The performance of scavina hybrids in Trinidad and their future role, cacao híbrido, Marasmius perniciosus Stahel
The Scavinas are Forastero selections originating from Pound's 1938 Upper Amazon collections in Ecuador. They came into prominence in the 1940's on account of their high yielding ability combined with an apparent immunity to Witches' broom disease (Marasmius perniciosus Stahel). Their only drawback was small seed size. The first crosses with ICS clones at River Estate were planted in 1951 and the best cross. ICS 6 x SCA 6, gave a yield of 3300 kg/ha of dry cocoa in the 9th year, far in excess of anything previously obtained in Trinidad. Over the past twenty years more than 200 crosses have been made involving Scavina clones, mainly SCA 6 and 12. Yields have invariably passed the 1000 kg/ha mark by the 7th year and in older experiments several crossed have approached 3000 kg/ha around the 10th-12th years. The search for the best genotypes to cross with the Scavinas continues, making use of various techniques such as inbreeding, sib and back crossing, 3-way crosses and incorporating germplasm from other countries. Nearly 1100 Witches' broom seed inoculation tests, used to screen for resistance in the greenhouse, have been complete since 1954, largely on Scavina hybrids. In terms of precocity, yield, combining ability and resistance to Witches' broom SCA 6 and SCA 12 are the out standing parents tested to date in Trinidad. Future emphasis will be placed on increasing seed size and Witches' broom resistance and incorporating resistance to Black Pod (Phytophthora palmivora) and Ceratocystis fimbriata. In Ecuador ICS 6 x SCA 6 is one of the outstanding hybrids for yield. However, evidence in the field and from inoculation tests indicates that both SCA clones and their hybrids have completely lost their resistance to Witches' broom, probably a result of the development of more virulent strains of the fungus. Loss of resistance with age is also apparent in Trinidad. Although there is a large quantity of genetical material now available in Trinidad including F4 Scavinas it is of vital importance to collect new sources of resistance to the major diseases of the crop to widen the basis of breeding for resistance
| Main Authors: | , , , , , , , |
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| Format: | biblioteca |
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St. Augustine (Trinidad y Tobago)
1972
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| Subjects: | THEOBROMA CACAO, HIBRIDOS, PROGRAMAS DE MEJORAMIENTO, RESISTENCIA A LA ENFERMEDAD, RENDIMIENTO, CRUZAMIENTO, RETROCRUZAMIENTO, INOCULACION, CRINIPELLIS PERNICIOSA, PHYTOPHTHORA PALMIVORA, CERATOCYSTIS FIMBRIATA, CLONES SCAVINA, TRINIDAD Y TOBAGO, |
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| Summary: | The Scavinas are Forastero selections originating from Pound's 1938 Upper Amazon collections in Ecuador. They came into prominence in the 1940's on account of their high yielding ability combined with an apparent immunity to Witches' broom disease (Marasmius perniciosus Stahel). Their only drawback was small seed size. The first crosses with ICS clones at River Estate were planted in 1951 and the best cross. ICS 6 x SCA 6, gave a yield of 3300 kg/ha of dry cocoa in the 9th year, far in excess of anything previously obtained in Trinidad. Over the past twenty years more than 200 crosses have been made involving Scavina clones, mainly SCA 6 and 12. Yields have invariably passed the 1000 kg/ha mark by the 7th year and in older experiments several crossed have approached 3000 kg/ha around the 10th-12th years. The search for the best genotypes to cross with the Scavinas continues, making use of various techniques such as inbreeding, sib and back crossing, 3-way crosses and incorporating germplasm from other countries. Nearly 1100 Witches' broom seed inoculation tests, used to screen for resistance in the greenhouse, have been complete since 1954, largely on Scavina hybrids. In terms of precocity, yield, combining ability and resistance to Witches' broom SCA 6 and SCA 12 are the out standing parents tested to date in Trinidad. Future emphasis will be placed on increasing seed size and Witches' broom resistance and incorporating resistance to Black Pod (Phytophthora palmivora) and Ceratocystis fimbriata. In Ecuador ICS 6 x SCA 6 is one of the outstanding hybrids for yield. However, evidence in the field and from inoculation tests indicates that both SCA clones and their hybrids have completely lost their resistance to Witches' broom, probably a result of the development of more virulent strains of the fungus. Loss of resistance with age is also apparent in Trinidad. Although there is a large quantity of genetical material now available in Trinidad including F4 Scavinas it is of vital importance to collect new sources of resistance to the major diseases of the crop to widen the basis of breeding for resistance |
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