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  • Author or Editor: J. C. Bouwkamp x
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Abstract

Yield trials of named cultivars and advanced breeding lines are used frequently by breeders to make final determinations concerning the naming and release of breeding lines. Often a single-row per line replicate is planted and harvested due to constraints of time, space, and/or planting materials. An implicit assumption is that there is no effect on an entry by adjacent rows. The assumption was tested using data from 7 years of sweet potato yield trials. Data were not analyzed for the 1977 crop due to unavailability of the plot plan. In 1980, no yield trial was conducted and in 1982 sequential harvests of random portions of each row rendered analyses for competition inappropriate.

Open Access
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Abstract

Response to mid-day wilting (dehydration avoidance) among sweet potato [Ipomoea batatas L. (Lam)] genotypes is a consistent trait within and among years. This response is significantly related to storage root dry weight and net photosynthesis in most years. The relationship is more obvious among relatively high-yielding clones or when data are obtained over several years. Reduced mid-day wilting increases yield in high-yielding genotypes through increased net photosynthesis and increased partitioning of assimilates to storage roots. Increased storage root dry weight is also related to the percentage of water in the vines at near full-turgor through increased partitioning to roots and reduced mid-day wilting. Wilting response and vine moisture together account for nearly 25% of the variation in yield of high-yielding clones tested over 5 years with irrigation.

Open Access
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Twenty-seven trials were conducted with 20 sweetpotato [Ipomoea batatas (L.) Lam.] clones in seven locations over 4 years in Cameroon to provide data for the evaluation of statistical methods appropriate for assessing yield stability. Four stability assessment methods were used. Clones 048, TIb 1, 1639, TIS 2498, and TIS 2544 were identified as stable for storage root yield by all four methods. The Eberhart and Russell and Perkins and Jinks methods are statistically related, each detected 9, 8, 9, and 10 clones as stable for total yield, marketable yield, and total and marketable root counts, respectively. Some clones considered stable for yield were found to be unstable for root counts. This result suggests that stability of a complex trait (such as yield) may not depend on stability of component traits. The Shukla method and the Francis and Kannenberg method were considered to be the most effective and useful of those tested. The Shukla method found more clones to be stable; also, the very high-yielding and very low-yielding clones were judged to be unstable. The Francis and Kannenburg method was very convenient, easy to use, and was appropriate for grouping clones of greater and lesser desirability and stability.

Free access

Abstract

Selection of seedlings for early development of storage roots, either directly or indirectly using cold temperature (7°-10°C), increased the proportion of high-yielding genotypes in subsequent populations. Although both techniques described are somewhat inefficient, retaining some low- and high-yielding genotypes, they may be useful in selection at the seedling stage, permitting the breeder to evaluate a larger number of seedlings.

Open Access
Authors: and

Abstract

A green and tan dry podded line of snap bean was compared with respect to respiration rate, chlorophyll degradation, % dry matter of the leaves, effects of light and Ethrel treatment on abscission of petiole expiants, and fresh weight increase of leaf discs floated on a nutrient solution. The green dry podded Une respired at a higher rate, degraded chlorphyll at a slower rate and contained a higher percentage of dry matter than the tan dry podded line. Petiole explants from the green dry podded line abscised faster in the dark and slower in the light than petiole explants from the tan dry podded line. Ethrel treatment of petiole explants resulted in promotion of abscission in both phenotypes but did not change the relative rates of abscission. Fresh weight increase in leaf discs floated in nutrient solution was greater than for the green dry podded line than the tan. These observations suggest that the green dry podded line has a higher endogenous level of kinetin or kinetin-like substance.

Open Access

Abstract

It has been reported (2, 3, 4) that the nematicides Nemagon and Telone C increased carotene content in carrots and sweet com. Since the carotene content of sweet potatoes is important nutritionally, an attempt was made to extend the observations to this crop and to various nematicides.

Open Access

Abstract

The effects of varying levels of Al on fibrous root growth variables of vine tip cuttings of sweet potato [Ipomoea batatas (L.) Lam] were tested in a quartz-sand medium in the greenhouse. A significant negative relationship between Al level and root growth was noted. Root weight was increased slightly on some clones at Al levels up to 250 μM. Aluminum levels > 500 μM considerably reduced root growth. Root lengths relative to the control were used in the screening of 379 sweet potato clones and in the preliminary identification of 60 tolerant and 55 sensitive clones. The tolerant clones had greater relative root length than the sensitive ones. In a field study, no significant differences in marketable root yield were noted between lime treatment (pH 5.4) and sulfur treatment (pH 4.2). The sulfur treatment, however, increased nonmarketable yield. The sensitive clones produced greater nonmarketable yield than the tolerant ones. A negative relationship between Al tolerance and yield in nonstress condition was indicated; tolerant clones generally yielded less than sensitive ones in nonstress field tests. Root lengths in the no-Al treatment in the greenhouse were significantly correlated with the marketable root yield and number in the limed field treatments.

Open Access

Abstract

It has long been known that female asparagus plants have a higher mortality rate than males. Several explanations have been postulated, among them, competition by males which are more vigorous. Row maps were made in fields ranging from 1 to 19 years old and the distribution and location of males and females in the rows were analyzed. Statistical analysis indicated that the higher mortality rate of females could not be attributed to competition of adjacent males.

Open Access

Abstract

Triacontanol, applied at 100 ppb to sweet potato (Ipomoea batatas (L.) Lam increased percent dry weight and percentage nitrogen (dry weight basis) of leaves soon after treatment but had no measurable effect on root yields, root protein or percentage dry matter of the roots.

Open Access

Abstract

Yields and size distribution of sweetpotato (Ipomoea batatas Lam) propagated from root pieces were similar to those grown from sprouts when comparable stands were obtained.

Open Access