Spaced‐Plant‐Population‐Progress Test1

Abstract

This paper describes a precise and efficient method of measuring the progress realized and expected in a population improvement breeding program. The spaced‐plant‐population‐progress (SPPP) test described here included 100 spaced plant progenies of each entry arranged in 100 blocks with one plant of each entry per block. Analysis of variance of the first‐year spaced‐plant yield data from two tests of Pensacola bahiagrass (Paspalum notatum var. saure Parodi) populations being improved by recurrent restricted phenotypic selection (RRPS) gave significant (P = 0.05) mean differences among selection cycles for all but one entry comparison. The SPPP test also supplied variances and coefficients of variation (CVs) for each population that served as relative indices of the variability left in each population and the progress that might be expected from the next cycle of selection. In a precise seeded plot test, relative first‐year mean yields of the F1 hybrid of clones 2 ✕ 4 (from Cycle 4) and Cycle 9 compared with the commercial check were 167 and 175%, respectively, and were not different (P = 0.05). In the SPPP test, their respective relative mean yields, 226 and 267%, were different (P = 0.01). Likewise, the difference between mean yields of Cycles 8 and 9 that was significant (P = 0.05) with the SPPP test was not significant in the replicated seeded plot test. The SPPP test gives valid relative yields but over estimates the yield potential of a population that will be grown in solid stands established from seed. Samples of 50 or 25 plants compared in SPPP tests gave more variable mean yields and larger variances than the 100‐plant populations.