Recurrent Selection for Tolerance to Bean Yellow Mosaic Virus in Arrowleaf Clover

Abstract

Arrowleaf clover (Trifolium vesiculosum Savi) is an important forage crop in the southeastern USA, but production and persistence of arrowleaf can be limited by virus diseases. We conducted five cycles of recurrent phenotypic selection from 1986 through 1991 for tolerance to bean yellow mosaic virus (BYMV) isolate KY 204‐1 in arrowleaf clover. Six‐week‐old seedlings were mechanically inoculated with BYMV and evaluated at 100 d of age. From 300 to 1100 plants were screened per cycle, and the most tolerant 1 to 4% were hand‐crossed and their progeny advanced to the next cycle. Seedling dry weights and virus disease ratings were used to estimate the level of virus tolerance of each plant. Rating methods were modified during evaluation of Cycle 5; growth parameters and chlorophyll levels were used as selection criteria. Results were compared with those from the susceptible cultivars, Yuchi, Meechee, and Amclo. Field evaluations compared survival of inoculated Cycle 3A germplasm (1991), and survival, yield, and flowering of Cycles 3A and 5 germplasm (1992), with those of the three susceptible cultivars and non‐inoculated controls. Five cycles of recurrent phenotypic selection in arrowleaf clover resulted in a population possessing tolerance to BYMV. A lethal wilt gene was eliminated from the population, and field survival and dry matter production under disease pressure greatly improved. Tolerant plants maintained normal chlorophyll levels and near normal flowering rates when infected with BYMV, thus ensuring successful seed production.

Genetics of resistance to alfalfa mosaic virus in red clover

“…Pederson and McLaughlin (1994) found that the reaction of white clover clones to AMV in the field was not well related to performance of progeny under mechanical inoculation in the greenhouse. However, Pemberton et al (1994) showed improved field performance in the presence of bean yellow mosaic virus in populations selected in the greenhouse for tolerance to this same virus. The present study has shown that resistance to AMV in red clover is under polygenic control.…”

“…The fact that only two (R × R) × ( R × R) crosses produced sufficient progeny (Table 1) can be explained by cross-incompatibilities caused by the small base population. Pemberton et al (1994) carried out five cycles of recurrent phenotypic selection for tolerance to bean yellow mosaic virus in arrowleaf clover (Trifolium vesiculosum Savi) and produced a highly tolerant population.…”

Long‐Term Forage and Cow–Calf Relationships for Bermudagrass Overseeded with Arrowleaf Clover or Annual Ryegrass Managed at Different Stocking Rates

“…In 1979, a forage breeding program was initiated at the Texas Agriculture Experiment Station (TAES), Overton, to develop improved, disease‐resistant cultivars. ‘Apache’ arrowleaf clover, released by TAES in 2004 (Smith et al, 2004), was developed through multiple cycles of recurrent selection for tolerance to Bean yellow mosaic virus (Pemberton et al, 1989, 1991, 1994) and soil‐borne fungal pathogens such as Pythium ultimum Trow (Pemberton et al, 1998). The release of Apache has restored the utility of arrowleaf clover for livestock production systems in the southern United States.…”

“…mosaic virus (Pemberton et al, 1989(Pemberton et al, , 1991(Pemberton et al, , 1994 and soil-borne fungal pathogens such as Pythium ultimum Trow (Pemberton et al, 1998). The release of Apache has restored the utility of arrowleaf clover for livestock production systems in the southern United States.…”

Registration of ‘Apache’ Arrowleaf Clover

“…The dominant allele, L , imparting the systemic wilting response to BYMV, is present in 15 to 23% of the Yuchi arrowleaf clover population. One cycle of selection, with mechanical inoculation with BYMV‐KY204‐1 eliminated the susceptible ( LL and Ll ) genotypes (Pemberton et al, 1994).…”