeding selection with the dry weight per unit length of the bottom elongate stem, the genetic advance of other lodging resistance characters was inconsistent between the two combinations.There is a greater effect of the single character with the stem density, it has the highest average efficiency.6. The impacts of selecting directly different lodging-resistance characters on the morphological and yield characters are greatly different among the characters and the combinations. The plant height, length of spike, length of the top second internode, length of the top third internode, number of fertile spikelets per spike, number of sterile spikelet, number of kernels per ear, number of ears per plant and the grain weight per plant were conducive to breeding selection with the barycenter height. However, the number of ears per plant (19.705%,3.968%) was conducive to breeding selection with the mechanical strength, the genetic advance of other characters was inconsistent between two combinations. Length of the top third internode, number of ears per plant and the grain weight per plant were conducive to breeding selection with the lodging index, the genetic advance of other characters was inconsistent between two combinations. Number of ears per plant, 1000-grain weight, and the grain weight per plant were conducive to breeding selection with the stem dry density, and the relative genetic progress of the grain weight per plant in A and B combinations was higher(4.436%,6.896%). Number of ears per plant (19.045% , 0.818%) and 1000-grain weight(0.383%,10.317%) were positively conducive to breeding selection with the dry weight per unit length, but the grain weight per plant was the negative synergies. The overall results showed that the stem density was the good indicators to the lodging-resistance evaluation in wheat varieties, and the synchronous improvement of the biological and economic yield can be achieved according toselect stem density.