Genetic variability for root characteristics and drought tolerance in cowpea

مرکز و کتابخانه مطالعات اسلامی به زبان های اروپایی

منو

" Genetic variability for root characteristics and drought tolerance in cowpea "
Y. Mai-Kodomi J. H. M. Yopp, Oval, Jr.

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113231
Doc. No	:	TLpq304298659
Main Entry	:	J. H. M. Yopp, Oval, Jr.
	:	Y. Mai-Kodomi
Title & Author	:	Genetic variability for root characteristics and drought tolerance in cowpea\ Y. Mai-KodomiJ. H. M. Yopp, Oval, Jr.
College	:	Southern Illinois University at Carbondale
Date	:	1996
student score	:	1996
Degree	:	Ph.D.
Page No	:	240
Abstract	:	Drought tolerant (DT) cowpeas are needed because of the erratic rainfall in Niger and northern Nigeria where the major portion of the world's cowpea crops is grown. A method for screening cowpea seedlings for DT characteristics in boxes was described for the first time. Watering was withheld after the emergence of the first true leaves of the cowpea plants. Drought susceptible (DS) lines wilted, turned yellow and died and had a high rate of water loss. DT lines wilted more slowly lived longer. Some lines were intermediate between these extremes. Type one DT (DT1) lines remained green until they died. In type two (DT2) lines, the unifoliate leaves died after yellowing but the growing tip continued to remain green and turgid. This is the first description of the two types of DT. They differ from each other in unifoliate and trifoliate leaf moisture content (MC). The boxes were used to screen progeny lines, selected surviving plants can be transplanted to continue the breeding program. Pot-grown plants subjected to drought during their reproductive stage gave a similar result to that of the box screening. A box screening using different soil types showed the necessity to adapt the level of moisture available to the plants to the season and location of screening. Nine other crops screened were all less DT than cowpea. To screen other crops with this method initial MC should be adjusted. Genetic variability existed for root length (RL) of plants grown on soil contained in vinyl tubes. With two water regimes, DS lines had higher RL reductions. Root mass of pot grown cowpea lines was significant but RL was a better criterion to screen cowpea for root characteristics. When grown on stored moisture in the field, DS lines had lower yield of both seed and biomass. The best line in the field was intermediate in the box screening but had a high RL. In a rainy season test in three locations, DT1 lines lost their advantage of higher yield over DS lines. DS usd\timesusd DT1 and DS usd\timesusd DT2 crosses showed a single gene inheritance with the dominant allele conferring DT in both cases. A DT1 usd\timesusd DT2 cross suggested that the genes controlling DS, DT1 and DT2 may be multiple allelic. This was the first attempt to elucidate the genetics of DT in cowpea. With such simple inheritance, it may be easy to transfer these types of DT to all cowpea cultivars targeting the Sahelian zone.
Subject	:	Agronomy
	:	Biological sciences
	:	Botany