Ajala, M.O’s Research

· Rehabilitation of substandard seed

Although, the environmental conditions required for good seed storability and viability can be precisely determined, the control of deterioration where such condition are less favorable, such as obtained in peasant agriculture in the humid tropics, has not been given the deserved close attention. We suggested chemical treatment of seeds stored at high temperature and high relative humidity, characteristic of small scale farming in the humid tropics as a mode of reducing seed viability and seed vigour losses. Thus, Zn at 100 mg/L enhanced viability and seedling growth of deteriorated soybean, just as Gibberellic Acid and Chloroethyl Phosphonic Acid (CEPA) both at 10 mg/L individually had promotive effects on rice viability and subsequent plant growth. Publication nos 2, 3 and 7 have explored these areas, noting changes in mineral reserves during seed storage and employing physiologically active chemicals and hormones to preserve seed quality and regulate germination behaviour. Our work also established that chemical seed treatment could delay seed deterioration process under adverse storage conditions (Publi. nos.8, 12, 13 and 17) but quantifying the longevity of seed after these treatments would further elucidate the adverse effects sometimes through probit modeling on seed’s survival. (Publication. nos. 4, 13 and 21)

 

· Improvement of Seed Production Methods

One problem encountered in soybean seed production in the humid tropics was the mode of fluctuation in germination and field emergence of seeds from year to year to the extent that target population densities could not be met. Our work revealed that soybean seeds harvested 10 days before or a few days after harvest maturity were better in terms of  germination and emergence(Publication no.5). In selecting seed lots for planting and determining the rate at which farmers need to plant, factors such as laboratory germination test, seedling vigour tests and field conditions expected at planting time must be considered. These findings are reported (in Publication 6 and 29) for pigeon pea and winged beans, where high correlation of seedling vigour was found with field emergence. For sesame crop, we recommended a population of 166,667 plants ha -1 as the best planting rate for good seed yield and yield components of sesame genotypes, despite their diverse genetic background under tropical rain fed conditions (Publication. 18). Use of dry heat treatment was carried out to improve germination and vigour of newly released West African rice seed and we discovered that application of a temperature range between 50 – 600C for 24 hours was sufficient to break dormancy in many varieties (Publication. 19) but many beneficial carry over effects  beyond germination and vigour stages were documented in our work as revealed in Publication 20. In another study, we discovered a close relationship among seed germination, seedling vigour and field emergence in sesame. This indicated that these traits could be improved by selecting for seeds of high germinability (Publication 16). In the variation and correlation studies in fruit yield and seed quality components of tomato (Publication 27), we found high heritability for 1000 seed weight, number of seeds/fruit, fruit colour, fruit size and days to 50% flowering, indicating that these varieties were not easily influenced by the environment.

 

· Enhancement of  Seed Quality

Seed quality losses arising from excessive field exposure, high moisture content and mechanical damage are minimized through timely harvesting, prompt and adequate drying as well as careful handling, which altogether contribute to a sound seed history favorable for storage. Publication no.1 addresses the issues of seed mechanical damage arising from variation in moisture levels, and suggests a range within which cowpea pods could be threshed. The influence of seed quality attributes on field emergence of pigeon pea and winged bean was fully discussed  in Publ. no 6. Other contributions to the enhancement of seed quality have come from our Publications 4, 6, 7, 8,12, 13, 15, 23, 28, 29 and 32..

 

· Genetic Studies

Genotypic differences in quality of seeds provide an opportunity for employing genotypic selection as a method of improving seed quality. Studies on genetic improvement of seed potentials have been well covered in Publications 9, 15, 30, 31 and 33,while research on the sciences and techniques of seed production has emphasized practical applications as indicated previously in  Publications 5,6,18,19,20 as well as 25, 26 and 32. Specifically, our work on West African okra      (Publications 14 and 24) reviewed the possibility of genetic improvement in seed yield. In consonance with the above study on the same crop, West African okra, it was further pointed out that genetic diversity existed among the generations evaluated with additive genetic effects moderating the inheritance of 100-seed wt (Publications 24). Our research work on heritability, character correlation and path-coefficient analysis among six inbred lines of maize showed that the total number of grain per ear could be used as the most reliable selection index for yield improvement in maize inbred lines ( Publication 22). Studying the performance and stability of seed yield in 14 sesame genotypes revealed that all the genotypes differed significantly for seed yield and genotype x environment (G X E) interaction. Of note is the fact that these genotypes were distinct and pertinent in commercial seed production and future breeding programmes ( Publication 27).

 

· Improvement in field performance

For many crop species, the laboratory germination overestimates the field emergence, as the ideal conditions obtainable under laboratory testing are seldom prevalent in field situations. My research work on pigeon peas and winged beans, and later on our work on  sesame and soybean have pointed out the most sensitive indicators in the prediction of field emergence (Publication  nos. 6, 11, 16 and 25). In the drought stress evaluation of tropical maize hybrids, our findings emphasized drought tolerance stress index (DTSI) as a useful tool for determining drought stress ( Publication 25),with accompanying satisfactory productivity.

 

· Need for  Database

Recognizing the need to provide crop variety database, which will increase the efficiency of crop improvement, our work provided  vital information on maize crop variety, which would allow for focused decision-making on seed production (Publication no. 10).In addition, plant breeders could also use the information system for breeding plans  while also serving as decision support system (DSS) for policy makers.