Tuberosum Group Andigena Research Articles

Potato germplasm with combined resistance to leafroll virus and viruses X and Y

Potato germplasm with high levels of combined resistance to potato viruses X, Y, and leafroll was identified and used to produce improved parental clones with similarly high levels of resistance. Resistance was determined from the amount of tuber infection following inoculation of plants in the field. Parental germplasm with the best multiple resistance came from two backgrounds, eitherSolanum tuberosum group Andigena derived from the Cornell University neo-tuberosum program, or from complex hybrids ofS. tuberosum and wild solanums that were produced by the Max Planck Institute and the Polish Institute for Potato Research. Two Aberdeen, ID selections, A85519-6 and A85530-10, with gp. Andigena ancestry, have had no tuber-borne infection of PVX, PVY, or PLRV during four years of intensive field testing. We have not been successful in combining virus S resistance with resistance to the other viruses.

Transmission and yield effects of a gibberellin mutant allele in potato

A selected clone ofSolanum tuberosum Group Andigena PI 347773 (clone Adg 11.1) and the cultivar Superior had previously been shown to be heterozygous at a gibberellin related dwarfing locus, ga1. Experiments were conducted to test for gametophytic selection for alleles at the ga1 locus in reciprocal crosses and for the effect of genotype on tuber yield. The genotypes of individuals from superior-Adg 11.1 reciprocal F1 families were determined by test crossing. Genotypic classes could be distinguished by the percentages of dwarf seedlings in their test cross progeny. No differences were found in the genotypic distributions of the reciprocal families, which indicates gametophytic selection at this locus is not the cause of reciprocal yield differences. Superior-Adg 11.1 individuals classified by ga1 locus genotype were evaluated for tuber yield. Tuber yields were highly correlated with genotype in both reciprocal families. Yields followed the pattern of simplex>duplex>triplex, indicating that the recessive mutant ga1 allele exhibited a dose effect stimulating yield.

Fertility of somatic hybrids from protoplast fusions of Solanum brevidens and S. tuberosum

Two sets of somatic hybrids between Solanum brevidens (2x) and S. tuberosum (2x and 4x) were evaluated for male fertility, meiotic regularity and female fertility. The somatic hybrids were tetraploids from 2x + 2x fusions and hexaploids from 2x + 4x fusions. Pollen stainability ranged from 0 to 83% in tetraploids and from 0 to 23% in hexaploids. The tetraploids had more regular meiosis, lower levels of micropollen and fewer unassociated chromosomes than hexaploids. However, except for a low level of selfing, the pollen of both sets of hybrids was ineffective in pollinations. The tetraploids, as females, crossed poorly with 2x and 4x tester species and selfed only at low levels. The hexaploid fusion hybrids also crossed poorly with the 2x tester species and selfed only to a limited degree; however, they crossed well with 4x testers. Seed set in crosses with S. tuberosum Group Andigena, and S. tuberosum Group Tuberosum cultivars 'Kathadin' and 'Norland' averaged 16.7, 15.6 and 28.6 seeds per fruit, respectively. Progeny from these crosses had 5x or nearly 5x ploidy levels. The results indicate that reasonable levels of female fertility can be obtained in somatic fusion hybrids of S. brevidens and S. tuberosum.

Heterosis and combining ability ofSolanum tuberosum Group Andigena haploids

Combining ability analysis was done on a diallel cross of a random sample of four different cultivated diploid potato populations (Solanum tuberosum Group Andigena haploid, Gp. Tuberosum haploid, Gp. Phureja and Gp. Stenotomum) to determine the amount of heterosis and the gene action involved in the inheritance of tuber yield, fresh vine yield, total plant accumulation (tuber+vine) fresh and dried, dry vine yield and density (specific gravity). The analyses of variance on data from two locations demonstrated significant general combining ability for most traits, indicating a preponderance of additive gene action. Specific combining ability was not significant for any of the traits. Heritabilities for the more important traits such as tuber yield and density were large enough to ensure progress from selection.

Haploid extraction inSolanum tuberosum group Andigena

Haploids were extracted from 66 differentSolanum tuberosum Group Andigena introductions usingS. tuberosum Group Phureja clone 1.22 as pollinator. The overall frequency of haploids was 13 per 100 fruit, with a high of 106. The overall average number of seeds per fruit was 1.4. Some Group Andigena clones produced primarily haploid, others primarily triploid, and still others primarily tetraploid progeny. The “triploid block” is still evident in these materials even though some clones produce primarily triploid progeny. It is suggested that the ploidy level of progeny produced in 4x - 2x crosses may be under relatively simple genetic control.

CYTOPLASMIC STERILITIES THAT SEPARATE THE GROUP TUBEROSUM CULTIVATED POTATO FROM ITS PUTATIVE TETRAPLOID ANCESTOR.

It has been proposed that the cultivated potato, Solanum tuberosum Group Tuberosum Dodds, evolved from S. tuberosum Group Andigena Dodds, the commonly cultivated potato of South America (Salaman, 1949; Simmonds, 1964; Hawkes, 1967). Both taxa are tetraploids (2n = 48), and it has also been suggested that either S. tuberosum Group Stenotomum Dodds (Hawkes, 1967) or S. vernei Bitt. et Wittm. (Brucher, 1964) is the diploid progenitor of Group Andigena. One complication in the interpretation of the evolutionary pathway is the presence in Group Tuberosum potatoes of non-chromosomal (plasmon) factors that condition sterilities when they are combined with plasmon sensitive genes of both these suggested diploid ancestors (Grun, 1970a, b). The result is that when derived diploids of Group Tuberosum are crossed with either putative diploid ancestor, using Group Tuberosum as the pistillate parent, the progeny are largely to completely male sterile, and some are female sterile. Apparently Group Tuberosurm acquired this plasmon sensitivity during one of the following steps of its evolution: 1) the step from Group Stenotomum or S. vernei to a tetraploid precursor of Group Andigena; 2) during the evolution of Group Andigena; 3) during the step from Group Andigena to Group Tuberosum. This final step could have occurred in the northern hemisphere or in Chile or both, depending

ANEUPLOIDS FROM NATURAL AND COLCHICINE-INDUCED AUTOTETRAPLOIDS OFSOLANUM

Haploids grown from unfertilized egg cells of autotetraploid Solanum (4x = 48) were found to be either euploid (2x = 24) or hyperploid (25 through 28 chromosomes), the proportion of hyperploids being 7.6% for S. tuberosum Group Tuberosum, 1.5% for S. tuberosum Group Andigena and 9.4% for the colchicine-induced autotetraploid S. chacoense. Female transmission of the extra chromosome in eight single trisomics varied from 10.0 to 47.1%. Pachytene analysis was carried out in one clone with 27 chromosomes and in two single trisomic clones from S. chacoense. The three extra chromosomes in the first clone were identified as chromosome 2 (nucleolar chromosome), chromosome 5 and chromosome 9 following the numbering system of Yeh and Peloquin (1965). One single trisomic appeared trisomic for chromosome 5, the other probably for chromosome 7. Association of the chromosomes at MI, AI and AII was studied in eight single, two double and one triple trisomic plants. Two plants showed desynapsis. From the meiotic studies of the synaptic trisomics it was apparent that all arc primary trisomics.

CHANGES OF CYTOPLASMIC FACTORS DURING THE EVOLUTION OF THE CULTIVATED POTATO.

Two proposals have been made concerning the origin of the tetraploid cultivated potato, Solanum tuberosum Group Tuberosum Dodds. Hawkes (1956, 1967) suggested that the primitive cultivated diploid S. tuberosum Group Stenotomum Dodds gave rise, following doubling of chromosome number, to cultivated S. tuberosum Group Andigena Dodds in fields at high altitudes in the Andes of Bolivia or Peru. Subsequent human selection among Group Andigena biotypes in South America and Europe was felt to have given rise to the Group Tuberosum cultivated potato. The alternative suggestion of Briicher (1964) was that S. vernei Bitt. et Wittm., a wild diploid weedy species of northwestern Argentina, gave rise to Group Andigena forms following autoploidy, human selection again leading to Group Tuberosum. On grounds of morphology the two proposals both appear to be plausible. Earlier studies (Koopmans, 1954, 1955; Buck, 1960; Grun et al., 1962; Grun and Aubertin, 1965, 1966; De la Puente and Peloquin, 1968) demonstrated that changes of factors that condition cytoplasmic male sterility have played an active role in evolution of Solanum. The present study is an attempt to determine, by study of reciprocal F1 hybrids, the degree to which cytoplasmic factors and cytoplasm-sensitive genes of the cultivated potato resemble those of the putative diploid progenitors.

Resistance in tuber-bearing solanum species to root knot nematode, Meloidogyne incognita

Forty-one clones of 34 accessions belonging to 25 tuber-bearingSolanum species were tested for their reaction to root knot nematode,Meloidogyne incognita. A high degree of resistance was found inS. bulbocastanum, S. gandarillasii, S. lignicaule, S. ajanhuiri andS. tuberosum groupandigena. S. vernei andS. spegazzinii were the most resistant species.

Regional variation in leaf form and other characters of solanum tuberosum Group Andigena

Study of seedling progenies grown at Edinburgh showed that the terminal leaflet becomes an increasingly important part of the leaf as one proceeds northwards from Southern Bolivia to Colombia, the frequencies of lateral leaflets, interjected leaflets, and secondary leaflets consequently declining. Actual leaf length, and the breadth of the terminal leaflet, are least in South-Central Peru, and increase towards the extremities of the geographical range. Flowering in the seedling year was most frequent in progenies from South-Central Peru. while low-dormancy of tubers was most frequent in those from Ecuador, these characters not showing clear geographical trends.