PHYSIOLOGICAL AND STRUCTURAL CHARACTERIST ICS OF GENE RESOURCES OF WHEAT WITH HIGHER SINK CAPACITY OF THE SPIKE

Seven gene sources of wheat (Triticum aestivum L.) with higher sink ca pacity of the ear representing donors of spike fertility genes (SFG) w ith normal spike morphotype (NS) have been evaluated. In comparison wi th the control cultivar Hana the kernel dry mass per spike of the gene sources was higher by 17 to 120 %. This increase was due to significa ntly higher number of kernels per spike (Tab. I). All the tested gene sources have a higher number of kernels per spikelet. Considerable dif ferences between cv Hana and the gene sources have been found in sever al morphological and anatomical structures (Tab. II). NS sources were found to have significantly longer peduncle and its specific dry weigh t (mg.cm-1) as well as diameter were bigger. Only NS 8 sources having the longest stem differed neither in specific stem weight, nor in pedu ncle diameter. Anatomical analysis of the peduncle in the 1 cm distanc e below the ear revealed an increase in the cross sectional area of va scular bundles and their phloem. At maturity, all the gene sources but NS 16 were found to have higher stem length when compared with the co ntrol cultivar The same is true as to stem and spike dry mass is conce rned (Tab. III). However, the dry matter allocation into the spike and the harvest index decreased in gene sources with stem length from 90 to 100 cm. During the vegetative period dry matter production was meas ured in two gene sources differing in stem length. By the end of the e ar formation period, i.e. by the time of terminal spikelet (TS) format ion on the shoot apex, no differences were found in stem dry mass. How ever, at anthesis, stem dry mass of the gene resources was significant ly higher than that of cv. Hana (Tab. IV). This increase was due to hi gher dry mass of the two uppermost leaf blades and of the spike itself . During the period from TS formation to anthesis dry matter allocatio n into the spike was most apparent. The portion of stem dry matter all ocated into the spike was 20, 27, and 33 % m cv. Hana, NS 16 and NS 20 , respectively. Harvest index of the gene sources was equal or even lo wer than that of cv. Hana. Higher sink capacity of the spike of the NS gene sources seems to be positively supported by an increased total d ry mass of the stem and its allocation into the spike during the perio d before anthesis. Seedlings of the gene sources were found to be sens itive to giberellic acid (GA3). As an exception, the NS 21 was giberel lin insensitive indicating the presence of a dwarf gene. This finding corresponds with the hypothesis first indicated by Smocek (1990) that the dwarf genes Rht and spike fertility genes (SFG) function independe ntly or nearly independently enabling thus their cumulation in one gen otype. Evaluating the kernel quality, all the gene sources were higher in protein content (14.4 to 16.0 % of kernel dry matter). According t o the wet gluten content as contained in flour and its swelling capaci ty, the gene sources NS 16, NS 20 and NS 25 were qualified as being of a good baking quality. There are some negative features of the SFG so urces with the NS spike type. They are late flowering, less tillering and more sensitive to lower temperature. For this reason they cannot b e considered as suitable for direct use as commercial cultivars. Howev er, they seem to be of extreme value for including into breeding progr ammes ensuring new possibilities for an increase in spike productivity .