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  • Author or Editor: Alfred Jones x
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Abstract

Twenty-four traits in generations 2 to 7 of a randomly intercrossing sweetpotato [(Ipomoea batatas (L.) Lam.] population were studied. Mean changes detected were: increased flowering, reduced leaf whorl purpling, increased vine purpling, decreased vine diam, decreased root wt, fewer smooth skinned types and some increase in vine length. Changes in the fusarium wilt index were not significant but distributional changes were important; fewer plants with high levels of resistance occurred in the later generation. Reductions in vine diam and in root wt were considered independent of each other. There was no indication that the natural selection for increased flowering was responsible for either vine diam or root wt reductions.

Open Access

Abstract

Sweetpotato breeders are confronted with the problem of extremely low seed set. Based on counts made of seed set in tagged flowers, only about 2 or 3% of the potential seed production is realized (2). This problem is compounded by the occurrence of flower bud abscission prior to opening. Although low seed set may be primarily due to genetic incompatibility, sterility or physiological disharmony in developing seed, insect or disease damage could also be involved. This study provides information on the fungi of sweetpotato floral parts and preliminary results of their effect on seed set.

Open Access
Authors: and

Abstract

Viability studies were conducted on 18 lots of seed of sweet potato (Ipomoea batatas (L). Lam.) spanning a 21 year storage period. For the last 10 years, these seeds had been stored at 18° C and 45-50% relative humidity, but prior to that storage conditions varied. Weight per 100 seeds ranged from 1.7 to 2.4 g. No effect of seed age was found on germination (radical protrusion), which averaged 90% after sulfuric acid scarification, or on emergence which averaged 72%. The condition of the seed prior to storage seemed to have more effect than how long they were stored.

Open Access
Authors: and

Abstract

Three greenhouse tests to determine the reactions of sweet potato (Ipomoea batatas (L.) Lam.) breeding lines and their respective open-pollinated offspring to 2 species of root-knot nematodes were conducted. Resistances occurred in high frequency to both the southern root knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) and the Javanese (tropical) root knot nematode (M. javanica (Treub) Chitwood). Reaction to M. incognita was studied in 2 consecutive years with different sets of parental lines using an egg mass index. Estimated heritability (h2) in 1976 was 0.75 ± 0.23 and in 1977 was 0.57 ± 0.37. Three indices of reaction to M. javanica and respective h2 estimates were: Egg mass index, 0.69 ± 0.18; galling index, 0.78 ± 0.19; and necrosis index, 0.72 ± 0.20. Resistances to the 2 species were not correlated, indicating independent inheritance. Development of cultivars with high levels of resistance to each or to both of the above diseases is possible.

Open Access
Authors: and

Abstract

Thirty random seedlings from each of 50 random parents of a sweet potato (Ipomoea batatas (L.) Lam.) mass selected population were evaluated in the greenhouse and their subsequent field performances were recorded. Simulated selection sequences were also studied. A sequence with mass selection first on maternal hill weight, high seed set, and high seed weight followed by a 50% culling level within families on the basis of low greenhouse seedling vigor resulted in average progeny field yields 45% above that of no selection. The results showed seed weight to be a potentially useful selection criterion for root yield. Individual seedling root weight in the greenhouse was not a good predictor of field yield.

Open Access

Abstract

Insect resistance in sweet potatoes (Ipomoea batatas (L.) Lam.) was more effective than fonofos, O-ethyl-S-phenylethylphosphonodithioate, in reducing insect injury to the roots. The most recent resistant line tested did not sustain economic injury from relatively high insect infestations even without the protection of an insecticide. Fonofos at 2.24 and 4.48 kg/ha did not prevent economic injury to the susceptible ‘Goldrush’.

Open Access

Abstract

The fertility of 6 successive generations of open pollinated sweetpotatoes was studied in each of 4 months. Breeding by open pollination increased the percentages of plants in flower, the number of flowers per plant, and total seed production. Both capsule and seed numbers per flower were higher in the first and last generations than in intervening generations. Self-compatibility, when determined by numbers of pollen tubes per stigma, was not affected by the breeding procedure. Mean numbers of pollen tubes per flower following cross pollination were higher in the later generations. Month to month effects were important in the case of all measurements. Flowering was most profuse in the middle of the season; seed set was highest early in the season; and pollen germination after selfing or crossing was highest at the beginning and end of the season.

Open Access

Abstract

Character associations in a sweet potato [Ipomoea batatas (L.) Lam.] population after 4 cycles of selection for resistance to soil insects and in a control population with no selection were studied by use of contingency tables of pairs of traits. Possible common factors were indicated for resistances to the sweet potato flea beetle and the wireworm-Diabrotica-Systena (WDS) complex. Selection changed the means and distributions of 6 of 13 unselected root and vine traits. None of these changes were directly associated with insect resistances, but that in root cracking was caused by the grading techniques. Two traits appeared genetically associated (cortex thickness and leaf-whorl color), and 2 appeared to be expressions of the same character change (flesh-color changes were also expressed as skin-color changes). The selected population had shorter internodes than the unselected. These changes in unselected traits were probably due to drift caused by small population sizes in the selected generations. No barriers to development of insect-resistant cultivars were detected.

Open Access

Abstract

Application of systemic fungicides to sweet potato (Ipomoea batatas (L.) Lam.) increased the total number of healthy seed harvested 50% by increasing pod set, number of seed per pod and the proportion of healthy seed. Insecticides aldicarb and naled gave dramatic responses and increased the number of seedlings obtained per parent plant 2- to 5-fold. Insect damage appeared to be an important cause of low seed set and low seed quality in sweet potato.

Open Access

Abstract

Two breeding lines of sweet potato [Ipomoea batatas (L.) Lam.] were released in 1975. They possess unusual combinations of disease and insect resistances with other useful characteristics. Both lines originated from mass selection for multiple disease and soil insect resistances in a sweet potato population incorporating a wide gene base. Both lines flower and set seed without any special treatment; traits of particular value in breeding

Open Access