Interaction of Plant Spacing and Combining Ability in an Eight‐Clone Diallel of Medicago sativa L.¹

Abstract

The diallel progenies of 8 alfalfa clones were grown in rows 1 and 3 feet apart and spaced 2, 8, and 24 inches within rows. Yield, plant width, plant height, crown width, and vigor were measured in each of 2 years; leafhopper yellowing and leafstem ratio were measured in 1 year. The general combining ability, specific combining ability, maternal, reciprocal, and their interaction effects with spacings and years were studied.General and specific combining abilities were significant for all characters measured. Maternal effects for some characters were significant, while reciprocal effects were generally nonsignificant. General combining ability effects and specific combining ability effects were consistent across spacing‐year treatments. Maternal effects were less consistent across treatments, yet were positively correlated between treatments. Since the number of plants per linear foot of row in the 2‐inch spacing within rows 1 foot apart was very close to the number of plants in a 2‐year‐old broadcast seeding, the data suggested that progenies could be evaluated in spaced plantings with small quantities of seed.

Combining ability, genotype x environment interactions and genotypic correlations of agronomic characters in Medicago sativa L.

“…Various workers have used the field results of open-pollinated progenies as a test of the combining abilities of the alfalfa parents (TYSDAL et al, 1942;TYSDAL & CRAN-DALL, 1944;BOLTON, 1948). More recently, diallel crosses have been used extensively to identify potential parents on the basis of general and specific combining abilities (CARNAHAN et al, 1960;THEURER & ELLING, 1963;WILCOX & WILSIE, 1964;EVANS et al, 1966). Such a breeding technique is most effective in selecting suitable clones for use as parents of two-clone or multi-clone synthetic crosses.…”

Competition among components of synthetic varieties in alfalfa

“…(Evans et al ., 1966 ;Hill et al ., 1971 ;Busbice et al ., 1974 ;Rowe & Gurgis, 1982) . According to the results of this research, the yielding ability of a synthetic variety cannot be predicted from the pure stand yield of the polycross progenies of its constituent clones because of the weak relationship between pure stand yield and yield under competition of the progenies .…”

Genetics of resistance to kernel infection by Aspergillus flavus in maize *

“…An appropriate design matrix was developed for SAS (Statistical Analysis System, Cary, NC, USA), as described by Kang (1994). The program allowed us to partition reciprocal effect for percentage kernel infection into maternal (general reciprocal) and non-maternal (specific reciprocal) components (Cockerham 1963, Cockerham and Weir 1977, Evans et al 1966, Stuthman et al 1971. Non-maternal effect = reciprocal effect -female maternal effect + male maternal effect.…”