JASP 3 -- 1985.pdf - International Herbage Seed Group

64 JOURNAL OF APPLIED SEED PRODUCTION, VOL. 3, 1985within the two (genetically different) populations.In 1980, the largest influence on seed yield was exerted byfloret utilization, but, as mentioned before, this might havebeen caused by its method of determination. Indirect effectsthrough the other components did not influence the directeffect a great deal, resulting in a high correlation betweenseed yield and floret utilization. The second highest effect in1980 came from inflorescence number, which was high in1981 as well. But contrary to 1980, the effect of inflorescencenumber in 1981 was reduced by a negative, indirecteffect via 1000-gmin weight, while the two other indirecteffects were negligible.The direct and indirect effects of the number of germinatingseeds per inflorescence in 1981 was very small givingevidence that this characteristic was in no way related to seedyield.The highest effect in 1981 was given by 1000-grain weight- an indirect negative effect via inflorescence number madethat the correlation between 1000-grain weight and seedyield was small. The same correlation in 1980 was largelycomposed of the indirect effect of floret utilization.Spikelet number had a relatively large influence in 1980,but the indirect effects via inflorescence number and floretutilization, made the correlation nil. The presence of manyspikelets had a positive effect on seed yield, but due to thelower weight of seeds, overall yield was smaller. A pathanalysis was also done for seed yield per inflorescence (Table6).In 1980, the largest direct effect on seed yield per inflorescencewas exerted by percent floret utilization. The secondlargest effect came from number of spikelets: a high numbercontributed towards a higher yield per inflorescence, but atthe same time seed weight and floret utilization were reducedas can be seen from the negative effects of these characteristics.Thousand-grain weight influenced seed yield positively.A larger influence than this effect was exerted by theindirect effect via percent floret utilization.Thousand-grain weight had the largest direct effect onseed yield per inflorescence in 1981. Spikelet number exertedsome influence. Though the influence of the number ofgerminating seeds per inflorescence was small, it is interestingto note that the direct, negative effect was compensatedby the indirect, positive effect via 1000-grain weight resultingin the absence of a clear correlation between both characteristics.Therefore, many germinating seeds per inflorescencedid not contribute to a higher seed yield per inflorescenceas these seeds had a low weight.The multiple regression of seed yield per plant is given inTable 7.Respectively 57 and 46% of the variation observed in seedyield per plant was explained by the independent variables,which was significant at P=O.Ol.In 1980, the largest relative influence was exerted bypercent generative tillers, percent floret utilization and tillernumber. These variables were not completely independentfrom each other. The squared multiple correlation coefficientwith the other 9 variables was 0.882, 0.446 and 0.916,respectively. Only subset equations with 7 independent vari-Table 7. Multiple regression with seed yield per plant as dependent variable.VariableTiller numberMildewGrowth stageIncrease infl. no.Plant heightLodgingInfl. number1000-grain weightSpikelet numberFloret util./germ. seeds% Veg. tillers% Gen. tillersConstantFR219801 20.318 1.80.123 0.70.126 0.90.243 0.5-0.258 1.10.009 0.20.348 2.74.077 5.8-0.029 0.90.996 2.4-44.6845.6 (10/43)0.56519813 1 2 30.59 0.020 0.2 0.040.05-0.001 0.0 0.000.10 -3.434 1.4 0.460.07 0.388 0.9 0.125.249 2.4 0.280.31 0.230 1.6 0.470.02 0.085 2.0 0.270.34 -0.046 0.4 0.040.67 0.139 1.2 0.190.10 -0.535 1.5 0.270.70 -0.465 1.3 0.2646.5783.1 (11/40)0.4611 = partial regression coefficient2 =!-value3 = relative influenceF-value- between brackets: degrees of freedomR 2 = squared multiple correlation coefficient